Methicillin resistant staphylococci associated with bovine mastitis and their zoonotic importance

Abstract

Aim: The present study was conducted to determine the zoonotic importance of methicillin resistant staphylococci associated with bovine mastitis and their potential role in transmission to animal handlers. Materials and Methods: A total of 158 milk samples from bovine mastitis cases and 126 nasal swabs from the animal handlers were sampled in and around Pondicherry (Southern India). The Presence of Staphylococcal organism was confirmed by PCR amplification using the genus specific primers and among the isolated Staphylococci; methicillin resistance was identified by genetic amplification of mec A methicillin resistant gene. Then the amplified gene from the bacteria expressing the mecA gene (PBP2a) (~2kb fragment) was further sequenced using four sets of primer pairs and aligned for determining their genetic relatedness between the sequences. Both phenotypic and genotypic analysis was carried out for the six MRS isolates (three bovine and three human) in this study. Results: Out of 158 mastitis milk samples; 96 and 19 bovine isolates were found to be positive for Staphylococcal genus specific PCR and methicillin resistant (mecA) gene PCR, respectively. Similarly, Out of 126 human nasal swabs, 64 and 13 human isolates were found to be positive for Staphylococcal genus specific PCR and mec A gene PCR, respectively. Among the 160 staphylococcal isolates (Bovine and Human origin); 51 were identified as coagulase-positive staphylococci (CPS) and remaining as coagulase-negative staphylococci (CONS). The results obtained in this study revealed the presence of many species of Staphylococci but the predominant species were Staphylococcus aureus and S. epidermidis. The Sequence analysis of the mec A gene of human isolates obtained in this study had a maximum identity (99% -100%) with the bovine isolates. Conclusion: The phenotypic and genotypic analysis carried out for the six MRS (Methicillin Resistant Staphylococci) isolates in this study were indistinguishable and epidemiologically related, which may indicate the transmission of MRS between bovine and humans. The occurrence of methicillin resistance among staphylococci isolated from cases of bovine mastitis is increasing, necessitating the periodic surveillance for antimicrobial resistance patterns of Staphylococci in order to control the spread of MRS.

Keywords

• bovine mastitis
• coagulase-negative staphylococci (CONS)
• methicillin resistant Staphylococcus aureus (MRSA)
• sequence analysis