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Antimicrobial susceptibility of Staphylococcus capitis from two Scandinavian hospitals

Abstract number: P935

Objective: The aim of the study was to examine the antimicrobial susceptibility of clinical Staphylococcus capitis isolates from one Norwegian and one Swedish hospital.

Methods: A total of 54 clinical S. capitis isolates, 22 Norwegian and 32 Swedish, were identified by standard methods and examined for susceptibility to 15 antibiotics using agar disk diffusion (n = 11) and Etest (n = 4). Breakpoints applied were defined by the Norwegian Working Group for Antibiotics except for vancomycin (VA) and teicoplanin (TP) for which EUCAST breakpoints were used. Inducible clindamycin (CM) resistance was examined by double disk diffusion, and oxacillin (OX) resistance by mecA PCR. Screening for glycopeptide resistance was done by Etest macro method, brain heart infusion agar supplemented with VA 6 mg/L or TP 5 mg/L and Mueller-Hinton agar with TP 5 mg/L. Molecular typing was done by PFGE.

Results: Rates of reduced susceptibility among the Norwegian isolates were: chloramphenicol 4.5%, CM 36.4%, erythromycin 36.4%, fusidic acid 13.6%, gentamicin (GM) 40.9%, norfloxacin 31.8%, OX 50%, tetracycline 13.6%, co-trimoxazole 9.1%, and VA 13.6%. In the Swedish isolates reduced susceptibility was detected to the following antibiotics: GM 100%, OX 100%, TP 75%, and VA 90.6%. All isolates from both hospitals were susceptible to linezolid, rifampicin, tigecycline and quinupristin-dalfopristin. A positive glycopeptide resistance screening result was obtained in 78.1%-100% of the Swedish and 0–45.5% of the Norwegian isolates depending on the method used. Divergent results were observed between different glycopeptide resistance screening methods in 16 of the isolates. The Norwegian isolates showed considerable heterogeneity both with respect to antimicrobial susceptibility (16 different profiles) and genotype (16 PFGE patterns). In contrast, a high degree of homogeneity was observed with only three different susceptibility profiles and PFGE patterns in the Swedish collection of isolates.

Conclusion: The S. capitis strains studied showed considerable heterogeneity in antimicrobial susceptibility, but were uniformly susceptible to four of the drugs tested. Reduced susceptibility to vancomycin was detected in isolates from both hospitals. Discrepant results were observed between different glycopeptide resistance screening methods. Species specific antimicrobial susceptibility data for a larger collection of epidemiologically unrelated S. capitis strains are warranted.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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