Antimicrobial resistance (AMR) in Campylobacter from chicken has increased in the United Kingdom in the past two decades, according to a report.

The report, from the UK Health Security Agency (UKHSA) and published by the Food Standards Agency (FSA), summarized 20 years of data on AMR in Campylobacter in chicken. Variables included sample type, origin and production method.

AMR is when bacteria adapt to become resistant to the effects of antimicrobials, such as antibiotics. This resistance makes such infections in humans more difficult to treat using drugs.  

Campylobacter is the main cause of bacterial food poisoning in the UK and it is estimated there are more than 500,000 cases annually. Treatment in rare cases of severe infection usually involves a macrolide such as azithromycin or a fluoroquinolone like ciprofloxacin.

Decline in use not seen in resistance rates
The study found resistance to quinolones such as ciprofloxacin and nalidixic acid and tetracycline was common in Campylobacter jejuni and Campylobacter coli from UK chicken. However, resistance to erythromycin and streptomycin was much rarer and resistance to gentamicin was very rare.

Dr. Paul Cook, FSA’s science lead in microbiological risk assessment, said overall data shows an increase in AMR in Campylobacter to certain antimicrobials but the trend has stabilized since 2014.

“Any increase of AMR in Campylobacter is a concern and continued surveillance is essential. We will continue to carry out AMR surveillance in chicken and other meats and to monitor any long-term trends in resistance, while promoting good food hygiene practice to reduce exposure to AMR bacteria and protect consumer safety,” he said.

Multidrug-resistant profiles, meaning resistance to at least three unrelated antimicrobial classes, were at very low levels in Campylobacter jejuni and at low levels in Campylobacter coli. It was found in 136 Campylobacter coli and 42 Campylobacter jejuni isolates.

“Despite the use of antimicrobials in UK poultry production reducing dramatically in the past decade this has not been accompanied by reductions in resistance rates for all antimicrobials,” found the report.

Resistance rates by drug
Antimicrobial resistance data for 5,267 Campylobacter jejuni and 1,997 Campylobacter coli isolates collected between 2001 and 2018 were analyzed. This showed, on average, 29 percent of the Campylobacter jejuni and 32 percent of Campylobacter coli isolates were resistant to ciprofloxacin but only 1.6 percent of Campylobacter jejuni and 13.2 percent of Campylobacter coli isolates were resistant to erythromycin.

Overall, 48.2 percent of both the Campylobacter jejuni and Campylobacter coli isolates were resistant to tetracycline. Resistance to streptomycin was detected in 1 percent of Campylobacter jejuni and 8.9 percent of Campylobacter coli isolates. only four isolates were resistant to gentamicin.

Campylobacter jejuni isolates with resistance to ciprofloxacin increased from 13 percent in 2001 to 52 percent in 2018. Data from 2020 shows 58.5 percent of 265 Campylobacter jejuni isolates had a genetic determinant predicting resistance to Ciprofloxacin. There was also a rise from 16 percent of isolates with resistance to nalidixic acid in 2001 to 52 percent in 2018.

The percentage of Campylobacter coli isolates with resistance to ciprofloxacin increased from 15 percent in 2001 to 51 percent in 2017. Genetic determinants predicting resistance were detected in 43.7 percent of isolates between 2018 and 2020. Resistance to nalidixic acid went up from 16 percent in 2001 to 50 percent in 2017.

The rate of Campylobacter jejuni isolates resistant to erythromycin was below 5 percent in all years. In samples from 2018 to 2020, no resistance was detected in 773 Campylobacter jejuni isolates.

Tetracycline resistance in Campylobacter jejuni increased from 27 percent in 2001 to 66 percent in 2018 but was stable from 2014 to 2020. The percentage of Campylobacter coli isolates with resistance rose from 23 percent in 2001, to over 55 percent in all years after 2013.

Chicken from non-standard production was associated with a higher probability of Campylobacter coli with resistance to ciprofloxacin and tetracycline. However, resistance to erythromycin seemed lower in samples from chicken reared as free range or organic. Chicken from non-UK production had a slightly higher level of Campylobacter coli isolates with resistance to ciprofloxacin and nalidixic acid.