Staphylococci

Question 1

• gram positive cocci
• arranged in clusters
• catalase positive, oxidase negative
• major component of normal skin and nares flora

Answer 1

staphylococcus

Question 2

• most virulent species of the genus
• common flora on skin and mucus membranes
• spread by direct contact
• antibiotic resistance a major concern

Answer 2

staph aureus

Question 3

foodborne s. aureus intoxication:

• source?
• transmissions?
• symptomes: rapid onset with _____ hours
• duration: _____ days
• treament?

Answer 3

source: meat, ham, pastries, and milk products left at room temp
transmission: infected food handlers

1-6 hours

1-3 days (n/v/d/stomach cramps)

symptoms, replace fluids, abx not helpful

Question 4

adherence factor that binds IgG, Fc region of anitbody, prevents opsonization and phagocytosis of staph aureus

Answer 4

protein A

Question 5

• recalcitrant to abx therapy
• result from attachment to device and biofilm replacement
• causes 76% of all orthopedic infections
• removal and temporary insertion of spacer, then replacement

Answer 5

device related staph aureus infections

Question 6

• cellulitis, impetigo, folliculitis, abscess
• cellulitis: warm, red, soft swollen tissue, tender to touch
• impetigo: erythematous papules and pustules with yellow honey crusting, on face, large bullae

Answer 6

staph aureus skin and soft tissue infections

Question 7

abscesses/furuncle more likely to be caused by staph aureus or group A strep?

Answer 7

staph aureus

Question 8

• diffuse exfoliation (ritter’s)
• exfoliative dermatitis caused by ETA and ETB
• localized tender erythema, systemic spread, fever, blisters
• children less than 5yo
• mortality and scarring are rare

Answer 8

scalded skin syndrome

Question 9

• superantigen
• sudden fever followed by headache, sore throat, diffuse red rash, skin desquamation
• shock within 48hr

Answer 9

staph aureus toxic shock syndrome

Question 10

• binds to T cell receptor and MHCII molecules
• massive release of cytokines
• capillary leakage
• hypotension, shock, death

Answer 10

TSST-1 toxin

Question 11

• infection of bone or bone marrow
• hematogenous spread or trauma
• sudden onset of pain over infected bone with fever, redness, refusal to bear weight
• in adults: crhonic, follows trauma or implanted device

Answer 11

osteomyelitis due to staph aureus

Question 12

• most common cause of acute bacterial endocarditis
• high mortality, prompt antimicrobial therapy
• usually involves heart valves

Answer 12

s. aureus endocarditis

Question 13

respiratory infections due to s. aureus?

Answer 13

pneumona, empyema, cystic fibrosis precedes entry of pesudomonas

Question 14

defenses against staph?

Answer 14

• C3b opsonizes bacteria and enhances phagocytosis

- neutrophils: engulf bacteria, intracellular killing by O2 radicals

Question 15

topical antibiotics for s. aureus?

Answer 15

bacitracin, mupirocin

Question 16

antibiotics for MSSA s. aureus?

Answer 16

1st gen cephalosporins (cephalothin, cephalexin, cefazolin) or amoxicillin/nafcillin/oxacillin

Question 17

antibiotics for MRSA?

Answer 17

clindamycin, bactrim, doxycycline, linezolid, vancomycin, daptomycin

Question 18

VISA/VRSA treatment?

Answer 18

linezolid, daptomycin, quinupristin/dalfopristin

Question 19

vancomycin resistant s. aureus acquired resistance from?

Answer 19

resistance plasmid from enterococci

Question 20

• normal skin flora
• opportunistic pathogen forming biofilm
• coagulase negative
• bacteriocins inhibit growth of other gram positives
• MDRs common

Answer 20

staph epidermidis

Question 21

• coagulase negative

- UTIs in sexually active young women

Answer 21

staph saprophyticus