Staphylococci, coagulase negative
MICROBIOLOGY
- Coagulase-negative staphylococci (CoNS) are aerobic, Gram-positive coccus occurring in clusters [Fig].
- Predominantly found on the skin and mucous membranes.
- Heterogeneous group
- Catalase positive but coagulase negative (S. aureus is coagulase positive).
- Major pathogens:
- S. epidermidis: colonies typically small, white-beige (about 1-2 mm in diameter).
- S. haemolyticus: colonies typically small, golden yellow (about 1-2 mm in diameter).
- S. lugdunensis: colonies are usually sticky, smooth, glossy, yellow-orange (2-4 mm).
- Perhaps the most virulent of CoNS, it behaves similarly to S. aureus.
- Over 40 recognized species of CoNS are capable of causing human disease.
- Others seen on occasion: Staphylococcus auricularis, Staphylococcus capitis, Staphylococcus hominis, S. pettenkoferi, Staphylococcus saprophyticus, and Staphylococcus simulans.
- Many strains tend to produce biofilm, allowing for adherence to medical devices.
- Susceptibility profile for CoNS. Breakpoints vary by species.
- Vancomycin (CLSI): MIC cutoffs
- Sensitive: ≤ 4 mg/L
- Intermediate: 8-16 mg/L
- Resistant: ≥ 32 mg/L
- Note: EUCAST states resistance is MIC > 4 mg/L
- Oxacillin (CLSI)
- S. epidermidis sensitive if ≤ 0.25 mg/L and Resistant if ≥ 0.5 mg/L.
- S. lugdunensis sensitive if ≤ 2 mg/L and resistant if ≥ 4 mg/L.
- Usually resistant to penicillin and typically (> 80%) to methicillin (oxacillin, nafcillin).
- mecA gene encodes for low-affinity penicillin-binding protein.
- Resistance can be heterotypic, so multiple isolates should be obtained to determine whether they are susceptible to beta-lactams, as only a minority of isolates typically express resistance phenotypes.
- Linezolid resistance is described but remains rare.
- Vancomycin (CLSI): MIC cutoffs
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Last updated: July 13, 2024
Citation
Auwaerter, Paul G. "Staphylococci, Coagulase Negative." Johns Hopkins ABX Guide, The Johns Hopkins University, 2024. Pediatrics Central, peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540517/all/Staphylococci__coagulase_negative.
Auwaerter PG. Staphylococci, coagulase negative. Johns Hopkins ABX Guide. The Johns Hopkins University; 2024. https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540517/all/Staphylococci__coagulase_negative. Accessed December 11, 2024.
Auwaerter, P. G. (2024). Staphylococci, coagulase negative. In Johns Hopkins ABX Guide. The Johns Hopkins University. https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540517/all/Staphylococci__coagulase_negative
Auwaerter PG. Staphylococci, Coagulase Negative [Internet]. In: Johns Hopkins ABX Guide. The Johns Hopkins University; 2024. [cited 2024 December 11]. Available from: https://peds.unboundmedicine.com/pedscentral/view/Johns_Hopkins_ABX_Guide/540517/all/Staphylococci__coagulase_negative.
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