Genotype sequencing shows household plumbing the source of some M. avium infections among local patients, Lankenau researcher finds

Main Line Health clinicians treating patients with Mycobacterium avium complex (MAC) infections should consider alerting those patients that the disease-causing bacteria may have come from their water supply at home.

Leah Lande, MD, a specialist in pulmonary and critical care at Lankenau Medical Center, was the lead author of a study that recovered M. avium from 30 of 37 households tested in Montgomery and Delaware counties, including 19 of 21 M. avium patient households. For 11 of those 21 M. avium patients, the genotype of bacteria from their respiratory samples matched those collected from their home plumbing, demonstrating that their home water supply was very likely the cause of their illnesses.

The researchers found the bacteria in showerheads, sink faucets, shower pipes, humidifiers connected to central heating units (with household plumbing as their water source), refrigerator ice/water dispensers, hot water heaters and other home plumbing.

MAC infections can be life-threatening, especially for those with chronic structural lung disorders, such as COPD or bronchiectasis, or who are immunocompromised. These infections are particularly difficult to treat, noted Dr. Lande. Even when patients are successfully treated, the infection can recur, so finding the bacterial reservoir is crucial, she continued.

“While it’s known that environmental sources, such as commercial and household plumbing, can be reservoirs for nontuberculous mycobacteria, the most important finding was that for 11 of 21 M. avium patients in our study, the isolates we recovered from their respiratory systems and from their household plumbing were genetically identical,” said Dr. Lande, who also serves as a clinical assistant professor at the Lankenau Institute for Medical Research (LIMR). “For seven of the 21 M. avium patients, the respiratory isolate genotype did not match that found in the patients’ own homes but did match that found in neighboring households, suggesting clonal infection in our municipal water supply.”

The samples were taken in 2010 to 2012, and one of Dr. Lande’s study colleagues performed the tedious task of genomic sequencing. “The sequencing took a long time, which is why we’re just announcing the results now,” said Dr. Lande.

In all, the researchers tested the household plumbing of 26 MAC patients of Lankenau Medical Center, all of whom lived within 20 miles of one another. Patient median age was 77 years, and all were women. The researchers also tested the household plumbing of 11 control participants from the same areas in Montgomery and Delaware counties as the patient group. In the control group, median age was 64 years, and all were women.

All 37 households tested were supplied by the same water company that retrieves water from the Schuylkill River and was processed by the same treatment plant.

M. avium was recovered from 30 of the 37 patient and control households tested. Many of the households that tested positive were in Narberth, Bala Cynwyd, Gladwyne, Ardmore, Wynnewood, Lansdowne and Upper Darby, to name a few areas. Dr. Lande said the water company serving these regions informed her it is not required by federal law to test for M. avium.

“People are frequently exposed to M. avium, but the percentage of those who acquire an infection from it is low,” explained Dr. Lande. “It’s usually only those who are susceptible, such as those with chronic lung disease, who will become sick. So our findings shouldn’t concern the general population.

“That said,” she continued, “we wanted to alert Main Line Health clinicians that this is occurring in our area. Physicians may want to advise their patients from our area who’ve had MAC infections to consider instituting precautions to avoid inhalation of aerosolized water to help reduce their chance of reinfections.”The researchers’ study, “Mycobacterium avium in Community and Household Water, Suburban Philadelphia, Pennsylvania, USA, 2010–2012,” was published in the journal Emerging Infectious Diseases published by the Centers for Disease Control and Prevention. The full manuscript is available here: https://wwwnc.cdc.gov/eid/article/25/3/18-0336_article

Future studies

Dr. Lande said she and her colleagues will expand this study in the future. They are currently working with an epidemiologist from the National Institutes of Health (NIH) to measure the effect of instituting environmental and behavioral changes in order to minimize exposure to MAC in the environment and potentially improve outcomes in MAC patients.

 

Another study, whose full results will be presented at the upcoming American Thoracic Society meeting by pulmonary/critical care fellow Spencer Whealon, DO, showed that 94% of MAC and bronchiectasis patients were aspirating during sleep, compared with only 11% of control patients. They hypothesize that silent aspiration may be contributing to the pathogenesis of bronchiectasis and pulmonary MAC infection.

 

In a planned third study, also in collaboration with NIH, the researchers will place specialized filters on water sources in patients’ homes and then measure the air samples to determine mycobacterial load.

 

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