Antimicrobial drug resistance and genetic diversity of commensal Escherichia coli from caeca of chickens in Grenada.

ABSTRACT

The main goal of this study was to generate baseline data on resistance to 11 antimicrobial drugs of global importance among commensal Escherichia coli from healthy chicken in Grenada. For this purpose, a total of 183 commensal Escherichia coli isolates from 197 chickens (147 broilers and 50 layers) originating from 11 poultry farms in Grenada were studies using a standard disk diffusion method. The isolates were further studied for their haemolytic properties using sheep blood agar, and genotypes using the enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR). Sixty-six isolates were positive for alpha haemolysis, and the remaining were non-haemolytic. There was no difference in antimicrobial susceptibility between haemolytic and non-haemolytic isolates. Resistance was highest against tetracycline (58.5%) followed by streptomycin (44.3%) and lowest to chloramphenicol (0.55%). Only three isolates (1.6%) showed resistance to fluoroquinolones. Resistance rates to tetracycline, streptomycin, and gentamicin were significantly lower among isolates from layers, compared with those from broilers. Multiple resistance to three or more classes of drugs was found in 10.4% of total isolates; the most common R-profile was Amp, Str, Tet. Twenty genotypes were identified among 24 randomly selected isolates that originated from 11 unrelated farms and 5 geographical locations. Isolates sharing similar genomic fingerprints by ERIC-PCR had different resistance profiles, whereas isolates with different genotypes shared similar profiles. In conclusion, this study showed the genetic diversity of chicken isolates from Grenada, and their significance and the epidemiological significance of ERIC-PCR genotypes among poultry isolates need further study.