Occurrence and Antimicrobial Susceptibility Profile of Vancomycin Resistance among Clinical Isolates of Staphylococcus aureus in Enugu Metropolis, Nigeria

Introduction: Staphylococcus aureus is a significant cause of community-acquired and healthcare-acquired infections worldwide. Methicillin-resistant Staphylococcus aureus infections have been treated with vancomycin, a last-resort antibiotic. This study aimed to investigate the occurrence of vancomycin resistance among Staphylococcus aureus isolates obtained from different clinical samples.

Materials and Methods: The study was conducted from February to August 2022 in the Microbiology Laboratory of the University of Nigeria Teaching Hospital Ituku-Ozalla, Enugu. A total of 150 Staphylococcus aureus isolates from different clinical samples were used for the study. The antimicrobial susceptibility profile was done using the Kirby-Bauer disc diffusion procedure. Methicillin resistance was detected using the cefoxitin disc diffusion technique. VRSA was confirmed using the broth dilution method.

Results: Isolates showed high resistance to cephalosporins; 100% resistance to cefixime, to cefotaxime 98.7%, to cefuroxime 93.3%, and to ceftriaxone 80%. There was also high resistance of isolates to imipenem 98.7%, Augmentin 92.2%, erythromycin, and azithromycin 81.3% and 80.0% respectively. Of the 150 isolates, 51(34.0%) were methicillin-sensitive Staphylococcus aureus (MSSA) and 99(66.0%) were MRSA. Of the 99 MRSA strains, 9 (9.1%) were vancomycin-resistant (VRSA), 24 (24.2%) were vancomycin intermediate (VISA) and 66 (66.7%) were vancomycin-sensitive (VSSA). The overall prevalence of VRSA was 6%.

Conclusion: The isolates had a high resistance to the antibiotics used in our study. The proportion of MRSA was high. A high percentage of VRSA/VISA was also detected. To prevent the further spread of VRSA, rigorous monitoring of vancomycin treatment, response, and the development of appropriate control guidelines are strongly recommended and required.