Antibiotic resistance among verocytotoxigenic Escherichia coli (VTEC) and non-VTEC isolated from domestic animals and humans

Abstract

2570Two hundred verocytotoxigenic and 216 non-verocytotoxigenic Escherichia coli (VTEC and non-VTEC), isolated from a variety of sources were tested for their resistances to 11 antimicrobial agents. The strains included isolates from domestic food animals and both symptomatic and asymptomatic infections in man. A much higher level of resistance was found among the non-VTEC than among the VTEC, regardless of source. The resistant VTEC isolated from animals were predominantly from specimens associated with sick animals. Antibiotic resistance was detected in only four of the 59 (6·8 %) VTEC of human origin, whereas more of the human non-VTEC possessed antibiotic resistance determinants. It was particularly noteworthy that 24/87 (28 %) strains isolated from healthy babies, who had neither contact with antibiotics nor had gastrointestinal symptoms for at least 2 weeks prior to the specimen being taken, were resistant to one or more of the antibiotics tested. INTRODUCTIONExtensive studies over the years, both by ourselves and others around the world, have shown that verocytotoxigenic Escherichia coli (VTEC) are commonly isolated from the faeces of ruminants such as cattle and sheep (Beutin et al., 1993;Djordjevic et al., 2001;Dorn et al., 1989;Fagan et al., 1999;Hornitzky et al., 2001;Kudva et al., 1997; Richter et al., 1997;Wells et al., 1991). In addition, there has been increasing concern of the possible development of resistance to antimicrobial agents in the Enterobacteriaceae, especially E. coli, as a result of the use of such agents in animal feed (Willis, 2000). With the recent emergence of strains of Salmonella Typhimurium DT104, resistant to four or more antimicrobial agents (Threlfall et al., 1997), the problem of such resistant organisms evolving and being transmitted through the food chain from cattle and sheep to man is becoming increasingly important throughout the world (Glynn et al., 1998;Levy & Cruz, 1999). In his review, Willis (2000) concludes that 'there is now good evidence that the use of antibiotics in agriculture is contributing to the problem of antibiotic resistance amongst pathogenic bacteria.'In her book, Garrett (1995) discusses the problems associated with the acquisition of antibiotic resistance factors by the intestinal organisms of domestic animals, as a result of the use of antibiotics in animal husbandry. She then discusses the emergence of VTEC, especially E. coli O157 : H7, and suggests that these may well also have emerged due to such antibiotic use. It seemed that if this hypothesis were true then VTEC isolated from cattle and sheep would be resistant to antibiotics. It was specifically to address this question that this study was initiated, especially as there are few studies in which the antibiotic sensitivities of VTEC have been determined. Most of these deal with human VTEC. Zhao et al. (2001) demonstrated that 39/50 (78 %) VTEC, mainly O157 : H7, but also including a range of serotypes, exhibited resistance to two or more antimicrobial classes. Most of these were isolate...

Changes in Multidrug Resistance of Enteric Bacteria following an Intervention To Reduce Antimicrobial Resistance in Dairy Calves

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Molecular Characterization of Multidrug-Resistant Escherichia coli Isolates from Irish Cattle Farms

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Multidrug-resistant Shiga toxin-producing Escherichia coli in dogs with diarrhea

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