However, the researchers say, relatively little is known about the role of the food chain in the transmission of AMR bacteria in general, including the transmission and prevalence of AMR bacteria in chicken and chicken products, before retail. 

The project’s findings showed that while target bacteria like Campylobacter spp. and E. coli were initially present in birds entering chicken processing plants, their presence and numbers significantly decreased along the poultry processing line, especially following specific procedures such as defeathering and evisceration.

The researchers’ literature review found that few published studies have investigated the transmission of AMR bacteria or ARGs during poultry processing, with existing research suggesting that AMR and ARGs in outgoing meat are primarily influenced by farm-level factors rather than in-plant procedures. There is limited published evidence on the transmission and persistence of AMR bacteria and genes occurring in the processing environment.

In addition to the literature review, a key component of the project was a field and laboratory study conducted to assess the presence and potential transmission of AMR Campylobacter spp. and E. coli during the processing of chicken in two similar-sized, large-scale UK chicken processing sites producing whole chickens and chicken meat for major UK retailers at different points in the year.

AMR testing revealed varying patterns among Campylobacter spp. and E. coli isolates. Campylobacter spp. showed highest resistance to tetracycline (53 percent) and lowest to erythromycin (7 percent), while E. coli exhibited highest resistance to ampicillin (80 percent) and lowest to chloramphenicol (13 percent). 

The field and laboratory study also found that:

• Of the 376 samples collected from the poultry plants during the project, 65.1 percent of samples were positive for presence of Campylobacter spp., and 95.6 percent were positive for presence of E. coli.
• Levels of Campylobacter spp. isolated from sample collected from the two UK plants ranged from 1.00±0.0 to 3.9±0.5 log10 Colony Forming Units (CFU) per sample, with the highest level recorded from chicken litter and the lower levels recorded from post intervention equipment, scalding water, clean crates, and on carcasses at dispatch.
• Levels of E. coli isolated from sample collected from the two UK plants ranged from 2.0±0.0 to 8.3±0.2 log10 CFU per sample, with the highest level recorded from chicken litter and the lower levels recorded from post intervention equipment, post intervention carcasses, scalding water, post chill, inside outside wash, and clean crate processing stages.
• Campylobacter spp. and E. coli were detected at different stages throughout the production process in both plants, with higher numbers measured at the earlier stages of the process in both plants.
• At some stages of the process, no Campylobacter spp. or E. coli were isolated in either plant.
• Generally, levels of Campylobacter spp. decreased to non-detectable levels in samples taken further along the processing stages. For E. coli, while there was a general decrease in the level of the organisms, samples tested at the later stages of processing remained still positive for the presence of E. coli.
• Approximately 7 percent of the Campylobacter jejuni isolates were resistant to three or more classes of antimicrobial (tested against examples of four different classes).
• Approximately 60 percent of the E. coli isolates were resistant to three or more classes of antimicrobial (tested against examples of eight different classes).

“Further studies are needed to confirm these results and assess the role of poultry products in spreading AMR/ARGs of concern to human health,” the researchers note.

The entire FSA report—"Transmission of AMR Campylobacter and Escherichia Coli During the Processing of Chicken Meat"—can be found here.