Erschienen:
American Society for Microbiology, 2018
Erschienen in:Journal of Clinical Microbiology
Sprache:
Englisch
DOI:
10.1128/jcm.00826-17
ISSN:
0095-1137;
1098-660X
Entstehung:
Anmerkungen:
Beschreibung:
<jats:title>ABSTRACT</jats:title>
<jats:p>
Similar to
<jats:italic>mecA</jats:italic>
,
<jats:italic>mecC</jats:italic>
confers resistance against beta-lactams, leading to the phenotype of methicillin-resistant
<jats:named-content content-type="genus-species">Staphylococcus aureus</jats:named-content>
(MRSA). However,
<jats:italic>mecC</jats:italic>
-harboring MRSA strains pose special difficulties in their detection. The aim of this study was to assess and compare different phenotypic systems for screening, identification, and susceptibility testing of
<jats:italic>mecC</jats:italic>
-positive MRSA isolates. A well-characterized collection of
<jats:italic>mecC</jats:italic>
-positive
<jats:named-content content-type="genus-species">S. aureus</jats:named-content>
isolates (
<jats:italic>n</jats:italic>
= 111) was used for evaluation. Routinely used approaches were studied to determine their suitability to correctly identify
<jats:italic>mecC</jats:italic>
-harboring MRSA, including three (semi)automated antimicrobial susceptibility testing (AST) systems and five selective chromogenic agar plates. Additionally, a cefoxitin disk diffusion test and an oxacillin broth microdilution assay were examined. All
<jats:italic>mecC</jats:italic>
-harboring MRSA isolates were able to grow on all chromogenic MRSA screening plates tested. Detection of these isolates in AST systems based on cefoxitin and/or oxacillin testing yielded overall positive agreements with the
<jats:italic>mecC</jats:italic>
genotype of 97.3% (MicroScan WalkAway; Siemens), 91.9% (Vitek 2; bioMérieux), and 64.9% (Phoenix, BD). The phenotypic resistance pattern most frequently observed by AST devices was “cefoxitin resistance/oxacillin susceptibility,” ranging from 54.1% (Phoenix) and 83.8% (Vitek 2) to 92.8% (WalkAway). The cefoxitin disk diffusion and oxacillin broth microdilution assays categorized 100% and 61.3% of isolates to be MRSA, respectively. The chromogenic media tested confirmed their suitability to reliably screen for
<jats:italic>mecC</jats:italic>
-harboring MRSA. The AST systems showed false-negative results with varying numbers, misidentifying
<jats:italic>mecC</jats:italic>
-harboring MRSA as methicillin-susceptible
<jats:named-content content-type="genus-species">S. aureus</jats:named-content>
. This study underlines cefoxitin's status as the superior surrogate
<jats:italic>mecC</jats:italic>
-positive MRSA marker.
</jats:p>