The use of antibiotics as food additives in poultry and their effect on antibiotic resistance

The widespread use and misuse of antimicrobials beyond human medicine, assisted in the alarming emergence of resistance amongst the bacterial strains. Aim: to determine the effect of the use of antibiotics as food additives on the intestinal flora of poultry. Methods: one hundred and eighty chickens at the age of two weeks were divided equally into six groups. Five of these groups were used for the test and the sixth served as a control group. Each of the test groups was fed with a different type of antibiotic which served as food additives. The control group was fed an antibiotic-free diet. The antibiotics used were amoxycillin, ciprofloxacin, tetracycline, gentamicin and co-trimoxazole. Rectal swabs were collected from the chickens at the age of two and six weeks respectively. The specimens were processed for the isolation and antibiotic sensitivity of E. coli from each group. After slaughtering the chickens, the presence of the antibiotic residue in the tissues was tested. Pieces of tissues were applied on a sensitivity agar using standard E coli as a test organism. Results: significant increase in antibiotic resistance was noticed in the test groups (P < 0.05). The change in resistance was insignificant in the control group (P > 0.05). The pieces of tissues from the test groups inhibited the growth of E coli indicating the presence of antibiotic residue. No inhibition of growth was detected in the control group. Conclusion: the use of antibiotics as food additives in animals and poultry can lead to the emergence of resistant bacterial strains in their intestinal flora and can leave antibiotic residue in their tissue.