CHICAGO, Nov. 28 (Xinhua) -- A study led by Washington University School of Medicine in St. Louis has shed light on how the superbug methicillin-resistant Staphylococcus aureus (MRSA), often referred to as staph, is introduced into households and, once there, how it can spread among family members.
The study, published this week, focused on the households of 150 otherwise healthy children with a median age of three years old. The children had been treated for staph infections at hospitals and pediatric practices from 2012 through 2015. Also enrolled were nearly all of the kids' family members, which totaled 692 people, and 154 cats and dogs.
Researchers visited each home five times during a one-year period to obtain swab samples from people's nostrils, armpits and groins. As for the cats and dogs, the researchers collected samples from inside the nose and along the animals' backs, the main petting zone. They found MRSA on nearly half of the people and on one-third of the pets at least once over the year.
Pets offered one of the study's most interesting findings. The study's senior author, Stephanie A. Fritz, a Washington University associate professor of pediatrics in the Division of Pediatric Infectious Diseases, said, "We thought they might be a reservoir for the staph germ and play a role in its spread. But our study showed that cats and dogs were more likely to get staph from humans than the other way around."
Additionally, the researchers tested for staph on 21 household surfaces such as refrigerator door handles, sink faucets, bathroom countertops, bed sheets, bath towels, light switches, telephones, television and videogame controllers, and computer keyboards and mice.
A molecular analysis of each staph sample -- 3,819 in all -- served as a bacterial fingerprint, allowing the researchers to pinpoint exact transmission dynamics of specific strains.
"Previous studies have not distinguished between staph strains," Fritz said. "By parsing it out, we were able to determine different risk factors for how the staph germ gets into the house and then, once there, how it is spread."
The prevailing wisdom is that staph is transmitted from person to person, and that is often true. "But our study shows that the household environment also serves as a key reservoir for ongoing staph transmission. In fact, there were a number of instances in which the environment was the only potential source for transmission," Fritz said.
"Household acquisition of MRSA is driven equally by the introduction of new staph strains into a home and transmission of established strains among family members within a household," Fritz added.
The study's participants also answered more than 100 questions about hygiene and other personal habits.
The study found that, people who practice frequent handwashing after using the bathroom, before preparing food, before eating and after changing a diaper are less likely to bring staph into their homes; and children, especially those attending daycare, are more likely to bring staph into their homes.
The study also found that, the spread of MRSA is more likely when there is considerable MRSA contamination on environmental surfaces; in homes with lower cleanliness scores; in rented and crowded homes; when people share bedrooms, beds, hand, face or bath towels or hygiene items such as razors and toothbrushes with someone carrying the transmitted strain.
Hygiene habits that reduce the risk of picking up the staph germ in the household include showering instead of taking a bath, brushing teeth at least twice a day, and using an antibacterial liquid hand soap, according to the study.
Once rare, MRSA infects hundreds of thousands of people in the United States each year and kills about 20,000. Antibiotic overuse has made MRSA more common and difficult to treat because of the bacteria's contagiousness coupled with its resistance to standard infection-fighting drugs. Infected individuals also face a high risk of recurrence.