Prevalence and antibiotyping of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) in domestic animals in India

Highlights

• Prevalence of Staphylococcus aureus was comparatively high in domestic animals compared with previous reports.

• Susceptibility testing revealed 21 antibiotypes against 14 antimicrobial agents tested.

• Prevalence of MRSA of 57.5% (23/40) in S. aureus obtained from pyogenic clinical cases in domestic animals in India.

Abstract

Objectives

Domestic animals can serve as a reservoir for antimicrobial-resistant Staphylococcus aureus and may lead to the emergence of drug-resistant human isolates. The present study aimed to assess the prevalence and antibiotypes of S. aureus and methicillin-resistant S. aureus (MRSA) cultured from clinical pyogenic cases of domestic animals in India.

Methods

A total of 100 samples were collected during the study (August 2014 to July 2015) from different pyogenic conditions of cattle (n = 21), buffaloes (n = 63) and dogs (n = 16). Samples were processed for isolation and phenotypic identification of S. aureus. Species identification was confirmed by PCR, and all of the isolates were screened for the mecA gene. Antimicrobial susceptibility testing was performed by the disk diffusion method for 14 antimicrobial agents.

Results and conclusion

The study revealed a 40.0% prevalence of S. aureus in pyogenic clinical cases of domestic animals. The species-wise prevalence of S. aureus was 38.1% both in cattle and buffaloes and 50.0% in dogs. The study revealed 21 antibiotypes among the S. aureus isolates. The rate of resistance was highest for amoxicillin (95.0%), followed by penicillin G (82.5%). Among the 40 S. aureus isolates, 23 (57.5%) exhibited methicillin resistance and carried the mecA gene. To the best of our knowledge based on the available literature, this is the first report of its kind from this country.

Introduction

The bacterium Staphylococcus aureus is distributed worldwide and is responsible for several diseases of humans and animals ranging from mild infections to life-threatening bacteraemia [1], [2]. The bacterium naturally resides in the anterior nares of wild and domestic animals as well as humans [3]. Staphylococcus aureus is of concern because of its ability to overcome the effects of multiple antimicrobial agents and to develop drug resistance [4], [5]. More than 40 antimicrobial resistance genes (ARGs) located on plasmids and transposons have been identified [6]. These play a major role in the transfer of resistance to non-resistant bacteria of animal and human origin [6], [7]. In recent years, there has been an apparent increase in reports of antimicrobial-resistant S. aureus infections in domestic animals [6], [8]. These antimicrobial-resistant staphylococci can further act as donors of ARGs [7]. Based on the drug resistance pattern, antimicrobial-resistant S. aureus are also known as oxacillin-resistant S. aureus (ORSA), methicillin-resistant S. aureus (MRSA), glycopeptide-resistant S. aureus (GRSA), vancomycin-intermediate S. aureus (VISA) and vancomycin-resistant S. aureus (VRSA) [5], [9], [10], [11], [12]. These resistant S. aureus have been reported from almost all domestic animals in India, namely cows, dogs, horses, sheep, cats and pigs [10], [13]. Thus, continuous monitoring through ongoing surveillance and control of antimicrobial-resistant S. aureus, in particular MRSA, in domestic animals is required to avoid human infections. Hence, the present study was planned to assess the prevalence and antibiotypes of S. aureus in clinical pyogenic cases of domestic animals in India.