Multidrug Resistance and Virulence Gene Profiles of E. coli in Broiler Chickens: A Study From Noakhali, Bangladesh.

Avian pathogenic Escherichia coli (APEC) is the primary cause of colibacillosis, a significant bacterial disease in poultry associated with high mortality rates and substantial economic losses. In Bangladesh, the poultry sector is crucial in ensuring food security and supporting livelihoods, yet APEC poses a significant challenge. The extensive use of antibiotics has heightened antimicrobial resistance (AMR), undermining the efficacy of therapeutic alternatives and raising public health issues. The present study assessed the prevalence, AMR, and virulence gene profiles of APEC and their environs (environmental E. coli [EEC]) in Bangladesh. All isolates demonstrated significant resistance, with more than 90% resistant to the most frequently used antibiotics (tetracycline, ciprofloxacin, ampicillin, and levofloxacin). The EEC isolates demonstrated a notably higher level of resistance compared to APEC (p < 0.05), indicating a greater exposure to antimicrobials in the environment. The prevalence of multidrug resistance (MDR) was also notably high (98.94%). The study also profiled virulence-associated genes (VAGs), with the iron acquisition gene iroN being the most prevalent (69.5%), followed by ompT (58.8%) and hlyF (53.7%), indicating strong pathogenic potential in both APEC and EEC. However, the VAGs' distribution showed no significant difference between APEC and EEC, suggesting possible environmental reservoirs for the pathogenic strains. The existence of multiple VAGs, along with elevated resistance levels, emphasizes the dual threat posed by these isolates to both poultry and public health. Overall, the findings underscore the urgent need for improved biosecurity practices, prudent antibiotic use, and ongoing surveillance to mitigate the risks posed by resistant and virulent bacterial strains.