Revealing inducible clindamycin resistance in methicillin-resistant S aureus: A vital diagnostic imperative for effective treatment.

Abstract

Introduction: The World Health Organization added methicillin-resistant S aureus (MRSA) to the list of "priority pathogens," given its capacity to cause life-threatening infections. Clindamycin is a preferred treatment for non-complicated S aureus-induced skin and soft tissue infections. Its good tissue penetration and oral absorption make it suitable for outpatient therapy. However, the emergence of inducible and constitutive (MLSB) resistance led to clinical challenges, primarily due to the potential oversight of inducible resistance in routine antimicrobial sensitivity testing.

Materials and methods: This cross-sectional study was conducted at a tertiary care hospital during 2020-2022. A total of 158 MRSA isolates from various clinical specimens were analyzed. The Kirby-Bauer disk diffusion method using cefoxitin disk and D-test were used to identify MRSA and detect inducible clindamycin resistance (ICR), respectively.

Results: Among the 158 MRSA isolates, 34.17% showed constitutive clindamycin resistance (MLSBc), while 22.15% displayed ICR (MLSBi). In addition, 10.13% of isolates demonstrated the MS phenotype, clindamycin, and erythromycin susceptibility, with 53 (33.54%) isolates susceptible to both antibiotics. The relative risk of clindamycin treatment failure was 7.66 times higher if the D-test was not used.

Conclusion: To prevent clindamycin treatment failures, the D-test must be implemented to detect ICR in MRSA isolate. Neglecting simple and cost-effective tests may lead to inaccurate susceptibility reporting, jeopardizing treatment success.