Spread of Antibiotic-Resistant E. coli, Salmonella and Campylobacter in Poultry

Jim Crocker
28th February, 2025

Spread of Antibiotic-Resistant E. coli, Salmonella and Campylobacter in Poultry
Image Source: Sagar Khatri (photographer)

Key Findings

  • In Canada, antibiotic-resistant Salmonella was most common in farm-raised chickens, while Campylobacter was widespread in breeder flocks
  • Critical human antibiotics like ciprofloxacin showed high resistance in these bacteria, making infections harder to treat
  • Breeder chickens play a key role in spreading resistant bacteria, highlighting the need for a unified strategy to reduce antibiotic use in poultry farming
Antimicrobial resistance (AMR) poses a significant threat to public health, as it can render common infections difficult to treat. In the poultry industry, the use of antimicrobials is a crucial factor influencing the development and spread of resistant bacteria. The Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS), part of the Public Health Agency of Canada, conducted a comprehensive study to monitor AMR in broiler chickens at various stages of production[1]. The study focused on three key bacteria: Escherichia coli (E. coli), Salmonella, and Campylobacter. These bacteria are commonly associated with foodborne illnesses and can develop resistance to antibiotics used in both human medicine and animal agriculture. By sampling broiler breeder flocks slaughtered between 2018 and 2021, along with data from broiler flocks at farms and slaughter plants, the researchers aimed to understand the prevalence and resistance patterns of these bacteria within the poultry production chain. One of the notable findings was that Salmonella was most frequently detected in farm broiler chickens, with a prevalence of 46%. In contrast, Campylobacter was more prevalent in broiler breeders, occurring in 73% of samples. This aligns with previous research that identified contact with animals as a significant route for Salmonella transmission[2]. Additionally, the study found high levels of ciprofloxacin resistance in Campylobacter across all production stages, particularly in farm broiler chickens, where resistance reached 24%. Ciprofloxacin is a critical antibiotic in human medicine, and its resistance in foodborne bacteria is a major concern. E. coli, often used as an indicator organism for AMR, showed low-level resistance to ceftriaxone and occasional non-susceptibility to ciprofloxacin. Interestingly, fully susceptible E. coli was most common in broiler breeders (54%) compared to farm (36%) and slaughtered (35%) broiler chickens. This suggests that while resistance is present, there is still a significant proportion of bacteria that remain susceptible to these antibiotics. Salmonella presented a different resistance profile. Broiler breeders had the highest resistance to most antimicrobials tested, with only 16% of Salmonella isolates being fully susceptible. In contrast, 42% of Salmonella from farm and slaughtered broiler chickens remained susceptible. The study also highlighted that Salmonella serovars varied between production stages, with Salmonella Kentucky being the most predominant. This variation in serovars and their resistance patterns underscores the complexity of controlling AMR in poultry production. The prevalence of resistant Salmonella in broiler breeders echoes findings from earlier studies that emphasized the role of breeder flocks in the transmission of Salmonella to hatcheries and the broader poultry production chain[3]. By identifying specific serovars and their resistance profiles, the current study provides critical insights into how these bacteria spread and persist within the industry. Another important aspect of the study was the regional variation in resistance profiles and the presence of resistance to critically important antimicrobials for human medicine. This suggests that AMR in poultry is not uniform across different regions, potentially influenced by varying antimicrobial use practices and biosecurity measures. The study also examined the impact of antimicrobial use strategies. In 2014, the Chicken Farmers of Canada implemented a strategy to reduce antimicrobial use in response to CIPARS’ observations and farmers’ data. This move aimed to mitigate the development and spread of AMR within the industry. The findings indicate that while reductions in antimicrobial use can positively influence resistance patterns, challenges remain, particularly with bacteria like Campylobacter that exhibit high levels of resistance. Comparing these results with international studies, such as the Danish research on extended spectrum cephalosporinase (ESC)-producing E. coli, reveals common challenges in controlling AMR across different countries[4]. The Danish study found that even with low antimicrobial use, resistance genes like blaCMY-2 could persist and spread horizontally among E. coli populations. Similarly, the Canadian study highlights that resistance can be maintained and transmitted within poultry production systems, emphasizing the need for comprehensive and harmonized antimicrobial use strategies sector-wide. Overall, the CIPARS study underscores the critical role of broiler breeders in the maintenance and transmission of AMR in poultry. By carrying bacteria resistant to antimicrobials used in human medicine, these breeder flocks contribute to the broader issue of AMR in the food supply. The study advocates for a harmonized, sector-wide antimicrobial use (AMU) strategy to effectively address and mitigate AMR in poultry production. Incorporating findings from earlier research, the study provides a clearer picture of how AMR develops and spreads within the poultry industry. It highlights the interconnectedness of various stages of production and the persistent challenge of controlling resistant bacteria in a system where antimicrobials are routinely used. Moving forward, strategies that reduce antimicrobial use, improve biosecurity, and monitor resistance patterns will be essential in combating AMR and ensuring the safety of the food supply.

MedicineAgricultureEnvironment

References

Main Study

1) Widespread dissemination of Salmonella, Escherichia coli and Campylobacter resistant to medically important antimicrobials in the poultry production continuum in Canada

Published 25th February, 2025

https://doi.org/10.1371/journal.pone.0319086

Related Studies

2) Estimates of the burden of illness for eight enteric pathogens associated with animal contact in Canada.

https://doi.org/10.1017/S0950268817002436

3) A temporal study of Salmonella serovars from environmental samples from poultry breeder flocks in Ontario between 1998 and 2008.

Journal: Canadian journal of veterinary research = Revue canadienne de recherche veterinaire, Issue: Vol 77, Issue 1, Jan 2013

4) Spread of extended spectrum cephalosporinase-producing Escherichia coli clones and plasmids from parent animals to broilers and to broiler meat in a production without use of cephalosporins.

https://doi.org/10.1089/fpd.2014.1742


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