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Pet dogs and cats could be passing on potentially deadly antibiotic-resistant bacteria to their owners.
Separate studies in Germany and Portugal have found that some pets harbour microbes that can withstand important antibiotics, including one used as a last resort. Other work suggests resistant bacteria are found in pet food, especially the increasingly popular raw food products.
One of the new studies analysed raw, tinned and dry dog food brands sold commercially in Europe. Although some live gut bacteria were present in all three types, raw food had by far the highest level of microbes resistant to multiple antibiotics.
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Such bacteria were in all nine samples of raw food, one out of 22 of the tinned samples and in none of the 15 dry foods. “The main risk is that these bacteria can be a reservoir in pets’ and humans’ gut of resistance genes able to be transferred to other [disease-causing] bacteria,” says Ana Freitas at the University of Porto in Portugal, who was involved in the study.
Read more: Antibiotic resistance genes can be passed around by bacteria in dust
Two new studies of faecal samples taken from pets and their owners suggests transfer to humans may sometimes happen, although neither yet has data on whether the animals were given raw or cooked food.
In work by Carolin Hackmann at the Charité – University Hospital Berlin, Germany, and her colleagues, 23 out of 45 dogs studied carried antibiotic-resistant bacteria, as well as one out of 71 cats. In two dogs, the microbes matched strains of bacteria found in their owners’ stool samples. This small number suggests pets aren’t a major source of drug-resistant microbes in their owners, says Hackmann.
In a Portuguese study, two out of 55 dogs had gut microbes with resistance to the last-resort antibiotic colistin, which could be needed to treat bacterial pneumonia in intensive care. One dog shared this strain with its owner – although without further genetic analysis, it is unknown which direction the microbe had travelled.
All the research was submitted to the European Congress of Clinical Microbiology and Infectious Diseases that had been due to take place in Paris this month.
Read more: Resistant bacteria don’t just evade drugs – they are fitter too
These last resort antibiotics could be needed if people develop bacterial pneumonia arising from coronavirus infection, although there haven’t been any known covid-19 pneumonia cases in which pet food was implicated.
Even before the current covid-19 pandemic, antibiotic resistance was seen as one of the biggest public health threats because it can make conditions such as pneumonia, sepsis and wound infections untreatable.
While doctors are trying to slow the spread of antibiotic resistance by prescribing these medicines only when necessary, resistant bugs are also common in farm animals because the drugs are widely used in agriculture.
The findings reinforce the need for people to practise good hygiene around their pets’ food and when picking up their faeces, says Constança Pomba at the University of Lisbon in Portugal, who was involved in one of the studies. “The level of sharing from the households that we have studied is very low. But this is a concern,” she says.
Brendan Clarke, head of the Raw Feeding Veterinary Society, says a large internet survey of pet owners suggested it was very rare for people to catch infections from raw pet food. “We’ve got to be careful we don’t scaremonger.”
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