VANCOMYCIN RESISTANT STAPHYLOCOCCUS AUREUS FROM CLINICAL ISOLATES AND ANTIBIOTIC SUSCEPTIBILITY PATTERN IN BENIN CITY, EDO STATE, NIGERIA

ABSTRACT

Staphylococcus aureus is one of the most common causes of bloodstream, skin, surgical site, wound and nosocomial infections as well as pneumonia. The increase in the prevalence and endemicity of methicillin resistant Staphylococcus aureus (MRSA) led to frequent use of vancomycin which has led to emergence of strains of vancomycin resistant Staphylococcus aureus (VRSA). This study was aimed at determining vancomycin resistance among clinical isolates in Benin City, Edo state, Nigeria. A total of 400 clinical isolates of Staphylococcus aureus from different specimens were employed for this study. The isolates were identified with the conventional methods and antibiotic susceptibility tests were performed using Kirby-Bauer disc diffusion method according to performance standards of Clinical and Laboratory Standard Institute guidelines. Methicillin resistance was detected using cefoxitin 30µg disc. Vancomycin resistance was done using the minimum inhibitory concentration test macro broth dilution method. The data obtained were analyzed with Chi square (X²) test and odd ratio analysis using the statistical software INSTAT® (Graphpad Inc., La Jolla, CA, USA).The overall prevalence of methicillin resistant Staphylococcus aureus (MRSA) was 32.25%. The result of the MIC for vancomycin showed that 18 isolates had MIC of ≥4µg/ml. The prevalence of vancomycin resistant Staphylococcus aureus (VRSA) was 4.5%, while the prevalence of VRSA among MRSA isolates was 14.0%. There was no significant association between inpatients and outpatients and prevalence rate of MRSA and VRSA respectively (P=0.4585 and P=0.9212 respectively). Participants within the age bracket of ≤1-10years had the highest prevalence of MRSA (42.2%) and VRSA (12.5%). There was a significant association between the age of participants and prevalence rate of VRSA. (P= 0.0438). The highest prevalence of VRSA (33.3%) was recorded among isolates from catheter tip while wound swab recorded lowest prevalence (3.0%). There was a very significant association between nature of specimen and prevalence rate of VRSA isolates (P= 0.0036). Augmentin and Piperacillin/Tazobactam was found to be the most effective antibiotics among the antibiotics used against Staphylococcus aureus, MRSA and VRSA. The prudent use of methicillin and vancomycin and continuous surveillance susceptibility testing and screening is advocated.