Automated Vitek-2 System versus D Test in Detection of Inducible Clindamycin Resistance Staphylococcus aureus

Document Type : New and original researches in the field of Microbiology.

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Department of Medical Microbiology and Immunology, Faculty of Medicine - Benha University

Abstract

Background: Macrolide, lincosamide and streptogramin type B (MLSB) antibiotics have great importance in the treatment of Staphylococcus aureus infections and existence of isolates that have the ability to resist against MLSB antibiotics is troublesome. Routine testing of staphylococcal isolates for inducible clindamycin resistance (ICR) is supported
by the Clinical Laboratory Standards Institute (CLSI). Automated system Vitek 2 offers a schedule that reveals inducible clindamycin resistance directly. it is simple and more cost-efficacious than the more terrible CLSI reference methods. Objectives: Evaluation the utility of automated vitek-2 system in detection of inducible clindamycin resistance S.
aureus compared to D zone test and detection the predominance of erm A and erm C genes among isolated strains. Methodology: 25 clinical staphylococcus aureus isolates (Erythromycin intermediate and resistant, Clindamycin susceptible) were examined for ICR both by D- test and Vitek-2 system. multiplex PCR was carried out for the isolates to
reveal ermA and ermC genes. Results: Out of the 25 isolates, ICR was detected by Vitek-2 in 11 isolates (44%). Two of the isolates were not detected by Vitek-2 but confirmed by D-test. Sensitivity, specificity, positive and negative predictive values were calculated as 85.7%, 100%, 100% and 84.6% respectively. erm C and A genes were detected in (40%) and (24%) of the studied isolates respectively. Both C and A genes were detected in (12%). Conclusion: Vitek-2 is considered a potentially reliable test for detection of ICR,further studies are advised on considerable number of isolates.

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