Original Research Article
Year: 2017 | Month: January | Volume: 7 | Issue: 1 | Pages: 63-67
Vancomycin Resistance among Methicillin Resistant Staphylococcus Aureus Isolates From Tertiary Care Hospital
Thakar V1, Sahu A2, Lahiri K.K3, Modak M4
1Asst Prof, 2Resident, 3Prof & Head, 4Prof,
Department of Microbiology, Bharati Medical College & Hospital, Pune.
Corresponding Author: Thakar V
ABSTRACT
Background: Staphylococcus aureus is one of the most common causes of nosocomial infections. Vancomycin is the drug of choice to treat infections caused by MRSA.
Objectives: The study determines Vancomycin MIC of MRSA strains by both agar dilution and Vitek methods. Presence of VAN a gene was also determined.
Materials and Methods: Study was conducted from April 2015-March 2016.A total 70 Staphylococcus aureus strains were included. Methicillin resistance was determined by using Cefoxitin disc (30ug) as per CLSI guidelines. Vancomycin resistance was detected by both agar dilution and Vitek methods. PCR was done to determine presence of VAN A gene among VISA strains.
Results: Among 70 S.aureus strains, 40 (57%) strains were methicillin resistant. Maximum MRSA strains (55%) were isolated from pus samples. 6 VISA (Vancomycin intermediate S. aureus strains) strains were detected by agar dilution method. Vitek was able to detect 3 VISA strains. All VISA strains were sensitive to Rifampicin and Linezolid by disc diffusion method. All VISA strains were negative for VAN A gene by PCR.
Conclusion: Disc diffusion method misclassifies vancomycin intermediate isolates as fully susceptible strains. Clinical laboratories must perform MIC method to correctly identify VISA strains and avoid treatment failure.
Key words: MRSA, VISA, MIC.