What is the 2 common foci of S.aureus CAI?
Bone/Joint
Heart
What is associated with S.aureus HAI?
Lines
How to classify S.aureus?
Gram positive cocci in clusters
Catalase positive
Coagulase positive
What is the source of Staphylococci?
How about coagulase negative staph?
Skin
Coagulase negative staph impt part of normal skin flora
Where is S.aureus carried?
Carried by about 30% of normal population at anterior nares/other sites
Virulence factors of S.aureus
- Protein A (cell-wall associated adhesion molecule)
- Coagulase cause tissue damage(extracellular proteins )
- Alpha toxin - pore forming haemolysin which lyses many host cell types (epithelial, endothelial, monocytes, macrophages, neutrophils)
- Enterotoxins - food poisoning
- Toxic shock syndrome toxin 1 (TSST-1)
- Epidermolytic toxins
Features of S.aureus enterotoxin
- Multiply at room temperature in some contaminated foods
- Tolerates high salt concentration
What does S.aureus enterotoxin cause?
Rapid onset of symptoms (preformed enterotoxin)
- Vomiting prominent but diarrhoea may also occur)
Where does S.aureus enterotoxin originate?
Food handler colonised/infected with enterotoxin-producing strain
What does S.aureus TSST-1 lead to?
Superantigen cross-links MHC II to TCR away from complementary determining region
Many T cells activated with massive release of cytokine (cytokine storm) and shock develops -> multiorgan failure, death
What does S.aureus epidermolytic toxins cause?
- Scalded skin syndrome
- SSTI: folliculitis, impetigo, boil, carbuncle, cellulitis, wound infection at surgical sites
- Localised pemphigus neonatorum, bullous impetigo (often results in abscess/pus)
- Generalised (large areas of skin lost): Ritter’s disease in neonates, toxic epidermal necrolysis in adults
What diseases does S.aureus cause?
- Osteomyelitis
- Septic arthritis
- Acute endocarditis (esp. in IVDA, tricuspid valve of right side)
- Pneumonia following influenza
- SSTI
- Toxic shock syndrome
- Food poisoning
- Abscess of any tissue/organ (brain, kidney, muscle)
How to treat S.aureus?
- Drain pus (remove foreign material and dead tissue)
- Cloxacillin/co-amoxiclavs/cephalosporins
- Erythromycin
- MRSA: Vancomycin, ceftaroline/ceftobiprole
- Topical agent Mupirocin
How does MRSA arise?
PBP2
Gene mecA imparts resistance to beta-lactam antibiotics (penicillins, cephlasporins, carbapenems)
What are the typings available?
AMR profiles
Sequence (multilocus, whole genome)
What is a problem with coagulase negative Staphylococci?
Contaminate blood cultures
Device associated infections (lines, prostheses)
Examples of coagulase negative staphylococci
S. epidermidis, S.saprophyticus, S.lugdunensis
What are coagulase negative Staphylococci resistant to?
Vancomycin
What does S.saprophyticus cause? How to treat?
UTI in sexually active young women
Co-trimoxazole
What to assess for S.lugdunensis ? What is the flora?
Endocarditis as it behaves like S.aureus
Perineal flora
