Phylogenetic Groups and Antimicrobial Susceptibility Patterns of Escherichia coli from Healthy Chicken in Eastern and Central Uganda

Antimicrobial resistance is an emerging problem in both humans and animals due to misuse and excessive use of drugs. Resistance in commensal E. coli isolates can be used to predict emergence of resistance in other gut microflora. The aim of this study is to determine the phylogenetic groups and antimicrobial resistance patterns of E. coli from healthy chickens in Uganda. The phylogenetic grouping of 120 fecal E. coli isolates from eastern and central Uganda was derived using the triplex PCR assay and their susceptibility patterns determined by agar disc diffusion method to 5 antimicrobial drugs. Most E. coli is segregated into phylogenetic group A comprising 84%, while 12% and 4% were in groups D and B1, respectively. Similarly most E. coli from central (87%) and eastern Uganda (82%) belonged to group A. Overall, 85 (70%) of E. coli were resistant to antimicrobial drugs, of which 72/101 (70%) are in PG A, 10 of 14 (71.4%) in PG D, and 3 of 5 (60%) in PG B1. Significantly, most of the isolates in PG A from both central (66.7%) and (60.6%) eastern Uganda were resistant to one antimicrobial. Resistance to tetracycline alone or in combination with other drugs for central and eastern Uganda in PG A is 51% and 55%, respectively. Multidrug resistance to tetracycline and ciprofloxacin or nalidixic acid was 10% and 18% in isolates from central and 10% and 12% in isolates from eastern region, respectively. Phylogenetic group A accounts for most of the E. coli in chicken from Uganda. No difference in the resistance rates between the phylogenetic groups of E. coli has been observed. The high prevalence of resistant E. coli strains from different phylogenetic groups in healthy chickens suggests antimicrobial drug selection pressure due to excessive drug in the rearing layer chickens.