A study by scientists at the Center for Infection and Immunity (CII) at Columbia University's Mailman School of Public Health finds New York City house mice carry bacteria responsible for mild to life-threatening gastroenteritis in people, and some of these bacteria may be resistant to antibiotics.
Researchers studying the bacteria collected 416 mice from residential buildings at seven sites across four boroughs of the city, over the course of the year.
Lead researcher Simon Williams, from Columbia University in New York City, said: "From tiny studios to penthouse suites, New York City apartments are continually invaded by house mice".
Researchers emphasized that more study is needed before they could definitively say that serious and antibiotic-resistant infections could be passed from mice to people.
The researchers also published a second study in the same issue that focuses on viruses found in the house mice. If mice in NY are carrying these pathogens and bacterial genes, it's highly likely that mice in cities all over the world are, too. House mice have been known to carry bacteria as they burrow their way into homes.
In the countryside, it might be different, Viney said, "because then the density of people is less, so mice would be in closer contact with wild animals, perhaps livestock, cows and sheep and pigs".
When they dug deeper, the investigators found evidence of genes that can make the bacteria resistant to common antibiotics.
They found Shigella/enteroinvasive E coli in 14% of the mice (60/416), Clostridium perfringens in 12% (48/416), atypical enteropathogenic E coli in 4% (18/416), Clostridium difficile in 4% (18/416), and Salmonella spp in 3% (13/416).
"We found a whole series of bacteria that are associated with human disease".More news: Chevy Chase Trust Stake Inc. Bought 12440 Shares of Netflix, Inc. (NFLX)
For one of the two papers, Lipkin and his team searched for and analyzed bacteria in the droppings of the captured mice.
Salmonella enterica was one of the bacteria found in the mice.
A leading cause of bacterial food poisoning, Salmonella alone causes 1.2 million reported cases, including 450 deaths, in the U.S. each year. "We would like to very clearly sort out the extent" that mice contribute to antibiotic resistance, Lipkin said.
"You can think of this as the legacy of the meat market", he said.
No one knows, for example, whether antibiotic resistance genes emerged in hospitals, in cities or in rural areas. "There is much less attention paid to things we come into contact with in the developed world like ticks and rodents", says Lipkin. Polymerase chain reaction (PCR) screening identified a wide range of gastrointestinal disease-causing bacteria.
"This gives us a sense of how pervasive antibiotic resistance is", said Schaffner.
Together, the findings show that mice may be an untapped reservoir of potentially risky infections, and suggest that mouse populations should be studied when outbreaks of such infections occur - just as mosquitoes are investigated when cases of West Nile or Zika start to surge.
The researchers say their study is the first to document C. difficile DNA in house mice in an urban setting.