Both hospital and residential sinks are breeding grounds for pathogens capable of causing illnesses including pneumonia, wound infections, and Legionnaires’ disease, a severe type of pneumonia stemming from Legionella bacteria, according to researchers at Flinders University in South Australia. Their findings were published this summer in the journal Science of the Total Environment.

“This research shows that hand basins may be playing a significant and underestimated role in health care-associated infections (HAIs),” Harriet Whiley, PhD, an associate professor of environmental health in Flinders’ College of Science and Engineering, said in a news release about her team’s research.

On top of that, residential sinks showed not only a higher number of Legionella bacteria compared to hospital sinks, but also a more diverse bacterial community, Whiley said.

The slimy substance that builds up on sink drains, bowl edges, and faucet bases is far from harmless gunk. It’s a fine layer of bacteria called biofilm, which can pose a public health risk. Handwashing sinks are a recognized source of HAIs, which globally impact 7% of high-income and 15% of low- and middle-income hospital patients, according to the World Health Organization. In this study, researchers sought to explore the bacterial diversity of sink biofilm in homes and hospitals.

The team analyzed 40 biofilm samples that had been “opportunistically” collected from the faucets and drains of nine hospital sinks in New South Wales and eleven residential sinks in South Australia. Researchers collected the residential samples from bathroom sinks and hospital samples from patient ensuite bathrooms, communal hallway sinks, and a staff room sink.

In addition to Legionella, they found more than a dozen potentially pathogenic bacteria including Staphylococcus, which causes staph infections, and Vibrio, the culprit behind cholera (Vibrio cholerae) and rare flesh-eating infections (Vibrio vulnificus). Some of the identified bacteria aren’t typically found in water. Residential sinks had significantly higher relative abundances of seven kinds of potentially pathogenic or corrosive bacteria.

“This poses a risk to patients receiving health care in the home, which has been emerging as an alternative to extensive inpatient hospital stays to reduce the burden on the health care system,” lead researcher and doctoral candidate Claire Hayward said in the news release.

Hospitals have infection control practices in place that include the routine cleaning of sinks. Patients receiving residential health care need to be informed of how they can adequately disinfect sinks at home, Hayward said.

The harboring of dangerous microbes in sink biofilms could increase the rise of antimicrobial resistance, she added.

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How to clean, sanitize, and disinfect household sinks

Assuming you wash your hands before each meal and after each bathroom break—not to mention food preparation and teeth brushing—the kitchen and bathroom sinks in your home take a beating, bacterially speaking. Thoroughly washing such hard surfaces in your home is a three-step process that should always occur in the following order, according to the Centers for Disease Control and Prevention:

1. Cleaning
   • Physically removes most dirt, germs, and impurities
   • Use soap or detergents with water to scrub, wash, and rinse
   • Should be performed regularly
2. Sanitizing
   • Reduces the number of germs to levels considered safe
   • Use weaker bleach solutions or sanitizing sprays
   • Sanitize objects and surfaces that come in contact with mouths (such as toys, infant feeding supplies, countertops, and other surfaces that touch food)
3. Disinfecting
   • Kills remaining germs, further lowering the risk of spreading disease
   • Use an EPA-registered disinfectant or a stronger bleach solution
   • Disinfect surfaces when someone is sick, or if someone is at higher risk of getting sick due to a weakened immune system

For more on bacteria:

• Your Apple Watch or Fitbit may be a breeding ground for E. coli and staph bacteria. Here’s how to clean your fitness tracker
• Your reusable water bottle may be a breeding ground for strep and fecal bacteria. Here’s how to keep it clean
• Superbugs could lower your life expectancy by nearly 2 years, report says. What to know about antimicrobial resistance
• Drug-resistant E. coli may be in the meat you just bought for dinner. Here’s how to keep your kitchen safe