doi: 10.14202/vetworld.2024.480-499

Article history: Received: 18-10-2023, Accepted: 24-01-2024, Published online: 29-02-2024

Corresponding author: Rebanta K. Bhattarai

E-mail: rkbhattarai@afu.edu.np

Citation: Bhattarai RK, Basnet HB, Dhakal IP, and Devkota B (2024) Antimicrobial resistance of avian pathogenic Escherichia coli isolated from broiler, layer, and breeder chickens, Veterinary World, 17(2): 480–499.

Background and Aim: Antimicrobials are extensively used in poultry production for growth promotion as well as for the treatment and control of diseases, including avian pathogenic Escherichia coli (APEC). Poor selection, overuse, and misuse of antimicrobial agents may promote the emergence and dissemination of antimicrobial resistance (AMR) in APEC. This study aimed to assess antimicrobial susceptibility patterns and detect antibiotic resistance genes (ARGs) in APEC isolated from clinical cases of colibacillosis in commercial broiler, layer, and breeder chickens.

Materials and Methods: A total of 487 APEC were isolated from 539 across 300 poultry farms in various regions of Nepal. Antimicrobial susceptibility patterns was determined using the Kirby-Bauer disk diffusion and broth microdilution methods. The index of AMR, such as multiple antibiotic resistance (MAR) index, resistance score (R-score), and multidrug resistance (MDR) profile, were determined. Polymerase chain reaction was employed to detect multiple ARGs and correlations between phenotypic and genotypic resistance were analyzed.

Results: The prevalence of APEC was 91% (487/539). All of these isolates were found resistant to at least one antimicrobial agent, and 41.7% of the isolates were resistant against 8–9 different antimicrobials. The antibiogram of APEC isolates overall showed the highest resistance against ampicillin (99.4%), whereas the highest intermediate resistance was observed in enrofloxacin (92%). The MAR index and R-score showed significant differences between broiler and layers, as well as between broiler breeder and layers. The number of isolates that were resistant to at least one agent in three or more antimicrobial categories tested was 446 (91.6%) and were classified as MDR-positive isolates. The ARGs were identified in 439 (90.1%) APEC isolates, including the most detected mobilized colistin resistance (mcr1) which was detected in the highest (52.6%) isolates. Overall, resistance gene of beta-lactam (blaTEM), mcr1, resistance gene of sulphonamide (sul1) and resistance gene of tetracycline (tetB) (in broiler), were detected in significantly higher than other tested genes (p < 0.001). When examining the pair-wise correlations, a significant phenotype-phenotype correlation (p < 0.001) was observed between levofloxacin and ciprofloxacin, chloramphenicol and tetracycline with doxycycline. Similarly, a significant phenotype-genotype correlation (p < 0.001) was observed between chloramphenicol and the tetB, and colistin with blaTEM and resistance gene of quinolone (qnrA).

Conclusion: In this study, the current state of APEC AMR in commercial chickens is revealed for the first time in Nepal. We deciphered the complex nature of AMR in APEC populations. This information of molecular surveillance is useful to combat AMR in APEC and to contribute to manage APEC associated diseases and develop policies and guidelines to enhance the commercial chicken production.

Keywords: antibiotic resistance gene, multiplex PCR, colibacillosis, multiple antibiotic resistance index, mcr1, commercial chicken.

This document is about a research article on the antimicrobial resistance of avian pathogenic Escherichia coli isolated from broiler, layer, and breeder chickens.

The study aimed to assess the antimicrobial susceptibility patterns and detect antibiotic resistance genes (ARGs) in avian pathogenic Escherichia coli (APEC) isolated from clinical cases of colibacillosis in commercial broiler, layer, and breeder chickens in Nepal.

A total of 487 APEC isolates were collected from 539 dead chickens affected with colibacillosis from various regions of Nepal.

All of the APEC isolates were found to be resistant to at least one antimicrobial agent, with the highest resistance observed against ampicillin (99.4%).

The prevalence of multiple antibiotic resistance (MDR) in APEC isolates was 91.6%, with the most common resistance gene being mobilized colistin resistance (mcr1), detected in 52.6% of isolates.

The study highlights the need for monitoring and controlling antimicrobial resistance in commercial chicken production in Nepal to prevent the spread of resistant pathogens and protect both animal and human health.

The document discusses the pairwise correlation among different antimicrobials and the phenotypic resistance to various antibiotics in Avian pathogenic Escherichia coli (APEC) isolates from different types of commercial chickens.

The document includes tables that provide information on the antimicrobial-resistant patterns and MAR index of APEC isolates, the distribution of multidrug resistance (MDR) profiles of APEC isolates, and the distribution of antibiotic resistance genes (ARGs) in APEC strains from different types of commercial chickens.

The document highlights significant correlations between certain antimicrobials and phenotypic resistance, such as the strong correlation between T resistance and DXT and C, and the significant correlation between CIP and LEV, GEN, and C.

The document also discusses the genotypic correlation between ARGs and antimicrobial resistance phenotypes, with certain ARGs showing significant correlations with specific antimicrobials.

The study in Nepal sheds light on the limitation of relying solely on phenotypic resistance in routine AMR surveillance, as it does not consistently align with genotypic resistance.

The study comprehensively characterized the antibiotic susceptibility pattern, MDR profiles, their correlation, and the molecular identification of ARGs in APEC isolates from colibacillosis-infected broiler, broiler breeder, layer, and layer breeder chickens.

Most APEC isolates exhibited MDR along with the presence of ARGs, with the mcr1 gene being the most prevalent.

The study found diverse antimicrobial sensitivity and resistance patterns across different types of chickens, with none of the antibiotics being 100% effective except for CO in layer breeders.

The study highlights the importance of monitoring both phenotypic and genotypic resistance to accurately evaluate the AMR landscape in a particular area.

The document provides a comprehensive review of the prevalence, molecular characteristics, and antibiotic resistance patterns of avian pathogenic Escherichia coli (APEC) in poultry, specifically in Nepal and other countries.

It highlights the importance of APEC as a cause of colibacillosis in poultry and the potential for transmission to humans through the food chain.

The document discusses the role of antimicrobial use in poultry production as a contributing factor to the emergence and spread of antibiotic-resistant APEC strains.

It emphasizes the need for surveillance, monitoring, and control measures to mitigate the impact of APEC on poultry health and public health.

The document also provides references to various studies, reports, and guidelines related to APEC, antimicrobial resistance, and foodborne diseases, which can serve as valuable resources for further research and policy development.