ABSTRACT
The stable fly Stomoxys calcitrans (Linnaeus, 1758) has been described as a potential spreader of infectious agents to cattle herds. Among the agents transmitted by this fly, Escherichia coli has attracted attention due to its potential to cause gastrointestinal disorders as well as environmental mastitis in dairy cows. Therefore, the aim of this study was to isolate and to assess the genetic diversity and the clonal relatedness among E. coli isolates from the milk of dairy mastitis and from stable flies anatomical sites by the Random Amplification of Polymorphic DNA (RAPD-PCR) technique. The molecular typing revealed a high degree of genetic polymorphism suggesting that these microorganisms have a non-clonal origin. Identical electrophoretic profiles were observed between E. coli isolates from different flies, different mammary quarters of the same cow and from cows on a single farm. These results reveal the circulation of the same bacterial lineages and suggest the role of the stable fly in bacterial dispersion. Considering the high pathogenic potential of this bacterial species, our findings alert to a more effective health surveillance.(AU)
A mosca dos estábulos Stomoxys calcitrans é descrita como um importante dispersor de agentes infecciosos aos bovinos. Dentre os agentes veiculados por esta mosca a bactéria Escherichia coli ganha relevância devido ao seu potencial em desenvolver alterações gastroentéricas, bem como mastite bovina ambiental. Desta forma, objetiva-se com este estudo isolar e acessar a diversidade genética e relação de clonalidade entre isolados de E. coli provenientes de casos de mastite e de moscas dos estábulos utilizando a técnica da Amplificação Randômica do DNA Polimórfico (RAPD). A tipagem molecular revelou elevado polimorfismo genético sugerindo que esses microrganismos têm origem não clonal. Perfis eletroforéticos idênticos entre si foram observados entre amostras isoladas de diferentes moscas, quartos mamários de uma mesma vaca, bem como de diferentes vacas dentro de uma mesma propriedade. Esses resultados revelam a circulação de uma mesma linhagem bacteriana e sugerem o papel da Stomoxys calcitrans na dispersão bacteriana. Considerando o elevado potencial patogênico dessa espécie bacteriana, nossos achados alertam para uma vigilância sanitária mais efetiva.(AU)
Subject(s)
Animals , Escherichia coli/isolation & purification , Mastitis, Bovine/diagnosis , Milk/microbiology , Muscidae/microbiology , Cattle/microbiology , Random Amplified Polymorphic DNA Technique/veterinaryABSTRACT
Enteroaggregative Escherichia coli (EAEC) strains have been implicated as emerging aetiological agents of diarrhoea worldwide. In the present study, 43 EAEC strains were serotyped and characterized according to random amplification of polymorphic DNA profiles, PFGE, multilocus enzyme electrophoresis (MLEE) and the presence of putative virulence genes (hly, aero, kps, fim, aggA, aafA, aggR, astA, she, aap, shf and pet). The EAEC strains consisted of a diversity of serotypes including eight O-non-typable and 35 O-typable strains arranged into 21 O : H combinations. Amplification of specific genes revealed that all strains carried at least two of the virulence sequences investigated. fim, aggR and aap were the most frequent genes in both groups studied. hly, aero and aggA sequences were more prevalent in the diarrhoeal group. kps occurred exclusively in strains isolated from symptomatic children and showed strong association with diarrhoeal disease. The molecular approaches used to investigate the relatedness among EAEC strains revealed a high degree of polymorphism, suggesting that these micro-organisms have a non-clonal origin. A closer relationship was observed among EAEC strains sharing O : H types. No significant clustering could be identified related to the virulence traits investigated; however, the she locus showed clonal distribution by MLEE typing. These results are in accordance with previous findings in revealing the conservation of particular EAEC factors, despite the high degree of diversity related to both genotypic and phenotypic markers.
