Similaridade genética entre cepas de microorganismos patogênicos isolados de leitarias e de aves silvestres capturadas nestes estabelecimentos

Abstract

Cows may come in contact with pathogenic microorganisms from a variety of sources, such as contaminated water, food, humans, and other animals, and can eliminate these pathogens in milk. Wild birds are found in the most diverse habitats and can easily disperse micro-organisms, whether pathogenic or not, into the environment or even transmit them to domestic and human animals, as well as contaminated by them. The objective of this study was to verify the genetic similarity between pathogenic strains isolated from feces of lactating cows, milk from these same animals, feces from wild birds captured around dairy farms and surface samples from the hand of milkers. The capture of the birds was done with mist nets, placed in strategic places in the properties. Fecal samples were obtained by inserting sterile swabs into the rectum of the cows and into the sewer of the captured birds. The milk samples were collected at the beginning of the milking and samples were taken from the hands surface of the computers during this process. The microorganisms studied were Staphylococcus aureus, Yersinia enterocolitica, Salmonella enterica, and Listeria monocytogenes. S. aureus resistance to methicillin was tested. The similarity between the molecular profiles of the isolates of the same species was verified by rep-PCR. Samples were collected at six dairy farms, yielding 88 cow feces samples and the same number of milk samples from the same cows, 11 milking hand surface samples and feces samples from 106 wild birds. S. aureus was isolated from four Turdus rufiventris and a Cyanoloxia brissonii, of which four were MRSA. Y. enterocolitica was isolated from two T. rufiventris and one Columbina picui. These microorganisms, including MRSA, were also isolated from feces and milk from lactating cows. There was no isolation of Salmonella and Listeria. In the same property, S. aureus isolated from feces of a T. rufiventris and samples of milk and feces from two cows presented identical molecular profiles, indicating the occurrence of contamination between the domestic animals and the wild birds. In the specific case of MRSA, considering the origin of the resistance developed by these strains, it can be concluded that the initial contamination started from humans or domestic animals to the wild, although these could later serve as disseminators. The results highlight the importance of milk being produced with a strict hygiene protocol, in milking parlors that do not allow animals to enter the process, that the dairy herd is constantly monitored for the pathogens present and also that the milk undergoes heat treatment before of its consumption.