Lecture | Staphylococcus Flashcards
(143 cards)
1
Q
Greek term that means “bunches of grapes”
A
Staphle
2
Q
gram positive cocci, so round, that may appear in singles, in pairs, in clusters, or even in tetrads.
A
Staphylococcus spp.
3
Q
non-motile and non spore forming
A
Staphylococcus spp.
4
Q
When it comes to growing of Staphylococcus spp. in culture, they can be considered as
A
aerobic or facultatively anaerobic
5
Q
means you have to grow them in an environment without oxygen.
A
obligate anaerobes
6
Q
In culture, colonies are produced after how many hours
A
18-24 hours of incubation.
7
Q
appearance of Staphylococcus spp.
A
medium size, cream colored, white, or rarely light gold and buttery looking especially Staphylococcus aureus.
8
Q
Common isolates in the clinical laboratory and are responsible for several suppurative infections.
A
Staphylococci
9
Q
term of infection by pus-producing organism
A
suppurative infection
10
Q
most virulent species of staphylococci
A
S. aureus
11
Q
S. aureus is present among the indigenous flora of the
A
skin, eye, upper respiratory tract, gastrointestinal tract, urethra, and frequently in our vagina.
12
Q
infections are frequently acquired when colonizing strains gain access to a normally sterile site as a result of
A
trauma or abrasion to the skin or mucosal surface
13
Q
S. aureus is the most common cause of
A
Spinal epidural abscess, suppurative intracranial, septic arthritis, and osteomyelitis.
14
Q
infection especially in pre-pubertal children.
A
septic arthritis
15
Q
may be recovered from brain abscesses, typically following trauma.
A
suppurative intracranial phlebitis
16
Q
It causes various cutaneous infections and purulent abscesses.
A
S. aureus
17
Q
skin and soft tissue infections can be superficial, such as
A
impetigo or cellulitis.
18
Q
Cutaneous infections can progress to deeper abscesses, such as
A
carbuncles
19
Q
Cutaneous infections can progress to deeper abscesses and involve other organ systems and produce
A
bacteremia and septicemia.
20
Q
cause of infective endocarditis
A
S.aureus
21
Q
S.aureus is a common cause of toxin-induced diseases, such as
A
food poisoning
22
Q
What is SSS
A
scalded skin syndrome
23
Q
What is TSS
A
toxic shock syndrome
24
Q
“protein A” has sites that is able to bind the
A
FC portion of IgG.
25
Protein A protects the organism from
opsonization and phagocytosis of neutrophils
26
Coagulase is an enzyme that can even lead to
fibrin formation around the bacteria
27
an enzyme around the bacteria that protect the bacteria from phagocytosis
Coagulase
28
Coagulase helps this to disrupt the beta lactam portion of the molecule rendering the antibiotic useless against this organism
penicillinase or beta-lactamase
29
4 Types of Hemolysin
1. Alpha toxins
2. Beta toxins
3. Delta toxins
4. Gamma toxins
30
able to destroy or hemolysed your red blood cells, neutrophils, macrophages, and platelet.
Hemolysin
31
disrupts smooth muscle in blood vessels
Alpha toxins
32
toxic to erythrocytes, leukocytes, hepatocytes, and platelets
Alpha toxins
33
acts on sphingomyelin in the plasma membrane of erythrocytes
Beta toxins
34
Beta toxins is also called
sphingomyelinase C or “hot-cold” lysin
35
"hot-cold” feature associated with Beta toxin is seen as enhanced hemolytic activity on
incubation at 37° C and subsequent exposure to cold (4° C)
36
Beta toxins is exhibited in this test
Christie, Atkins, and Munch-Petersen (CAMP) test
37
performed in the laboratory to identify group B streptococci.
Christie, Atkins, and Munch-Petersen (CAMP) test
38
bacterias capable of producing delta toxin
S.aureus, S. epidermidis, and S. haemolyticus
39
toxin that is cytolytic to erythrocytes and demonstrates nonspecific membrane toxicity to other mammalian cells.
Delta toxins
40
produced by all strains of S. aureus
Gamma toxins
41
Gamma toxins function in association with PVL. pvl stands for?
PantonValentine leukocidin
42
an exotoxin lethal to polymorphonuclear leukocytes.
PVL
43
PVL has been implicated as contributing to the invasiveness of the organism by
1. suppressing phagocytosis
44
associated with severe cutaneous infections and necrotizing pneumonia.
PVL
45
Spreading factor; Permits bacteria to spread through connective tissues
Hyaluronidase
46
breaks down the proteoglycans in our connective tissue
Hyaluronidase
47
lyses the formed-fibrin clots
Staphylokinase
48
similar to streptokinase produced by Streptococcus
Staphylokinase
49
Able to degrade fats and oils that are often accumulated the surface of our body
Lipase
50
degradation of fats and oil facilitates the ability of S. aureus to colonize especially in our
sebaceous glands
51
Destroys protein
Protease
52
Exotoxin TSST-1 is also known as
pyrogenic exotoxin C
53
Responsible for the Toxic shock syndrome
Exotoxin TSST-1
54
illness most common in women 15-25 years of age who use tampons during menstruation
Toxic shock syndrome
55
cause of the majority of staphylococcal food poisoning cases
Enterotoxins A-E
56
cause the epidermal layer of the skin to slough off
Exfoliative Toxins
57
known to cause staphylococcal SSS (Skin Scald Syndrome)
Exfoliative Toxins
58
Most significant Exfoliative Toxins
epidermolytic toxin A & B
59
Associated with our community acquired methicilin-resistant Staphylococcus aureus
Panton-Valentine leukocidin toxin
60
cause fever, desquamation, hypotension, and could even lead to bacterial shock and death
exotoxin-TSST 1 or the pyrogenic exotoxin C
61
common source of hospital-acquired infections
S. epidermis
62
contaminant in improperly collected blood culture specimens
S. epidermis
63
less virulent than S.aureus and are opportunistic pathogens.
S.epidermis
64
cause of UTIs; Prosthetic valve endocarditis
S.epidermis
65
commonly isolated CoNS. It has been reported in wounds, bacteremia, endocarditis, and UTIs
S.haemolyticus
66
Usually involve implantation of medical devices; infection can even resemble S.aureus infection
S. lugdunensis
67
Identification of this bacteria is important because this particular genus is resistant to oxacillin
S. lugdunensis
68
associated with UTIs in young sexually active females; it is the second most common cause, after E. coli
S. saprophyticus
69
they are both community-associated and hospital acquired infections.
S. lugdunensis and S. aureus
70
organism is more virulent than other is known to contain the gene mecA
S. lugdunensis
71
gene which encodes oxacillin resistance.
gene mecA
72
also display resistance to your vancomycin.
S.haemolyticus
73
Opportunistic Pathogens
1. S. Warneri
2. S. Capitis
3. S.simulans
4. S. Hominis
5. S. Schleiferi
74
3 Modes of Transmission
1. Endogenous strain
2. Direct contact
3. Indirect contact
75
MOT: sterile site by traumatic introduction
Endogenous strain
76
MOT: person-to- person, fomites
Direct contact
77
MOT: aerosolized
Indirect contact
78
Laboratory dx: Specimen
No special considerations
79
Laboratory dx: Microscopy
Gram positive cocci
80
used to eliminate contamination by gram-negative organisms in heavily contaminated specimens such as feces.
Phenylethyl alcohol (PEA) or Columbia colistin-nalidixic acid (CNA)
81
Staphylococcus aureus growing on Sheep Blood Agar would produce
beta-hemolytic, creamy, buttery-looking colonies.
82
name “aureus” has something to do with the production of the
Staphyloxanthin or golden yellow pigment
83
a coagulase positive organism.
Staphylococcus aureus
84
coagulase negative staphylococci
S.epidermis & S.saprophyticus
(non-staphylococcus aureus organisms)
85
mannitol sugar agar contains a high concentration of salt with a percentage of
7.5%-10%
86
phenol red as the pH indicator
Mannitol Salt Agar
87
makes the medium selective for Staphylococcus
high NaCl concentration (7.5%) in MSA
88
incorporation of this distinguishes S. aureus from most CoNS (Coagulase negative staphy)
mannitol and phenol red
89
S. aureus ferments mannitol and produces a
yellow halo
90
S. aureus ferments mannitol and produces a yellow halo as a result of
acid production altering the pH
91
CHROMagar is for the identification of
methicillinresistant Staphylococcus aureus (MRSA)
92
CHROMagar for the identification of methicillinresistant Staphylococcus aureus (MRSA) isolates through
selective and differential formation of mauve-colored colonies
93
grow on media containing blood, orming colonies about one tenth the size even after 48 hours or more of incubation
small colony variants (SCVs)
94
appear as small, pinpoint, nonhemolytic, and nonpigmented colonies on blood agar.
small colony variants of S. aureus
95
Catalase Test is used to differentiate
Catalase positive Micrococcus & Staphyloccocus from Catalase negative Streptococcus
96
Catalase is an enzyme that converts the hydrogen peroxide into?
oxygen and water
97
positive result of Catalase test
presence of bubbles (effervescence)
98
this bacteria is coagulase positive both in slide and tube test
S.aureus
99
Bound coagulase, or “clumping factor” is performed on
Slide Test
100
Free coagulase or staphylocoagulase is performed on
Tube Test
101
formerly referred to as cell-bound coagulase and causes agglutination
Clumping factor
102
directly converts fibrinogen to fibrin
Clumping factor
103
resembles thrombin and indirectly converts fibrinogen to fibrin
coagulase-CRF complex
104
positive result of slide coagulase test
clumping/agglutination within 30 seconds
105
positive result of tube coagulase test
clot formation
106
a negative result of slide test should always be followed up by
a tube coagulase test.
107
an extracellular molecule that causes a clot to form when bacterial cells are incubated with plasma.
Staphylocoagulase
108
Staphylocoagulase reacts with a thermostable, thrombin-like molecule called
coagulase- reacting factor (CRF)
109
In Tube coagulase test, look for clot formation after
4 hours of incubation at 37° C
110
If no clot appears fter 4 hours of incubation at 37° C during Tube coagulase test, what should be done
tube should be left at room temperature and checked the next day.
111
Fibrinolysin activity is enhanced at
37° C.
112
organisms that may present false positive result in slide test
S.Lugdugensis and S.schleiferi
113
organisms that may present false positive result in Tube Test
S.Intermedius and S.hyicus
114
Testing for pyrrolidonyl arylamidase activity can be used to differentiate S. aureus (negative) from
S. lugdunensis, S. intermedius, and S. schleiferi (positive).
115
It is hydrolyzed to L-pyrrolidone and β-
naphthylamine, which combines with p- dimethylaminocinnamaldehyde to form a red compound.
substrate pyroglutamylβ-naphthylamide (L-pyrrolidonyl- β-naphthylamide)
116
Bright red precipitate
PYR Test
117
Voges- Proskauer positive result
1. formation of acetoin from glucose or pyruvate
2. Red color = S. aeurus
118
a test to determine whether an organism that is inoculated in the plate is susceptible to 5-ug novobiocin disk.
Novobiocin Susceptibility Test
119
this organism is resistant to novobiocin and lack of a Zone of inhibition.
S. saprophyticus
120
In Microdase test, Staphylococcus epidermidis screening plate may show resistance to
Bacithracin (Taxo A) and furazolidone (Fx)
121
a modified oxidase test, detects your Cytochrome C; and used for differentiating Micrococcus spp. from Staphylococcus spp.
Microdase Test
122
In Microdase Test, Micrococcus spp. turn color ? within how how many mins
blue within 2 minutes.
123
bacteria is positive for both the 2-hour PYR and ornithine decarboxylase tests.
S. lugdunensis
124
kits use plasma-coated carrier particles
latex.
125
detect both clumping factor (with fibrinogen) and protein A
latex kit
126
kits that detect both clumping factor (with fibrinogen) and protein A and contain antibodies that bind capsular antigens 5 and 8, or other surface molecules.
Third-generation agglutination kits
127
These kits often have a higher specificity and sensitivity than the traditional plasma slide test and are quicker than the tube coagulase test.
latex kit
128
more sensitive, they are generally less specific.
Third-generation agglutination kits
129
Using Third-generation agglutination kits, False-positive results can occur with
S. saprophyticus, S. hominis, and S. haemolyticus.
130
mediated by the mecA gene, which encodes an altered penicillin-binding protein, PBP-2a
B-Lactamase
131
The mainstay of antistaphylococcal therapy is the use
methicillin, naficillin, and oxacillin
132
due to the gene mecA which is carried on a mobile cassette known as SCCmec
MRSA
133
using cefoxitin disk, MRSA zone of inhibition is
>22 mm is reported as susceptible
134
using cefoxitin disk with zone sizes that is less or equal (
oxacillin resistant , MRSA
135
To screen isolates of S.aureus for oxacillin resistance, we use
Mueller Hinton agar supplemented with 4% sodium chloride and containing your 6 ug/ml of oxacillin inoculated unto a cotton swab and incubated 24 hours at 35C
136
gold standard for MRSA detection
Molecular nucelic acid probes or pCR amplification
137
Macrolide Resistance
1. Clindamycin
2. Efflux pump, MRSA
3. Methylase enzyme that alters the ribosomal binding site.
4. D-zone test
138
useful when discrepant macrolide test results are obtained (e.g., erythromycin resistant and clindamycin susceptible).
modified double disk diffusion test (D-zone test)
139
to determine the organism’s susceptibility to Clindamycin, what is used?
modified Kirby-Bauer test or D zone test
140
most commonly used cell wall–active agent that retains activity and is an alternative drug of choice for the treatment of infections with resistant strains
Vancomycin
141
Any clinical isolates that are identified as oxacillin-resistant S. aureus or coagulase-negative staphylococci and been found to be resistant to
vancomycin
142
resistant to vancomycin should be considered resistant to all other
beta-lactam antibiotics.
143
Alternatives for vancomycin
Linezolid & Daptomycin
