Prevalence of Clindamycin resistance among Staphylococcus aureus in a tertiary care hospital in South India

Abstract

Background: Staphylococcus aureus, a pyogenic bacterium, causes a wide spectrum of diseases, ranging from minor skin infections to fatal necrotizing pneumonia. The emergence and spread of MRSA (Methicillin Resistant Staphylococcus aureus), VISA (Vancomycin Intermediate Staphylococcus aureus) and VRSA (Vancomycin Resistant Staphylococcus aureus) has left us with very few antibiotics to treat Staphylococcal infections. Clindamycin is the most important antibiotic to treat infections with Methicillin Resistant Staphylococcus aureus (MRSA). In vitro routine diagnostic tests for Clindamycin susceptibility fail to detect inducible Clindamycin resistance due to erm genes resulting in treatment failures and Clindamycin sensitive strains possess msr gene. Such resistance is detected by phenotypic methods like D – test and Agar dilution method and genotypic methods like PCR detect the ermA, ermC and msrA gene. Methods: A total of 200 Staphylococus aureus isolates from various clinical samples were subjected to study by D - Test and Agar Dilution as per CLSI guidelines and gene detection was done by PCR. Result: Among the 200 Staphylococcus aureus isolates, 103 (51.5%) were erythromycin resistant. Out of which, 72 (69.9%) were MRSA and 31 (30.1%) were MSSA. Among the 72 MRSA isolates 30 (41.7%) were iMLSB phenotype, 17 (23.6%) were cMLSB phenotype and 25 (34.7%) were MS phenotype. Among the 31 (30.1%) MSSA, 14 (45.3%) were iMLSB phenotype, 15 (48.3%) were MS phenotype and 2 (6.4%) were cMLSB phenotype. Among the 63 (31.5%) Clindamycin resistant isolates 43 (68.2%) showed the presence of ermA gene and 20 (31.2%) had ermC gene. Among the 40 MS phenotype, 36 (90%) showed msrA gene. Conclusion: Keeping the mode of action, adverse reactions and pharmacokinetics of certain antibiotics like Vancomycin in mind, Clindamycin should be preferred as the drug of choice for the treatment of severe and resistant Staphyloccous aureus infections. Key Words: Inducible Clindamycin Resistanc