HomePhilippine Journal of Veterinary Medicinevol. 54 no. 1 (2017)

High Level Resistance and Multi-Resistance to Medically Important Antimicrobials in Escherichia coli Isolated from Healthy Pigs at Slaughter in Laguna, Philippines

Mildred A. Padilla | Marietta Q. Amatorio



The disc diffusion assay was used to evaluate the susceptibility of Escherichia coli isolates from slaughter pigs to a panel of 12 antimicrobials used in human medicine. Samples of colon contents were collected from 120 pigs at three abattoirs in Laguna. E. coli showed high level resistance (95%) and multiresistance (76.3%) to >3 classes of antimicrobials important for human treatment. Most commonly observed resistance was towards chlorampenicol (78%), trimethoprim (68%), sulfamethoxazole-trimethoprim (65%), ampicillin (62%) and tetracycline (60%). Some were resistant to streptomycin (48%), nalidixic acid (32%) and ciprofloxacin (28%); and few were resistant to gentamicin (18%) and kanamycin (2%). Resistance was not detected to cefotaxime and ceftriazone. Of concern is the resistance to critically important classes of antimicrobials for treatment of human infections: fluoroquinolones, aminoglycosides and penicillins. Twenty-six resistance

phenotypes comprised up to nine compounds from six classes. Concurrent resistance to ampicillin, chlorampenicol, trimethroprim and trimethoprim-sulfamethoxazole was the most common co-resistance phenotype (35.7%). The high level resistance of E. coli in different combinations of medically important antimicrobials raises concern about potential spread of resistant E. coli to humans through contaminated pork. The fndings point to the need for surveillance of antimicrobial resistance and drug usage in pigs.