Clinical and Microbiological Aspects of β-lactam Resistance in Staphylococcus lugdunensis.

McHardy, IH; Veltman, J; Hindler, J; Bruxvoort, K; Carvalho, MM; Humphries, RM; (2016) Clinical and Microbiological Aspects of β-lactam Resistance in Staphylococcus lugdunensis. Journal of clinical microbiology. ISSN 0095-1137 DOI:

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Antimicrobial susceptibility results from broth microdilution MIC testing of 993 S. lugdunensis isolates recovered from patients at a tertiary care medical center from 2008-2015 were reviewed. Ninety-two oxacillin-susceptible isolates were selected to assess the accuracy of penicillin MIC, penicillin disk diffusion and three β-lactamase tests, including the cefoxitin-induced nitrocefin test, penicillin cloverleaf assay and penicillin disk zone-edge test. Results of all phenotypic tests were compared to blaZ PCR. 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, antimicrobial agents prescribed, if any, and clinical outcome.MIC testing revealed 517/993 (52.1%) isolates were susceptible to penicillin, and 946/993 (95.3%) were susceptible to oxacillin. Induced-nitrocefin test was 100% sensitive and specific for the detection of β-lactamase as compared to blaZ PCR, whereas the penicillin disk zone-edge and cloverleaf tests showed sensitivities of 100% but specificities of only 9.1% and 89.1%, respectively. Penicillin MIC 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 similar resistance levels described here can help promote use of these agents versus vancomycin by effectively designing their antimicrobial susceptibility reports to convey this message.

Item Type: Article
Faculty and Department: Faculty of Public Health and Policy > Dept of Global Health and Development
PubMed ID: 27927926
Web of Science ID: 393617300029


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