Virulence factors of Escherichia coli isolated from diarrheic calves

Abstract

One hundred seventy-three Escherichia coli strains isolated from calves from northwestern São Paulo State, having diarrhea were examined for the production of thermolabile (LT) and thermostable (ST) enterotoxins and for the presence of virulence factors associated with bovine colibacillosis. Eighty-five (49.1%) of the E.coli strains produced toxins; 53 isolates were detected as producing STa toxin, and 9 also produced LT toxin. By PCR, 23 isolates were shown to harbor only the LT-II gene. Nine (5.2%) isolates harbored Shiga toxin genes: four carried the stx2 gene, four the stx1 gene and one carried both. Three of the isolates showing stx1 also carried the eae gene. Among the E. coli isolates examined for susceptibility to 10 antimicrobial agents, resistance to cephalothin (46.1%), was most commonly observed, followed by resistances to tetracycline (45.7%), trimethoprim-sulfadiazine (43.3%) and ampicilin (41.0%). All isolates showed resistance to at least two antimicrobial agents; multidrug resistance was quite frequently encountered. Results showed that bovine E. coli produces some toxins and virulence factors, some of which may be involved in human disease. The isolates showed a high level of resistance to antimicrobial agents constituting a public health concern.Keywords: calf, diarrhea, Escherichia coli, virulence factor, antimicrobial agent RESUMO Cento e setenta e três cepas de Escherichia coli isoladas de bezerros com diarréia provenientes da região noroeste do estado de São Paulo foram examinadas para a produção de enterotoxinas termolábil (LT) e termoestável (ST), e examinadas quanto à presença de fatores de virulência associados a colibacilose bovina. Oitenta e cinco (49,1%) das cepas de E. coli produziram toxinas, 53 cepas foram detectadas como produtoras de toxina STa, e nove dessas cepas também produziam toxina LT. Foram identificadas pela reação em cadeia de polimerase 23 cepas portadoras do gene LT-II. Nove (5,2%) das cepas apresentavam os genes de toxina

Beef Carcass Contamination by Shiga Toxin–ProducingEscherichia coliStrains in an Abattoir in Brazil: Characterization and Resistance to Antimicrobial Drugs

“…In the present study, high levels of resistance as well as MDR were detected among the isolates agreeing with other reports from Brazil (Lira et al, 2004;Rigobelo et al, 2006), all of them showing resistance predominantly to cephalothin, tetracycline, streptomycin, and less frequently to nalidixic acid. These findings agree with data from previous studies showing that resistance is common among strains isolated from food, animals, and humans (Sáenz et al, 2001;Schroeder et al, 2002).…”

“…The low level of STEC strains detected as contaminants in the carcass, in this study, contrasts with the high number of these strains detected in feces of healthy or diarrheic cattle in Brazil (Irino et al, 2005;Rigobelo et al, 2006;Aidar-Ugrinovich et al, 2007) what could suggest a efficient work during removal of the hide or the gastrointestinal tracts during slaughtering.…”

“…Other virulence factors such as intimin (eae) and hemolysin (hlyA) are thought to enhance pathogenicity, but are not required for strains to produce severe disease, including hemolytic uremic syndrome (HUS) (Acheson, 2000;Caprioli et al, 2005). STEC occurrence in feces of healthy or diarrheic cattle in Brazil has been reported with a high prevalence of strains and a great diversity of serotypes (Irino et al, 2005;Rigobelo et al, 2006;Aidar-Ugrinovich et al, 2007;Farah et al, 2007).…”

“…During the processing of carcasses, fecal contamination or transfer of bacteria from the animal's hide to the carcass can promote transmission of pathogenic E. coli to food supplies (Bell, 1997;Barkocy-Gallagher et al, 2001). Antimicrobial drug resistance data of fecal E. coli strains from animals were difficult to find in the literature from Brazil, most of them showing high levels of resistance against several antimicrobial agents from commensal E. coli isolated from diarrheic calves (Rigobelo et al, 2006) as well as from STEC strains isolated from meat (Rodolpho and Marin, 2007).…”

Patotipos de Escherichia coli causadores de diarreia em bezerros: uma atualização

“…Porém os resultados entre os estudos divergem, devido a diversos fatores como a região geográfica estudada, época do ano, número de animais e método de diagnóstico empregado. A frequência de ETEC varia desde zero até 30% (Lage et al 1993, Mendonça et al 1996, Langoni et al 2004, Rigobelo et al 2006, Oliveira Filho et al 2007, Coura 2011, Moura et al 2012, Andrade et al 2012. EPEC varia desde 1,42% até 42,5% (Rigobelo et al 2006, Aidar-Ugrinovoch et al 2007, Coura 2011, Moura et al 2012, Andrade et al 2012 e STEC e EHEC varia entre 2,7% até mais de 50% (Rigobelo et al 2006, Aidar-Ugrinovoch et al 2007, Coura 2011, Andrade et al 2012.…”