Novel strategies for rapid identification and susceptibility testing of MRSA

ABSTRACT

Introduction

Methicillin-resistant Staphylococcus aureus (MRSA) is associated with adverse clinical outcomes and increased morbidity, mortality, length of hospital stay, and health-care costs. Rapid diagnosis of MRSA infections has been associated with positive impact on clinical outcomes.

Areas covered

We searched relevant papers in PubMed for the last 10 years. In major papers, we scanned the bibliographies to ensure that important articles were included. This review describes screening and diagnostic test methods for MRSA and their analytical performances with a focus on rapid molecular-based assays including those that are on the horizon. Future novel technologies will allow more rapid detection of phenotypic resistance. In the case of whole-genome sequencing, detection of mutations may predict resistance, transmission, and virulence.

Expert opinion

Currently there are many diagnostic options for the detection of MRSA in surveillance and clinical samples. In general, these are highly accurate and have resulted in improvements in targeted management and reduction in hospital or intensive care unit length of stay for both MSSA and MRSA. Impact on mortality has been variable. Promising novel technologies will not only accurately identify pathogens and detect their resistance markers but will allow discovery of virulence determinants that might further affect patient management.

KEYWORDS:

• mecA
• mecC
• MRSA
• penicillin-binding proteins
• phenotype
• molecular
• resistance
• syndromic panels
• susceptibility testing
• whole-genome sequencing

Article highlights

• Methicillin-resistant Staphylococcus aureus (MRSA) remains a formidable pathogen that continues to evolve.

• Several mechanisms are responsible for beta-lactam resistance including altered penicillin-binding proteins (pbp) encoded by mec A and mec C genes, hyperproduction of β-lactamase, and mutations in pbp genes.

• To contain the spread of MRSA, various chromogenic culture-based methods and molecular assays have been implemented to screen patients, followed by decolonization of those individuals found to be positive.

• Susceptibility testing methods utilize both oxacillin and cefoxitin results in algorithms to predict mec A and mec C mediated resistance. More rapid phenotypic methods (results in 4–6 h) are in development.

• A large number of multiplex molecular platforms for direct detection of susceptible S. aureus and MRSA in clinical samples including positive blood cultures, lower respiratory secretions, skin, and skin structure specimens as well as joints are available; most do an excellent job of detecting this pathogen.

• Whole-genome sequencing has become the method of choice for strain characterization of S. aureus for epidemiological purposes although data analysis and interpretation still require standardization.

Declaration of interest

K Carroll has received research funding paid to her institution from Accelerate Diagnostics, Inc., BD Diagnostics, Inc., Curetis Diagnostics, Inc., GenMark, Inc., MeMed, Inc. Dr. Carroll is on the Scientific Advisory Board for Pattern Biosciences, Inc. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer disclosures

A reviewer on this manuscript has disclosed that they have served as a paid consultant for GSK and for Baxter within the past 3 years. The reviewer is not currently serving as a consultant for any profit-making organization. Peer reviewers on this manuscript have no other relevant financial or other relationships to disclose.

Additional information

Funding

This paper was not funded.