Dataset Information

Improved Detection of mecA-Mediated β-Lactam Resistance in Staphylococcus lugdunensis Using a New Oxacillin Salt Agar Screen.

ABSTRACT: Oxacillin resistance mediated by mecA in Staphylococcus lugdunensis is emerging in some geographic areas. We evaluated cefoxitin disk diffusion (DD) and a new oxacillin agar (supplemented with 2 μg/ml oxacillin and 2% sodium chloride) screen for the detection of mecA-mediated resistance in S. lugdunensis. A total of 300 consecutive, non-duplicated clinical S. lugdunensis isolates from diverse sources in Hong Kong in 2019 were tested. The categorical agreement and errors obtained between cefoxitin DD test, oxacillin agar screen and mecA PCR were analyzed. Isolates with discordant results were further tested by MIC, penicillin binding protein 2a (PBP2a) assays, population analysis and molecular typing. PCR showed that 62 isolates were mecA-positive and 238 isolates were mecA-negative. For cefoxitin DD results interpreted using S. aureus/S. lugdunensis breakpoints, the categorical agreement (CA) for two brands of Muller-Hinton agars, MH-II (Becton Dickinson) and MH-E (bioMérieux) were both 96.0%; MEs were both 0%; and VMEs were 19.4 and 12.9%, respectively. The new oxacillin agar reliably differentiated mecA-positive and mecA-negative isolates (100% CA) without any ME or VME results. The 8 isolates with false susceptibility in the cefoxitin DD testing had cefoxitin and oxacillin MICs in the susceptible range. The isolates showed heterogeneous oxacillin resistance with resistant subpopulations at low frequencies. All had positive PBP2a results and were typed as sequence type 27/SCCmec V. The findings highlight the inability of cefoxitin DD and MIC tests for reliable detection of some mecA-positive S. lugdunensis isolates.

SUBMITTER: Ho PL

PROVIDER: S-EPMC8378274 | biostudies-literature | 2021

REPOSITORIES: biostudies-literature

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Improved Detection of mecA-Mediated β-Lactam Resistance in Staphylococcus lugdunensis Using a New Oxacillin Salt Agar Screen.

Ho Pak-Leung PL Law Ying-Hang YH Liu Melissa Chun-Jiao MC Lau Andes A Tong Man-Ki MK Chow Kin-Hung KH Wu Alan Ka-Lun AK Tse Cindy Wing-Sze CW Cheng Vincent Chi-Chung VC Que Tak-Lun TL

Frontiers in microbiology 20210806

Oxacillin resistance mediated by mecA in Staphylococcus lugdunensis is emerging in some geographic areas. We evaluated cefoxitin disk diffusion (DD) and a new oxacillin agar (supplemented with 2 μg/ml oxacillin and 2% sodium chloride) screen for the detection of mecA-mediated resistance in S. lugdunensis. A total of 300 consecutive, non-duplicated clinical S. lugdunensis isolates from diverse sources in Hong Kong in 2019 were tested. The categorical agreement a ...[more]

PMID: 34421864

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Project description:Antimicrobial susceptibility results from broth microdilution MIC testing of 993 Staphylococcus lugdunensis isolates recovered from patients at a tertiary care medical center from 2008 to 2015 were reviewed. Ninety-two oxacillin-susceptible isolates were selected to assess the accuracy of penicillin MIC testing, the penicillin disk diffusion test, and three β-lactamase tests, including the cefoxitin-induced nitrocefin test, penicillin cloverleaf assay, and penicillin disk zone edge test. The results of all phenotypic tests were compared to the results of blaZ PCR. The medical records of 62 patients from whom S. lugdunensis was isolated, including 31 penicillin-susceptible and 31 penicillin-resistant strains, were retrospectively reviewed to evaluate the clinical significance of S. lugdunensis isolation, the antimicrobial agents prescribed, if any, and the clinical outcome. MIC testing revealed that 517/993 (52.1%) isolates were susceptible to penicillin and 946/993 (95.3%) were susceptible to oxacillin. The induced nitrocefin test was 100% sensitive and specific for the detection of β-lactamase compared to the blaZ PCR results, whereas the penicillin disk zone edge and cloverleaf tests showed sensitivities of 100% but specificities of only 9.1% and 89.1%, respectively. The penicillin MIC test had 100% categorical agreement with blaZ PCR, while penicillin disk diffusion yielded one major error. Only 3/31 patients with penicillin-susceptible isolates were treated with a penicillin family antimicrobial. The majority of cases were treated with other β-lactams, trimethoprim-sulfamethoxazole, or vancomycin. These data indicate that nearly all isolates of S. lugdunensis are susceptible to narrow-spectrum antimicrobial agents. Clinical laboratories in areas with resistance levels similar to those described here can help promote the use of these agents versus vancomycin by effectively designing their antimicrobial susceptibility reports to convey this message.

Dataset Information

Improved Detection of mecA-Mediated β-Lactam Resistance in Staphylococcus lugdunensis Using a New Oxacillin Salt Agar Screen.

Publications

Improved Detection of <i>mecA</i>-Mediated β-Lactam Resistance in <i>Staphylococcus lugdunensis</i> Using a New Oxacillin Salt Agar Screen.

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