4.28 staph Flashcards
(34 cards)
Methicillin resistance
MecA gene encoding for PBP2a variant
Low grade and high grade beta lactam resistance
Low grade: mutated PBP
High grade: beta lactamase
How to detect methicillin resistance
Detect mec via PCR
Detect PBP2a with mAb latex bead assay
VRSA
Acquire genes from VRE
VISA
Overproduce PBP2 to get thick cell wall
Cell wall pathogenicity factors
Peptidoglycan
Trichroic acid
Polysaccharide capsule
Cell surface proteins / MSCRAMMs
Fibronectin binding (to bm and ct) Collagen binding (to bone and cartilage) Fibrinogen binding (to clots) Protein A (to Fc of IgG to reduce opsonization & phagocytosis)
Extracellular enzymes
Coagulase Catalase Hyaluronidase Protease Lipase Nuclease
What converts fibrinogen to fibrin to stimulate clot formation
Coagulate
What inactivates toxic oxygen radicals so prevents phagocytes killing
Catalase
What promotes spread and invasion
Hyaluronidase
What provides nutrients
Protease
Lipase
Alpha hemolysin
Pore formation, kill by osmotic shock
Beta hemolysins
Digests sphingomyelin
What exotoxins is against neutrophils
Leukocidin
What are the exotoxins
Pyrogenic toxins (TSST1 & SE) Exfoliative toxins
What causes staphylococcal scalded skin syndrome
Exfoliating toxins
SSSS in children
Ritter’s disease
Localized SSSS
Bullous impetigo
What helps attach to nasal mucosa
LTA
What helps colonize traumatized skin and soft tissue
MSCRAMMs
Job’s syndrome has what defect
Chemotaxis of PMNs
Agammaglobulinemia has what defect
Opsonization defect
Chronic granulomatous disease has what defect
PMNs can’t activate release of radicals within phagocytic vacuoles
