| ID | ● Clustered GPC (Tend to divide in 3 planes) - DDx: Staph aureus ● Catalase pos / Coag neg / DNAse neg/variable ● Normally identified by biochemistry pattern (VITEK2, API) or MALDI-TOF | | --- | --- | | Clinical syndromes | Low pathogenicity ● OI / Prosthetic material infection

● Pathogenicity caused by:

• 60%: S.epidermidis
• 15%: S.hominis
• 10%: S.haemolyticus
• S.capitis
• S.saprophyticus | | Lab ID | Coagulase POSITIVE • Staph aureus (has Protein A, Clumping Factor, and Capsule 5 / 8 proteins - all induce coagulation) • Clumping factor +: S.schleiferi, S.lugdunensis (NB: S.lugdunensis has bound coagulase only, which doesn’t diffuse into media, so is slide + but tube -).
  • Capsule 8 +: S.hominis, S.haemolyticus

• There are also ‘animal versions’ of S.aureus:

• S.intermedius (canine)
• S.delphini
• S.pseudintermedius
• S.hyicus (Coag variable)

Coagulase NEGATIVE

Novobiocin-Res: This is a lab antibiotic used to identify S.saprophyticus from other CoNS. DDx: • S.saprophyticus (causes UTI in young women; Rx for 7d) • DDx: S.cohnii, S.sciuri, S.xylosis

Novobiocin-Sens: • Epidermidis group (most pathogenic):

• S.epidermidis
• S.hominis
• S.haemolyticus
• S.capitis
• S.warneri
• S.simulans • Caprae • Auricularis • Pasteuri • Saccharolyticus (NB: Anaerobic) | | Rx | ● Beta-lactams mostly not useful ● Glycopeptides:
• Vancomycin preferable
• Teico: Variable MICs - check first ● Linezolid ● Cotrimoxazole ● Daptomycin (unless LRTI) ● Other: Gentamicin, Macrolide

Particular Spp: ● SHAE: Resistant normally to Glycopeptides, Gent, Macrolide ● SSAP: Rx UTI with 7d Trimethoprim, Nitrofurantoin, Quinolone | | AMR | Tend to develop biofilms also → easy colonisation of plastic

Beta-lactam: • 90% CoNS have BlaZ penicillinase • 80R% CoNS have MecA gene → PBP2a

Vancomycin (NB: Esp. S.haemolyticus): • VanA • Peptidoglycan hyperproduction |

Got a correction for the above? email [email protected] or tweet us @IDiots_pod

Feel like giving back? Donations of caffeine gratefully received! https://www.buymeacoffee.com/idiotspod

Old prep note available here:

03_Coag-neg Staph.docx