Part 2 Clinical Bacteriology (Staph) Flashcards
(150 cards)
1
Q
acid-fast rods are
A
Mycobacterium species
2
Q
Mycoplasma species do not have
A
cell wall
don’t stain with Gram stain
3
Q
which are spirochetes too thin to be seen when stained with
Gram stain
A
Treponema
Leptospira
4
Q
What are intracellular bacteria and are difficult to visualise within the cytoplasm of the cell
A
Chlamydia
Rickettsia
5
Q
What are intracellular bacteria and are difficult to visualise within the cytoplasm of the cell
A
Chlamydia
Rickettsia
6
Q
Gram-positive cocci are
A
staphylococcus,
Streptococcus,
Enterococcus
7
Q
Major Gram-negative cocci genus
A
Neisseria
8
Q
Major Gram-positive rods genus
A
Corynebacterium,
Listeria,
Bacillus,
Clostridium,
Actinomyces,
Nocardia
9
Q
Gram-negative rods in the Enteric tract That are pathogenic inside and outside tract
A
Escherichia,
Salmonella
10
Q
Gram-negative rods in the Enteric tract that are Pathogenic primarily inside tract
A
Shigella,
Vibrio,
Campylobacter,
Helicobacter
11
Q
Gram-negative rods that are Enteric tract organisms which are Pathogenic outside tract
A
Klebsiella–Enterobacter–Serratia group,
Pseudomonas,
Proteus–Providencia–Morganella
group,
Bacteroides
12
Q
Gram-negative rods that are Respiratory tract organisms
A
Haemophilus,
Legionella,
Bordetella
13
Q
Gram-negative rods that are Organisms from animal sources
A
Brucella,
Francisella,
Pasteurella,
Yersinia
14
Q
Not readily Gram stained
Not obligate intracellular bacteria examples
A
Mycobacterium,
Mycoplasma,
Treponema,
Leptospira
15
Q
Not readily Gram stained and are Obligate intracellular bacteria
A
Chlamydia,
Rickettsia
16
Q
Which obligate aerobes grows best
in the 20% oxygen of room air and not at all under anaerobic conditions
A
Pseudomonas aeruginosa
17
Q
Facultative anaerobes such as - can
grow well under aerobic and anaerobic conditions because
A
Escherichia coli
(Switches to fermentation in no air)
18
Q
Aerotolerant organisms such as - can grow to some extent in air but multiply much more rapidly in a lower oxygen concentration.
A
Clostridium histolyticum
19
Q
Microaerophilic organisms such as - require a reduced oxygen concentration (approximately 5%) to grow optimally
A
Campylobacter jejuni
20
Q
obligate anaerobes such as - require an almost total absence of oxygen
A
Bacteroides fragilis
Clostridium perfringens
21
Q
Many anaerobes use what rather than
oxygen as the terminal electron acceptor.
A
Nitrogen
22
Q
main reason why the growth of anaerobes is inhibited by oxygen is the reduced amount (or absence) of
A
catalase
superoxide dismutase (SOD)
23
Q
Catalase and SOD eliminate which toxic compounds formed during production of energy by the organism
A
hydrogen peroxide
superoxide
24
Q
Give an example of a Microaerophile
A
Campylobacter jejuni
25
Anaerobic Spore-forming gram positive rod example
Clostridium
26
Anaerobic Non–spore-forming gram positive rod examples
Actinomyces,
Bifidobacterium,
Eubacterium,
Lactobacillus,
Propionibacterium
27
Anaerobic Non–spore-forming gram negative rod examples
Bacteroides,
Fusobacterium
28
Anaerobic Non–spore-forming gram positive cocci
Peptococcus,
Peptostreptococcus,
Streptococcus
29
Anaerobic Non–spore-forming gram negative cocci example
Veillonella
30
Examples of soil organisms
Clostridiumbotulinum
Clostridium tetani
Clostridiumperfringens
31
Diseases caused by members of the anaerobic normal flora are characterized by
abscesses
32
anaerobic normal flora
are characterized by abscesses, which are most frequently located in
brain,
lungs,
female genital tract,
biliary tract,
intra-abdominal sites.
33
Anaerobes are characterized by their ability to grow only in
an atmosphere containing less than 20% oxygen
34
important findings on physical examination that arouse suspicion of an anaerobic infection are
foul-smelling discharge,
gas in the tissue,
necrotic tissue.
35
infections that frequently involve anaerobes are
pulmonary aspiration,
bowel surgery,
abortion,
cancer,
human and animal bites
36
What specimens are appropriate that does not contain members of the normal flora to confuse the interpretation
blood,
pleural fluid,
pus,
transtrachealaspirates
37
Drugs commonly used to treat anaerobic infections are
penicillin G,
cefoxitin,
chloramphenicol,
clindamycin, metronidazole.
38
many isolates of the important pathogen B. fragilis produce β-lactamase and are thus
resistant to penicillin
39
aminoglycosides such as gentamicin are not effective against anaerobes because
they require an oxygen-dependent process for uptake into the bacterial cell
40
Microscopically, staphylococci appear in
grapelike clusters,
41
Microscopically streptococci appear
in chains
42
Biochemically, staphylococci produce
produce catalase (they degrade hydrogen peroxide),
whereas streptococci do not.
43
Staphylococcus aureus causes
abscesses
various pyogenic infections
endocarditis,
septic arthritis,
osteomyelitis
food poisoning,
scalded skin syndrome
toxic shock syndrome
44
most common causes of
hospital-acquired pneumonia,
septicemia,
surgical-wound infections is
Staphylococcus aureus
45
Staphylococcus aureus is an important cause of skin and soft tissue infections, such as
folliculitis,
cellulitis,
impetigo
46
most common cause of bacterial conjunctivitis
Staphylococcus aureus
47
Methicillin-resistant S. aureus (MRSA) is the most common cause of
skin abscesses
48
What is important cause of pneumonia, necrotizing fasciitis, and sepsis in immunocompetent patients
Methicillin-resistant S. aureus (MRSA)
49
Staphylococcus epidermidis causes
prosthetic valve endocarditis and
prosthetic joint infections
50
What is the the most common
cause of central nervous system shunt infections and an important cause of sepsis in newborns
Staphylococcus epidermidis
51
What causes urinary tract infections, especially cystitis
Staphylococcus saprophyticus
52
What syndrome is a disease of unknown etiology that may be caused
by certain strains of S. aureus.
Kawasaki syndrome
53
spherical gram-positive cocci arranged in
irregular grapelike clusters are
Staphylococci
54
All staphylococci produce …
catalase
55
no streptococci
produce catalase
56
What does catalase do
degrades H2O2 into O2 and H2O
57
Catalase is
an important virulence factor
58
Bacteria that make catalase can survive
the killing effect of H2O2 within neutrophils.
59
Scalded skin syndrome. Note widespread areas of “rolled up” desquamated skin in infant, Caused by
exotoxin produced by Staphylococcus aureus
60
Impetigo. Lesions of impetigo are crops of
vesicles with a “honey-colored” crust Impetigo is caused by
either Staphylococcus aureus or Streptococcus pyogenes
61
Folliculitis. Note the multiple, small pustules on the chin and neck
Staphylococcus aureus is the most common cause of folliculitis
62
Staphylococcus aureus
Positive coagulase production
Beta hemolysis
Protein A surface
Abscess, food poisoning, toxic shock syndrome
63
Staphylococcus epidermidis
No Coagulase Production
No Hemolysis
Sensitive to novobiocin
Infection of prosthetic heart valves and hips;
common member of skin flora
64
Staphylococcus saprophyticus
No Coagulase Production
No Hemolysis
Resistant to novobiocin
Affects Urinary tract
65
Thrombin catalyzes
activation of fibrinogen
to form the fibrin clot
66
Staphylococcus aureus produces a carotenoid pigment called — , which imparts a golden color to its colonies
staphyloxanthin
67
staphyloxanthin enhances the pathogenicity of the organism by
inactivating the microbicidal effect of superoxides and other reactive oxygen species within neutrophils
68
Staphylococcus epidermidis produces
white colonies
69
The virulence of Staphylococcus epidermidis is
significantly less than that of S. aureus.
70
S. aureus usually ferments mannitol and
hemolyzes red blood cells,
whereas S. epidermidis and S. saprophyticus do not.
71
source of iron required for growth of S. aureus
Hemolysis of red cells by hemolysins
72
The iron in hemoglobin is recovered by S. aureus
utilized in the synthesis of cytochrome enzymes used to produce energy
73
More than 90% of S. aureus strains contain plasmids that encode β-lactamase, the enzyme that
degrades many, but not all, penicillins
74
Some strains of S. aureus are resistant to the β-lactamase–resistant penicillins, such as
methicillin
nafcillin,
Due to changes in the penicillin-binding proteins (PBP) in their cell membrane
75
Genes on the bacterial chromosome called mecA genes encode
altered penicillin-binding proteins
76
methicillin-resistant S. aureus (MRSA) causes
healthcare-acquired (HCA-MRSA) and
community-acquired (CA-MRSA) infections
77
Almost all strains of CA-MRSA produce
P-V leukocidin
78
Strains of S. aureus resistant to vancomycin
intermediate resistance to vancomycin (VISA)
full resistance to vancomycin (VRSA)
79
genes that encodes vancomycin resistance in S. aureus is the same as the genes that
provides vancomycin resistance in enterococci, what do they do
genes are located in a transposon on a plasmid
encode the enzymes that substitute
d-lactate for d-alanine in the peptidoglycan
80
(Staphylococcus aureus)
Protein A is an important virulence factor because
binds to the Fc portion of IgG at the complement-binding site,
preventing the activation of complement
81
Staphylococcus aureus
Protein A leads to
no C3b is produced,
the opsonization and phagocytosis of the organisms are greatly reduced
82
Why is Protein A is used in certain tests in the clinical laboratory
binds to IgG and forms a “coaggluti-
nate” with antigen–antibody complexes.
The coagulase-negative
staphylococci do not produce protein A.
83
Staphylococcus aureus
What do Teichoic acids do
mediate adherence of the staphylococci to mucosal cells
84
Staphylococcus aureus
Lipoteichoic acids play a role in the induction of septic shock by
cytokines such as interleukin-1 (IL-1)
and tumor necrosis factor (TNF) from macrophages
85
Staphylococcus aureus
Polysaccharide capsule is also an important virulence factor
capsule is poorly immunogenic,
which has made producing an effective
vaccine difficult.
86
peptidoglycan of S. aureus has endotoxin-like properties, for instance
stimulate macrophages to produce cytokines
can activate the complement and coagulation cascades
explains the ability of S. aureus to cause the clinical findings of septic shock yet not possess endotoxin
87
main site of colonization of S. aureus
nose
88
common site of S. aureus colonization especially in hospitals
Skin of hospital personnel and patients
Hand contact is an important mode of transmission, and handwashing decreases
transmission.
89
Staphylococcus aureus is also found in the vagina of approximately 5% of women
which predisposes them to toxic shock syndrome
90
Additional sources of staphylococcal infection are
shedding from human lesions and
fomites such as towels and
clothing contaminated by these lesions
91
What can predisposition to infections by S. aureus
Diabetes and
intravenous drug
92
What disease can cause patients to be prone to to S. aureus infections characterized by a defect in the ability of neutrophils to kill bacteria
Patients with chronic granulomatous disease (CGD)
93
Staphylococcus epidermidis is found primarily
human skin and can enter the bloodstream at the site of intravenous catheters that penetrate through the skin
94
Staphylococcus saprophyticus is found primarily on
mucosa of the genital tract in young women and from that site can ascend into the urinary bladder to cause urinary tract infections
95
Staphylococcus aureus causes disease both
producing toxins
and by inducing pyogenic inflammation
96
The typical lesion of S. aureus infection is
an abscess
97
Foreign bodies, such as —- are important predisposing factors to infection by S. aureus
sutures and intravenous catheters
98
Several important toxins and enzymes are produced by S. aureus, The three clinically important exotoxins are
enterotoxin,
toxic shock syndrome toxin,
and exfoliatin.
99
Enterotoxin causes
food poisoning characterized by
prominent vomiting and
watery, nonbloody diarrhea
100
Enterotoxin acts as a superantigen within the gastrointestinal tract to stimulate
release of large amounts of IL-1 and IL-2 from macrophages and
helper T cells
101
Enterotoxin causes vomiting caused by
prominent vomiting appears to
be caused by cytokines released from the lymphoid cells,
which stimulate the enteric nervous system to activate the vomiting
center in the brain
102
Enterotoxin is hard to bypass because
heat-resistant, usually not inactivated by brief cooking.
It is resistant to stomach acid and to enzymes in the stomach and jejunum.
103
Toxic shock syndrome toxin can be seen in
tampon-using menstruating women
individuals with wound infections
nasal packing used to stop bleeding from the nose
104
TSST is a superantigen and causes toxic shock by stimulating the release of
large amounts of IL-1,
IL-2,
and TNF
105
Toxic shock occurs in people who
do not have antibody against TSST.
106
Toxic shock occurs in people who
do not have antibody against TSST.
107
Exfoliatin causes
scalded skin” syndrome in young children.
108
Exfoliatin is epidermolytic
acts as a protease that cleaves
desmoglein in desmosomes
leading to the separation of the
epidermis at the granular cell layer
109
Complement is
a system of plasma proteins that interacts with pathogens to mark them for destruction by phagocytes
110
leukocidins kill leukocytes, causing
necrosis of tissues
111
Alpha toxin causes
marked necrosis of the skin
and hemolysis.
112
cytotoxic effect of alpha toxin is attributed to
formation of holes in the cell
membrane
and loss of low-molecular-weight substances from the damaged cell.
113
P-V leukocidin is
a pore-forming toxin that kills cells,
especially white blood cells,
by damaging cell membranes
114
P-V leukocidin is an important virulence factor for
CA-MRSA
plays a role in the severe skin and soft tissue infection caused by this organism
115
A severe necrotizing pneumonia is caused by
strains of S. aureus that produce P-V leukocidin
116
Pathogenesis Of Staphylococcus aureus The enzymes include
coagulase,
fibrinolysin,
hyaluronidase,
proteases,
nucleases,
and lipases
How does coagulase work?
by clotting plasma, serves to wall off the infected site, thereby retarding the migration of neutrophils into the site
117
Staphylokinase is a fibrinolysin that can
lyse thrombi
118
Local Pyogenic infections caused by S. aureus are
Skin infection
(e.g., impetigo,
surgical-wound infections)
119
Disseminated Pyogenic infection caused by S. aureus lead to
Sepsis,
endocarditis
osteomyelitis,
arthritis
120
Staphylococcus aureus: Pyogenic Diseases
Causes skin and soft tissue infections such as
abscess,
impetigo
furuncles,
carbuncles
paronychia,
cellulitis,
folliculitis
necrotising fasciitis
hidradenitis suppurativa,
conjunctivitis,
eyelid infections- blepharitis, hordeolum
postpartum breast infections-mastitis
121
Lymphangitis can occur from s aureus, what is it
an infection and inflammation of the lymph vessels
person may notice red or dark streaks extending from the site of an injury, along with swelling, pain, and warmth
122
Severe necrotizing skin and soft tissue infections are caused by
MRSA strains that produce P-V leukocidin.
123
MRSA strains that produce P-V leukocidin that typically cause Severe necrotizing skin and soft tissue infections are usually acquired from
community-acquired rather than hospital-
acquired
124
Staphylococcus aureus
Osteomyelitis and septic arthritis may arise either by
hematogenous spread from a distant infected focus or
be introduced locally at a wound site
125
most common cause of post surgical wound infections
Staphylococcus aureus
126
S. aureus and S. epidermidis are the most common causes of infections at the site where
cardiac pacemakers are installed.
127
Staphylococcal pneumonia often leads to
-empyema (collection of pus in the pleural cavity, gram-positive, or culture from the pleural fluid)
-lung abscess
(A lung abscess involves the lung parenchyma, whereas an empyema involves the pleural space)
128
CA-MRSA causes (pneumonia)
a severe necrotising pneumonia.
129
Conjunctivitis typically presents with
unilateral burning eye pain,
hyperaemia of the conjunctiva,
pus discharge
(hyperaemia - excess of blood in the vessels supplying an organ)
130
S. pneumoniae and Haemophilus influenzae causing conjunctivitis are more common in
Children
131
Toxic shock syndrome is characterized by
fever;
hypotension;
a diffuse, macular, sunburn-like rash that goes on to desquamate;
and involvement of three or more of the following organs: liver,
kidney,
gastrointestinal tract,
central nervous system,
muscle,
blood.
132
syndrome occurs most often in young children, Scalded skin syndrome is characterized by
fever,
large bullae,
an erythematous macular rash.
Large areas of skin slough, serous fluid exudes, and electrolyte imbalance can occur
Hair and nails can be lost
133
Kawasaki disease (KD) features resemble
toxic shock syndrome caused by the superantigens of S. aureus
134
Staphylococcus epidermidis infections are almost always
hospital-acquired
135
S. saprophyticus infections are almost always
community-acquired.
136
Staphylococcus epidermidis is part of the normal human flora on the skin and mucous membranes but can enter the
bloodstream (bacteremia) and cause ?
metastatic infections, especially at the site of implants
137
Staphylococcus epidermidis commonly infects
intravenous catheters
prosthetic implants (heart-[endocarditis])
vascular grafts
prosthetic joints [arthritis or osteomyelitis])
138
Strains of S. epidermidis that produce a glycocalyx are more likely to
adhere to prosthetic implant materials and are more likely to infect these implants
139
Staphylococcus lugdunensis is a relatively uncommon coagulase -negative staphylococcus that causes
prosthetic valve endocarditis and skin infections.
140
commonly used screening device for
S. aureus
Mannitol-salt agar
141
Staphylococcus aureus ferments mannitol, which
lowers the pH, causing the agar to turn yellow,
142
Cultures of coagulase-negative staphylococci typically yield
white colonies that are nonhemolytic
143
The two coagulase-negative staphylococci are distinguished by their reaction to
antibiotic novobiocin
144
90% or more of S. aureus strains are resistant to penicillin G, Most of these strains produce β-lactamase, how are they treated
β-lactamase–resistant penicillins
nafcillin or cloxacillin,
some cephalosporins, or vancomycin.
Treatment with a combination of a β-lactamase–sensitive penicillin: amoxicillin
and β-lactamase inhibitor: clavulanic acid
145
β-lactam drug useful for the treatment of MRSA infections.
Ceftaroline fosamil
146
The treatment of toxic shock syndrome involves
fluids,
pressor drugs,
inotropic drugs
administration of a β-lactamase–resistant penicillin such as nafcillin
Pooled serum globulins
147
effective as a topical antibiotic in skin infections caused by S. aureus
Mupirocin
148
What can be added to mupirocin in skin
infections caused by S. aureus
A topical skin antiseptic, such as chlorhexidine
149
Staphylococcus epidermidis is highly antibiotic resistant, Most strains produce β-lactamase but are sensitive to
β-lactamase–resistant drugs such as nafcillin
150
Staphylococcus saprophyticus urinary tract infections can be treated with
trimethoprim-sulfamethoxazole or
A quinolone, such as ciprofloxacin.
