Abstract

Clindamycin is commonly used in treatment of erythromycin resistant Staphylococcus aureus causing skin and soft tissue infections. In vitro routine tests for clindamycin susceptibility may fail to detect inducible clindamycin resistance due to ‘erm’ genes resulting in treatment failure thus necessitating the need to detect such resistance by a rapid method. In the era of automation, vitek-2 system provides a panel for detection of inducible clindamycin resistance with conjunction of other antimicrobial susceptibility testing. The present study evaluated the performance of a vitek-2 card for detection of inducible clindamycin resistance in a tertiary care hospital. Non-duplicate clinical isolates of hundred S. aureus were obtained from various clinical samples. Antimicrobial susceptibility testing was carried out, including detection of clindamycin resistance and methicillin resistance pattern by vitek-2 identification and antimicrobial susceptibility testing (ID/AST) system by using AST-GP67 card. The results were compared to those of D-test as per CLSI guidelines on erythromycin resistant isolates. EPI INFO software, Licensed by CDC Atlanta was used for analysis of data. The sensitivity and specificity for the vitek-2 card was 95.4 and 100%, respectively in comparism to disk approximation test (D-test),. The performance of vitek-2 card was 100% specific and rapid for detection of inducible clindamycin resistance with other antimicrobial susceptibility results.

Key words: Automated system, constitutive macrolide-lincosamide-streptogramin B (MLS _B) phenotype, inducible MLS_B phenotype, methicillin resistance Staphylococcus aureus (MRSA), msrA gene (MS phenotype).