Antimicrobial Resistance Phenotypes of Escherichia coli Isolated from Tropical Free Range Chickens

Antimicrobial resistance is one of the major problems facing the world and it is increasing in high rates in developing countries. In this study, antimicrobial phenotypes of resistant Escherichia coli isolates from tropical free range chickens were investigated using Kirby-Bauer disc diffusion method. A total of 77 E. coli isolated from cloaca swabs were examined for susceptibility to antimicrobials of veterinary and human importance. Sixty seven out of 77 isolates showed resistance to at least one antibiotic, while 54 out of 67 isolates were multidrug resistant. The highest rate of resistance was against tetracycline (75 %) followed by ampicillin (63.63 %), ofloxacin (54 %), co-trimoxazole (53 %) and cefotaxime (29 %). The lowest resistance was against chloramphenicol (5 %), and cefoxitin (6 %). To the best of our knowledge, this is the first study in Tanzania to investigate antimicrobial resistance in E. coli isolates from tropical free range chickens. Notably, we report for the first time the occurrence of third generation cephalosporins resistant E. coli strains. These are essential first line drugs used to treat severe enteric bacterial infections in human medicine. Since sampled chickens did not receive any medication or vaccination, it is evident that the environment is the likely source of multidrug resistant bacteria. There is a risk of resistant bacteria transmission to humans through contaminated poultry products and the environment.