The superbug MRSA (methicillin-resistant Staphylococcus aureus) can spread easily from people to household pets, according to a new study that underscores the importance of frequent hand washing.
MRSA was once rare, and so-called staph infections used to be more easily treated with antibiotics, researchers note in the Lancet Infectious Diseases. But due in part to overuse of antibiotics, MRSA now infects hundreds of thousands of people and kills about 20,000 people each year in the U.S. alone.
For the current study, researchers took a closer look at what might happen inside the home to spread infections, focusing on the households of 150 otherwise healthy children who had been treated for MRSA infections along with 692 family members and 154 household cats and dogs.
“The household environment plays a key role in the transmission of MRSA in the community setting,” senior study author Dr. Stephanie Fritz of Washington University in St. Louis said in a statement. “This suggests that aggressive attempts to rid MRSA from household surfaces may significantly lower the number of MRSA infections we’re seeing now.”
“It wasn’t just one patient who would get a staph infection but multiple members of a family,” Fritz added. “Within a year, we’d see many patients return with recurring infections.”
Staphylococcus aureus bacteria generally live harmlessly on the skin in about one-third of the human population. The bacteria can spread through skin-to-skin contact or by touching contaminated surfaces.
A typical staph infection resembles a pus-filled bug bite and when it goes untreated or patients don’t respond to treatment it can cause complications like pneumonia, severe organ damage and death if it enters the bloodstream, bones or organs.
In the study, researchers visited each home five times during a one-year period to obtain swab samples from people’s nostrils, armpits and groins. For cats and dogs, researchers collected samples from inside the nose and along the animals’ backs, where they’re most often petted.
Almost half of the people and nearly one-third of the cats and dogs had MRSA at last once over the course of the yearlong study period.
“It’s sometimes thought that cats and dogs spread harmful germs,” Fritz said.
“We thought they might be a reservoir for the staph germ and play a role in its spread,” Fritz added. “But our study showed that cats and dogs were more likely to get staph from humans than the other way around.”
Additionally, researchers tested for staph on 21 household surfaces such as refrigerator door handles, sink faucets, bathroom counter tops, bed sheets, bath towels, light switches, telephones, television and video game controllers, and computer keyboards and mice.
People who transmitted MRSA to other individuals or animals were 25% more likely to share bath towels than people who didn’t spread staph, the study found. And, people who caught MRSA from others in their homes were 23% less likely to be homeowners and 33% more likely to share bedrooms with infected individuals, the study found.
Pets were often transmission recipients, but rarely the sole transmission source of MRSA.
New strains of MRSA were 14% less likely to show up in households where people frequently washed their hands.
People who practice frequent hand washing (with soap or hand sanitizer) after using the bathroom, before preparing food, before eating and after changing a diaper are less likely to bring staph into their homes, the study results suggest.
Children, especially those attending day care, are more likely to bring staph into their homes, making frequent hand washing even more essential for these families.
One limitation of the study is that results might be different in households without young children or with only adults in the home, the study authors note.
Even so, the findings underscore that good hygiene habits can help prevent the spread of MRSA within households, the study team concludes.