Isolation & molecular characterization of Campylobacter jejuni and virulent gene associated avian fecal Escherichia coli in broiler, Bangladesh Md. Sirazul

Abstract

The intestinal environment of broilers is a potential Campylobacter jejuni and avian fecal Escherichia coli (AFEC) reservoir. Understanding the intestinal microbiota in broilers and their subsequent human transmission is a key public health concern here, where C. jejuni and intestinal virulent associated gene (VAG) carriage E. coli are simultaneously studied in apparently healthy birds from broiler farms, live bird markets (LBMs) and supershops. In the period from June 2019 to February 2020, pooled cloacal samples were collected from broiler farms located in 6 districts of Bangladesh and pooled meat samples were collected from LBMs and super shops in Chattogram. Data on farm management, biosecurity, and hygiene practices were collected through a face-to-face interview during sampling using a structured questionnaire. To examine the occurrence of C. jejuni and VAG AFEC in broiler chickens, microbial culture and PCR-based methods were applied. Positive PCR amplicon was confirmed by gene sequencing and phylogenetic analysis was subsequently performed. To evaluate the risk factors, epidemiological data were analyzed using univariable logistic regression models followed by multivariable logistic regression. Among the 216 farms, 27 were positive to C. jejuni; thus, the farm level prevalence was estimated to be 12.5% (95% CI: 8.5%–17.7%). Remarkably, at LBMs and super shops, a higher prevalence of 27.08% (95% CI: 15.28%–41.84%; N=48) of C. jejuni was recorded in broiler meat. In risk factor analysis, downtime of less than 14 days, no separate footwear for shed entry, increased number of flock rotations per shed per year, and entry of more than 1 person to sheds were found to be significantly associated with C. jejuni infection. Phylogenetic analysis showed a close connection between C. jejuni strains isolated from Bangladesh and other strains isolated from humans, pigs and bats of India, South Africa and Grenada. VAGs AFEC was isolated from the apparently healthy chickens with a prevalence of 55.6% (95% CI: 48.7%–62.3%). Virulence Associated Genes; astA, iucD, iss, irp2 and cva/cvi were detected in a rate of 46.3%, 25.5%, 17.6%, 12.9% and 2.8%, respectively. Geographical locations and flock age of less than 21 days were significantly associated with the VAGs AFEC positive status in broilers. The results of this study showed a high level of microbial contamination of zoonotic importance and the presence of pathogenic bacteria in the intestine and meat of Bangladeshi broilers. Potential sources of contamination and anthropogenic factors associated with the alarming occurrence of C. jejuni and VAGs AFEC noted in this study would assist in developing interventions under the 'One Health' banner that includes chickens, humans and environmental perspectives to minimize the increasing risks of broiler-associated pathogens.