Reported at the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Global Congress, which took place in Barcelona, Spain from April 27–30, 2024, a study conducted by researchers at the University of Bristol has found high levels of antimicrobial resistance (AMR) among Escherichia coli on raw chicken meat sold at retail in the UK, as well as in chicken-based raw dog food samples.

The study analyzed 58 total samples of uncooked meat at retail intended for human consumption—15 each of beef, chicken, and lamb, and 13 of pork—as well as 15 samples of chicken-based raw dog meat. To test for drug-resistant E. coli, the meat samples were enriched and plated onto agar containing common antibiotics, some of which are considered critically important for human health: amoxicillin, amoxicillin-clavulanate, cefotaxime, ciprofloxacin, spectinomycin, and streptomycin.

Of the meat samples intended for human consumption, chicken had the highest sample-level positivity rate for resistant E. coli, with 100 percent of samples testing positive for E. coli resistant to spectinomycin and streptomycin. Nearly half (47 percent) of chicken samples contained E. coli with resistance to critically important fluoroquinolones. In comparison, for lamb, pork, and beef, the rates of E. coli resistant to spectinomycin were 27 percent, 38 percent, and 27 percent, respectively; 40 percent, 38 percent and 47 percent to streptomycin, respectively; and 7 percent, 8 percent, and 13 percent to fluoroquinolones, respectively.

Like retail chicken meat intended for human consumption, levels of AMR in E. coli in chicken-based raw dog food were concerningly high; 87 percent of samples tested positive for spectinomycin and streptomycin resistance, and nearly half (47 percent) were resistant to important fluoroquinolones. Additionally, sample-level positivity for resistance to critically important cefotaxime was 27 percent for raw dog food.

The most common E. coli sequence types (STs) found in the dog food samples were ST10, ST162, and ST744—the same STs that were strongly associated with dogs fed a raw food diet (isolated from fecal samples), per the authors’ findings from a previous study.