Center for Biofilm Engineering

Germs Throw Cold Water on Hot Tub Hygiene

by Cathryn M. Delude, Boston Globe Correspondent

Cue the ''Psycho'' music. There's a stranger in your shower, though it's not a knife-wielding murderer. It's a mysterious consortium of bacteria embedded in shower curtain slime. They also hover in the mist above hot tubs and swim with you in pools. Before you ease onto those pulsating jets of water to soothe your aches and pains, consider that the bacteria in indoor hot tubs, pools, and even decorative fountains and waterfalls may pose a health risk.

The Centers for Disease Control and Prevention in Atlanta has tracked respiratory infections associated with hot tubs and pool use for some time. Recent reports from the Mayo Clinic and the National Jewish Medical and Research Center describe how formerly healthy patients who used indoor hot tubs had developed a productive cough, fever and fatigue, and eventually needed lung biopsies, respirators, intravenous antibiotics and steroids in an attempt to treat their illness. If patients continued using their hot tubs, their conditions worsened. Baffled doctors consulted the research centers, which recommended removing the hot tubs. After the hot tubs were removed, the patients recovered from what the researchers termed ''hot tub lung.''

Technically, hot tub lung covers several conditions, including pneumonia and a hypersensitivity reaction that is not actually an infection. Researchers attribute hot tub lung to bacteria that thrive in the slime on pipes and other wet surfaces. This slime forms as bacteria settle on a surface and begin to secrete a gluey, adhesive substance. That bacteria-laden slime, which is known as a biofilm, forms in the pipes and filters of hot tubs. The tub's powerful jets force some of the biofilm free, and tiny biofilm flakes bubble to the surface and aerosolize into the mist, which people soaking in the tub inhale.

Some of the bacteria that thrive in biofilms belong to the mycobacteria family, which are common in soil and water. Most mycobacteria are harmless, but some cause tuberculosis and leprosy. Others are ''MACs,'' or mycobacterium avium complex, which cause a pulmonary infection that looks like tuberculosis, but is not as dangerous and is not contagious. According to microbiologist Norman Pace of the University of Colorado, MAC infections commonly appear in elderly women who like to garden: ''I suspect they stir up the soil mycobacterium that usually don't harm us, but because their immune systems are weaker with age, they are getting sick.''

Another bacterium that can grow in biofilms is Legionella, the culprit behind the outbreak of Legionnaires' disease during a Philadelphia hotel convention some years ago. Legionella normally inhabit the algae film on ponds, but they also occupy the biofilms in air conditioning condensers and hot-water systems. Bill Costerton, a biofilm researcher at Montana State University at Bozeman, said he believes such outbreaks are just the tip of the iceberg; untold millions have inhaled similar biofilm flakes over the years. While those biofilms set up long-term lodging in our lungs, a healthy immune system can keep the bacteria in check. But if we become stressed, ill or old, we may succumb to some hard-to-diagnose respiratory infection that will never be traced to an air-conditioned room or a hot tub we visited in our youth.

Researchers stress the need for more studies to determine the nature of these bacterial biofilms and their risks to both immune-compromised and healthy people. Studies on hot tubs in hospitals and other therapeutic facilities will be controversial, according to Pace, because they may show that people are getting sick from facilities they are visiting for their health. And yet, Pace said, there is not much more those facilities can do currently to protect their visitors. Most already follow rigorous hygiene standards, but their best efforts still may not be sufficient. Biofilms can persist through disinfection because their slime protects the bacteria from chemicals. Likewise, many bacteria actually thrive in hot water, while the heat reduces the effectiveness of disinfectants. Scientists are developing ways to prevent biofilms from accumulating, but so far, slime has the upper hand.

Several years ago, researchers also isolated tiny amounts of MAC bacteria from the scum on shower curtains. While shower-curtain MACs pose little risk to us because they rarely aerosolize, some researchers hypothesize that they may be the source of pneumonias that late-stage AIDS patients often contract.

After reading about MACs in shower curtain scum, Pace became curious about what else was in there. He found that about 45 percent of the bacteria belong to the sphingomonas species, which are well-known slime producers. He was surprised to find that another 45 percent are methanobacteria, which eat methane and break down components in plastic and other materials. These methane lovers are probably not dangerous, but they may nurture both slime-producing bacteria and disease-causing stowaways. Pace surmised that the slime producers somehow depend on the methane lovers. In turn, the slime provides a safe haven for a few MACs and other potentially harmful bacteria.

Ultimately, finding ways to prevent slime could be hot tub lung's last gasp. Meanwhile, we need to drain our hot tubs, dry out the biofilms, disinfect the pipes and filters, and scrub, scrub, scrub. If you should come down with an unexplained respiratory infection, researchers recommend discussing your use of indoor hot tubs and pools with your doctor.

There's still a lot to learn about everyday hygiene and the microbes we want to subdue. ''This research illustrates,'' Pace said, ''that the unknown character of the microbial world is not only all around us, but we are literally immersed in it.''

This story ran on page B13 of the Boston Globe on 5/6/2003.
© Copyright 2003 Globe Newspaper Company.

Published with permission:

Cathryn M. Delude
The Writing Company
http://www.thewritingco.com
Cathryn@thewritingco.com

Back to top