Multidrug-resistant E. coli has been found in 40% of supermarket meat samples tested in a Spanish study. E. coli strains capable of causing severe infections in people were also highly prevalent, this year’s European Congress of Clinical Microbiology & Infectious Diseases is expected to hear.

The World Health Organization class antibiotic resistance as one of humanity’s most significant public health threats. Multidrug-resistant bacteria can spread from animals to humans through the food chain. Still, due to commercial sensitivities, data on levels of antibiotic-resistant bugs in food is not made widely available.

Assessment of levels of multidrug-resistance
Dr. Azucena Mora Gutiérrez and Dr. Vanesa García Menéndez, of the University of Santiago de Compostela-Lugo, Lugo, Spain, together with colleagues from other research centers, designed a series of experiments to assess the levels of multidrug-resistant and extraintestinal pathogenic 

Enterobacteriaceae (Klebsiella pneumoniae, E. coli and other bacteria that can cause multidrug-resistant infections such as sepsis or urinary tract infections) in meat on sale in Spanish supermarkets.

They analyzed 100 meat products (25 each of chicken, turkey, beef and pork) chosen randomly from supermarkets in Oviedo in 2020.

Most (73%) of the meat products contained levels of E. coli within food safety limits.

Despite this, almost half (49%) contained multidrug-resistant and/or potentially pathogenic E. coli. From those, 82 E. coli isolates were recovered and characterized. In addition, 12 K. pneumoniae isolates were recovered from 10 of the 100 meat products.

Forty of the 100 meat products contained multidrug-resistant E. coli (56 of the 82 E. coli characterized). These included E. coli that produced extended-spectrum beta-lactamases (ESBLs), enzymes that confer resistance to most beta-lactam antibiotics, including penicillins, cephalosporins and the monobactam aztreonam.

Differences in production and slaughter
The percentage of positive samples for the carriage of ESBL-producing E. coli per meat type was: 68% turkey, 56% chicken, 16% beef and 12% pork. This higher presence of ESBL-producing E. coli strains in poultry compared to other types of meat is likely due to differences in production and slaughter.

Twenty-seven percent of the meat products contained potentially pathogenic extraintestinal E. coli (ExPEC). ExPEC possesses genes that allow them to cause disease outside the gastrointestinal tract. ExPEC causes the vast majority of urinary tract infections (UTIs), is a leading cause of sepsis and is the second most common cause of neonatal meningitis.

Meanwhile, 6% of the meat products contained uropathogenic (UPEC) E. coli – UPEC is part of the ExPEC group; these possess specific virulence traits that allow them to cause UTIs.

Just 1% of the meat products contained E. coli harboring the MCR-1 gene. This gene confers resistance to colistin, an antibiotic of last resort used to treat infections caused by bacteria resistant to all other antibiotics.

Is regular assessment needed?
The study’s authors say that their research shows consumers may also be exposed to these bacteria through beef and pork. They call for regular assessment of levels of antibiotic-resistant bacteria, including ExPEC E. coli, in meat products.

“Farm-to-fork interventions must be a priority to protect the consumer. For example, implementation of surveillance lab methods to allow further study of high-risk bacteria (in farm animals and meat) and their evolution due to the latest EU restriction programs on antibiotic use in veterinary medicine,” adds Dr. Mora.

“Strategies at 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.”