Micro Midterm Flashcards
(500 cards)
1
Q
What color are gram positive bacteria on a typical gram stain? What about gram negative?
A
Gram positive: blueish or purple; gram negative: pink
2
Q
Are these bacteria gram positive or gram negative?
A
Gram positive, note the purple color. This is bacillus.
3
Q
What shape are cocci bacteria?
A
Typically spherical, in clusters, pairs, or chains
4
Q
Can all bacteria be visualized with the gram stain?
A
No, some need other stains e.g. spirochetes
5
Q
Do bacteria have organelles?
A
No, they are prokaryotes
6
Q
What is the outermost coat of the gram-negative cell wall?
A
A phospholipid membrane (there are two of them, one for the cell well and one that functions as the plasma membrane)
7
Q
What is the cell wall of gram-positive bacteria made of?
A
Peptidoglycan: peptide cross links between polysaccharide chains
8
Q
Are lipopolysaccharides characteristic of gram positive or gram negative bacteria?
A
Gram negative, as they integrate into the outer phospholipid membrane
9
Q
Does Staphylococcus epidermidis normally cause disease on the skin?
A
No, it is benign. Staph aureus is the more virulent strain that can cause acne and other skin infections.
10
Q
Is the peptidoglycan layer of the cell wall thicker in gram positive or gram negative bacteria?
A
Gram positive bacteria have thicker peptidoglycan
11
Q
Bacteria can be colonize or can cause disease. The ability to cause disease is determined by
– […] factors
– Host factors
– Environmental factors
A
Bacteria can be colonize or can cause disease. The ability to cause disease is determined by
– Virulence (bacterial) factors
– Host factors
– Environmental factors
12
Q
Bacteria can be colonize or can cause disease. The ability to cause disease is determined by
– Virulence (bacterial) factors
– […] factors
– Environmental factors
A
Bacteria can be colonize or can cause disease. The ability to cause disease is determined by
– Virulence (bacterial) factors
– Host factors
– Environmental factors
13
Q
Bacteria can be colonize or can cause disease. The ability to cause disease is determined by
– Virulence (bacterial) factors
– Host factors
– […] factors
A
Bacteria can be colonize or can cause disease. The ability to cause disease is determined by
– Virulence (bacterial) factors
– Host factors
– Environmental factors
14
Q
Besides direct damage caused by the organism, what can infectious disease symptoms manifest via?
A
The immune response mounted by the host
15
Q
What is hemolysis as it relates to bacteria?
A
The pattern that the colonies form on a blood agar plate, related to their ability to break down blood cells
16
Q
Is this α or β hemolysis?
A
β: halo like growth around streaks
17
Q
What kind of typing is this? Which side is positive?
A
Lancefield typing; left is positive
18
Q
What are non-suppurative complications?
A
When the host response causes the clinical manifestations of the disease
19
Q
What bacterium causes pharyngitis, cellulitis, impetigo, and necrotizing fasciitis?
A
Streptococcus pyogenes
20
Q
Is Streptococcus pyogenes α or β hemolytic?
A
β hemolytic
21
Q
What clinical manifestation is this? What bacterium is immediately suspect?
A
Pharyngitis; Streptococcus pyogenes
22
Q
What clinical manifestation is this? What bacterium is suspected?
A
Erypsipelas; Streptococcus pyogenes
23
Q
What skin condition is this? What bacterium is immediately suspect?
A
Impetigo; Streptococcus pyogenes
24
Q
What does it mean to talk about suppurative complications of an infection?
A
Clinical manifestations directly caused by the organism itself; e.g., pharyngitis or a rash
25
Are acute rheumatic fever, glomerulonephritis, scarlet fever, and toxic shock suppurative or non-suppurative complications?
Non-suppurative
26
What does the word "suppurative" derive from (e.g. what does suppuration refer to?)
Pus formation
27
Is acute rheumatic fever more rare or less rare over the age of 30 than below?
It is very rare over 30
28
Does acute rheumatic fever associate with a preceding S. pyogenes throat infection, or a skin infection, or both?
Only throat infections
29
When a bacteria is said to belong to Group A, B, etc. what grouping system is being referenced?
The Lancefield grouping system
30
What is the Lancefield grouping system based on? Does it apply to α hemolytic or β hemolytic bacteria?
The carbohydrate composition of bacterial antigens in their cell walls; Lancefield only worked on β hemolytic bacteria
31
Clinical manifestations of acute rheumatic fever include:
* [...]
* Carditis (heart failure, new murmur,
pericarditis)
* Sydenham’s chorea
* Erythema marginatum
Clinical manifestations of acute rheumatic fever include:
* Painful, migratory arthritis
* Carditis (heart failure, new murmur,
pericarditis)
* Sydenham’s chorea
* Erythema marginatum
32
Clinical manifestations of acute rheumatic fever include:
* Painful, migratory arthritis
* [...] (heart failure, new murmur,
pericarditis)
* Sydenham’s chorea
* Erythema marginatum
Clinical manifestations of acute rheumatic fever include:
* Painful, migratory arthritis
* Carditis (heart failure, new murmur,
pericarditis)
* Sydenham’s chorea
* Erythema marginatum
33
Clinical manifestations of acute rheumatic fever include:
* Painful, migratory arthritis
* Carditis (heart failure, new murmur,
pericarditis)
* Sydenham’s [...]
* Erythema marginatum
Clinical manifestations of acute rheumatic fever include:
* Painful, migratory arthritis
* Carditis (heart failure, new murmur,
pericarditis)
* Sydenham’s chorea
* Erythema marginatum
34
Clinical manifestations of acute rheumatic fever include:
* Painful, migratory arthritis
* Carditis (heart failure, new murmur,
pericarditis)
* Sydenham’s chorea
* [...] marginatum
Clinical manifestations of acute rheumatic fever include:
* Painful, migratory arthritis
* Carditis (heart failure, new murmur,
pericarditis)
* Sydenham’s chorea
* Erythema marginatum
35
What is the pathogenesis of post-streptococcal glomerulonephritis?
Antibodies, complement components react with streptococcal antigens to form immune complexes which deposit in the renal glomerulus
36
Does post-streptococcal glomerulonephritis most often affect children or adults?
Children
37
What are these clinical manifestations characteristic of? Hint: this patient had a known exposure to *Streptococcus pyogenes*.
Scarlet fever
38
What toxins cause streptococcal toxic shock syndrome?
Pyrogenic exotoxins (SPEA, SPEB, SPEC)
39
If a patient is in shock and undergoing multi-organ system failure following a streptococcal infection, what syndrome may be occurring?
Streptococcal toxic shock syndrome
40
What do the exotoxins involved in streptococcal toxic shock bind to? What does this cause the release of?
T lymphocytes and class II MHC complexes of antigen-presenting cells; leads to massive cytokine release
41
Is *Streptococcus agalactiae* in group A or B? Is it α hemolytic or β hemolytic?
Group B; β hemolytic
42
What bacterium is highly associated with neonatal sepsis and maternal sepsis, as well as soft-tissue infection in diabetics?
*Streptococcus agalactiae*
43
Are enterococcal species more resistant or less resistant to cephalosporins and β-lactam based drugs?
More resistant
44
Enterococcus can cause:
* [...]
* Biliary tract infection
* Peritonitis
* Bacterial endocarditis
* Nosocomial superinfection: particularly bacteremia
Enterococcus can cause:
* Urinary tract infection
* Biliary tract infection
* Peritonitis
* Bacterial endocarditis
* Nosocomial superinfection: particularly bacteremia
45
Enterococcus can cause:
* Urinary tract infection
* Biliary tract infection
* Peritonitis
* Bacterial [...]
* Nosocomial superinfection: particularly bacteremia
Enterococcus can cause:
* Urinary tract infection
* Biliary tract infection
* Peritonitis
* Bacterial endocarditis
* Nosocomial superinfection: particularly bacteremia
46
Enterococcus can cause:
* Urinary tract infection
* Biliary tract infection
* Peritonitis
* Bacterial endocarditis
* Nosocomial superinfection: particularly [...]
Enterococcus can cause:
* Urinary tract infection
* Biliary tract infection
* Peritonitis
* Bacterial endocarditis
* Nosocomial superinfection: particularly bacteremia
47
Are strep viridans species α hemolytic or β hemolytic? How are they distinguished from pneumococci?
α hemolytic; distinguished from pneumococci with the optochin test, which strep viridans are not sensitive to
48
What is the major agent causing bacterial endocarditis?
Streptococci, in particular strep viridans
49
Can *Staphylococcus aureus* cause bacterial endocarditis?
Yes
50
Are streptococcal strains gram positive or negative?
Gram positive
51
*S. mutans* and *S. sanguis* are both streptococcal bacteremia that comprise what group?
Strep viridans, or α hemolytic streptococci
52
How many kinds of hemolysis are there for a bacterial culture on blood agar? What are they?
Three: α, β, γ
53
Is *Streptococcus pyogenes* sensitive to bacitracin? Does an antibody to M protein enhance immune response?
Yes, it is sensitive to bacitracin; yes, antibody to M protein is protective
54
What are three pyogenic consequences of streptococcus pyogenes infection?
Pharyngitis, cellulitis, impetigo
55
What does "pyogenic" mean?
Causes creation of pus
56
What genus do *E. faecalis* and *E. faecium* belong to?
Enterococcus
57
How are enterococci divided by Lancefield grouping?
They are divided into group D and non-group D
58
What streptococcal bacteria normally colonize the oropharynx?
*Strep viridans*
59
What bacterium most typically causes dental caries (cavities)?
*S. mutans*
60
What is the hardest genus of streptococcus to kill with antibiotics?
Enterococcus
61
What is a mnemonic for three common causes of *S. pyogenes* based on "PH"?
PHaryngitis to rheum PHever and glomerulonePHritis
62
What is a mnemonic for rheumatic fever symptoms?
JONES:
- Joints
- Heart (is round like an O)
- Nodules
- Erythema marginatum (pink rings on the trunk)
- Syndenham's Chorea (abnormal involuntary movement disorder)
63
Is *Staphylococcus aureus* gram positive or negative? Does it form chains or clusters?
Positive; clusters
64
Is *S. aureus* coagulase positive or negative?
Positive
65
What bacteria are these?
 
*Staphylococcus aureus*; clusters + gram positive
66
Virulence factors for *S. aureus* include [...], surface factors, and secreted proteins.
Virulence factors for *S. aureus* include biofilm, surface factors, and secreted proteins.
67
Virulence factors for *S. aureus* include biofilm, [...], and secreted proteins.
Virulence factors for *S. aureus* include biofilm, surface factors, and secreted proteins.
68
Virulence factors for *S. aureus* include biofilm, surface factors, and [...] proteins.
Virulence factors for *S. aureus* include biofilm, surface factors, and secreted proteins.
69
What protein in *S. aureus* correlates with virulence and binds to the Fc terminal of IgG inhibiting complement fixation? What else does this inhibit?
Protein A; phagocytosis
70
*S. aureus* can surround their cell walls with a [...] capsule, which inhibits opsonization.
*S. aureus* can surround their cell walls with a polysaccharide capsule, which inhibits opsonization.
71
*S. aureus* can surround their cell walls with a polysaccharide capsule, which inhibits [...].
*S. aureus* can surround their cell walls with a polysaccharide capsule, which inhibits opsonization.
72
What part of *S. aureus* is protein A integrated into?
The cell wall
73
Are coagulase positive staphylococci more or less virulent than coagulase-negative ones?
More virulent
74
Do staphylocci infections typically produce pus?
Yes
75
What is the primary host immune response to staphylococcus infection?
Primarily mechanical and in the epidermis, but opsonization and neutrophil phagocytosis are also significant
76
Can *S. aureus* cause skin and soft tissue infections? What about endocarditis? Septic arthritis?
Yes to all
77
What toxin does *S. aureus* produce that causes toxic shock syndrome?
TSST1
78
What bacteria produces an abscess like this?
*S. aureus*
79
Can impetigo be caused by *S. aureus?*
Yes
80
What color is the crust around impetigo lesions?
Golden
81
What is skin infection is this picture characteristic of?
Cellulitis, probably by *S. aureus*
82
What is this infection called? Is this the same as a stye? What bacterium is it associated with?
Chalazion; it is different from a stye (it is a cyst blocking a tarsal gland, not a sebaceous gland); *S. aureus*
83
What are these?
Microemboli associated with endocarditis
84
What are serious neurologic targets of metastatic infection caused by *S. aureus*?
Brain abscesses or spinal epidural abscess
85
Can *S. aureus* cause knee arthritis?
Yes, it can infect it causing septic arthritis
86
What does "nosocomial" mean?
Hospital-acquired (usually referring to an infection)
87
What does MRSA stand for? What infection source is it associated with?
Methicillin-resistant *Staphylococcus aureus*; nosocomial infections
88
What bacteria commonly causes acute food poisoning? How long does this illness last?
*Staphylococcus aureus*; 24 hours
89
How long is an *S. aureus* bacteremia usually treated? What is the reasoning behind this?
4 weeks; undertreating a bacteremia can lead to the development of a resistant strain
90
How do you treat MRSA?
Synthetic cell-wall active penicillins: Oxacillin, nafcillin, cefazonin; or vancomycin
91
Does vancomycin work on gram positive or gram negative bacteria?
Gram positive
92
Is *S. epidermidis* coagulase positive or negative?
Negative
93
Does *S. epidermidis* typically cause any disease while inhabiting the skin?
No, but it is important in association with medical devices
94
What is the thick, multilayered slime created by *S. epidermidis *that covers catheters during invasion and protects it from antibiotics called?
Biofilm
95
What bacterium is associated with infections from intravascular devices?
*S. epidermidis*
96
What location of infection is *S. saprophyticus* commonly associated with?
Urinary tract infection
97
*S. saprophyticus *most likely has unique surface proteins that permit it to bind to which receptors in the genitourinary tract?
Mucosal receptors
98
What drug is this?
Vancomycin
99
Wha tis the mechanism of Vancomycin?
It inhibits bacterial cell wall synthesis by binding firmly to D-ala-D-ala of the peptidoglycan, preventing elongation and cross-linking
100
What are two mechanisms of resistance to vancomycin?
- Altered peptidoglycan binding site: D-ala-D-ala to D-ala-D-lactate
- Thickened cell wall
101
Is vancomycin active against gram-positive or gram-negative bacteria or both?
Gram-positive
102
What is the drug of choice for treating MRSA and penicillin-resistant pneumococcus?
Vancomycin
103
What are two major toxic side effects of vancomycin?
Nephrotoxicity and hypersensitivity (red man syndrome or anaphylaxis)
104
Why is vancomycin given slowly?
To avoid histamine reactions resulting from rapid infusion, such as red man syndrome
105
Why might a pretreatment of antihistamine be used before a rapid infusion of vancomycin?
To avoid anaphylaxis or red man syndrome
106
Is vancomycin bactericidal or bacteriostatic?
Slowly bactericidal, mostly bacteriostatic
107
What drug is this?
Daptomycin
108
Does daptomycin act against gram-positive or gram-negative bacteria?
Gram-positive
109
What is the mechanism of daptomycin?
It binds the cytoplasmic membrane and causes rapid depolarization
110
Is daptomycin bactericidal or bacteriostatic?
Rapidly bactericidal
111
Does daptomycin have gram-negative activity?
No
112
What ion does daptomycin use to bind to the cytoplasmic membrane?
Ca++
113
If an enterococcus is vancomycin resistant, what cyclic lipopeptide antibacterial can be used?
Daptomycin
114
What is the interaction between daptomycin and pulmonary surfactant? Can daptomycin be used to treat pneumonias?
Pulmonary surfactant breaks it down; no
115
Does daptomycin have adverse musculoskelatal effects?
Yes, including myalgias, weakness, rhabdomyolysis, and cramps
116
What serum levels can be measured to monitor musculoskeletal adverse effects of daptomycin?
Creatinine phosphokinase
117
What is a protein synthesis inhibitor in gram-positive cocci that acts on...
- Initiation?
- Elongation?
- Transpeptidation?
- Initiation: linezolid
- Elongation: doxycycline
- Transpeptidation: clindamycin
118
Are protein synthesis inhibitors for gram positive cocci bactericidal or bacteriostatic?
Bacteriostatic
119
What drug family do doxycycline, minocycline, and demeclocycline belong to? What is their mechanism?
Tetracycline; inhibitor against protein elongation
120
What dietary substance should not by consumed with doxycycline?
Dairy, because it forms nonabsorbable chelates with Ca++
121
Doxycycline binds to which tissues undergoing calcification?
Teeth and bones
122
Is doxycycline excreted in the urine? Metabolized in the liver?
Yes to both
123
What effect on teeth can occur with doxycycline?
Discoloration of teeth or stunting of growth
124
Does clindamycin affect enterococcal bacteria?
No
125
Does clindamycin affect aerobic or anaerobic bacteria?
Anaerobic
126
Can clindamycin treat an infection in the CNS?
No, it does not reach therapeutic levels in CSF
127
The disc on the left is erythromycin, and the one on the left is clindamycin. What is significant about the flattened part of the area of impeded growth facing the erythromycin disc? Is this bacteria resistant to clindamycin?
![]()
This indicates that erythromycin is activating genes that provide resistance to clindamycin; therefore, this bacteria is inducibly clindamycin resistant.
128
What are two side effects of clindamycin?
Rash and clostridium difficile colitis
129
What is the bioavailability of oral linezolid?
100%
130
What is the mechanism of linezolid?
Inhibits protein synthesis initiation in gram positive bacteria
131
What are three main safety concerns with linezolid?
Thrombocytopenia/neutropenia, metabolic acidosis, serotonin syndrome
132
What side effect of linezolid is characterized by mental status changes, fever, hypertension, tachycardia, hyperreflexia, myoclonus, and tremor?
Serotonin syndrome
133
Is hyperthermia a more severe toxicity finding than altered mental status?
Yes
134
What is the mechanism of trimethoprim-sulfamethoxazole?
It is a folic acid antagonist
135
How do humans acquire folic acid? How do bacteria acquire folate?
Humans ingest it; bacteria synthesize it
136
What synthesis process requires folate-derived cofactors in bacteria?
Synthesis of DNA and RNA
137
Are folic acid antagonists bacteriostatic or bactericidal?
Bacteriostatic
138
What is the drug of choice for treatment of *Pneumocystis jirovecii* and *Nocardia*?
TMP-SMX, a combo of sulfamethoxazole and trimethoprim
139
Can TMP-SMX reach the CSF?
Yes
140
Side effects of TMP-SMX include: [...], rashes, hemolytic anemia, and kernicterus (a bilirubin-induced brain dysfunction)
Side effects of TMP-SMX include: hypersensitivity, rashes, hemolytic anemia, and kernicterus (a bilirubin-induced brain dysfunction)
141
Side effects of TMP-SMX include: hypersensitivity, [...], hemolytic anemia, and kernicterus (a bilirubin-induced brain dysfunction)
Side effects of TMP-SMX include: hypersensitivity, rashes, hemolytic anemia, and kernicterus (a bilirubin-induced brain dysfunction)
142
Side effects of TMP-SMX include: hypersensitivity, rashes, hemolytic [...], and kernicterus (a bilirubin-induced brain dysfunction)
Side effects of TMP-SMX include: hypersensitivity, rashes, hemolytic anemia, and kernicterus (a bilirubin-induced brain dysfunction)
143
Side effects of TMP-SMX include: hypersensitivity, rashes, hemolytic anemia, and [...] (a bilirubin-induced brain dysfunction)
Side effects of TMP-SMX include: hypersensitivity, rashes, hemolytic anemia, and kernicterus (a bilirubin-induced brain dysfunction)
144
What bacterium causes this skin infection?
*Staphylococcus aureus*
145
What genus of bacterium causes this infection?
*Staphylococcus* species
146
What six antibacterials can be used to treat MRSA?
Vancomycin, daptomycin, clindamycin, doxycycline, linezolid, TMP-SMX
147
What is the common mechanism for penicillin, cephalosporin, carbapenems, and monobactam?
They are inhibitors of peptidoglycan crosslinking
148
Which side is gram +, and which is gram -?
Left is gram + (thick peptidoglycan); right is gram - (two cell membranes)
149
What drugs are these?
Top: penicillin; bottom: cephalosporin. Notice the CH3R1 group and six-membered ring on cephalosporin, distinguishing it from other β-lactams. Penicillin has a five-membered ring with a dimethyl group.
150
What drug derived from mold acts on this crosslinking process in peptidoglycan? What enzyme is being inhibited?
Penicillin; a transpeptidase
151
What is the most common method of resistance to penicillin?
Beta-lactamase, a gene that breaks penicillin down
152
Where does beta-lactamase cleave penicillin?
The beta-lactam four atom ring
153
Can plasmids contain multiple resistance factors?
Yes
154
What channels do β-lactams use to enter the peptidoglycan layer of gram negative bacteria?
Porin channels
155
What is the mechanism of vancomycin and bacitracin?
Both inhibit peptidoglycan synthesis
156
Do vancomycin and bacitracin inhibit peptidoglycan crosslinking?
No, they inhibit polymerization of the peptide to the polysaccharide chain
157
Are gram negative and gram positive bacteria equally susceptible to vancomycin treatment? Why or why not?
Gram negative are intrinsically resistant; vancomycin cannot cross the outer membrane
158
What do enterococci synthesize instead of the terminal D-ala-D-ala on peptidoglycan to prevent vancomycin from binding?
D-ala-D-lactic acid
159
What is another name for transpeptidases in bacteria named after the drug that affects them?
Penicillin-binding proteins
160
What class of drugs does erythromycin belong to? What is their mechanism? How is resistance generated?
Macrolides; they inhibit protein synthesis by acting on the bacterial ribosome; the 50S subunit is modified so the drug cannot bind
161
How can resistance to tetracyclins be generated by bacteria?
They actively transport it out of the cell
162
What is the mechanism of metronidazole?
It enters bacteria and is metabolized by bacterial enzymes that allow it to cause DNA damage
163
What are two antibiotics that are DNA-dependent RNA polymerase inhibitors?
Rifampicin and actinomycin D (the latter is only a laboratory reagent)
164
Why do folic acid antimetabolites like sulfonamides and trimethoprim have antibacterial activity?
Bacteria need to metabolize folic acid to synthesize nucleotides (humans can acquire them from the diet)
165
How might resistance to trimethoprim develop, unrelated to modifications in the target enzyme itself?
Overproduction of the target enzyme can prevent the inhibitor from sufficiently affecting folic acid metabolism
166
What kind of antibiotic-antibiotic interaction is this? (The y-axis is log bacterial cell count)
Indifference
167
What kind of antibiotic-antibiotic interaction is this?
Antagonism
168
What is the best possible antibiotic-antibiotic interaction?
Synergy
169
Can aminoglycosides still kill bacteria without protein synthesis?
No
170
What antibiotic (whose mechanism is still unclear) is used against TB?
Isoniazid
171
Is the number of antibiotics discovered per year increasing or decreasing?
Decreasing
172
Why is it less profitable to build a new antibiotic than, for instance, a new anti-cholesterol drug?
Antibiotics are usually not taken chronically and so patients and hospitals will almost always spend less on them than other drugs
173
What experiment did Avery et al. perform in 1944 to show that bacterial virulence is a genetic property?
Virulent bacteria could be non-encapsulated and mixed with encapsulated non-virulent bacteria which would then be able to infect and kill mice
174
Are bacteria typically haploid or diploid?
Haploid
175
How do bacteria normally exchange genetic material with other cells, conferring antimicrobial resistance?
Plasmids
176
What is the spontaneous frequency of a mutation that knocks out or knocks in an operon in bacteria, per replication?
10-6
177
What are three methods of genetic exchange used by bacteria?
Transformation, conjugation, and transduction
178
Could mutations alone explain the rapidity at which bacteria acquire resistance to drugs?
No, the exchange of genetic material is also significant
179
Can all bacteria use transformation to take up DNA from the environment?
No
180
How is bacterial conjugation different from transformation?
During conjugation, an extension of the membrane from one bacterium to another (a pillus) whereby the cytoplasms of the two cells can mix allows genetic material to move from one cell to the other. Transformation involves uptake of extracellular DNA.
181
As double-stranded DNA enters the bacterium during transformation, what happens to it?
One strand of it is degraded, and then it forms a triple-strand with genomic DNA
182
During conjugation of two bacteria, are the cell walls of each organism interrupted?
Yes
183
What process is being observed here via EM? What is the significance of one cell looking "hairy" while the other is not?
Conjugation of bacteria; the hairy cell is the F+ cell and the other is the F- cell
184
Can plasmids be exchanged during conjugation?
Yes, along with chromosomes
185
What structures allow transduction to occur between bacteria?
Bacteriophages
186
What are these? What genetic exchange process for bacteria do they facilitate?
Bacteriophages; transduction
187
When bacteriophages add DNA to a bacterium, is it necessarily killed?
No, it is only killed in the lytic cycle, not the lysogenic cycle
188
What are phages capable of only the lytic cycle called?
Virulent
189
Can all phage species undergo the lytic cycle? What happens to the bacterium in this cycle?
Yes; it is killed
190
If bacteriophages create and replicate their own DNA during the lytic cycle, how could it be used to transfer host genetic material to another bacterium (transduction)?
Host genetic material (e.g. part of a chromosome) could be packaged by accident into a phage created within a bacterium, which goes on to inject it into another cell
191
What genetic studies can be facilitated by measures of cotransduction?
Linkage, or an estimate of how far apart two bacterial genes are to each other on a chromosome
192
What are DNA sequences that can jump from one position to another called?
Transposons
193
How long are insertion sequences (IS elements), a type of transposon? What is encoded by them?
1-3kb; a transposase protein that facilitates the transposition action, along with regulatory proteins
194
What sort of DNA element is this?
A transposon, specifically an insertion sequence (note IS elements)
195
What are DNA elements that encode a site-specific recombinase along with its recognition region called? What public health issue are they relevant for?
Integrons; multiple antibiotic resistance
196
What can destroy DNA that enters a bacterium?
Nucleases, or it can be inherently unstable and self-destruct
197
What type of recombination does RecA facilitate?
Homologous recombination
198
What is the most frequent cause of genetic variation in bacteria? How frequently does it occur per generation?
Homologous recombination, with a frequency of 10-1 to 10-2 per generation
199
Is plasmid transfer in bacteria more frequent per generation than transposition?
Generally more frequent
200
What was the first bacterial genome sequenced?
*Haemophilus influenzae* in 2003
201
Are aminoglycosides, fluoroquinolones and lipopeptides like daptomycin time-dependent or concentration-dependent?
Concentration-dependent
202
For concentration-dependent drugs, is a large bolus administered, or frequent smaller doses?
A large bolus
203
What is the minimum inhibitory concentration of an antibiotic/bacteria combination?
The lowest concentration that will inhibit the visible growth of bacteria *in vitro*
204
Can broth microdilution measure minimum inhibitory concentration (MIC)?
Yes
205
What method is microdilution (to measure minimum inhibitory concentration) based on?
Broth macrodilution
206
Is the epsilometer more or less accurate than broth macrodilution at measuring minimum inhibitory concentration (MIC)?
Less
207
Does Kirby Bauer disc diffusion produce the minimum inhibitory concentration of a drug-bacteria combination?
No
208
Is the zone size measured by Kirby Bauer proportional to bacterial resistance or susceptibility?
Proportional *to* susceptibility
209
Can an antibiotic be bactericidal against some organisms and bacteriostatic against others?
Yes, e.g., vancomycin
210
Would a person already severely ill from bacterial infection preferably receive a bactericidal or bacteriostatic agent?
Bactericidal
211
What is the identifying prefix for cephalosporin antibiotics?
Cef- or Ceph-
212
What are the four families of β-lactam antibiotics?
Penicillins, cephalosporins, carbapenems, and monobactams
213
What is the unifying suffix for penicillin-class β-lactam antibiotics?
#NAME?
214
Name the two rings in this generalized antibiotic structure. What family does this structure describe?
Top, thiazolidine ring; bottom, β-lactam ring; penicillins (identified by the thiazolidine ring)
215
Where is penicillin-binding protein located within a bacterium?
The cell membrane (the inner one, for gram-negative bacteria)
216
Do natural penicillins have activity against streptococci? What about staphylococci?
Yes against streptococci; usually not against staphylococci
217
Are there synthetic penicillins that act against staphylococci?
Yes
218
What penicillin is very completely absorbed after oral administration?
Amoxicillin
219
Which penicillin is not cleared renally?
Nafcillin
220
What diagnoses are penicillin still used for today?
Group A and Group B Strep, caused by *S. pyogenes *and *S. agalactiae*, respectively, and syphilis, caused by *Treponema pallidum*
221
What is the oral formulation of pencillin called? What is the IV forumation called?
Penicillin V - oral; penicillin G - intravenous
222
What bacteria causing skin infections is mostly resistant to penicillin because of the production of β-lactamases?
*Staphylococcus aureus*
223
Can anti-staphylococcal penicillins be cleaved by β-lactamases (penicillinases)?
Usually, no.
224
What are three anti-staphylococcal penicillins? What is the route of administration?
NOD: Nafcillin, oxacillin, dicloxacillin; oral
225
Is methicillin still used clinically?
Usually no, because of nephrotoxicity
226
What common infection are NOD (Nafcillin, oxacillin, dicloxacillin) used to treat?
Skin or bloodstream infections with *Staphylococcus aureus*
227
What is another name for extended-spectrum penicillins?
Amino-penicillins
228
What are two extended-spectrum penicillins taken orally?
Ampicillin and amoxicillin
229
Do ampicillin and amoxicillin have gram-negative activity?
Yes, although *Klebsiella* is resistant
230
What penicillins have good activity against enterococci?
Amino-penicillins like ampicillin and amoxicillin
231
What is the drug of choice for listeria monocytogenes?
Amino-penicillins: ampicillin, amoxicillin
232
What should this 12 year old patient be tested for? What is the treatment for the common infection that results in this appearance of the tonsils?
Strep type A (*S. pyogenes*); it can be treated with penicillin or amoxicillin
233
Why is *Mycoplasma* resistant to penicillins?
It has no cell wall
234
What two penicillin resistance strategies can a gram-negative bacteria develop that a gram-positive bacteria cannot?
Change in the outer membrane porins, or an efflux pump in the outer membrane
235
What mutation commonly causes the resistance to penicillins seen in MRSA?
An alteration to penicillin-binding protein (transpeptidases) that decreases affinity for β-lactams
236
What drug is this? What bond would be broken by a β-lactamase?
Ampicillin; this bond would be broken:
237
What is the point of a β-lactamase inhibitor?
It inhibits the β-lactamases that break down β-lactam antibiotics, so the β-lactam can inhibit transpeptidases
238
What class of drugs do clavulanic acid, sulbactam, and tazobactam belong to?
β-lactamase inhibitors
239
What three drugs can be combined with penicillins to increase gram-negative activity by inhibiting β-lactamases?
Clavulanic acid, sulbactam, and tazobactam
240
What does the sulbactam in an ampicillin-sulbactam combination do?
It inhibits β-lactamases that would break down the ampicillin
241
What does the clavulanic acid in the amoxicillin-clavulanic acid combination formulation do?
It is a β-lactamase inhibitor that inhibits breakdown of the amoxicillin
242
What are two common adverse reactions to penicillin that present as skin symptoms?
Hypersensitivity and rash
243
Can penicillins cause anaphylaxis?
Yes
244
What is this patient experiencing after administration of penicillin?
Angioedema, an adverse reaction do to hypersensitivity of the immune system
245
Are rash and hypersensitivity reactions to penicillin common? What other drug allergies can be suspected after such a reaction?
Yes; increased chance of reactivity to other β-lactams (cephalosporins, carbapenems) excepting monobactams
246
Almost 100% of patients with what viral infection develop a maculopapular rash to amoxicillin?
EBV-associated mononucleosis
247
What kidney-related adverse reaction can occur with penicillins? What antibiotic is no longer used because of this risk?
Nephritis (acute kidney injury); methicillin
248
What kind of colitis can result from penicillin administration?
*Clostridium difficile* colitis
249
What type of antibiotic is this? What are its identifying features?
Cephalosporin; β-lactam 4-membered ring in center, and 6-membered dihydrothiazine ring to the right
250
How many generations of cephalosporins have been made? What increases over the generations?
5; gram-negative activity
251
Can cephalosporins cross the blood-brain barrier?
Yes, after the 3rd and 4th generation
252
Do cephalosporins treat *Enterococcus* or *Listeria*?
No
253
Can cephalosporins treat MRSA?
Only the "5th" generation, ceftaroline
254
What is the 1st generation cephalosporin? What is its oral formulation called?
Cefazolin; cephelexin is the oral formula
255
Can cefazolin be used against group A and group B strep, and *S. viridans*?
Yes
256
Are cephalosporins affected by β-lactamases?
No, they are not β-lactam drugs
257
Is cefazolin more active against gram-positive or gram-negative bacteria?
Gram-positive
258
Can cefazolin be used for UTIs and skin infections?
Yes
259
Do cephalosporins have similar adverse reactions as penicillin?
Yes
260
What is the cross-reactivity of cephalosporins with people that have penicillin allergies? Should they be used in a patient that has had hives in reaction to penicillin?
About 1-10%; no
261
What does this patient have on his arm, given the following culture?
*Staphylococcus aureus*
262
If a patient who has a history of IV drug abuse has high fevers and a methicillin susceptible *S. aureus* infection, what are some reasonable treatments?
Anti-staphylococcal penicillins: Nafcillin
Cephalosporins: Cefazolin
These will kill methicillin-susceptible *S. aureus*, and both drugs are unaffected by penicillase (most *S. aureus* harbors penicillase)
263
Besides age and allergies, what else should be evaluated before prescribing β-lactam or cephalosporin antibiotics?
Kidney function
264
If a skin infection has gram positive cocci that are identified as β hemolytic, what bacterium related to the one causing strep throat should be suspected?
*S. pyogenes*
265
What are examples of non-suppurative consequences of a *S. pyogenes* infection?
Scarlet fever, acute rheumatic fever, glomerulonephritis
266
Are penicillins bacteriostatic or bactericidal?
Bactericidal
267
What potential problem when treating abscesses with oral antibiotics, assuming the right one was prescribed at the right dosage and the organism is susceptible?
Distribution of the drug into the abscess, since the neutrophils surrounding the abscess can block access of the antibiotic to the area with the most bacteria
268
When the serum C3 complement level is measured as low, what does this indicate?
It has been consumed (broken down to C3b and C3a), so the immune system was exposed to an antigen that activated the complement pathway (alternatively: there is a C3 deficiency, but this is rare)
269
Acute rheumatic fever is most often associated with streptococcal strains rich in what protein?
Protein M
270
Are streptococcal strains rich in M protein more or less virulent? Why?
They are relatively resistant to phagocytosis and multiply quickly in tissues
271
What exotoxin is secreted by extra-virulent *S. pyogenes* that causes necrotizing fasciitis? What life-threatening syndrome can this exotoxin cause?
Superantigen, which hyperactivates T cells; it can cause toxic shock syndrome
272
What is the course of treatment for necrotizing fasciitis?
Aggressive surgical debridement, and secondarily, IV antibiotics
273
Which researcher on tuberculosis developed postulates that led to a new understanding of infectious disease and a Nobel?
Robert Koch
274
What is the property of tuberculosis bacteria's cell wall that makes it resistant to disinfectants and traditional stains?
It is lipid rich
275
What is the major component of mycobacterium's cell wall?
Mycolic acid
276
Why do mycobacteria clump together?
Hydrophobicity of the cell wall
277
Are mycobacteria motile? Are they spore-forming?
No to both
278
What is the gram staining of mycobacteria?
Gram null to weakly gram positive
279
What kind of staining, also called Ziehl-Neelsen or Kinyoun, reveals mycobacteria?
Acid fast staining
280
Of the four Runyon classes of mycobacteria, which grows fastest?
Runyon class IV
281
Is mycobacterium tuberculosis in a Runyon class? If so, which one?
No, it is not in a class.
282
Do mycobacteria encourage or discourage phagocytosis by immune cells? What happens to a phagosome containing a mycobacteria?
Phagosome formation is encouraged; phagosome maturation is blocked, so the bacterium can survive
283
What fusion event is inhibited after phagocytosis of mycobacteria to allow them to survive?
Phagosome-lysosome fusion is inhibited
284
What immune proteins that normally surround intruders to aid in their destruction are rendered ineffective by mycobacterium?
Antibody and complement proteins
285
Is the incidence of TB in the United States among native-born persons still declining?
Yes
286
Approximately what fraction of the world's population carries mycobacterium tuberculosis?
One third
287
The spread of what disease in the 1980's led to an uptick in tuberculosis infection?
HIV/AIDS
288
What can a tuberculosis patient do to expose other people to the bacterium, besides blood-to-blood contact? Can TB bacilli remain infectious in the air?
Coughing, sneezing, speaking, or singing; yes, it can remain suspended in the air for several hours
289
During the primary infection process for mycobacterium tuberculosis, is there a host immune response?
No, the bacteria replicate freely in alveolar macrophages
290
What channels does the tuberculosis bacterium use to spread after infection of the alveoli?
Lymphatics and bloodstream
291
What immune response (humoral or cell-mediated) contains the primary infection by TB? What histological immune structures form in the lungs during the killing of the bacilli?
Cell-mediated immune response; granulomas
292
What is this histological feature, characteristic of TB infection?
A granuloma
293
Within caseating centers of granulomas, does TB replicate faster or slower? Why?
Slower; because of the lower pH and the anoxic environment.
294
In 90% of patients, what is the endpoint of primary tuberculosis? Is it symptomatic?
Latent tuberculosis; usually it is not
295
Is latent tuberculosis contagious?
No
296
What is the common test for latent TB infection? What is a requirement for this test, without which it will return a false negative?
PPD (the tuberculin skin test); you need a functional immune system
297
How long does it take for delayed hypersensitivity reactions to tuberculins to be detectable by a PPD after the initial infection? How long are the tuberculins implanted in the skin before reading?
6-8 weeks; 48-72 hours
298
What is a more sensitive assay for past exposure to tuberculosis bacterium? How does it work?
Interferon γ release assay; it is an ELISA test that detects release of interferon γ from sensitized patients after incubation with two peptides from TB
299
What is the standard approach to latent tuberculosis?
Chest x-ray, sputum analysis, and Isoniazid for 9 months
300
What are the common presenting symptoms of active tuberculosis?
Cough, hemoptysis (bloody cough), night sweats, anorexia, weight loss
301
Can tuberculosis infect tissues besides the longs?
Yes, including the bones, lymph nodes, brain, GI tract...
302
This sample is from a TB patient. What has occurred that is characteristic of its pathology?
Caseating necrosis
303
What staining is used here to visualize bacteria? Which bacterium is this characteristic of?
Acid fast staining; mycobacterium, particularly tuberculosis
304
What is common in HIV patients with tuberculosis infections?
It spreads to other tissues quickly, e.g., the fingers
305
What is visible on a CT scan of the lungs of most tuberculosis patients?
Nodules (they can be bilateral or unilateral and in any lobe, as the following CT shows)
306
What is the mnemonic for the 4-drug regimen to treat active tuberculosis?
RIPE:
- Rifampin
- Isoniazid
- Pyrazinamide
- Ethambutol
307
Which part of the bacterium does isoniazid act upon?
The cell wall
308
What dietary warning is given to people on prolonged isoniazid for tuberculosis infection?
Do not consume alcohol
309
What is the mechanism of Rifampin? Is it bactericidal or bacteriostatic?
It inhibits DNA-dependent RNA polymerase in mycobacteria; bactericidal
310
What is the primary adverse effect of Rifampin? Why?
Hepatotoxicity; it induces hepatic cytochrome p450 enzymes
311
What is the primary adverse affect of isoniazid, requiring a dietary warning?
Hepatotoxicity
312
Production of what component of mycobacterium is inhibited by isoniazid? Is it bacteriostatic or bactericidal?
Mycolic acid synthesis, the main component of the cell wall; bactericidal
313
Is pyrazinamide bacteriostatic or bactericidal? What globally common infection is it used to treat?
Bacteriostatic; tuberculosis
314
What does ethambutol inhibit that makes it a good treatment for tuberculosis? Is it bacteriostatic or bacteriocidal?
Cell wall polysaccharide synthesis
315
What is the primary adverse effect of ethambutol?
Optic neuritis
316
Are certain strains of TB resistant to isoniazid and/or rifampin?
Yes
317
What can be used to supplement treatment for MDR or XDR tuberculosis?
Other antibacterials: streptomycin, linezolid, fluoroquinolones, kanamycin, ...
318
Why are multiple antibiotics administered concurrently to eradicate a TB infection in a patient?
To prevent development of a resistant strain
319
What is the most significant gram-negative microbe in the GI tract?
E. coli
320
Can *E. coli* cause neonatal sepsis or meningitis?
Yes
321
What bacterium is this?
 
*E. coli*, identified by gram negative rods and fermentation of lactose on MacConkey agar
322
There are 3 important surface antigens on E coli. How are they named?
O, H, and K
323
In the strain serotype *E. coli O157:H7*, what is the meaning of the second part of this name?
It refers to surface antigens O and H
324
When a patient complains of dysuria and changes in frequency of urination, a UTI is suspected. What is significant about a co-presentation with flank pain and cost-vertebral angle tenderness?
An upper UTI may be suspected as opposed to a lower UTI. This might include e.g. pyelonephritis
325
What is the most common cause of UTIs?
*E. coli*
326
What does dysuria mean?
Painful urination
327
Which pili on *E. coli* allows certain strains to adhere to the urinary epithelium?
P-pili
328
What is the typical IV therapy for pyelonephritis?
Fluroquinolones (e.g. Ciprofloxacin) or ceftriaxone
329
What is the typical course of treatment for a lower UTI?
Fluoroquinolones, ceftriaxone, or trimethoprim-sulfamethoxazole
330
What is the typical cause of "traveler's diarrhea"?
*E. coli*, caused by a lack of immunity to bacteria in the local water
331
ETEC, EPEC, EIEC, EHEC, STEC, and EAEC are all strains of...
Diarrhea-causing *E. coli*
332
In enterotoxigenic *E. coli*, is the mucosa of the GI tract disrupted?
No
333
What long structures surround E coli, mediating its attachment to various surfaces?
Pili
334
Which pili mediates adhesion of ETEC to the GI tract?
CF pili
335
What other microbial toxin is the Heat Labile Toxin of ETEC similar to?
Cholera toxin
336
What enzyme is stimulated by Heat Labile Toxin and what doe sthis cause? What organism secretes this toxin?
Adenylate cyclase, causing export of Na+, K+, and water into the GI lumen (diarrhea); enterotoxigenic *E. coli* (ETEC)
337
What enzyme is stimulated by Heat Stable Toxin, released by enterotoxigenic *E. coli*?
Guanylate cyclase
338
Enterotoxigenic *E. coli* secretes two toxins abbreviated LT and ST. What are their full names?
Heat labile toxin and heat stable toxin
339
What does the stimulation of guanylate cyclase by heat stable toxin cause? What organism secretes it as an exotoxin?
Secretion of Cl-, HCO3- and water; ETEC (enterotoxigenic *E. coli*)
340
What organism causes hemolytic-uremic syndrome (HUS)?
Enterohemorrhagic *E. coli*
341
What has happened to these RBCs? What strain of E. coli can do this?
Fragmentation (happens in small blood vessels); Enterohemorrhagic *E. coli*
342
How is enterohemorrhagic *E. coli* acquired?
Consumption of raw beef, food contaminated by animal feces, or animal contact
343
What is the hallmark symptom of enterohemorrhagic *E. coli* infection?
Bloody diarrhea
344
What are two common abbreviations for the organism that causes hemolytic uremic syndrome?
EHEC or STEC, both referring to enterohemorrhagic *E. coli*
345
What toxin is produced by EHEC that triggers hemolytic uremic syndrome?
Shigatoxin
346
What is the best way to test for EHEC infection?
Test for Shiga toxin in the stool
347
Can sorbital agar reliably identify EHEC?
It can only identify the O157:H7 strain—it will not identify other strains of EHEC
348
Where are the typical genomic locations for virulent factors of *E. coli* strains, like exotoxins?
Phages, plasmids, or pathogenicity islands
349
What does enteroinvasive *E. coli* cause (EIEC)?
Dysentery
350
When *E. coli* is suspected for a case of dysentery, what can be used on the stool to diagnose it?
A stool smear to reveal WBCs
351
Is there disruption of the mucosa in EIEC?
Yes, bacteria invade the enterocytes (enteroinvasion)
352
What do enteroaggregative *E. coli* form on the wall of the GI epithelium?
A biofilm, inhibiting proper absorption across the intestinal membrane
353
Why is bacterial neonatal sepsis and meningitis treated with ampicillin in addition to cefotaxime?
Cefotaxime is for *E. coli*, but the ampicillin is intended to kill listeria, another top bacterial etiology for these symptoms
354
What is notable about the strains of *E. coli* that cause nosocomial infections?
They are typically resistant to many antibiotics
355
What bacterium is seen here, in this sampling of CSF from a patient with altered mental status?
Gram negative; probabably meningococcus
356
Is meningitis more common in children or adults?
Children under 2 years of age
357
Removal of what organ can cause in increase in risk for meningitis?
Spleen
358
How is neisseria meningitidis transmitted?
Respiratory droplets, which is why it is more likely to cause epidemics in overcrowded conditions
359
What is "meningococcus" an abbreviation for?
*Neisseria meningitidis*
360
What does *N. meningitidis* secrete to allow survival in the respiratory tract?
IgA protease
361
What is the function of the pili on *N. meningitidis* in the respiratory tract, besides conjugation?
Attachment to the respiratory epithelium
362
What is the capsule of *N. meningitidis* made of?
Polysaccharides
363
What form of endotoxin is secreted by *N. meningitidis* that can cause sepsis?
Lipooligosaccharide
364
What is the defining feature of the rashes caused by meningococcemia?
They are all non-blanching
365
Which serogroup of *N. meningitidis* has no vaccine? Why not?
Serogroup B, because it has a polysaccharide capsule similar to human sialic acid
366
Is LOS different from LPS? If so, how?
Yes; they are a subtype of LPS present in bacteria that colonize mucosal surfaces not bathed in bile, such as N. meningitidis
367
What is the difference with the conjugate vaccine for meningitis as opposed to the polysaccharide vaccine?
The conjugate vaccine has proteins, which are more immunogenic
368
Does *N. meningitidis* produce β-lactamases?
No
369
What can be used to treat *N. meningitidis*?
Penicillin works, but ceftriaxone is more common
370
Empiric treatment of bacterial meningitis in adults when nothing is seen on gram stain consists of what drugs?
Ceftriaxone (against meningococcus, *Haemophilus* and pneumococcus), vancomycin (against β-lactam pneumocci), and sometimes ampicillin (against *Listeria* *monocytogenes*)
371
Is *Listeria* gram positive or negative? What is its shape?
Gram positive; rod (bacillus)
372
What is the motility style of *Listeria*?
Tumbling, end over end
373
Which age groups does *Listeria* affect? What other population is particularly at risk?
Infants and the elderly (bimodal); the immunocomprised, such as pregnant women
374
Is ceftriaxone used to treat *L. monocytogenes*?
No, ampicillin is more reliable
375
What can be used to prevent spread of meningitis to those in close contact?
Chemoprophylaxis
376
What is a nickname for *N. gonorrhoeae*?
Gonococcus
377
What is the difference in the capsule between *N. meningitidis* and *N. gonorrhoeae*?
*N. gonorrhoeae* does not have a true polysaccharide capsule
378
What is the energy source for *N. gonorrhoeae* in culture? Is this different from *N. meningitidis*?
Glucose only; yes, *N. meningitidis* can also use maltose
379
What part of *N. gonorrhoeae* makes development of a vaccine difficult?
Antigenic variability of the pili
380
Is the age distribution of *N. gonorrhoeae* infections modal or bimodal?
Modal, with the highest range around 15-25 years of age
381
What inflammatory disease can be caused by chronic *N. gonorrhoeae* infection?
Pelvic inflammatory disease
382
Which diagnostic tool is used most often in clinical practice for gonococci?
DNA amplification probes
383
What is the mainstay of therapy for *N. gonorrhoeae*? Do they have β-lactamase? What co-infection is assumed?
Cephalosporins, e.g., ceftriaxone; yes; *Chlamydia*
384
When a patient presents with respiratory symptoms, and a cultured bacterium grows on chocolate agar and with VX factor, what organism is suspected?
*Haemophilus influenzae*
385
What is this feature seen on a blood agar plate? What organism is it significant for?
Satellite colonies; *Haemophilus influenzae*
386
Is the present vaccine for *Haemophilus influenzae* a polysaccharide vaccine or a conjugate vaccine?
Conjugate
387
Does the *Haemophilus* genus cause any STDs?
Yes, chancroid, by *Haemophilus ducreyii*. It is characterized by painful fluid-filled lesions on the genitals
388
What can *Moraxella catarrhalis* cause? Is it gram negative, or gram positive? Is it anaerobic or aerobic?
Otitis, sinusitis, and pneumonia (particularly with underlying emphysema); gram positive; aerobic
389
What is the gram negative coccobacillus that causes whooping cough?
*Bordetella pertussis*
390
Which vaccine was built to eliminate *Bordetella pertussis*?
DPT: diphtheria, pertussis, tetanus
391
Are incidents of pertussis on the rise or declining since the introduction of the DPT vaccine?
They are still rising
392
What capsulated bacterium produces a purpuric, petechial rash?
*N. meningitidis*
393
How many capsule serogroups of *N. meningitidis* are there? Does the vaccine cover all of them?
13; no, the vaccine covers 4 of the most common
394
What is the vaccine protecting against *Haemophilus influenzae* called?
HiB vaccine
395
Are *N. gonorrhoeae* susceptible to quinolones?
No, resistance has developed
396
What is used to combat *B. pertussis* in severe cases of whooping cough?
Azithromycin
397
What type of organisms is the spleen an important defense organ for?
Encapsulated organisms, e.g. *N. meningitidis* and *Listeria*
398
Can fats and sugars within the outer membrane of a gram negative bacterium trigger a fatal response?
Yes, because of inflammation
399
What is notable about this CT that is suggestive of S. pneumoniae?
The infection is well contained to one lobe
400
What bacterium is this?
*Strep pneumoniae*: a gram-positive, encapsulated diplococci, note the thick cell wall.
401
What is the hemolysis pattern of *S. pneumoniae*? Is it optochin sensitive or resistant? Does it have a Lancefield antigen?
α hemolysis; optochin sensitive; no Lancefield antigen
402
How is *S. pneumoniae* transmitted? What is colonized transiently that leads to no symptoms in most adults? Is smoking a risk factor?
Through droplets; the nasopharynx; Yes
403
What is the distribution of ages for *S. pneumoniae* infection? What other significant risk factor must be considered, which e.g. asplenia could contribute to?
Very young and very old; immunosuppression
404
Besides age, immunosuppression, and smoking, what are two other risk factors for *S. pneumoniae* infection?
CSF leaks and cochlear implants
405
How many serotypes of *S. pneumoniae* exist?
Over 90
406
Did a vaccine for pneumococcus exist in 1998?
No
407
What is serotyping of *S. pneumoniae* based on? Are antibodies against these molecules protective?
The capsular polysaccharide; Yes
408
Do symptoms of *S. pneumoniae* present acutely or chronically compared to a TB patient?
Acutely
409
What are nuchal rigidity, Kernig and Brudzinsky signs all indicative of?
Meningitis
410
What infection with a high mortality can cause fever, photophobia, headache, and altered mental status?
Meningitis
411
What physical exam procedure is this? What does it test for?
Kernig sign; meningitis
412
What physical exam technique is this? What is it testing for?
Brudzinski sign; meningitis
413
What is this a picture of? What condition is present?
The eardrum; otitis media. The following is a normal eardrum:
414
Can *S. pneumonia* cause bacteremia, sinusitis, and peritonitis?
Yes
415
What type of antibody can prevent adherence of *S. pneumoniae*, preventing infection?
Secretory IgA (sIgA)
416
What is the main virulence factor of *S. pneumoniae*?
The capsule
417
What is binding of the pneumococcus to an epithelial cell mediated by?
Adhesins
418
What can pneumococci secrete to defeat secreted IgA and adhere to epithelial cells anyway?
IgA protease
419
Which pathway for complement activation is inhibited by the capsule of *S. pneumoniae*?
The alternate pathway
420
What bacterium contains pneumolysin? Where is it stored in the bacterium? What is its function?
*S. pneumonia*; in the cytoplasm; it lyses phagocytic cells
421
Which system unrelated to the capsular specific antibodies is critical for clearing *S. pneumoniae* from the bloodstream?
The lymphoreticular system of the spleen
422
Why is the spleen more important for clearing capsulated organisms?
Phagocytosis by neutrophils is less efficient, so filtration in the spleen is a more significant way for these organisms to be cleared
423
What class of drugs is used to treat *S. pneumoniae*? How does resistance usually present?
β-lactams; resistance is usually from altered penicillin binding proteins
424
Do clavulinic acid or sulbactam help β-lactam treatment of *S. pneumoniae* that are becoming β-lactam resistant? Why or why not?
No; they are β-lactamase inhibitors, but this is not the typical way that resistance develops in *S. pneumoniae*
425
Can you overcome the weak binding of β-lactams to PBP's in somewhat resistant *S. pneumoniae* by increasing the dose?
Sometimes, yes
426
Which β-lactams are most often used against *S. pneumoniae*?
Amoxicillin, ampicillin, cefotaxime and ceftriaxone
427
Why is ceftriaxone particularly effective against *S. pneumoniae*, particularly with regard to preventing serious complications?
It can get into the CSF, and does well against the three most common causes of bacterial meningitis
428
What cause of meningitis is not covered by cephalosporins?
*Listeria monocytogenes*
429
Can ceftriaxone be administered orally? Can vancomycin be administered orally?
No to both
430
How is ceftriaxone excreted?
Biliary ducts
431
How is cefotaxime excreted? Does it have a shorter or longer half-life than ceftriaxone?
Kidneys; shorter half-life (8h) compared to ceftriaxone (12-24h)
432
What do fluoroquinolones inhibit causing bacterial death? Which fluoroquinolone cannot be used against respiratory infections?
Bacterial topoisomerase and DNA gyrase, thereby inhibiting DNA synthesis; Ciprofloxacin has no activity against gram positive organisms and thus is not indicated for respiratory infections (where *S. pneumoniae* is suspect)
433
What athletic activity is dangerous during administration of fluoroquinolones?
Weight lifting and running, because of the adverse effect of tendonitis and/or tendon rupture
434
If *S. pneumoniae* is resistant to β-lactams, what antibiotic can be used? Is it active against gram negatives, gram positives, or both?
Vancomycin
435
What is the empiric treatment for bacterial meningitis?
Vancomycin and ceftriaxone, which both reach the CSF and in conjunction combat β-lactam sensitive and resistant gram positive and gram negative bacteria
436
What oral treatment is given for pneumococcal pneumonia?
Amoxicillin and/or azithromycin, and levofloxacin
437
If an IV drug user comes in and reports symptoms indicating bacterial pneumonia, what else must be suspected?
Immunodeficiency, e.g. AIDS
438
What would otitis media or sinusitis with a suspected bacterial cause be treated with?
Amoxicillin (oral)
439
Why isn't the pneumovax vaccine immunogenic in children under 2? What vaccine is given to them instead, and why does that one work better?
It is a purified capsular polysaccharide antigen, which children of this age will not recognize as foreign (it is a T-cell independent antigen); the PCV-13 (Prevnar-13) vaccine has the polysaccharide conjugated to a diphtheria toxoid (T-cell dependent antigen), which the immune system will recognize as foreign at this age
440
After recommendation of the PCV7 vaccine in 2000, did rates of S. pneumoniae decrease in children, or across all age groups? What is this phenomenon called?
All age groups; herd immunity
441
What are environmental sources of pseudomonadaceae?
Soil, water, plant material, and environmental surfaces
442
What is this bacterium, which grows aerobically in immunocompromised hosts, particularly within burn injuries?
Pseudomonadaceae (gram negative bacilli)
443
Does *P. aeruginosa* ferment lactose?
No (right), which is different from *E. coli* (left)
444
Does *Pseudomonas* produce oxidase?
Yes
445
Is this a positive or negative oxidase test?
Positive
446
What is this morphology on agar to the right called?
Mucoid: it indicates formation of a biofilm
447
What features of *P. aeruginosa* are shown here?
Unipolar flagellum and adherence mediating pili
448
What can render a host particularly susceptible to *Pseudomonas* infections?
Neutropenia (e.g. by chemotherapy), severe burns, diabetes/foot ulcers, cystic fibrosis
449
What kind of *Pseudomonas* infection is most likely to manifest in a neutropenic patient?
Bacteremia or sepsis
450
What risk factors for *P. aeruginosa* infection associate a respiratory infection?
Cystic fibrosis or mechanical ventilation
451
What organism is associated with "hot tub folliculitis"?
*P. aeruginosa*
452
What condition caused by *P. aeruginosa* is seen here?
Ecthyma gangrenosum, a result of bacteremia
453
What are these two manifestations of *P. aeruginosa*, from left to right?
Hot tub folliculitis and infected pressure sore
454
What manifestation of *P. aeruginosa* is this?
Otitis externa
455
What injurious infection of *P. aeruginosa* can be seen here, which follows trauma to the eye, including that caused by contact lenses?
Corneal ulcers or endophthalmitis
456
What is the clinical (not genetic) marker of cystic fibrosis, which relates especially to *P. aeruginosa*?
They present with chronic lung infections and inflammation
457
With chronic infection by *P. aeruginosa* in cystic fibrosis patients, what are the two typical infections that precede it? Does the mucoid P. aeruginosa precede the non-mucoid, in the sequence of infections or the other way around?
*S. aureus* and *H. influenzae*; non-mucoid is typically first
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458
Are cephalosporins useful against *Pseudomonas aeruginosa*? What about carbapenems? Monobactams? Fluoroquinolones?
Yes to all, with various resistance factors seen in the wild
459
What two organisms (excepting *P. aeruginosa*) are linked to catheter-associated bacteremia and ventilator-associated pneumonia?
*Burkholderia cepacia* and *Stenotrophomonas maltophilia*
460
What classes of bacteria are aminoglycosides useful for treatment? Are they usually used as primary or secondary therapy?
Gram negative, aerobic bacteria, e.g. *P. aeruginosa*; usually secondary to another antibiotics
461
What is the basic structure of an aminoglycoside?
Amino sugar linked to a central hexose
462
What are the host cell entry, CSF, and tissue penetration characteristics of aminoglycosides? Why is this?
All are poor; they are polycationic and highly polar
463
What is the mechanism of action of aminoglycosides?
Interference with bacterial protein synthesis (initiation, see the A pathway here)
464
What is the most common mechanism of resistance to aminoglycosides?
Drug modification (acetylation or adenylation of parts of the drug by the bacterium)
465
What kind of antibiotic is kanamycin? Is it currently administered?
Aminoglycoside; no longer used
466
What is a common topical aminoglycoside?
Neomycin
467
What class of drugs are streptomycin, gentamicin, tobramycin, and amikacin?
Aminoglycosides
468
What are four aminoglycosides that can be administered intramuscularly? Are oral forms available?
Streptomycin, gentamicin, tobramycin, and amikacin; no
469
What are the main adverse toxicities of aminoglycosides?
Nephrotoxicity and ototoxicity, along with neuromuscular blockade
470
Important agents of nosocomial infection include:
– [...] (e.g., RSV, Parainfluenza, Influenza, Adenovirus)
– Methicillin-resistant *Staphylococcus aureus*
– Vancomycin-resistant *Enterococcus faecium*
– Multiresistant Gram-negative bacilli
– *Clostridium* *difficile*
Important agents of nosocomial infection include:
– Respiratory Viruses (e.g., RSV, Parainfluenza, Influenza, Adenovirus)
– Methicillin-resistant *Staphylococcus aureus*
– Vancomycin-resistant *Enterococcus faecium*
– Multiresistant Gram-negative bacilli
– *Clostridium* *difficile*
471
Important agents of nosocomial infection include:
– Respiratory Viruses (e.g., RSV, Parainfluenza, Influenza, Adenovirus)
– [...]-resistant *Staphylococcus aureus*
– Vancomycin-resistant *Enterococcus faecium*
– Multiresistant Gram-negative bacilli
– *Clostridium* *difficile*
Important agents of nosocomial infection include:
– Respiratory Viruses (e.g., RSV, Parainfluenza, Influenza, Adenovirus)
– Methicillin-resistant *Staphylococcus aureus*
– Vancomycin-resistant *Enterococcus faecium*
– Multiresistant Gram-negative bacilli
– *Clostridium* *difficile*
472
Important agents of nosocomial infection include:
– Respiratory Viruses (e.g., RSV, Parainfluenza, Influenza, Adenovirus)
– Methicillin-resistant *Staphylococcus aureus*
– [...]-resistant *Enterococcus faecium*
– Multiresistant Gram-negative bacilli
– *Clostridium* *difficile*
Important agents of nosocomial infection include:
– Respiratory Viruses (e.g., RSV, Parainfluenza, Influenza, Adenovirus)
– Methicillin-resistant *Staphylococcus aureus*
– Vancomycin-resistant *Enterococcus faecium*
– Multiresistant Gram-negative bacilli
– *Clostridium* *difficile*
473
Important agents of nosocomial infection include:
– Respiratory Viruses (e.g., RSV, Parainfluenza, Influenza, Adenovirus)
– Methicillin-resistant *Staphylococcus aureus*
– Vancomycin-resistant *Enterococcus faecium*
– [...] bacilli
– *Clostridium* *difficile*
Important agents of nosocomial infection include:
– Respiratory Viruses (e.g., RSV, Parainfluenza, Influenza, Adenovirus)
– Methicillin-resistant *Staphylococcus aureus*
– Vancomycin-resistant *Enterococcus faecium*
– Multiresistant Gram-negative bacilli
– *Clostridium* *difficile*
474
Important agents of nosocomial infection include:
– Respiratory Viruses (e.g., RSV, Parainfluenza, Influenza, Adenovirus)
– Methicillin-resistant *Staphylococcus aureus*
– Vancomycin-resistant *Enterococcus faecium*
– Multiresistant Gram-negative bacilli
– [...] *difficile*
Important agents of nosocomial infection include:
– Respiratory Viruses (e.g., RSV, Parainfluenza, Influenza, Adenovirus)
– Methicillin-resistant *Staphylococcus aureus*
– Vancomycin-resistant *Enterococcus faecium*
– Multiresistant Gram-negative bacilli
– *Clostridium* *difficile*
475
What two major classes of gram-negative bacilli are associated with nosocomial infections?
*Enterobacteriaceae* and *Pseudomonodaceae*
476
What units are most at risk for nosocomial infections?
Burn units, NICU, MICU/SICU, and oncology
477
What is the mean attributable cost to the hospital of a nosocomial bloodstream infection?
$36k
478
What standard precaution must be taken by all hospital workers with all patients to prevent nosocomial infections?
Hand hygiene
479
How long should we wash our hands with soap and water or Purell to prevent nosocomial infections?
\>15 seconds
480
What is the usual suspect for "typical" pneumonia?
*Streptococcus pneumoniae*
481
Is there a productive cough and copious sputum with typical or atypical pneumonia?
Typical pneumonia
482
What extrapulmonary symptoms typically manifest in atypical pneumonia? Do most patients seek medical care?
Muscle aches and headache, low fever; most do not
483
Is an elevated WBC more indicative or typical or atypical pneumonia?
Typical
484
What are the three major suspect bacteria for atypical pneumonia?
*Mycoplasma pneumoniae*, *Chlamydophila pneumoniae*, and *Legionella*
485
What bacterium causing atypical pneumonia is seen in this EM?
*Mycoplasma pneumoniae*
486
What is the incubation period of *M. pneumoniae*?
2-3 weeks
487
How is *M. pneumoniae* transmitted? Can it spread between people across a room?
Respiratory droplet; no, it requires close contact
488
What structural feature makes *M. pneumoniae* an unusual bacterium?
It lacks a cell wall
489
What is the shape of *M. pneumoniae*? Is it visible on a gram stain?
Short and rod-shaped; invisible on gram stain
490
Is *M. pneumoniae* easy to grow quickly in culture?
No, it has a long doubling time (6h)
491
Why was *M. pneumoniae* initially assumed to be a virus, in 1918?
It could pass through filters that only viruses could pass through
492
What is the age distribution of typical *M. pneumoniae* infections?
Unimodal, around adolescents and young adults
493
Do most patients survive *M. pneumoniae* infection without treatment?
Yes
494
Does *M. pneumoniae* grow inside or outside of cells?
Inside of them
495
What blood cell abnormality is a risk factor for *Mycoplasma pneumoniae*?
Sickle cell
496
Why does sickle cell predispose patients to *M. pneumoniae*?
Cold-agglutinins produced by polyclonal T cells and B cells during the immune response to *M. pneumoniae* bind to the I antigen on the RBC surface area, which is smaller for patients with sickle cell
497
What skin manifestation is associated with *M. pneumoniae*?
Erythema multiforme
498
Can *M. pneumoniae* cause meningitis?
Yes
499
Where in the respiratory tract does *M. pneumoniae* infection start?
Usually in the upper part, but it can spread anywhere within the tract
500
Is a cold-agglutinin test useful in diagnosing *M. pneumoniae*?
No, it is not sensitive or specific enough
