Antimicrobial Susceptibility Profile of Healthcare-Associated Methicillin Resistant Staphylococcus aureus with Special Reference to Vancomycin and Ceftaroline

Purpose: Healthcare-associated Methicillin Resistant Staphylococcus aureus (HA-MRSA) infection is a major public health concern around the world. HA-MRSA strains are normally multidrug resistant and treatment options are limited. Selection of appropriate antibiotics is crucial in treatment and management of cases. The aim of the present investigation was to study the infections caused by MRSA and to determine the antimicrobial susceptibility profile with special reference to vancomycin and ceftaroline among HA-MRSA isolates. Methods & Materials: The present cross-sectional study was carried out between February 2019 and March 2020 on HA-MRSA strains isolated from clinical specimens collected from patients in four tertiary care hospital in a city in coastal Karnataka. Methicillin resistance was detected using cefoxitin disk diffusion method and antimicrobial susceptibility testing was done using Kirby-Bauer disk diffusion method. Minimum inhibitory concentration of vancomycin and ceftaroline was determined by agar dilution method and Etest respectively. MLSB phenotypes were identified using double disk diffusion (D-test). Results: Out of 220 HA-MRSA isolates 186 (84.5%) were isolated from skin and soft tissue infections. The rates of MRSA isolated from the four tertiary hospitals were 33.1%, 31.0%, 32.7% and 33.7%. Out of 220 MRSA strains isolated, 159 (72.3%) were multidrug resistant. All MRSA were susceptible to ceftaroline, linezolid, teicoplanin and vancomycin. Out of 220 HA-MRSA, 35 (15.9%) were constitutive MLSB phenotypes, 63 (28.6%) were inducible MLSB phenotypes and 88 (40.0%) were macrolide-streptogramin B phenotypes. Conclusion: All HA-MRSA isolates were susceptible to linezolid, ceftaroline and vancomycin, indicating these antibiotics have role in the treatment of infections caused by MRSA. Inducible clindamycin resistance cannot be detected by routine antimicrobial susceptibility test. D-test should be performed on MRSA isolates resistant to erythromycin and susceptible to clindamycin to detect inducible clindamycin resistance and avoid clindamycin treatment failure.