Multidrug-resistant E. coli has been found in supermarket meat samples tested in a Spanish study.

Researchers said findings show consumers may be exposed to bacteria capable of causing severe infections through beef and pork. A full paper is not yet available but initial results were presented at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) this past week.

Dr. Azucena Mora Gutiérrez and Dr. Vanesa García Menéndez, of the University of Santiago de Compostela-Lugo, in Spain, were part of a team that designed a series of experiments to assess the levels of multidrug-resistant and extra-intestinal pathogenic Enterobacteriaceae such as Klebsiella pneumoniae, E. coli, and other bacteria, in meat.

Pathogenic E. coli variants cause either enteric or extra-intestinal infections in humans. The former group includes Shiga toxin-producing E. coli (STEC) and was not part of the study.

Results of analysis
Scientists analyzed 100 meat products including chicken, turkey, beef, and pork, chosen at random from supermarkets in Oviedo in 2020. Almost half contained multidrug-resistant and/or potentially pathogenic E. coli. From those, 82 E. coli isolates were recovered and characterized.

The antimicrobial susceptibility test revealed that 56 isolates of 40 meat samples were multidrug resistant. The highest prevalence of resistance was against ampicillin, aztreonam, nalidixic acid, ceftazidime, and cefuroxime.

Forty of the 100 meat products had multidrug-resistant E. coli. These included E. coli that produced extended-spectrum beta-lactamases (ESBLs), and enzymes that confer resistance to most beta-lactam antibiotics, including penicillins, cephalosporins, and the monobactam aztreonam.

There was a higher presence of ESBL-producing E. coli strains in poultry compared to other types of meat, which is likely due to differences in production and slaughter, said researchers.

Twenty-seven percent of the meat products contained potentially pathogenic extra-intestinal E. coli (ExPEC), which causes urinary tract infections.

Six percent contained uropathogenic (UPEC) E. coli, which is part of the ExPEC group. Two UPEC isolates from chicken and pork were typed and found to be similar to those reported in human clinical isolates.

One percent of samples contained E. coli harboring the MCR-1 gene. This gene confers resistance to colistin, a last-resort antibiotic used to treat infections caused by bacteria resistant to all other antibiotics.

Advice to the public
Scientists said there should be regular assessments on the levels of antibiotic-resistant bacteria, including ExPEC E. coli, in meat products.

“Strategies at the farm level, such as vaccines, to reduce the presence of specific multidrug-resistant and pathogenic bacteria in food-producing animals, would reduce the meat carriage and consumer risk,” said Mora Gutiérrez.

“The consumer plays a key role in food safety through proper food handling. Advice to consumers includes not breaking the cold chain from the supermarket to home, cooking meat thoroughly, storing it properly in the refrigerator, and disinfecting knives, chopping boards, and other cooking utensils used to prepare raw meat appropriately to avoid cross-contamination.”

Human and animal issues
Another study has found evidence that multidrug-resistant bacteria are being passed between cats and dogs and their owners.

Six pets in Portugal and one in the UK carried antibiotic-resistant bacteria similar to those found in their owners. It is unknown whether they were transferred from pet to human or vice versa. 

Researchers tested fecal samples from dogs and cats and their owners for Enterobacterales, a family of bacteria which includes E. coli and Klebsiella pneumoniae, resistant to common antibiotics.

“Owners can reduce the spread of multidrug-resistant bacteria by practicing good hygiene, including washing their hands after collecting their dog or cat’s waste and even after petting them,” said Juliana Menezes from the University of Lisbon in Portugal. 

(To sign up for a free subscription to Food Safety News, click here.)