A study has pointed to a reduction in Salmonella contamination rates of frozen breaded chicken sold in the United Kingdom.

Frozen, breaded, ready-to-cook chicken products have a browned, cooked external appearance, which may be perceived as ready-to-eat, leading to mishandling or undercooking by consumers.

Concerns about these products led the Food Standards Agency (FSA) and UK Health Security Agency (UKHSA) to look at the prevalence of Salmonella, E. coli and antimicrobial resistance (AMR) in items such as nuggets, dippers and goujons, at retail in the UK.

Overall, 310 samples were tested between April and July 2021, and Salmonella was detected five times. When samples were cooked according to instructions on the packet, Salmonella was killed. Another 20 similar products that contained Salmonella during a previous study in 2020-21 were also cooked based on the instructions, and no Salmonella was detected after cooking.

Link to illnesses

However, since many illnesses have been associated with such chicken products in the UK and other countries, it appears that either people do not always apply effective cooking processes or cross-contamination plays a significant role, according to the study.

Salmonella Infantis was found in three samples and Salmonella Java twice. One of the Salmonella Infantis isolates was linked to three recent cases; the second was behind two infections in early 2021. The two Salmonella Java isolates matched cases with sample dates between 2014 and 2018. Countries of origin of the five Salmonella contaminated samples were Hungary, Ireland and the UK. 

EU rules state that preparations made from poultry meat intended to be eaten cooked should not have any Salmonella in a 25-gram sample when placed on the market and examined during their shelf-life.

Higher concentrations of generic E. coli in foods are commonly recognized as an indicator of poor hygiene. E. coli was found in 113 samples, but only 15 had levels that indicated problems in the hygiene of the tested products. One E. coli isolate showed resistance to colistin and possessed the mcr-1 gene.

A study by Public Health England, now UKHSA, in 2020 found Salmonella in 40 of 456 samples of frozen, reformed chicken products, with Salmonella Enteritidis isolates from 17 samples linked to an outbreak. A series of outbreaks involving Salmonella in breaded chicken products from Poland in 2020 and 2021 affected more than 1,000 people and a number of products and brands.

Data from the latest study suggests there has been a decline in Salmonella contamination rates in frozen, breaded chicken products between 2020 and 2021. Affected supermarkets changed suppliers which appears to explain at least some of the improved results, as Salmonella contamination was linked to only a few producers.

AMR findings

Three Salmonella Infantis isolates were resistant to nalidixic acid, ciprofloxacin and tetracycline, with one also showing resistance to ampicillin, so was classified as multi-drug resistant. The Salmonella Java isolates were resistant to trimethoprim but also had reduced susceptibility to sulfamethoxazole.

E. coli with a presumptive AmpC or Extended-spectrum beta-lactamase (ESBL) (or both) phenotype were detected in 18 of 310 samples.

Resistance to three or more groups of antimicrobials, called multi-drug resistance, was seen in 22 of 110 isolates. Of these, one isolate was resistant to six different antimicrobial groups.

Results showed it is important to cook breaded and battered chicken products properly in line with instructions on the packaging. Adequate cooking, good kitchen hygiene such as handwashing between handling uncooked and cooked foods, and cleaning preparation surfaces and utensils properly after using them for uncooked food items, significantly reduces the risks posed by Salmonella and E. coli.

AMR in E. coli on beef and pork

In another survey, beef and pork on retail sale in the UK was sampled between October and December 2021 and investigated for the presence of AMR E. coli. Results showed the prevalence was low. E. coli isolates are useful indicators of AMR.  

A total of 105 beef and 105 pork samples were tested. Samples post enrichment yielded E. coli in one beef sample and four pork samples. The survey had lower sample numbers than previous studies because of a delayed start following the UK exit from the EU, and because of lab capacity.

Two pork samples were positive for AmpC-producing E. coli and two for ESBL-producing E. coli. The beef isolate had an E. coli with an AmpC + ESBL-expressing phenotype.

No meat samples, prior to enrichment, had background or AmpC-/ESBL-phenotype E. coli counts above EU detection levels, indicating low numbers of bacteria on samples.  

No beef or pork samples were positive for E. coli with resistance to so-called last resort carbapenem or colistin antimicrobials.

Resistance was seen to some cephalosporin antibiotics. The beef isolate was resistant to all four of the cephalosporin antibiotics it was tested against, whilst the pork isolates were resistant to at least two of these antibiotics. All five E. coli isolates were resistant to ampicillin, but showed no resistance to amikacin, temocillin or tigecycline.

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