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Tailoring Antimicrobial Susceptibility Testing to Individual Species of Coagulase-Negative Staphylococci: Next Up,
C Paul Morris1, Patricia J Simner2
1Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Abstract:
Accurate detection of methicillin resistance among staphylococci is vital for patient care. Methicillin resistance is most commonly mediated by acquisition of the mecA gene, which encodes an altered penicillin binding protein, PBP2a. Application of phenotypic methods to detect mecA-mediated beta-lactam resistance in staphylococci is becoming more complex as species-specific differences are identified among coagulase-negative staphylococci (CoNS). Previously, interpretative criteria and antimicrobial susceptibility testing (AST) methods specific to the CoNS group were used to evaluate Staphylococcus epidermidis A manuscript by S. N. Naccache, K. Callan, C.-A. D. Burnham, M. A. Wallace, et al. (J Clin Microbiol 57:e00961-19, 2019, https://doi.org/10.1128/JCM.00961-19) details experiments revealing that S. epidermidis, the most common clinically isolated CoNS, requires tailored use of previously described methods and interpretive criteria to reliably identify the presence of mecA-mediated methicillin resistance.
Insights
Accurate detection of methicillin resistance in staphylococci is crucial for patient care. New findings show Staphylococcus epidermidis requires specific testing methods and criteria for reliable mecA gene detection.
Area of Science:
- Microbiology
- Clinical Diagnostics
- Antimicrobial Resistance
Background:
- Accurate detection of methicillin resistance in staphylococci is vital for effective patient care.
- Methicillin resistance is primarily mediated by the mecA gene, encoding PBP2a.
- Phenotypic detection of mecA-mediated resistance is complicated by species-specific variations in coagulase-negative staphylococci (CoNS).
Purpose of the Study:
- To evaluate the reliability of current phenotypic methods for detecting methicillin resistance in Staphylococcus epidermidis.
- To determine if species-specific interpretative criteria are necessary for Staphylococcus epidermidis.
Main Methods:
- Review of existing antimicrobial susceptibility testing (AST) methods and interpretative criteria for CoNS.
- Experimental analysis of Staphylococcus epidermidis isolates to assess mecA-mediated resistance detection.
- Comparison of results using tailored versus general CoNS criteria.
Main Results:
- Standard CoNS methods and criteria are insufficient for reliable mecA detection in Staphylococcus epidermidis.
- Staphylococcus epidermidis requires specific, tailored approaches for accurate identification of methicillin resistance.
- Species-specific differences necessitate adjusted interpretative criteria for this common CoNS.
Conclusions:
- Reliable detection of methicillin resistance in Staphylococcus epidermidis necessitates tailored antimicrobial susceptibility testing methods and interpretative criteria.
- Current generalized methods for CoNS may lead to inaccurate resistance assessments.
- Further research into species-specific diagnostics is essential for optimizing patient care and antimicrobial stewardship.
