staphylococcus Flashcards

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1
Q

microscopic evaluation of s. aureus

A

staphyle - bunch of grapes; coccus - berries

grows in clusters, pairs, short chains

G+ cocci with low G+C content

non-spore forming, non-motile

heat resistant

yellow CFU on blood agar, beta-hemolytic auereus = golden

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2
Q

general properties of S. aureus

A

catalase, lipase, DNAse, coagulase +, mannitol fermenter

facultative anaerobe

ribotol-type teichoic acid

re-emerging as an important human pathogen due to rapid development of antimicrobial resistance and increased use of indwelling medical devices.

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3
Q

S. aureus diseases

A
skin inflammation
impetigo
SSSS
nectrotizing fasciitis
osteomyelitis
endocarditis
keratitis
indwelling medical device infection
TSS
food poisoning
pneumonia
septicemia
pyopneumothorax
empyema
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4
Q

TSS pathogenesis

A

ability of pyrogenic exotoxins to be superantigens; cause sustained release of TNF and IL-1 from macrophages; cause interferon-gamma and IL-2 from CD4+ cells; enhance host susceptibility to LPS; binds endothelial cells and may enhance capillary leakage

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5
Q

how many people killed as result of s. auerus

A

40,000 people/yr in USA

infections cost 10.7 billion/yr

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6
Q

what makes s. aureus a formidable pathogen?

A

s. auerus is the agent of numerous types of infecitons, syndromes, and toxinosis; produces numerous types of virulence factors that are coordinately regulated by adaptive systems; has the ability to persist in host cells and biofilms; pan-antibotic resistant strains of s. aureus have emerged; s. aureus highjacks our immune response to do its bidding

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7
Q

virulence factors of s. auerus

A

aherence - polysaccharid A; MSCRAMMS; coagulase

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8
Q

damage to host

A

5 cytotoxins
exfoliate toxin - SSSS
enterotoxins - TSS; food poisoning
TSST

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9
Q

immunoavoidance

A

leukocidin and gamma hemolusin
capsule
protein A
biofilms

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10
Q

extracellular enzymes

A

coagulase
lipase
hyaluronidase
staphylokinase

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11
Q

laboratory diagnosis

A

specimens vary with disease process; gram stains on direct specimens; culture and identifaciton (gram positive cocci in clusters, catalase positive, coagulase positive); spa typing (protein A sequence); MLST

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12
Q

prevention and control

A

isolation of MRSA patients; proper refrigeration of food; protect patients from acquiring infection; eliminate carrier state with oral antibiotic and/or a topical anti-staphylococcal drug like mupirocin

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13
Q

s. aureus spread

A

direct contact, aerosols, contaminated food

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14
Q

infections are either

A
toxin mediated (food poisoning, TSS, SSSS)
invasive (utilizes the array of virulence factors to cause disease)
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15
Q

staphylococcus epidermidis

A

normal flora of skin, nose, throat
can produce slime
causes opportunistic nosocomial infections
produces disseminated disease with multiple abscesses

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16
Q

staphylococcus saprophyticus

A

occasionally found on skin or gastrointestinal and genitourinary tracts; non-hemolytic, coagulase-negative; novobiocin resistant; very common cause of urinary tract infection in adolescent females