A CROSS-SECTIONAL STUDY ON PHENOTYPIC DETECTION OF METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS AND INDUCIBLE CLINDAMYCIN RESISTANCE IN A TERTIARY CARE HOSPITAL IN WESTERN INDIA

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) remains a major cause of hospital-acquired infections, with increasing concerns over resistance to clindamycin due to inducible mechanisms. Phenotypic detection of such resistance is critical for appropriate antibiotic therapy.

Objectives: To determine the prevalence of MRSA and inducible clindamycin resistance among clinical isolates of S. aureus and to compare resistance patterns between MRSA and MSSA strains in a tertiary care setting.

Methods: This cross-sectional study was conducted over eight months in a tertiary care hospital in Western India. A total of 100 S. aureus isolates from various clinical specimens were identified and tested for antibiotic susceptibility using the Kirby-Bauer disc diffusion method. MRSA detection was performed using the cefoxitin disc method, and erythromycin-resistant isolates were subjected to D-testing to detect inducible clindamycin resistance. Data were analyzed using descriptive statistics, chi-square tests, and odds ratios.

Results: MRSA was identified in 38% of isolates. Inducible clindamycin resistance (iMLSB) was detected in 30.4% of erythromycin-resistant isolates, with cMLSB in 10.7%, and MS phenotype in 26.8%. Constitutive resistance was exclusively observed in MRSA (p = 0.02). Resistance to clindamycin, erythromycin, ciprofloxacin, and gentamicin was significantly higher in MRSA compared to MSSA (p < 0.001). All isolates were susceptible to vancomycin and linezolid.

Conclusion: A high prevalence of MRSA and inducible clindamycin resistance underscores the necessity of routine phenotypic screening, particularly the D-test, for guiding effective antibiotic therapy. These findings support the need for ongoing surveillance and robust antimicrobial stewardship programs.