staphylococcus

Question 1

microscopic evaluation of s. aureus

Answer 1

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

Question 2

general properties of S. aureus

Answer 2

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.

Question 3

S. aureus diseases

Answer 3

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

Question 4

TSS pathogenesis

Answer 4

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

Question 5

how many people killed as result of s. auerus

Answer 5

40,000 people/yr in USA

infections cost 10.7 billion/yr

Question 6

what makes s. aureus a formidable pathogen?

Answer 6

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

Question 7

virulence factors of s. auerus

Answer 7

aherence - polysaccharid A; MSCRAMMS; coagulase

Question 8

damage to host

Answer 8

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

Question 9

immunoavoidance

Answer 9

leukocidin and gamma hemolusin
capsule
protein A
biofilms

Question 10

extracellular enzymes

Answer 10

coagulase
lipase
hyaluronidase
staphylokinase

Question 11

laboratory diagnosis

Answer 11

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

Question 12

prevention and control

Answer 12

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

Question 13

s. aureus spread

Answer 13

direct contact, aerosols, contaminated food

Question 14

infections are either

Answer 14

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

Question 15

staphylococcus epidermidis

Answer 15

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

Question 16

staphylococcus saprophyticus

Answer 16

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