Staphylococcus aureus: Difference between revisions

Revision as of 00:54, 5 August 2020

Facultative anaerobic, Gram-positive coccus
Catalase-positive and coagulase-positive
Microscopy: groups or clusters ("cluster of grapes")
Colony morphology: large, round, golden yellow colonies, often hemolytic on blood agar

Surface proteins for fibrinogen and other substances (used for binding to host endothelial cells)
Membrane-damaging toxins (hemolysins), including Panton-Valentine leukocidin (PVL)
Exfoliative toxins (A and B) which disrupt the junction between epidermal cells, causing scalded skin syndrome
Superantigens that bind to MHC molecules and T-cell receptors, leading to release of huge amounts of cytokines
- Toxic shock syndrome toxin 1 (TSST-1) is implicated in Staphylococcal toxic shock syndrome
- Exotoxins B and C cause Staphylococcal toxic shock syndrome and also food poisoning

Mechanisms of resistance are myriad
Two common ones:
- bla gene encodes penicillinase, conferring resistance to penicillin
- mecA encodes PBP2a, conferring broad beta-lactam resistance

Aka Ritter disease
Caused by exfoliative toxin A or B
Essentially bullous impetigo
Sunburn-like, bullous rash that can lead to skin loss (most common in kids with Staph infections of the nasopharynx or skin)

Food poisoning
Staphylococcal toxic shock syndrome
- Tampon-associated
- Post-surgical (ENT): more of historic with changes in packing
- Surgical site infections, even without obvious signs of localized infection

First-line: vancomycin
Others: linezolid (if lungs) and daptomycin (if blood), but also consider TMP-SMX, ciprofloxacin, doxycycline, and clindamycin

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 == Background ==
 === Microbiology ===
-* Facultative anaerobic, [[Stain::Gram-positive]] coccus
+* Facultative anaerobic, [[Stain::Gram-positive]] [[Cellular shape::coccus]]
-* [[Catalase test::Catalase-positive]] and [[Has coagulase test::coagulase-positive]]
+* [[Catalase test::Catalase-positive]] and [[Coagulase test::coagulase-positive]]
 * Microscopy: groups or clusters ("cluster of grapes")
 * Colony morphology: large, round, golden yellow colonies, often hemolytic on blood agar