Avaliação do papel de Stomoxys calcitrans (Linnaeus, 1758) na veiculação de Escherichia coli causadora de mastite bovina e outros agentes bacterianos

Abstract

This study had the objective of evaluating the capacity of Stomoxys calcitrans fly to vehicular bacterial agents causing bovine mastitis. Just as evaluate the enterobacterian microbiota on the external surface, mouth parts and abdominal digestive tract of the stable fly. And also realize a survey of the bacterial microbiota of the cases of bovine mastitis on the visited properties. There were taken mastitis milk samples and 20 specimens of stable flies on 10 visited properties in the municipatility of Barra Mansa and Resende, Rio de Janeiro State. The collected milk was submitted to bacterial isolation in the laboratory of Bacteriology UFRRJ. Samples were subcultures on MacConkey (MC) agar, Brain-Heart Infusion agar (BHI) and Manitol-Phenol Red agar. The flies were individually washed in BHI broth, sterilized and had its mouth parts and abdominal intestinal content dissected under stereoscope microscope. These structures were macerated in BHI broth and, after 24 hours at 37 ºC, subcultured at MC agar, Agar Eosin Methilen Blue (EMB) and enriched in Sodium Tetrathionate Broth after incubation, and were subcultured in Salmonella-Shigella agar. After this stage, each isolated colony was observed for differences in morphology as size and pigment production characteristics to be identified through biochemical specific tests. It was also realized an antimicrobial resistance test to verify to which antibiotics the isolated bacteria were sensible. When were coincidences between the enterobacterian species in the milk and on the flies evaluated segments, was realized a Random Amplified Polymorphic DNA (RAPD-PCR) as an instrument of evaluating the genetic diversity and the eletrophoretic profile similarity the bacterial subpopulations. In agreement with the obtained results, was verified that the mastitis milk had as etiological agents specially the species Staphylococcus aureus, coagulasenegative staphylococci and Escherichia coli. The antimicrobials with less resistance rate were Amoxilin-Clavulanic Acid and Norfloxacin. Regarding to the enterobacterian microbiota verified on S. calcitrans segments, Escherichia coli, Enterobacter agglomerans, Enterobacter cloacae e Salmonella spp were the most prevalent bacteria. The segment with the higher number of isolations was the external surface, with 73 (45.91%) distinct colonies isolated. The mouth parts had 46 (28.93%) colonies and the abdominal digestive tract 40 (25.16%) isolated colonies. The eletrophoretic profile similarity happened just on E. coli subpopulations on milk samples and S. calcitrans segments of the same property. This way, was possible to observe that the flies do not act as a vehicle of any bovine mastitis causative E. coli. Regarding to the identified E. coli, was verified that 13.79% were Shiga Toxin-Producing, and the genes stx1, stx2 and eae were identified. On the present study, was verified that this fly has the capacity to act as vehicle to enterobacterian, on its external surface as well as inside its body. The stable fly control may contribute to the improvement on animal productivity and sanity.