Melanie Cole (Host): Non Tuberculous Mycobacterial lung disease is particularly vexing for clinicians to diagnose and treat. Welcome to UAB Med Cast. I'm Melanie Cole Here to tell us about this is Dr. Bryan Garcia. He's an assistant professor and a specialist in critical care medicine and pulmonology at UAB Medicine. Dr. Garcia, it's a pleasure to have you with us again today. We're updating a previous podcast. Can you tell us why we're updating this? What's the prevalence of non tuberculous mycobacterial lung disease and what do we know about this disease?

Dr Bryan Garcia: Thank you for having me. So, the exact prevalence, I should say actually really the number of patients currently in the United States who have some form of infection caused by this group is probably around 70 to 80,000 patients within the United States. And to give you a sense of where that stands compared to other major infections in the United States compared to tuberculosis, which is probably around 8,000 or so patients weakness, maybe 10 times more people in the United States have a non tuberculous microbacterial infection than TB itself.

Melanie Cole (Host): Wow. That's quite a statistic that you just gave us. So one thing I found interesting is that these infections, unlike tb, which you just mentioned, don't require public health reporting. Dr. Garcia, do you feel that this hinders an accurate understanding? You were just talking about prevalence and that incredible statistic. Do you feel that that hinders epidemiology may not be reflective of changes in prevalence?

Dr Bryan Garcia: That's a great question. And, there are some states actually that do require, reporting of the identification of mycobacterial infections other TB, but Alabama is not one of them. And as a result, undoubtedly this is an underrecognized infection that we lack a knowledge of both at a clinical level and at an epidemiologic level. Particularly of importance is, for example, this infection we think is ubiquitous environmental and waterborne infection. And so this better understanding of the epidemiology and of the local incidence and prevalence would help us understand if these patients are indeed acquiring their infections from their local water sources.

Melanie Cole (Host): So then let's talk about that for a minute. Dr. Garcia, what is the mechanism of infection. If we're talking about soil and water, is it aerosolized? Aerobic? How is this ingested? How does it get into the pulmonary system?

Dr Bryan Garcia: So, Non tuberculous microbacterial infections can occur anywhere in the body. And outside of the lungs, they have to be directly, basically inoculated into the site. So, for example, I'll see patients who have been thrown from their cars in a crash and have had these large wounds. And landed in dirt, and now they have these microbacterial infections there. I see patients who have had, this is an increasingly common, hospital acquired infection due to surgeries, and I'll see people with surgical site infections. And then in the lungs, however, this is the most common site, more than 95% of non tuberculous microbacterial infections occur in the lungs.

If you have it in the lung, though, it will not go elsewhere, it will stay in your lung. And that is something that is important for patients and other physicians to understand is that we wouldn't expect it. I speak about this primarily in the non HIV population, so I think we should probably have a caveat that anything we discuss today is in the non HIV population. But one of the things I do mention to patients, Because you have pulmonary NTM, it will stay in your lungs. But the question is how did it get there? And that is a question that we don't have the answer to just yet. We have our suspicions and our hypotheses as to why it's there, but we don't know for sure.

Okay. One of the things I discussed with patients as it pertains to how did it get tear your lung is the concept of chronic silent aspiration. I tell patients that many of my patients I see have hyatel hernias. they describe GERD and so it's important to make sure that they are doing lifestyle modifications to reduce those risks. Why is that important is because mycobacteria is in the water that we drink, and so at night, if you drink a bunch of water and you have a little bit of this, come up with stomach acid. Little by little over time, very small amounts of this essentially provide the local fertilizer that's needed to then acquire a true infection of the lung by these organisms.

Is that the only mechanism or is that the definitive mechanism by which it is acquired? I can't answer that. There's definitely been studies that have shown that shower heads in patients homes. if you swab the shower head, you can identify, clones of the mycobacteria that the person expectorates, suggesting that it is aerosolized. And it does come from these nebulized or aerosolized warm, humid, environments. many patients describe an interest in gardening. We do wonder because we know it's in our soil. Is this how they were inoculated? And patients ask, should they stop drinking their water? Should they stop showering? Should they stop gardening?

And I don't have the answer to that. And the truth is, is because the organism is so ubiquitous, I tell patients, you're gonna come in contact with this no matter what. And there's something about you that made you get an infection from this because I'm coming in contact with it and I'm not having any problems.

Melanie Cole (Host): Is there a process then for checking areas where you suspect it might be present in people's homes since it might be so prevalent around the environment? Is there any way to know?

Dr Bryan Garcia: We don't commonly test for this. Patients ask me this, they ask me, should I stop showering? Should I just drink bottled water? And we really don't know, that there's anything that can be done right now that a patient could really reduce their exposure risk because it is so prevalent. We do know that this infection seems to be more prevalent along coastal regions. We do know that there's data that if you look at kind of heat maps, distribution of the United States, that this infection is most prevalent, along the Atlantic coast.

Down through Florida, around the peninsula and then up into the panhandle and all the way into Houston. It does have this propensity for these flooded regions, and we do wonder if that's one of the reasons why, this exists in these regions in what appears to be greater prevalence, but we don't know that for sure. We don't understand the real mechanisms for this, in their full entirety yet.

Melanie Cole (Host): Mysterious. So let's talk about the hallmarks of it. Some commonly encountered patterns that would signal that someone has an NTM pulmonary infection. Are there diagnostic criteria, Dr. Garcia? Because there are some related disorders where comparisons might be useful for that differential Diagnosises.

Dr Bryan Garcia: 85% of my patients who have pulmonary NTM fall into a unique phenotype. They are previously non-smokers most of them, they have no known history of preexisting lung disease and they are postmenopausal white females. And when we talk to them, and I tell them about this, and I tell them, most of these patients tell me that their family lineage was from Ireland, England, Scotland, and Northern Europe before coming to United States. This is the same region of the world where we know cystic fibrosis comes from.

And most physicians, although they don't take care of cystic fibrosis, especially pulmonologists, are aware and have seen patients during their training with cystic fibrosis and recognize that these patients too, get these types of infections. When we as physicians see patients in our who meet that mold? A postmenopausal white female who has the symptoms of NTM, which includes pulmonary symptoms like cough, shortness of breath, sputum production, maybe they cough up blood, as well as possibly systemic symptoms like fevers, chills, night sweats, fatigue, joint aches, brain fog.

In that phenotype of postmenopausal white female with worsening pulmonary symptoms, that we should be suspecting that this person might have a NTM infection. Bronchiectasis and NTM infection because it's such a unique phenotype that when you see them walk into your clinic, immediately, this should come to their minds. Because we are doing a better job diagnosing it both in the microbiology lab, as well as getting the scent of it using CT scans. We're seeing it being diagnosed more and more and more frequently. Now diagnosis of it is different than the decision to treat it. And these are completely separate, management pathways.

The diagnosis is still the physician is trying to understand, why is this person having worsening pulmonary symptoms once they have identified mac or mycobacteria, AUM complex. One of the subspecies of NTM or any of the other subspecies. Once they have identified the presence of that, then the next decision needs to be, does this person need treatment or not?

Melanie Cole (Host): Well, that is the question then. So do they, and if so, what?

Dr Bryan Garcia: So when I get to this point with my patients, does this person need treatment? What that means is they need to meet certain criteria and the American Thoracic Society and the Infectious Disease Society of America have met and they have made up three main criteria. So they keep it relatively simple. Number one, they need to have the infection in their lung, and they need to find it either two times in sputum or one time on a bronchoscopy. The second criteria is that they need to have radiographic evidence of the disease, and these infections can cause quite a broad array of different radiographic findings. But there are some unique findings.

Tree and bud changes that the radiologists will describe these little tiny micro nodules in the periphery. Those ones are more unique to this, but the truth is, is that NTM infections can cause essentially almost any type of radiographic appearance. The third portion of the criteria to initiate treatment is that the person needs to have symptoms. That you attribute to the infection and that those symptoms need to be significant enough that treatment is justified. And the reason that that is the case is because treatment is very difficult. Treatment is typically multiple antibiotics every day or every other day for 18 months or longer.

And that means side effects from the antibiotics. It means drug drug interactions that need to be, taken into account drug monitoring. And so that is why it's not such a simple organism to treat, and so we really need a patient to have symptoms that are significant enough that they want to go down the pathway of treatment.

Melanie Cole (Host): Where do you see this going in the next 10 years or so? It's such an interesting topic, Dr. Garcia. So what do you see happening similar to other things that we're seeing in the environment? Do you see better reporting? What do you see happen?

Dr Bryan Garcia: All of the above. We will see increasingly diagnosed for the reasons I mentioned. We also are able to identify these organisms better, that was a major problem in the past. In fact, many of my patients tell me that their family members, that their mother died of tuberculosis. And I think to myself, they probably didn't die of tuberculosis. They probably died of this, but we thought it was TB back in 1950. And then, something that's very important to consider is that our population is aging. This is a problem for people who are immunocompromised. That is true. I do see people who are on certain medicines to suppress their immune system that get this infection, but the primary risk factor for this disease is just aging itself.

And so the more elderly patients we have, the more people who we have living with chronic lung disease, the more that we are gonna see this infection as a chronic health disease that becomes more commonly, identified among pulmonologists and I anticipate actually all physicians who participate in primary care internal medicine, in pulmonology.

Melanie Cole (Host): What an interesting topic. I hope you'll join us again, Dr. Garcia, as you learn more and update us as things change or advance. Thank you for joining us. And a physician can refer a patient to UAB Medicine by calling the MIST line at 1-800-UAB-MIST, or by visiting our website at uabmedicine.org/physician. That concludes this episode of UAB Med Cast. I'm Melanie Cole.