Prevalence of antimicrobial resistant Escherichia coli isolated from pigs, cattle and sheep in Great Britain
The incidence of antimicrobial resistance and expressed and unexpressed resistance genes among commensal Escherichia coli isolated from healthy farm animals at slaughter in Great Britain in 1999 was investigated. The prevalence of antimicrobial resistance among the isolates varied according to the animal species. Of 836 isolates from cattle tested only 5.7% were resistant to one or more antimicrobials, while only 3.0% of 836 isolates from sheep were resistant to one or more agents. However, 92.1% of 2480 isolates from pigs were resistant to at least one antimicrobial. Among isolates from pigs, resistance to some antimicrobials such as tetracycline (78.7%), sulphonamide (66.9%) and streptomycin (37.5%) was found to be common, but relatively rare to other agents. The isolates had a diverse range of resistance gene profiles, with tet(B), sul2 and strAB identified most frequently. Seven out of 615 isolates investigated carried unexpressed resistance genes. One trimethoprim-susceptible isolate carried a complete dfrA17 gene but lacked a promoter for it. However, in the remaining six streptomycin-susceptible isolates, one of which carried strAB while the others carried aadA, no mutations or deletions in gene or promoter sequences were identified to account for susceptibility. The data indicate that antimicrobial resistance in E. coli of animal origin is due to a broad range of acquired genes.
A high prevalence of antimicrobial resistant Escherichia coli isolated from pigs and a low prevalence of antimicrobial resistant E. coli from cattle and sheep in Great Britain at slaughter. FEMS Microbiology Letters (OnlineEarly Articles).
Why does it matter?
Historically, antimicrobials have been used in animal production for both therapeutic and growth promotion purposes. The European Union has gradually banned the use of all growth-promoting antimicrobials. However, antimicrobials are still used as therapeutic agents in food production. In the UK, veterinary antimicrobial use ranges between 440 and 480 tonnes annually, over 80% of which are used in food-producing animals. The tetracyclines account for approximately half of this amount, with significant use also recorded for trimethoprim/sulphonamides, -lactams, aminoglycosides, macrolides and fluoroquinolones.
This study demonstrated that antimicrobial resistance is common among E. coli from healthy pigs in Great Britain, but relatively rare among E. coli from sheep and cattle. Resistance phenotypes among E. coli of animal origin are extremely diverse and are mediated by a wide range of different resistance genes, suggesting the presence of a large population of resistant E. coli, particularly among pigs. This resistance is of concern as it can potentially spread to humans, either via direct colonization of the human gut by animal strains of E. coli or through transmission of resistance genes to resident bacteria in the human gut.
Related:
- Beating antibiotic resistance
- MicrobiologyBytes: Antibiotics
Tags: Agriculture, Antibiotics, Bacteria, Biology, Biotechnology, Environment, Health, Microbiology, Science
