New research being presented at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID), held online this year, reveals that raw dog food is a major source of antibiotic-resistant bacteria, making it an international risk of public health.

With some of the many drug-resistant bacteria in raw dog food identical to those found in hospital patients in several different European countries, researchers say the tendency to feed dogs raw food may be driving the spread of bacteria. resistant to antibiotics.

Drug-resistant infections kill about 700,000 people a year globally and, with the figure projected to rise to 10 million by 2050 if no action is taken, the World Health Organization (WHO) classifies antibiotic resistance as one of the biggest threats of human public health.

To find out if pet food is a potential source of the spread of antibiotic-resistant bacteria, Dr Ana R. Freitas, Dr Carla Novais, Dr Luísa Peixe and colleagues from UCIBIO, Faculty of Pharmacy, University of Porto, Portugal analyzed the feed of dogs from supermarkets and pet stores for Enterococci.

Enterococci are opportunistic bacteria. They live harmlessly in the intestines of humans and animals, but can cause serious infections if they spread to other parts of the body.

A total of 55 dog food samples (22 wet, 8 dry, 4 semi-wet, 7 treatments and 14 frozen raw) from 25 nationally and internationally available brands were included in the study. Raw frozen foods included duck, salmon, turkey, chicken, lamb, goose, beef and vegetables.

Thirty samples (54%) contained Enterococci. More than 40% of Enterococci were resistant to the antibiotics erythromycin, tetracycline, quinupristin-dalfopristine, streptomycin, gentamicin, chloramphenicol, ampicillin, or ciprofloxacin. There was also resistance to vancomycin and teicoplanin (2% each) and 23% of enterococci were resistant to linezolid.

Linezolid is a recent antibiotic, used in severe infections when other drugs have failed, and is considered an important treatment by the WHO.

All raw dog food samples contained enterococci resistant to many drugs, including linezolid-resistant bacteria. In contrast, only three of the non-raw samples contained drug-resistant bacteria.

Genetic sequencing revealed that some of the multidrug-resistant bacteria in raw dog food were identical to the bacteria isolated from hospital patients in the UK, Germany and the Netherlands. Genetically identical bacteria have also been found in farm animals and wastewater in the UK.

In another experiment, researchers transferred antibiotic resistance genes from bacteria found in dog food to other, experimental bacteria – suggesting that this could also happen in nature.

Researchers conclude that dog food is a source of bacteria that are resistant to the latest antibiotics and can spread to humans. Dog food, they add, could be a neglected driver of antibiotic resistance globally.

Dr Freitas adds: “Close human contact with dogs and the commercialization of brands studied in different countries pose an international public health risk.

“European authorities need to raise awareness about the potential health risks when feeding pets raw foods and producing dog food, including ingredient selection and hygiene practices.

“Dog owners should always wash their hands with soap and water immediately after treating pet food and after taking feces.”

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