Emergence of HA-MRSA Associated Staphylococcal Cassette Chromosome mec (SCCmec) Elements Spillover to LA-MRSA

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) once confined to hospitals (HA-MRSA), in the last two decades, have emerged in the community in people with no exposure to hospital and also in livestock animals, referred to as community-associated (CA-) and livestock-associated (LA-) MRSA, respectively. Prevention of the dissemination of MRSA requires better knowledge of its distribution and transmission. The study aims to investigate samples from different animal farms and veterinary clinics for identification and typing of MRSA circulating among different farm animals. Phenotypic and genetic characteristics were evaluated based on morpho-cultural and biochemical properties and PCR amplification of nuc genes. Methicillin resistance was assessed on ORSAB media and PCR amplification of methicillin resistance mecA gene. SCCmec typing was performed by multiplex PCR to assess the epidemiological relationship between the isolates. Of the 406 samples, 72 confirmed the presence of S. aureus. Among S. aureus isolates, based on PCR amplification of mecA gene, 15 were identified as LA-MRSA. Majority of the LA-MRSA were found to be SCCmec type III with two isolates each from cattle and pig showed presence of both type I and III. The finding suggests the spillover of the SCCmec type III into livestock and emergence of new clones possessing both type I and III elements.