Levels of antimicrobial resistant (AMR) E. coli in chicken in the United Kingdom have remained stable in the past few years, according to a report.

Findings come from a survey of AMR in E. coli in fresh retail chicken in 2020 published by the Food Standards Agency (FSA). Generic E. coli bacteria can be useful indicators of AMR patterns.

Overall, 315 chicken meat samples were collected, mostly from England but some in Scotland, Wales, and Northern Ireland, from 10 supermarket chains. Almost all were of UK origin but five were from Poland and one from Ireland. Types of meat were whole chicken, chicken breasts and other cuts, including quarters, legs, thighs and drumsticks.

In total, 41 of the 315 samples analyzed were positive for Extended Spectrum beta-lactamase (ESBL) or AmpC-producing E. coli. Between 2018 and 2020, the percentage of samples positive was almost the same. There was an increase in the percentage of isolates with an ESBL-phenotype but a decrease in those with an AmpC-phenotype in this period.

Recovery of ESBL-phenotype E. coli ranged from zero percent to 22.1 percent of the samples tested per supermarket.

Colistin finding
Three samples from Poland had the mcr-1 transferable colistin resistance gene. This is the first known time that retail chicken samples were positive for mcr plasmid-mediated colistin resistant E. coli. A risk assessment deemed the risk to be very low.

FSA traceback found the three samples originated from two approved premises in Poland. It was confirmed that colistin was used on the flock of chickens.

The predominant gene types recovered from retail chicken meat differ to those causing disease in the UK, which suggests chicken is not a major source of ESBLs in humans.

None of the 41 E. coli isolates were resistant to the last resort carbapenem antimicrobials, which are used to treat severe infections when other options have failed.

About 60 percent of isolates were resistant to the quinolone antibiotics (ciprofloxacin or nalidixic acid) or to chloramphenicol. Most isolates were resistant to sulfamethoxazole and tetracyclines, and half were resistant to trimethoprim.

The project, run by Hallmark Meat Hygiene and the Animal and Plant Health Agency, was part of European surveillance but despite the fact the UK has left the EU, the FSA is going to continue to monitor AMR in retail meats.

From October to December 2021, there were 100 beef and 100 pork meat samples on retail sale in the four UK countries collected.

Analysis involves initial isolation and enrichment of E. coli from all meat samples, prior to testing for AMR, specifically ESBLs, AmpC and Carbapenemase-producing E. coli. Analysis for colistin resistance and the colistin resistant mcr genes will also be included.

The work will help determine if these meats pose a risk to public health in relation to AMR and allow monitoring of trends over time.

Research on AMR genes in RTE food
Another study has looked at the diversity of AMR genes in 52 ready-to-eat (RTE) foods, including milk, tomatoes, bananas, cheese and ham from the eight largest retailers in 2019.

In total, 256 samples were tested by researchers, including 33 types of produce, 17 of dairy, and two types of cooked meat. Researchers at Fera said there were insufficient sample numbers to allow comparison of exposure risk between foodstuffs.

Scientists detected 477 distinct AMR genes from 111 distinct AMR gene families in the samples of ready-to-eat food. Genes associated with colistin and methicillin resistance were rarely found. More than 50 different types of fluoroquinolone resistance genes were found in various types of produce. Carbapenem resistance and potential ESBLs were also found in a high proportion of individual diets.

However, the study did not analyze whether the genes were working and making the bacteria resistant to these antibiotics. It also found it was more efficient to extract bacterial DNA from fruit like apples that could be rinsed, rather than foods such as milk.

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