Nontuberculous mycobacteria (NTM) are opportunistic organisms compared to their deadly counterpart, Mycobacterium tuberculosis. However, they are growing in prominence, transmitting disease worldwide. Commonly found in dust and soil, NTM are worrying microbiologists and health experts alike. But is tap water an unsuspected vehicle for these deceptively harmful infections?
Understanding NTM biology, ecology, and clinical impact
NTM and their 190 recognized types are in some of the most accessible places. They spread infections and cause the most issues in those with lung disease or immunocompromised systems. NTM varieties do not include tuberculosis or the cause of Hansen’s disease.
Despite these omissions, NTM are still a strong disruptor to pulmonary and extrapulmonary health. They commonly exacerbate lung infections but can also infect any region affected by surgery, trauma, and even a medical device. Blood and lymph nodes are several other targets, demonstrating NTM’s versatility and burdens on medical systems.
NTM can be resistant to antimicrobials, but infections are curable. Patients often undergo treatment for six months to a year, using multiple antibiotics to tackle the infection. It is somewhat similar to treatment for M. tuberculosis, though accessibility to most treatments for these infectious diseases is becoming more challenging to find.
NTM are not particularly contagious bacteria, though they may appear to transmit from person to person because the surface area for them to thrive is large. NTM love humidity and moisture. People may assume the water from their sinks and showers is safe, but it can be highly contaminated, despite treatment.
Their environmental persistence is what makes them so alarming, and their concentration in reservoirs, like drinking water, is growing. Every source, from a natural river to a human-made ice machine, can be an NTM conduit.
Water systems are an avenue for NTM
NTM can enter municipal water systems in numerous ways. It naturally exists in organic water systems like lakes, streams, and swamps, but it can also form in fountains and other constructed water features. NTM can enter water distribution systems by cross-contamination, such as water tanks and pipe infrastructure. Eventually, runoff taints the soil, getting into food via agriculture.
The bacteria are also ideal producers of biofilms, building up in everything from water tanks to old city pipes. Biofilm’s composition makes it difficult to treat and eliminate from reservoirs. It protects the bacteria with many slimy layers, allowing it to keep growing. Dissolving it requires unique treatment methods compared to simply tackling NTM, demanding more advanced and targeted methods from treatment experts.
NTM infections transmit to humans in more ways than consumption. Aerosolization easily spreads strains like M. avium from showerheads and humidifier sprays. Inhaling dust is another source. It is resistant to desiccation, which allows NTM to flourish within the particles. Contact-based infections are also known, especially in fisheries and households maintaining fish tanks. Maintenance can expose families to NTM, but the fish could have also carried the bacteria from previous exposure.
Systematic reviews in the last several years point to a steadily growing rate of NTM infections, insinuating potential future outbreaks. Strains like M. avium and M. abscessus are some of the most notable, with increasing annual rates of change. Researchers note these trends should incite more investigation, as the cause for these shifts is still relatively under-researched.
Factors driving NTM proliferation in water systems
While the primary drivers of NTM proliferation are still up for debate, there are several hypotheses.
Aging infrastructure
Worldwide water infrastructure has aged, with outdated pipe materials and resistance to technological advancement preventing it from upgrading. Most of the U.S.’s lines are nearly a century old, with an average life expectancy of 78 years. An estimated $625 billion would be needed to upgrade it within the next two decades, eliminating countless opportunities for NTM to spread.
Biofilm accumulates faster in older systems, but it also has other problems. Water stagnates and slows flow, fostering the perfect environment for NTM to grow. Additionally, degrading materials that cause corrosion promote the spread because it is easier for biofilm to adhere.
Poor water treatment
Studies have examined a treatment plant’s effectiveness in eliminating NTM levels. During pre-treatment, staff used cetylpyrindinium chloride during the pre-treatment phase to remove some NTM. It had mixed results on various M. avium strains, only reducing the presence of Va14 by 20% and A5 by 80%.
While later stages could eliminate more, it shows why a stronger method is essential. Alternatively, plants will need to deploy diverse solutions. Other factors, like adjusting incubation temperatures and comparing slow- and rapid-growing types, are necessary for refining techniques. In the study, the plant also incorporated coagulation, sedimentation, biological filtration and many other measures. Many sample plates during the collection phase still contained quantifiable NTM or numbers that were too many to count.
Environmental influences
Treatment characteristics such as temperature, pH, and disinfectant concentrations need to be adjusted to be more effective at discouraging NTM growth in water systems. NTM struggles to survive in high-temperature and alkaline environments, and some treatment practices do not obtain the necessary levels to discourage growth.
Public health implications and at-risk populations
Immunocompromised individuals, those with internal medical devices, patients with trauma, those with chronic lung disease, and elderly individuals are all at higher risk of NTM exposure. Unfortunately, hospitals are not immune to NTM spread, making medical facilities another prominent transmitter.
Patients will begin to distrust hospitals and medical offices if regulation and policy fail to expand NTM oversight. Recent standards, such as ANSI/AAMI ST108 establish guidelines for water and steam quality when processing medical devices. Professionals must use drinkable water for rinsing, though it notes that treatment may be necessary. This is why risk analyses are required to identify microbial contaminants prior to device administration.
However, greater expansion is necessary to make tap water safer. The U.S. Center for Disease Control (CDC) offers surveillance recommendations, such as reporting outbreaks through its Emerging Infections Program community interface. It contributes to a wider body of research, sharing deeper insights with medical professionals about the vigilance of NTM.
The program has also revealed even more at-risk populations. CDC reports revealed trends with race and age. Non-Hispanic Black individuals have become a higher-risk demographic, highlighting issues of health inequity. Water treatment is less prominent in marginalized and minority communities, suggesting deeply embedded environmental injustice.
Source-to-tap mitigation strategies
Researchers are relying on source-to-tap investigations to discover the most practical and thorough techniques for fighting NTM. Water treatment innovations are at the forefront of progress, but work is far from complete. Reducing exposure comes in many forms, including but not limited to:
At-home water filtration: using recommended filters from all tap sources that can catch NTM and change them as directed.
Minimizing bathroom aerosols: enhancing ventilation in residential and commercial bathrooms to lower the chances of inhalation.
Staying away from high-risk areas: saunas, hot tubs, and other places without aerators can be NTM breeding grounds.
Being careful with humidifiers: filtering and sterilizing water before loading humidifiers.
Moistening soil: potting soils and peat moss are transmitters, so dampen surfaces and wear masks before use.
Maintaining water-dispensing devices: updating and cleaning showerheads, faucets, and other equipment to prevent biofilm buildup or rust.
Increasing water heater temperatures: raising temperatures to 131 degrees Fahrenheit can kill most NTM, but this requires households to be more cautious to avoid scalding.
These actions may seem insignificant, but treatment plants often only provide an initial cleanse, so all at-home measures are meaningful. A combination of purification and filtration can be even more powerful to supplement municipal efforts.
Clinicians will also recommend lowering unnecessary aspiration, such as preventing gastroesophageal reflux disease and not smoking. The excessive activity makes these individuals more prone to NTM illnesses.
Medical facility practices
Initial diagnostic inadequacies often prevent medical facilities from identifying NTM early enough. Advancements in PCR technology are allowing doctors to find the most infectious and widespread strains more easily. Furthering these technologies will help water experts locate the most contaminated water sources with greater accuracy.
Treatment plant strategies
There are more advanced measures from a treatment plant perspective. Industrial sensor-based technologies and artificial intelligence will be invaluable assets for making evidence-backed decisions about water quality. They can notify professionals when stagnation occurs or when biofilm buildup becomes an issue.
A multipronged approach will be vital for a treatment plant’s success. For example, incorporating point-of-use treatments like ultraviolet LED lights is effective against M. abscessus, while initial chlorination may inhibit growth for other strains. However, more research is needed for chemical treatments, as many NTM varieties are resistant to conventional disinfectants like chlorine.
Additionally, advocating for infrastructure advancements with more environmentally resilient materials and smarter oversight will be pivotal in discovering growth points and killing NTM colonies before they catalyze beyond control. Upgrading plumbing infrastructure and embedding it with corrosion-resistant materials that promote continuous flows will establish the ideal foundation for slowing NTM spread.
Safeguarding public health in the age of NTM
NTM will continue to persist without continued, cross-collaborative dedication from health care professionals, microbiologists, and water treatment experts. Experts can discover better water treatment methods and spread awareness, so people understand the signs of NTM-related infections.
Access to safe drinking water is a Sustainable Development Goal from the United Nations for a reason, and allowing NTM to spread due to inaction will cause more problems for future generations.
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