Antimicrobial Resistance in Pathogenic Escherichia coli from Animals

This chapter focuses on the prevalence of antimicrobial resistance phenotypes among Escherichia coli isolates associated with enteric and systemic colibacillosis in minor species, cattle, pigs, and poultry, as well as bovine mastitis and uterine and urinary tract infections in companion animals. Antimicrobial resistance phenotypes among avian pathogenic E. coli recovered from diseased turkeys are similar to those reported from chickens. Fluoroquinolones are highly efficacious antimicrobial agents commonly used in human medicine. This class of drugs has also been approved for certain bacterial diseases in animals, including acute bovine respiratory disease and avian colibacillosis. Resistance to narrow-spectrum cephalosporins and tetracyclines among E. coli isolates may be due to their use for intramammary treatment for clinical mastitis in dairy cows. Treatment in grower-finisher rations was significantly associated with resistance to ampicillin, spectinomycin, sulfisoxazole, and tetracycline. Nineteen percent of swine E. coli isolates were also shown to possess class 1 integrons bearing gene cassettes conferring resistance primarily to trimethoprim and streptomycin. Plasmids containing the oqxAB genes yielded high resistance to olaquindox as well as chloramphenicol in E. coli. Diarrhea associated with E. coli infection is responsible for high rates of morbidity and mortality in goat kids and lambs. Antimicrobials are essential tools of disease management regimens in food and companion animals worldwide. The most commonly used antimicrobial drugs in food and companion animals are from five major classes: β-lactams, tetracyclines, aminogylcosides, macrolides, and sulfonamides.