Transferable Plasmid Mediating Multi-Antibiotic Resistance in Non-Pathogenic Escherichia coli Isolates from Chicken Flocks

Thirty Escherichia coli strains isolated from chicken flocks were analyzed to determine their antibiotic resistance patterns and plasmid profile. Thirty E. coli isolates showed 21 patterns of resistance to the antimicrobial agents used in this study. All the E. coli isolates showed high resistance to multiple drugs with 100% resistance observed against Tetracycline, Ampicillin, Amoxicillin and Cloxacillin. Three E. coli isolates (10%) were resistant to all used antibiotics. After that, the most common antimicrobial resistance pattern of these isolates was contained Tetracycline, Ampicillin, Amoxicillin, Cloxacillin, Enrofloxacin, Trimethoprim, Flumequine and Oxytetracycline. In addition six E. coli isolates were sensitive to Trimethoprim.All multidrug resistant strains had different size plasmids of ~3.5-42 kb. After transformation just 42 kb plasmid was recovered. The present study confirmed high incidence of resistance in E. coli isolated from poultry, which is probably due to increased use of antibiotics as feed additives for growth promotion and prevention of disease, resistance transfer among different bacteria and possible cross-resistance between antibiotics used in domestic animals and those used in human medicine.