Minimum inhibitory concentration of vancomycin to methicillin resistant Staphylococcus aureus isolated from different clinical samples at a tertiary care hospital in Nepal.

Arjun Ojha Kshetry,Binod Lekhak,Shambhu Kumar Upadhaya,Bijendra R Raghubanshi,Asia Poudel,Raju Bhandari,Narayan Dutt Pant,Krishma Laxmi Shrestha,Sabita Khatri

doi:10.1186/s13756-016-0126-3

Abstract

BackgroundMethicillin resistant Staphylococcus aureus (MRSA) has evolved as a serious threat to public health. It has capability to cause infections not only in health care settings but also in community. Due to the multidrug resistance shown by MRSA, there are limited treatment options for the infections caused by this superbug. Vancomycin is used as the drug of choice for the treatment of infections caused by MRSA. Different studies from all around the world have documented the emergence of strains of S. aureus those are intermediate sensitive or resistant to vancomycin. And recently, there have been reports of reduced susceptibility of MRSA to vancomycin, from Nepal also. So the main purpose of this study was to determine the minimum inhibitory concentration (MIC) of vancomycin to methicillin resistant S. aureus isolated from different clinical specimens.MethodsTotal 125 strains of S. aureus isolated from different clinical samples at KIST Medical College and Teaching Hospital, Lalitpur, Nepal from Nov 2012 to June 2013, were subjected to MRSA detection by cefoxitin disc diffusion method. The minimum inhibitory concentrations of vancomycin to confirmed MRSA strains were determined by agar dilution method. Yellow colored colonies in mannitol salt agar, which were gram positive cocci, catalase positive and coagulase positive were confirmed to be S. aureus.ResultsAmong, total 125 S. aureus strains isolated; 47(37.6%) were MRSA. Minimum inhibitory concentrations of vancomycin to the strains of MRSA ranged from 0.125 μg/ml to 1 μg/ml.ConclusionFrom our findings we concluded that the rate of isolation of MRSA among all the strains of S. aureus isolated from clinical samples was very high. However, none of the MRSA strains were found to be vancomycin intermediate-sensitive or vancomycin-resistant.

Highlights

Methicillin resistant Staphylococcus aureus (MRSA) has evolved as a serious threat to public health
The study was conducted at KIST Medical College and Teaching Hospital, Lalitpur, Nepal from Nov 2012 to June 2013, using the total of 125 strains of Staphylococcus aureus isolated from different clinical samples
The strains showing diameter of zone of inhibition of ≤ mm were considered as methicillin resistant S. aureus (MRSA) while those with diameter of zone of inhibition of ≥ mm were identified as methicillin susceptible S. aureus (MSSA) [14]

Summary

Introduction

Methicillin resistant Staphylococcus aureus (MRSA) has evolved as a serious threat to public health. Staphylococcus aureus is present as the normal flora of humans; on skin and anterior nares and up to two-third of the population is colonized by it [1]. It is a pathogenic bacterium; which may be responsible for causing a broad spectrum of diseases in hospital as well as the community and can develop drug resistance to commonly used antibiotics in short period of time [2]. Despite the development of improved surgical techniques and antibiotic prophylaxis, the infections caused by S. aureus present as a serious public health problems [6]. No strains of S. aureus are known to be intrinsically resistant to any antibiotics developed till date [7]

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