Evaluation of Oxacillin and Cefoxitin Disk Diffusion and Microbroth Dilution Methods for Detecting mecA-Mediated β-Lactam Resistance in Contemporary Staphylococcus epidermidis Isolates. Academic Article uri icon

Overview

abstract

  • Methicillin (β-lactam) resistance in Staphylococcus epidermidis is mediated by the mecA gene, with resistance reported to be as high as 90%. The goal of this study was to evaluate oxacillin and cefoxitin disk diffusion (DD) and broth microdilution (BMD) methods for the detection of mecA-mediated β-lactam resistance in 100 human isolates of S. epidermidis (48 mecA-positive isolates and 52 mecA negative isolates). Oxacillin DD tests using the Clinical and Laboratory Standards Institute (CLSI) M100-S28 breakpoints for S. pseudintermedius/S. schleiferi accurately differentiated mecA-positive and -negative S. epidermidis isolates, with categorical agreement (CA) of 100% and no very major errors (VMEs) or major errors (MEs) identified. Likewise, oxacillin BMD and cefoxitin DD tests using the coagulase-negative Staphylococcus species (CoNS) breakpoints were highly reliable for detecting mecA-mediated β-lactam resistance in S. epidermidis isolates. For cefoxitin DD and BMD results interpreted using S. aureus/S. lugdunensis breakpoints, the CA was 97.6% and 96.2%, respectively. There were 4.9% VMEs for cefoxitin DD with 0% MEs, and 3.6% VMEs and 3.9% MEs for cefoxitin BMD. Oxacillin BMD using S. aureus/S. lugdunensis breakpoints yielded the highest VMEs at 17.4% and 90% CA. Our findings demonstrate that oxacillin DD tests using the CLSI M100-S28 breakpoints for S. pseudintermedius/S. schleiferi and oxacillin BMD and cefoxitin DD tests using the CoNS breakpoints reliably identified mecA-mediated β-lactam resistance in S. epidermidis Using mecA PCR as the gold standard, the PBP2a SA culture colony test (Abbott Diagnostics) exhibited 100% sensitivity and specificity whereas 2 false negatives were identified using the PBP2' latex agglutination test kit (Thermo Fisher Scientific) with sensitivity and specificity of 95.8% and 100%, respectively.

publication date

  • November 22, 2019

Research

keywords

  • Anti-Bacterial Agents
  • Cefoxitin
  • Microbial Sensitivity Tests
  • Oxacillin
  • Staphylococcus epidermidis
  • beta-Lactam Resistance

Identity

PubMed Central ID

  • PMC6879287

Scopus Document Identifier

  • 85075725664

Digital Object Identifier (DOI)

  • 10.1128/JCM.39.10.3700-3702.2001

PubMed ID

  • 31462553

Additional Document Info

volume

  • 57

issue

  • 12