Serogroup, pathotype and multiple drug resistance of Escherichia coli strains isolated from the cloaca of layer chickens in San Jose, Batangas, Philippines
by Genevieve L. Serrano and Gil M. Penuliar*
1Institute of Biology, College of Science, University of the Philippines Diliman,
Quezon City 1101, Philippines
Four hundred cloacal swab samples from layer chickens in ten layer farms in San Jose, Batangas, Philippines were obtained for the detection of pathogenic serogroups of Escherichia coli and determination of their resistance and susceptibility to different antibiotics and potential production of extended-spectrum β-lactamase (ESBL). A total of 226 isolates were phenotypically identified as E. coli through cultural, morphological, physiological and biochemical characterizations with ≥ 99% similarity to the reference E. coli in the API®20 ETM database. Only five E. coli isolates were serogrouped using four Denka Seiken polyvalent antisera (Polyvalent 1, 3, 4 and 7). Three (FK24, FK26 and FK33) of these isolates belonged to the enterotoxigenic E. coli (ETEC) pathotype serogroup consisting of O6, O27, O78, O148, O159 and O168. Another isolate (FK9) was of the enteropathogenic E. coli (EPEC) pathotype and could belong to the serogroup O18, O114, O142, O151, O157 and O158. Another isolate (FI22) belonged to the enteroinvasive E. coli (EIEC) pathotype serogroup which includes O28ac, O112ac, O124, O136 and O144. All the E. coli isolates from five farms (Farms A, E, F, G and K) were found to be multi-drug resistant or non-susceptible to at least 1 antimicrobial agent in at least 3 antimicrobial categories. Out of the 226 isolates, 90.3%, including the serogrouped E. coli strains, were multi-drug resistant. About 75.7% exhibited resistance to tetracycline while 74.8%, 72.1% and 65.5% exhibited resistance to trimethoprim/sulfamethoxazole, ampicillin and nalidixic acid, respectively. Susceptibility to imipenem, amikacin, nitrofurantoin, gentamicin, cefotaxime, ceftazidime and cefoxitin was still at least 75%, 100%, 89.4%, 88.5%, 86.7%, 86.3%, 84.5% and 78.8% of the isolates, respectively. Only one isolate, FG27, appeared to be a potential ESBL-producer.