Phenotypic Detection of Constitutive and Inducible Clindamycin Resistance among Clinical Isolates of Methicillin-resistant Staphylococcus aureus in A Tertiary Care Hospital in North India: A Cross-sectional Study

Staphylococcus aureus is the microbe implicated in the causation of numerous nosocomial and community-acquired ailments. Physicians have been facing enormous challenges day by day while treating methicillin-resistant Staphylococcus aureus (MRSA) efficiently because it shows extensive resistance to wide number of antibiotics. MRSA is frequently treated using antibiotics like macrolide-lincosamide-streptogramin B. Clindamycin is a useful alternative drug. Nevertheless, inducible resistance to clindamycin cannot be detected by standard in vitro sensitivity tests. The aim of the study was to identify MRSA isolates from clinical samples from a tertiary care centre in North India that possessed both constitutive as well as inducible clindamycin resistance. This is a one year (July 2023-June 2024) cross-sectional study carried out in the Department of Microbiology of Maharaja Agrasen Medical College, Agroha (Hisar). 1554 pus samples were collected, processed and antibiotic susceptibility was assessed using disk diffusion method. Cefoxitin disk was utilised for identification of the isolates as MRSA and by employing D-test, inducible clindamycin resistance was identified. S. aureus was isolated in 234 samples, of which 182 (78%) were MRSA and 52 (22%) were MSSA. Among MRSA strains, 36.2% showed inducible clindamycin resistance, 6.6% showed constitutive phenotype and 31.9% showed MS phenotype. It should be emphasized that it is possible to successfully cure MRSA infections using clindamycin but only after the simple and affordable D-test is employed in a bid to rule out inducible clindamycin resistance. Therefore, to avert unsuccessful therapy in MRSA infections, D-test should be carried out on a regular basis.