Thinking about a hot tub? Think again, doc warns
Thinking about a hot tub? Think again, doc warns
Atypicals thrive in warm, moist aerosols
You can be sure Gwen Huitt, MD, won’t be installing a hot tub in her house anytime soon. In fact, some would say that Huitt — an infectious disease professor who studies atypical mycobacteria — has a thoroughly atypical view of hot tubs.
An assistant faculty member in the pulmonary division at National Jewish Hospital in Denver, Huitt tells the following cautionary tale for those considering adding such an amenity.
A family of five had all been quarantined with suspected TB. Though they were taking first-line anti-TB drugs while awaiting culture results, all five felt perfectly awful. They were feverish, coughing, and so hypoxic they all needed supplemental oxygen.
"They were all exceedingly ill," Huitt recalls, so miserable, in fact, that they spent most of their time in the family hot tub, hoping the warm, moist aerosols created by the jets would help them recover more swiftly.
Huitt remembers the day she was making rounds while talking with a colleague about the unfortunate family. Something about the case didn’t ring true, she recalls.
"I wonder," she remembers asking her colleague, "do you know whether these people have a hot tub in their house?" A quick phone call put the two sleuths on the right track; sure enough, the family was infected with M. avium, not M. tuberculosis, and the hot tub was the source of the infection.
Such scenarios don’t always turn out that way. Even so, TB is frequently misdiagnosed when it comes to atypicals, says Huitt, who estimates she’s uncovered 20 such hot-tub-related cases. When it comes to terminology, by the way, she much prefers "nontuberculous mycobacteria" or even "mycobacteria other than tuberculous" — MOTT, for short. "They’re quite typical for what they are, actually," she adds.
Whatever name they go by, clinicians will see them more often, she says, and hot tubs probably will play a big role in the increase. "That’s going to be a huge problem," she says. "The incidence of indoor hot tub installation in new houses is on almost a vertical rise."
Ah, a nice slime layer
The trouble with hot tubs is that often the cleansing systems don’t kill environmental mycobacteria such as M. avium, M. chellonae, and M. abscessus. Far from it, in fact. "Hot tubs are a wonderful environment for these mycobacteria," Huitt says. The bugs form slime layers in the tubs, where they lay in wait for the tub’s water jets to be turned on. The result is an aerosolization of mycobacteria right at nose level, and in droplets the perfect size for getting down into the alveoli of the lungs, Huitt says.
With outdoor hot tubs, the danger may not be as great because some of the aerosolized bugs presumably blow away. But the droplets are still the right size and poised at the right level.
There are plenty of reasons to explain why atypicals are so often confused with TB. For one thing, they look the same in an acid-fast staining procedure. Plus, as is well-known to TB controllers, atypicals sometimes produce a positive reaction to the tuberculin skin test, although how often that reaction occurs is not yet thoroughly understood, Huitt adds.
As for symptoms of atypical infections, available evidence suggests there are variations on a common theme. Chiefly, that includes pronounced fatigue, accompanied by either a wet or a dry cough, sometimes accompanied by a low-grade fever (from 99 to 100 degrees Fahrenheit).
Pathogenesis "is insidious — the symptoms don’t come on in one night, but rather over months to a year," Huitt explains. "In most cases, it’s progressive and can cause bronchiectasis," or destruction of the lungs.
Clinicians are baffled often enough that by the time patients arrive at Huitt’s door, many have been subjected to a lung biopsy. That’s something that can be avoided, she adds, simply by taking a careful history. "All you need to ask is whether they have a hot tub, an indoor waterfall, an indoor pool, or any other such indoor water source," she says. If so, a high-resolution computerized tomography scan should be done to see if there are changes consistent with hypersensitivity pneumonitis.
As for treatment, more research is needed, she says. For infections with M. avium and intracellulare — the pair of atypicals known as M. avium complex — current guidelines recommend treatment with biaxin, rifampin, and ethambutol for 18 to 24 months. In severe cases, Huitt often adds the aminoglycoside amikacin.
In the case of M. avium infections, susceptibility testing isn’t routinely recommended, she notes. Even so, such patients sometimes have been dosed with biaxin by the time they’re correctly diagnosed, making biaxin resistance a possibility worth ruling out.
Oddly, the problem with atypicals sometimes isn’t true infection so much as simply a hypersensitive reaction, Huitt says. "Sometimes, the trouble is just that the body is overreacting to the bacteria it’s seeing," she says. "In other cases, it’s clearly causing an infection." Either way, it’s important to work quickly to prevent scarring of the lungs. For that reason, treatment should include steroids.
In hypersensitivity reactions, Huitt also advises giving at least two drugs to which whatever organism is isolated proves susceptible, for perhaps three to six months, depending on the severity of the hypersensitivity reaction.
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