Detection of methicillin resistance in Staphylococcus aureus isolated from pediatric patients: is the cefoxitin disk diffusion test accurate enough?

The MRSA-Screen test (Denka Seiken Co., Ltd., Tokyo, Japan), consisting of a slide latex agglutination kit that detects PBP 2a with a monoclonal antibody, was blindly compared to the oxacillin disk diffusion test, the oxacillin-salt agar screen, and PCR of themecA gene for the detection of methicillin resistance inStaphylococcus aureus. A total of 120 methicillin-susceptible S. aureus (MSSA) and 80 methicillin-resistant S. aureus (MRSA) isolates, defined by the absence or presence of the mecA gene, respectively, were tested. The MRSA-Screen test, the oxacillin disk diffusion test, and the oxacillin-salt agar screening test showed sensitivities of 100, 61.3, and 82.5% and specificities of 99.2, 96.7, and 98.3%, respectively. We conclude that the MRSA-Screen is a very accurate, reliable, and fast test (15 min) for differentiation of MRSA from MSSA colonies on agar plates.

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Evaluation of a cefoxitin disk diffusion test for the detection of mecA-positive methicillin-resistant Staphylococcus saprophyticus

International Journal of Antimicrobial Agents ◽

10.1016/j.ijantimicag.2006.01.009 ◽

2006 ◽

Vol 27 (6) ◽

pp. 500-504 ◽

Cited By ~ 16

Author(s):

M HIGASHIDE ◽

M KURODA ◽

S OHKAWA ◽

T OHTA

Keyword(s):

Disk Diffusion ◽

Diffusion Test ◽

Disk Diffusion Test ◽

Methicillin Resistant ◽

Staphylococcus Saprophyticus ◽

Cefoxitin Disk ◽

Cefoxitin Disk Diffusion

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Comparison of Different Phenotypic Approaches To Screen and Detect mecC-Harboring Methicillin-Resistant Staphylococcus aureus

Journal of Clinical Microbiology ◽

10.1128/jcm.00826-17 ◽

2017 ◽

Vol 56 (1) ◽

Cited By ~ 13

Author(s):

André Kriegeskorte ◽

Evgeny A. Idelevich ◽

Andreas Schlattmann ◽

Franziska Layer ◽

Birgit Strommenger ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Susceptibility Testing ◽

Disk Diffusion ◽

Broth Microdilution ◽

Disk Diffusion Test ◽

Methicillin Resistant ◽

Content Type ◽

Vitek 2 ◽

Cefoxitin Disk ◽

Cefoxitin Disk Diffusion

ABSTRACT Similar to mecA, mecC confers resistance against beta-lactams, leading to the phenotype of methicillin-resistant Staphylococcus aureus (MRSA). However, mecC-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 mecC-positive MRSA isolates. A well-characterized collection of mecC-positive S. aureus isolates (n = 111) was used for evaluation. Routinely used approaches were studied to determine their suitability to correctly identify mecC-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 mecC-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 mecC 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 mecC-harboring MRSA. The AST systems showed false-negative results with varying numbers, misidentifying mecC-harboring MRSA as methicillin-susceptible S. aureus. This study underlines cefoxitin's status as the superior surrogate mecC-positive MRSA marker.

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