ANTIMICROBIAL SENSITIVITY PROFILE OF FECAL Escherichia coli ISOLATED FROM BROILERS FED WITH DIFFERENT LEVELS OF CHLORTETRACYCLINE

Abstract

The objectives of the study were to determine and compare the susceptibility of E. coli isolated from cloacal fecal samples of broilers fed with 0 ppm, 75 ppm (subtherapeutic dose) and 400 ppm (therapeutic dose) of chlortetracycline (CTC). E. coli were isolated, screened, cultured from the 48 fecal samples collected at day 10 and 33, and subjected to sensitivity test against nine antibiotics by disc diffusion on Mueller-Hinton agar. Agar plates which developed zones of inhibition (ZOI) were counted and the diameter of the zone was measured. Data were analyzed using descriptive statistics. Results indicated that at day 10, E. coli samples from broilers fed with 75 ppm already developed resistance to trimethoprim sulfamethoxazole (TMPS) and tetracycline. However, susceptibility was still noted with the other seven antibiotics (14-20 mm). At day 33, E. coli showed resistance against ampicillin, chloramphenicol and TMPS at both 75 ppm and 400 ppm. Moreover, reduced percentage of plates with ZOI was noted among aminoglycosides at 75 ppm indicating resistance. When fed with 400 ppm, susceptibility of E. coli against tetracycline and aminoglycosides tended to increase (9-20 mm). This indicates that the use of subtherapeutic levels of CTC in feeds may cause E. coli multi-drug resistance in broilers.