Study of Antimicrobial Susceptibility of Staphylococcus Aureus to Pristinamycin by Disc Diffusion Method and MIC by E Test

Abstract

Background: Staphylococcus aureus is a dangerous pathogen for both community-acquired aswell as hospital- associated infections. It has acquired resistance to most of the antimicrobials that are currently available. The most notable example was the emergence of MRSA and VRSA. Pristinamycin, a streptogramin, is a drug which is used for the treatment of VISA and VRSA. It is used orally and topically for the treatment of cutaneous, bone, and other infections. In India, resistance to streptogramins/pristinamycin is being reported. Materials and methods: A hospital based cross sectional study was carried out for a period between January 2015 to June 2017 in the Microbiology Diagnostic Laboratory at Government Medical College, Nagpur. Staphylococcus aureus isolates obtained from various clinical specimens were selected for the study. Antimicrobial susceptibility testing was performed as per the CLSI guidelines (2016) by modified Kirby Bauer method. 9,10 Mueller-Hinton Commercially available antibiotic disc with proper diameter and potency were used. Pristinamycin (15 μg)disc was used. Results: In this study, MRSA was found to be 46.78% and Methicillin Sensitive S. aureus (MSSA) was found to be 53.31%. In our study, we found 18 (13.43%) MRSA isolates were resistant to pristinamycin. ristinamycin resistance detection by disc diffusion method and E strip was found to be statistically significant. Conclusion: Owing to erroneously more false positive results with disc diffusion method for pristinamycin, MIC determination should be done for these isolates. Pristinamycin can be used as an alternative to vancomycin and linezolid in MRSA and VRSA.