Exam 2 Flashcards
(157 cards)
1
Q
Standardized suspension of bacteria must be prepared using what?
A
0.5 McFarland Standard
using a Barium sulfate solution, the turbidity must equal to 1.5 x 10⁸ CFU/ml bacteria
2
Q
With Agar Disk Diffusion (Kirby-Bauer Method) in a Mueller Hinton agar, if the ions are too high % amino-glycosides tests …
A
falsely resistant
3
Q
With Agar Disk Diffusion (Kirby-Bauer Method) in a Mueller Hinton agar, if the ions are too low % amino-glycosides tests …
A
falsely susceptible
4
Q
What is cefinase used for?
A
disk test for beta lactamase detection
5
Q
Why do you need to detect beta lactamase?
A
it’s resistant to penicillin and ampicillin
6
Q
If the cefinase disk turns RED, what does that indicate?
A
positive for beta lactamase!!! interpret as resistant to penicillin and ampicillin
7
Q
If the cefinase disk stays the same, what does that indicate?
A
negative for beta lactamase. but it can still possibly be sensitive to penicillin… aka useless result,, tells you nothing
8
Q
What indicates you found the minimal inhibitory concentration (MIC)?
A
- do a serial dilution
- the first clear test tube will be the MIC
9
Q
What indicates you found the minimal bactericial concentration (MBC)?
A
- do a serial dilution
- plate the test tubes with clear broth
- the first plate without growth is the MBC
10
Q
What MBC/MIC ratio would be considered inhibitory?
A
> 4 (greater than 4)
11
Q
What MBC/MIC ratio would be considered -cidal?
A
≤ 4 (less than or equal to 4)
12
Q
T or F, Incubation of an isolate with an active antibiotic reduces the intensity and the number of the peaks
A
TRUE
13
Q
T or F, Incubation of an isolate with an inactive antibiotic will modify the spectra (peak)
A
FALSE
14
Q
What targets have manufactures addressed in Molecular Resistance Testing?
A
readily detectible, common in the population, and, when present, are always expressed
15
Q
What is BacCapSeq?
A
16
Q
What is the number one flaw to BacCapSeq?
A
you need KNOWN bacteria, so it cannot be used to find unknown bacterial genes
17
Q
What is target modification in antibiotic resistance?
A
a pathogen will mutate a gene or enzyme to prevent the antibiotics from binding to target sites
18
Q
What are examples of pathogens using target modification to become resistant to antibiotics?
A
- Mutations of gyrases and topoisomerases leading to fluoroquinolone resistance
- PBP2a – methicillin resistance
19
Q
What is an example of pathogens inactivating enzymes to become resistant to antibiotics?
A
Production of β-lactamases and aminoglycoside modifying enzymes to become resistant to penicillin/ampicillin
20
Q
What are the three categories of drug resistance?
A
Multi-drug resistant (MDR), Extensively-drug resistant (XDR), and Pan-drug resistant
21
Q
What is MDR (multi-drug resistant)?
A
acquired non-susceptibility to at least one agent in three or more antimicrobial categories
22
Q
What is XDR (extensively drug resistant)?
A
non-susceptibility to at least one agent in all but two or fewer antimicrobial categories
(susceptible to only one or two categories)
23
Q
What is PDR (pandrug resistant)?
A
non-susceptibility to all agents in all antimicrobial categories (resistant to all)
24
Q
How do you balance Mueller Hinton agar?
A
Ca+ and Mg+
(calcium and Magnesium)
25
What is the procedure for Agar Disk Diffusion?
1. Streak bacteria on plate with cotton tipped swab
2. Apply 6mm paper disks that contains single antibiotic
3. Incubate for 16-24 hrs at 35*C
4. Measure zone of diameter of inhibition of growth (mm)
26
If there are two rings around the antibiotic disk (agar disk diffusion), what ring do you measure? The outer or inner ring?
Inner ring (usually means a mixed specimen)
27
Does Agar Disk Diffusion have quantitative or qualitive results? able to determine MIC or MBC?
1. qualitive (Resistant, Intermediate, Susceptible)
2. MIC
28
Does E test (strip) have quantitative or qualitive results? able to determine MIC or MBC?
1. quantitive
2. MIC
29
What is the procedure for the E test?
Calibrated plastic strips impregnated with one antibiotic/concentration gradient (mcg/ml) embedded in plastic/carefully placed on the agar surface
30
How do you read an E test?
strip goes from high to low antibiotic conc.
Gradient created as antibiotic diffuses into agar in an elliptical shape
high conc. will look like an eclipse due to the lack of growth
MIC will be at the start of growth
low conc. will have... just growth due to low titer of antibiotics
31
What grows best for gradient diffusion tests?
Useful for some slow growing or fastidious organisms that cannot be tested by KB
32
What susceptibility test needs to be FURTHER DILUTED past the 0.5 McFarland standard?
broth dilution
33
What is the dilution for broth dilutions?
5x10⁵ organisms /ml in broth
34
What susceptibility tests need to be diluted to the 0.5 McFarland standard?
Agar Disk Dilution (Kirby-Bauer) and Gradient Dilution (like E test)
35
What are some characteristics of Staphylococcus?
Facultatively Anaerobic cocci that is catalase positive
36
What are some characteristics of Streptococci?
Facultatively Anaerobic cocci that is catalase negative
37
What clinically important Staphylococcus species are:
1. Coagulase positive
2. Coagulase negative (CoNS) [2]
1. S. Aureus
2. S. Epidermis and S. Saprophyticus
38
What clinically important Coagulase negative (CoNS) Staphylococcus species are:
1. novobiocin sensitive
2. novobiocin resistant
1. S. Epidermis
2. S. Saprophyticus
39
What tests are used to determine if the bacterium has coagulase?
1. Slide Test (clumping factor [liquid to clumps])
2. Tube Test (free coagulase [sediments at the bottom for positive results])
40
What color is S. Aureus on Mannitol Salt Agar? Why?
1. Yellow!
2. Growth and fermentation of mannitol is present
41
What does S. Aureus produce when it ferments glucose?
Fermentation of glucose produces mainly lactic acid
42
What are some skin/soft tissue disease caused by Staph. Aureus?
Abscess, Impetigo (blistered skin from bacterial infect.), Boil
43
What are some secondary infection disease caused by Staph. Aureus?
Pneumonia, Meningitis, Sepsis
44
What are some toxigenic disease caused by Staph. Aureus?
Staphylococcal Scalded Skin Syndrome, Toxic Shock Syndrome, Food Poisoning
45
What Staphylococcus is Coagulase Positive on slide, but Coagulase negative on test tubes? Positive for Pyrrolidinyl Aminopeptidase (PYR)?
S. Lugdunensis
46
Is Staph. Aureus normally found in the body? if so, where?
yes, in the upper respiratory tract and/or skin
47
What is Methicillin Resistant Staphylococcus aureus (MRSA)?
a strain of staph aureus that has mutated (mecA) to be resistant to methicillin (common name of penicillin)
48
How do you detect Methicillin Resistant Staphylococcus aureus MRSA?
in vitro with cefoxitin
49
What is the purpose of the Staphylococcal D Test?
test is employed to detect inducible clindamycin resistance
50
How do you determine the results of a Staphylococcal D Test?
1. Positive: If there is a "blunt", not a circle but similar to a "D" rather than a perfect resistance ring, normal
2. Negative: perfect circular ring, iMLS absent and susceptible to clindamycin
51
What staph species is a opportunistic social butterfly? (attacks the immunosuppressed and associated with "foreign bodies")
Staphylococcus Epidermidis
52
What is used to treat S. Epidermidis based UTIs?
quinolones
53
What is the 2nd most common cause of UTIs?
Staphylococcus Epidermidis
54
What type of hemolysis causes iron to oxidize changing the blood agar from red to the "green" color?
alpha-hemolytic (partial hemolysis)
55
What type of hemolysis causes complete rupture of RBCs causing a clear paths in the blood agar?
beta-hemolytic
56
Lancefield grouping for Streptococci is based on what present in the bacterial cell wall?
C-carbohydrates
57
What are the characteristics of Streptococcus Pyogenes (Group A Beta-Hemolytic Strep [GABHS])?
1. beta-hemolysis (Group A)
2. PYR positive
3. TMP-SMX* resistant
4. Bacitracin (A disc) sensitive
58
What color will the disk turn to in L-Pyrrolidonyl b-Naphthylamide Test (PYR test)?
bright pink or cherry-red
59
What test easily differentiates S. Pneumoniae from other strep. species?
Optochin Test!
Strep. Pneumoniae is the only Streptococci that is sensitive to optochin
60
How can you tell a part Strep group:
1. D
2. A
3. B
1. Strep., optochin resistant, bile resistant, no Hemolysis
2. Strep., optochin resistant, Beta Hemolysis, Bacitracin Sensitive
3. Strep., optochin resistant, Beta Hemolysis, Bacitracin resistant, CAMP positive
61
CAMP test, what is a:
1. Positive Reaction
2. Negative Reaction
1. No perpendicular line
2. Perpendicular line
62
What strep organism is CAMP test used to differentiate for?
S. Agalactiae (Group B Strep)
63
**What are characteristics of Viridans group Streptococci?
1. Alpha-hemolytic
2. Optochin (P-disk) Resistant
3. Negative Bile Solubility
4. Negative Bile Esculin
4. No growth in 6.5% NaCl
64
What will rapidly lyse S. Pneumoniae colonies?
Bile Salt
(Lysis depends on the presence of an intracellular autolytic enzyme, amidase. Bile salts activate the autolytic enzyme which induces clearing of the culture)
65
What's the difference between S. Anginosus and S. Aureus?
S. Anginosus is resistant to bacitracin
S. Aureus is sensitive to bacitracin
66
What is the only one in the viridans strep group that is Bile Esculin positive?
Strep Bovis
67
What are the characteristics of Strep Bovis?
1. γ- or α-hemolytic
2. Optochin / P disc resistant (unlike S. pneumoniae)
3. Bile solubility negative (unlike S. pneumoniae)
4. Bile esculin positive (unlike other viridans group strep)
5. No growth in 6.5% NaCl (unlike Enterococcus)
6. Lancefield Group D (like Enterococcus)
7. Bacteremia, septicemia, endocarditis
8. S. gallolyticus subsp. gallolyticus correlates with GI carcinoma
68
What percentage of Enterococcus is:
1. E. Faecalis
2. E. Faecium
1. 90-95%
2. 5-10%
69
What are the characteristics of Enterococcus?
1. Small, cream/white, smooth colonies
2. PYR positive
3. Bile esculin positive
4. Growth in 6.5% NaCl
5. Typically γ-hemolytic
6. Group D (like S. bovis group)
70
Is E. Faecalis or E. Faecium more likely to be Vancomycin (Van) resistant?
E. Faecium
71
What is Abiotrophia Defectiva?
Gram positive-variable, facultative aerobe that can cause life threatening complications
Requires chocolate or blood agar to be supplemented with L-Pyridoxal Hydrochlorine (Vitamin B6) to grow **
72
What is the morphology of C. Diphtheriae?
non-motile, noncapsulated, club-shaped, gram positive rod-shaped bacillus
looks like rosary beads "beaded appearance"
produces diptheriae exotoxin
73
What three organisms form colonies with a brown halo on tellurite containing media e.g. Cysteine Tellurite Agar?
C. diphtheriae, C.ulcerans, C. Pseudoturberculosis
74
What are the three types of C. diphtheriae morphological types found on tellurite containing media?
1. Mitis (black colonies with gray periphery
2. Gravis (large, gray colonies)
3. Intermedius (small, dull gray to black)
75
What does the diphtheriae exotoxin produced by C. diphtheriae do?*
inhibits protien synthesis by ADP-ribosylating elongation factor 2.
Shut down the chain!!
76
How do you diagnose C. Diphtheriae?
sample from throat or lesion is plated on tellurite and is confirmed by the bacteriologic laboratory team
77
Which Corynebacterium spp. is the worst (according to the prof)?
C. Jeikeium b/c of the high resistance to antibiotics
78
What is the morphology of C. Jeikeium?
1. strict aerobe (O2 dependent)
2. small gram positive bacillus (1 pointy end, 1 rounded end)
3. small, gray, shiny, gamma (none) hemolytic on blood agar
4. Lipophilic
5. Catalase positive
79
Why is listeria monocytogenes dangerous to humans?
1. Meningitis/Meingoenphalitis
2. Can cause preggo ladies to have abortions or still births
3. If there is growth in the vagina, it can cause infertility
80
What is the morphology of listeria monocytogenes?
1. small gram positive pill shaped
2. long filaments
3. tumbling/windmilling at 25C
4. non-motile at 37C
5. aerobic (O2 dep.) and Microaerophilic (thrives in low O2)
6. catalase positive, bile esculin positive, CAMP positive
81
What is needed for Listeria Monocytogenes to grow?
BLOOD!!!
grows well on Muller Hinton agar w/ Sheep Blood
82
What does Listeria Monocytogenes get confused with?
1. Enterococci (bile esculin positive)
2. Diphtheroids (catalase positive)
3. sometimes S. agalactiae (CAMP positive)
83
What is the morphology of Erysipelothrix rhusiopathiae?
Gram-positive, catalase-negative, rod-shaped, non-spore-forming, nonacid-fast, nonmotile bacterium
84
What is the zoonotic infections in humans caused by Erysipelothrix rhusiopathiae?
Erysipeloid
85
What can Erysipeloid (caused by Erysipelothrix rhusiopathiae) be mistaken for?
Erysipelas!!! caused by various members of the genus Streptococcus not E. Rhusiopathiae
86
What is E. rhusiopathiae resistant to?
Vancomycin
87
What is the ONLY GRAM POSITIVE BACILLUS that produces H2S????
E. rhusiopathiae
88
How can E. rhusiopathiae be separated from other corynebacterium like:
Arcanobacterium (Corynebacterium) pyogenes and Arcanobacterium (Corynebacterium) haemolyticum?
E. rhusiopathiae produces H2S in TSI slants and the others dont lol
89
What is the morphology of Arcanobacterium haemolyticum?
gram positive bacillus, catalase-negative, facultative anaerobic, beta-hemolytic, and not motile.
!! Do a gram stain!! For identification
90
What reaction on CAMP do you expect from Arcanobacterium haemolyticum?
Reverse Camp Reaction
looks like it is being pinched
blank arrow
91
How do you differentiate S. Pyogenes and Arcanobacterium haemolyticum?
S. Pyogenes is coccus-shaped
Arcanobacterium haemolyticum is rod-shaped
92
What is the morphology of Nocardia?
Gram positive bacilli
Pleomorphic (2+ forms), branching, fine, delicate filaments with fragmentation
93
What acid fast stain do you used for Nocardia?
1% sulfuric acid, modified (partial) acid fast stain
Nocardia will look pink, the background will be blue
94
What is the clinical Nocardia clinical significance?
can cause Actinomycotic fungal Mycetoma (tissue swelling, draining sinus tracts, granules)
95
What is the procedure for Bacillus anthracis?**
do not identify, only rule in/out, and if it is large Gram-positive rods, with white colonies and non-hemolytic
then send to state lab!!
96
What are the type of anthrax infections? the worst one?
1. Cutaneous (common), Injection, Pulmonary (worst), Gastrointestinal
97
What is the morphology for Neisseria Meningitidis?
1. Gram-negative
2. bean-shaped diplococci (leopard print)
3. capsulated with pili (bacterial sex organ)
4. parasite, cannot survive w/o host
5. Aerobic
6. Catalase positive
7. Oxidase positive***
8. requires incubation with CO2 to grow w/ enriched media (chocolate agar)
9. Maltose fermenter
98
What is the morphology of Neisseria Gonorrhoeae?
1. Oval shaped
2. Gram negative diplococci
3. pairs
4. capsulated and have pili
5. requires incubation with CO2 to grow w/ enriched media (chocolate agar)
99
Will a gram stain w/ gram negative diplococci from a woman's cervical secretions be considered diagnostic for N. gonorrhoeae?
no, there can be other similar normal bacteria in the cervix
100
T or F, due to it's high specificity, a Gram stain of a male urethral specimen that demonstrates "polymorphonuclear leukocytes with intracellular gram-negative diplococci" can be considered diagnostic for infection with N. gonorrhoeae in men.
True
101
What Neisseria species ferments glucose and maltose, but not sucrose?
Menigingitis
102
What Neisseria species ferments glucose, but not maltose and sucrose?
gonorrhea
103
What haemophilus parainfluenzae causes what?
causes pneumonia or bacterial endocarditis
104
What haemophilus ducreyi causes what?***
chancroid
105
What spp. requires both factor X (hemin) and factor V (NAD+) in chocolate agar to grow?
Haemophilus spp.
106
What is the morphology for Haemophilus spp.?
1. Gram Negative coccbacilli
2. Lipooligosaccharide
3. glistening colonies
107
What organisms are in HACEK group?
1. Haemophilus spp.
2. Aggregatibacter actinomycetemcomitans
3. Cardiobacterium hominis
4. Eikenella corodens
5. Kingella spp.
108
What are HACEK organisms?
fastidious Gram-negative bacteria associated with infective endocarditis
GNR that do not grow on MacConkey
109
What bacteria is transmitted by HUMAN bites?
Eikenella Corrodens
110
What bacteria is transmitted by DOG bites and can cause sepsis?
C. canimorsus and C. cynodegmi
111
What does NOT grow on MacConkey Plates? (gram negative, not HACEK)
C. canimorsus/C. cynodegmi,
Pasteurella Multocida
112
What does Pasteurella Multocida look like?
gram negative, encapsulated, non-hemolytic, grey, and coccobacillus shaped
113
What bacteria is transmitted by CAT bites and/or scratches (and sometimes dogs)?
Pasteurella Multocida
114
What is Bordetella pertussis?
whooping cough
115
What mediums are used to isolate Bordetella Perussis?
**Regan-Lowe**, Bordet-Gengou glycerine, charcoal blood agar
116
What happens after a cat/dog bite/scratch w/ P. multocida?
localised celluitis and lymphadenitis
117
What is pertussis toxin (ptx)?
toxin secreted by B. pertussis and adhesin; synergistic w/ FHA
118
What is FHA (fha) [B. pertussis toxin]?
binds to ciliated tracheal epithelial cells and macrophage CR3 promoting phagocytosis; synergistic w/ pertussis toxin
119
What is Adenylate Cyclase (cya) [B. pertussis toxin]?
cytotoxin that inhibits chemotaxis and induces apoptosis of macrophages
120
What is Tracheal cytotoxin (tct) [B. pertussis toxin]?
toxin; inhibits DNA synthesis; eliminates mucociliary clearance by ciliostasis and extrusion of ciliated cells
121
What is dermonecrotic toxin (dnt) [B. pertussis toxin]?
toxin; dermal necrosis and vasoconstriction; activates host GTP binding protein Rho
122
What does franciscella strains require to grow?
cystine and cysteine on chocolate or thayer martin agar
123
What organism is oxidase positive and urase positive (within 4 hrs)?
Brucella
124
How do you differentiate Brucella and Salmonella?
Isolate, check if gram negative (both are), and test for urease
if urease positive: brucella
if urease negative: salmonella
125
In what ways would you get Brucella?
ingestion, inhalation, inoculation, (person-to-person [rare])
126
What is the pathogenesis for Brucella thru ingestion?
Raw milk or unpasteurized dairy
127
What is the pathogenesis for Brucella thru inoculation?
inoculation of placental or uterine discharge, blood, and urine
128
What is the pathogenesis for Brucella thru inhalation?
inhalation of placental or uterine discharge, blood, and urine
129
How would you culture Legionella pneumonphila?**
buffered charcoal yeast extract (CYE) agar w/ L cysteine, iron, and antibiotics
130
What bacterium(s) have bi-polar staining?
Yersinia
Franciscella
Pasturella
Burkholderia
Elizabethkingia
131
All enterobacteriaceae are motile except...
1. Shigella
2. Klebsiella
132
All enterobacteriaceae are capsulated except...
Klebsiella
133
What is the morphology of Enterobacteriaceae spp.?
1. Gram negative Rods
2. Ferments Glucose w/ acid production
3. Oxidase Negative
4. Reduce nitrates to nitrite
(usually infects large intestine)
134
What group of e. coli together are called enteroadherent e. coli?
Enterotoxigenic E. coli,
enteropathogenic E. coli and enteroaggregative E. coli
135
What is enterotoxigenic e. coli?
major cause of traveler's diarrhea
resembles cholera
mortality in kids less than 5 y/o
136
What does Enterohemorrhagic E. coli produce?
both shiga toxin 1 (stx1, slt1, verotoxin 1) and shiga toxin 2 (stx2, slt2, verotoxin 2)
137
What causes Hemolytic uremic syndrome (HUS)? and how?
1. Enterohemorrhagic E.coli
2. due to it producing shiga-like toxin (SLT) and entering circulation
138
What bacterium causes a majority of UTI? (especially community acquired UTI [slutting around slay])
E. coli
139
What bacterium is a frequent cause of nosocomial pneumonia (hospital acquired)?
Klebsiella
140
If there is mucoid, lactose fermenting GNB from sputum of Pt w/ pneumonia... what is it most likely?
Klebsiella
141
What is the morphology of klebsiella?
enterobacteriaeae
ferments lactose
non-motile
indole negative
encapsulated
142
What is expected of Proteus spp. in testing?
1. SBA: swarming (like wiggly tree rings)
2. H2S positive
3. Urease positive
143
What is the only subspecies of salmonella that humans can get?
Salmonella enterica subspecies I(one) enterica
144
What is the most common salmonella in humans?
Salmonella enterica enterica typhi
145
How do you get in contact with salmonella?
Food comes in contact with feces
146
What is Typhus? (unrelated, it just can be mistaken for Typhoid fever i'm assuming)
disease caused by rickettsia or oriential bacteria. You can get it from infected mites, fleas, or lice
147
What is Typhus? (unrelated, it just can be mistaken for Typhoid fever i'm assuming)
disease caused by rickettsia or oriential bacteria. You can get it from infected mites, fleas, or lice
148
How do you differentiate salmonella from E.coli?
1. H2S positive on XLD agar
2. non-glucose fermenter
149
How do you get nontyphoidal salmonella?
1. animal reservoirs
2. mainly eggs/chicken
3. exotic pets or fresh produce
150
What is the expected result for shigella sonnei?
K/A
151
What bi-polar staining organism spp. is urea-positive?
Yerinia
152
At what temperature is Yersinia spp. motile?
22-26C
153
At what temperature is Yersinia spp. non-motile?
37C
154
What agar is used specifically for Yersinia?
Cefsulodin-Irgasan-Novobiocin (CIN) agar
155
What is the major vector for Yersinia?**
Fleas
156
Yersinia pseudotuberculosis and Y enterocolitica can multiply/grows best...
in the cold! also zoonotic and enterotxin
157
What do you use to determine oxafillin and methicilin resistance?
Cefexolin
