Prevalence of Inducible Clindamycin Resistance in Staphylococcus: A Study from a Rural Teaching Tertiary Care Hospital in Southern Haryana

Abstract

Introduction: Clindamycin is the most commonly prescribed Macrolides, Lincosamides and Streptogramin-B (MLSB) antibiotics to treat staphylococcal infections. It has excellent pharmacokinetic properties. Staphylococcus species shows either constitutive (MLSBc) or inducible (MLSBi) clindamycin resistance. Routine D-test recommended by Clinical Laboratory and Standard Institute (CLSI) can detect MLSBi phenotype and prevent treatment failure. Aim: To identify inducible clindamycin resistance in Staphylococci in a rural teaching Tertiary Care Hospital. Materials and Methods: It was a prospective, cross-sectional study. The clinical samples were cultured on blood agar and MacConkey agar. Staphylococcus isolates were identified based on their colony characteristics, gram stain and standard biochemical test. Antimicrobial susceptibility test was performed by Kirby Bauer’s disc diffusion method. To detect Methicillin resistance Cefoxitin disc (30 μg) was used. The isolates that were Erythromycin resistant and Clindamycin sensitive were further subjected to D test. CLSI 2019 guidelines were followed for performing the tests and its interpretation. Epi-info (version 7.2.3.1) Centre for Disease Control and Prevention (CDC), Atlanta, Georgia was used to analyse the data and interpretation of the results. Results: Total 150 Staphylococci were isolated from different samples. Staphylococcus aureus were 70% and Coagulase negative Staphylococcus (CoNS) were 30%. Pus was the most common specimen from which 43% Staphylococci was isolated. Sensitivity to vancomycin and linezolid were 100%. Staphylococcus aureus (38%) and CoNS (33%) were Methicillin resistant. Overall (63%) of staphylococcus isolates were resistant to erythromycin. The different susceptibility patterns to clindamycin in both Staphylococcus aureus and CoNS were noted. MLSBc phenotype was most prevalent (37.3%) followed by MS (13.4%) and MLSBi (12%) among erythromycin resistant Staphylococcus isolate. Sensitive (S) phenotype was detected in 56 (37%). MLSBi was more frequent in Methicillin Resistant Staphylococcus aureus (MRSA) (23%) and MRCoNS (27%) than in MSSA (5%) and MSCoNS (7%). Conclusion: D-test should be performed routinely to avoid false susceptible results leading to treatment failure.

Keywords

• disc approximation test
• macrolides
• inducible macrolides
• lincosamides
• streptogramin-b