Indian Journal of Microbiology Research

Antibiotic susceptibility pattern among clinical isolates of staphylococcus aureus with special reference to vancomycin

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Author Details: Usha M. G,Shwetha D C*

Volume : 5

Issue : 4

Online ISSN : 2394-5478

Print ISSN : 2394-546X

Article First Page : 488

Article End Page : 491


Introduction: Staphylococcus is a major pathogen of community and hospital acquired infections. Vancomycin is used in MRSA caused infections. Emergence of VISA and VRSA has been of great concern in clinical aspects.
Materials and Methods: All clinical samples were processed in the laboratory according to standard procedure. Inoculated plates were incubated at 37? C for 24-48 hours. Only S. aureus isolates were included in the present study. Antibiotic susceptibility testing was done by Kirby-Bauer disc diffusion method using a panel of drugs. Cefoxitin disc was used to identify methicillin resistance. The MIC of vancomycin for MRSA isolates was carried out by Agar dilution method and E-test according to standard methods. Heteroresistance to vancomycin was detected by using BHI screen agar.
Results: 190 S. aureus were isolated from various clinical samples. Most of the isolates were resistant to amoxyclav (96.2%) followed by ciprofloxacin (84.2%), erythromycin (33.2%), Clindamycin (31.2%), Cotrimoxazole (14.6%), Teicoplanin (4.2%), Mupirocin (2.1%) and none of the isolates were resistant to linezolid. Out of 190 S. aureus isolates, 97 (51.1%) were identified as MRSA. None of the isolates were resistant to vancomycin by agar dilution method and E-test method. Four out of 97 (4.1%) MRSA isolates showed intermediate susceptibility to vancomycin. Among the isolates with MIC of 2µg/ml, 5 (19.2%) showed heteroresistance to vancomycin by BHI screen agar method.
Conclusion: Rapid identification of patients harboring VRSA, VISA or hVISA and adherence to infection control protocols are very important in controlling the dissemination of these pathogens.

Keywords: MRSA, VISA, VRSA, Heterointermediate resistant Staphylococcus aureus (hVISA), Agar dilution method, E-test.

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