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30 Cards in this Set
- Front
- Back
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What are the three pathologic species of Staphylococcus?
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S. aureus
S. epidermidus S. saprophyticus |
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What culture characteristics does S. aureus have?
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* Gram + cocci, grows in grape-like clusters
* Gold pigmentation * Grows at 18-40C * Will grow in 10% NaCl |
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What are the main dx chars for S. aureus?
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* Gram +, grows in clusters
* Catalase + * Coagulase + |
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What populations are at risk for S. aureus invasive disease?
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1. Type 1 DM
2. HIV 3. Leukocyte disorders 4. IVDA 5. Dialysis 6. Surgery |
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Transmission method for MRSA?
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Contact, either fomite or person-to-person. Possibly STD.
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What two major strains of MRSA exist?
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Hospital-acquired and Community-acquired
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What's the prevalent community-acquired MRSA strain?
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USA300
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Does CA-MRSA afflict healthy hosts?
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YES
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What virulence factor accounts for the majority of S. aureus resistance?
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Enzyme Penicillinase blaZ (a beta-lactamase)
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What virulence factor accounts for MRSA resistance?
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SCCmec complex:
* mecA gene * ccr recombinase gene |
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To what class of antibiotic drugs are MRSA strains resistant?
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Beta-lactams:
* Cephalosporins * monobactams Macrolides (clinda, erythro) as well, to some degree |
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What are the antibiotic treatment options for MRSA?
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Vanco
Linezolid Daptomycin Synercid |
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What surface molecule is important in S. aureus pathogenesis?
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MSCRAMMs:
"Microbial-surface components recognizing adhesive matrix molecules" |
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What S. aureus virulence factor affects immunoglobulin binding?
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Protein A
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What S. aureus virulence factor allows it to survive macrophage attack?
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Produces catalase (anti-H2O2) and Superoxide Dismutase (anti-superoxide)
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What clinical S. aureus infects the epidermis?
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Impetigo and Bullae
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What clinical S. aureus infects the hypodermis?
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Cellulitis, folliculitis, furuncles, carbuncles
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What is a common superficial presentation for MRSA cellulitis?
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"Spider bite" lesion.
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What are two "distant diseases" associated with S. aureus toxin secretion?
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Staph Scalded Skin Syndrome
Staph Toxic Shock Syndrome |
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How does S. aureus cause food poisoning
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Preformed toxins in food. Organism doesn't multiply in gut, however.
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What's SSSS?
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Staph Scalded Skin Syndrome, from toxigenic S. aureus colonizing mucosa or skin producing exfoliative toxins
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Who's at risk for SSSS?
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Neonates. Clear fluid bullae, self-limiting disorder.
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What's one of the most common causes of food poisoning?
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S. aureus toxin-mediated poisoning.
* acute - vomiting w/in 1-6h of ingestion * nausea/vomiting/diarrhea * AFEBRILE * Supportive therapy |
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What's the most common cause of septic arthritis and osteomyelitis?
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S. aureus
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How can S. aureus infections be prevented?
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No immunization is available.
1) Cleanliness 2) Hand-washing 3) Aseptic lesion management |
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What lab tests differentiate S. aureus from S. epidermidis?
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1) Both G+, growing in clusters
2) S. epi is Catalase+, Coag- |
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Who is at risk for invasive S. epi?
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Pts with internal prosthetics (heart valves, joints, indwelling catheters)
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What is the major virulence factor of S. epi?
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Biofilm formation
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What lab tests differentiate S. aureus from S.saprophyticus?
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1) Both are G+, growing in clusters
2) S. sapro is Catalase+, Coag-, Novobiocin resistant (S. epi susceptible) |
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What gram-positive cocci is responsible for 10-20% of UTIs in young, sexually-active women?
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S. saprophyticus
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