Phenotypic and Genotypic Screening of Colistin Resistance Associated with Emerging Pathogenic Escherichia coli Isolated from Poultry

Abstract

Chickens continue to be an important reservoir of zoonotic multidrug-resistant illnesses. Antimicrobial resistance correlated with colistin has emerged as a critical concern worldwide in the veterinary field and the public health sector. The current study investigated the prevalence of multidrug-resistant avian pathogenic <i>Escherichia coli</i> among chicken farms in three Egyptian governorates, focusing on colistin resistance assessment. A total of 56 <i>Escherichia coli</i> isolates were recovered out of 120 pooled samples obtained from diseased chicken broilers (46.7%). The <i>E. coli</i> isolates were serotyped to nine different serotypes; the highest incidence was for O125 (<i>n</i> = 18). The <i>E. coli</i> isolates demonstrated multidrug-resistant patterns against 10 antibiotics, especially clindamycin, tetracycline, streptomycin and ampicillin, by 100, 100, 96.4 and 92.9%, respectively. On the other hand, colistin resistance was 41.1% using AST. All <i>E. coli</i> isolates displayed positive colistin resistance growth on chromogenic medium, but only 25% represented this positivity via MIC estimation and Sensititre kit. PCR results revealed that all isolates harbored <i>mcr</i>-1, but no isolates harbored the other 2-5 <i>mcr</i> genes. In conclusion, the study demonstrated the emergence of multidrug-resistant, especially colistin-resistant, <i>E. coli</i> among chicken broiler flocks, and <i>mcr</i>-1 is the master gene of the colistin resistance feature.