Fido and Fluffy could unleash drug-resistant microbes

BOSTON — New studies find a rise in drug-resistant urinary tract infections in pets, raising concerns that companion animals may serve as microbe reservoirs that could contribute to the spread of potential superbugs. About four in 10 U.S. households own dogs, which sleep with us, eat off our plates, lick our faces and leave plenty of poop to scoop. Cat ownership is nearly as prevalent.

It’s not clear whether pets are picking up the resistant microbes from their owners, or vice versa, said Cátia Marques, a veterinary medicine doctoral candidate. She presented the research, conducted by scientists from the University of Lisbon in Portugal, June 20 at a joint meeting of the American Society for Microbiology and the Interscience Conference on Antimicrobial Agents and Chemotherapy. More research is needed to answer that question, she said.

Either way, scientists worry that companion animals provide another haven for bacteria to mingle and pick up genes that give them resistance to drugs, said Michael Schmidt of the Medical University of South Carolina in Charleston, who was not involved in the new work. “It is a substantial issue,” he said.

Other research has examined human-pet sharing of bacteria, but the subject has been little explored for urinary tract infections, which are extremely common. The new research found a growing resistance in veterinary infections to antibiotics critical for treating human illness. In one study, samples of the bacterium Proteus mirabilis taken over 16 years in Portugal showed a steady climb in the prevalence of resistant strains. An example: Resistance to a class of drugs known as third-generation cephalosporins grew from 2 percent of samples in 2004 to 20 percent today. Other research found worrisome multidrug resistance in infections caused by Klebsiella. In a third study, which tested for resistance in urinary tract infections in pets across Europe, patterns of drug resistance in dogs and cats tracked that of humans, the researchers found.

In humans, doctors have watched warily as resistance to urinary tract infections has grown. In May, scientists reported the discovery of a woman with a urinary infection resistant to colistin, a rarely used drug of last resort (SN Online: 5/27/16). It’s not clear how the patient contracted the resistance, but given colistin’s role as a last-ditch drug, it raised the specter of an unstoppable microbe.

While the new research is broader, it isn’t the first study to raise concerns about the role of companion animals in difficult-to-treat urinary infections. In 2013, German researchers writing in the Journal of Antimicrobial Therapy described finding carbapenem-resistant Escherichia coli and Klebsiella urinary infections in six dogs — a discovery later called a phenomenon “of great concern” in a commentary in the same journal. E. coli and P. mirabilis are the two biggest causes of urinary tract infections. Carbapenem, which the researchers in Portugal did not test for, is also considered a drug of last resort for urinary infections.            

Whether humans are giving resistant organisms to their animals or vice versa, the findings emphasize that the battle against resistance needs a global strategy that involves veterinarians along with human doctors and patients, Marques said. “We need to have a common public health approach,” she said.

Schmidt also cautioned that people who are particularly vulnerable to urinary infections, such as pregnant women, take extra care around their pets, especially when cleaning up after them. “If you do have a companion animal and you’re prone to these infections,” he said, “be very strict with your hand hygiene before you eat.”