Infectious Disease: Nontuberculous Mycobacteria
Guest: Dr. Preston Church – Infectious Diseases, MUSC
Host: Dr. Linda Austin – Psychiatrist, MUSC
Dr. Linda Austin: I’m Dr. Linda Austin. I’m interviewing, today, Dr. Preston Church, who is Associate Professor of Medicine and a specialist in the area of infectious disease, as well as epidemiology, here at the Medical University of South Carolina. Dr. Church, you have a number of different interests in infectious disease, I understand, and one of them is an organism that will be new to many of us, including me, actually, which is, a big word, nontuberculous mycobacteria.
Dr. Preston Church: Or, otherwise known as NTM.
Dr. Linda Austin: NTM.
Dr. Preston Church: Right.
Dr. Linda Austin: Okay, let’s break down those words. Nontuberculous, what does that word mean?
Dr. Preston Church: It’s a way of distinguishing this group of bacterial infections that are probably best described as cousins of tuberculosis. So, these close cousins may cause a variety of disease, but would not be exactly the same as tuberculosis, and don’t have some of the features we see in tuberculosis.
Dr. Linda Austin: And, tuberculosis, itself, is a mycobacterium?
Dr. Preston Church: That is correct.
Dr. Linda Austin: Right. So, it’s like having the same last name, but not be in the direct family?
Dr. Preston Church: There you go.
Dr. Linda Austin: Right. Is this a relatively new illness? Is this kind of a Johnny- come-lately illness?
Dr. Preston Church: It’s, actually, probably been around for awhile. And, these have been known for decades. But, within the last 10 years, there have been a number of new developments that I think I have really heightened the awareness of the importance of this particular group. Twenty of thirty years ago, we may have only known about, perhaps, ten or fifteen different nontuberculous mycobacteria. We, now, are aware of probably at least 100 different types. Perhaps 60 of those are responsible for various forms of disease.
And, we see, actually, several different types of disease from these agents, depending on the patients that we’re looking at. So, the world of HIV, and the world of transplantation, have created large patient populations that have susceptibilities to certain of these agents, and certain types of disease presentations. But, we’ve also seen, or are looking to recognize, more and more, that there are large groups of people who may have underlying lung problems that are also very prone to either carrying these bacteria or being infected by these bacteria. And it’s a very complicated relationship.
Dr. Linda Austin: So, just to break this down a little bit then, it sounds as if this is a bacteria that doesn’t usually strike, say, young healthy adults, that the people who tend to succumb to it may have HIV, may be older, may have lung disease of some other sort, and that this is an opportunistic infection, then, that comes in. Am I correct?
Dr. Preston Church: It’s partially true. I think the one category that sort of deviates from that notion a little bit is that we recognize this infection in women who are commonly, actually, middle aged, say, perimenopausal, or postmenopausal. Those individuals, actually, one might frequently recognize as maybe having a more athletic type of build. There may be something about some shape to the chest, and therefore the lungs, that might predispose to this infection. All of the dynamics, actually, aren’t entirely clear. So, is it the nature of the lung that allows this infection to occur? Is it that this infection occurs that creates, actually, some pathology in the lung? It’s probably a two-way street that we don’t fully understand. But we certainly recognize the co-occurrence of these two things.
Dr. Linda Austin: So, tell me, then, about the illness itself. What’s the nature of the disease caused by this mycobacterium?
Dr. Preston Church: It’s very sneaky. So, let’s take this group of middle aged women, for example. What may happen is that we’ll often see these infections, maybe, sort of interwoven with an underlying problem that’s referred to as bronchiectasis. Bronchiestasis is sort of repeated episodes of inflammation of the airways of the lungs. It may just frequently be thought of as bronchitis. And we will see individuals who may get labeled as having asthma, having bronchitis. They will have attacks that come and go. They, often, might feel better with antibiotics.
These things may happen on and off for years without ever truly being recognized until perhaps, finally, one day a chest x-ray actually looks a little bit abnormal and someone can actually see a little evidence of change. Actually, oftentimes, by then, if we were to do more advanced imaging, we can often find that there’s been significant evidence of change. So, it can be very difficult to pick up, in fact, early on because it is slow. And the illness, especially during its early years, is often not very dramatic.
Dr. Linda Austin: So, it can last for years then? Is that right?
Dr. Preston Church: Yes. Absolutely.
Dr. Linda Austin: And, what is the natural course of the illness if it’s untreated?
Dr. Preston Church: First, I would have to say that the pace varies from individual to individual. But, if, again, we’re going to talk about this specific group of individuals, again, we may see waxing and waning infections or inflammation periods where there’s more shortness of breath, more cough, more discomfort. That may wax and wane for, perhaps, years. Gradually, portions of the lung may get significantly damaged. And, again, part of what’s difficult to tease out is that there may be the co-occurrence of other infections as well, and that all of these things sort of feed into each other to make the whole issue worse.
But, after, perhaps, periods of 10, 12, 15 years, actually, an individual may look very much like somebody who has emphysema, the same type of impairment to the lung, the same sort of coughing, and productive cough, like people often might associate with somebody who has lung disease from smoking.
Dr. Linda Austin: And, as with emphysema, can the damage to the lung tissue be permanent, and irreversible, at that point?
Dr. Preston Church: That’s correct.
Dr. Linda Austin: I see. Does the infection spread beyond the lungs?
Dr. Preston Church: For this type of case that we’re talking about, generally not. Now, individuals with immune deficiency either created by us, because of transplantation, or because of underlying disease, may have infection with some of these organisms that can occur in a single location, or it can be systemwide.
Dr. Linda Austin: How do you treat it? Is it easily treated, or difficult to treat?
Dr. Preston Church: Well, it depends on a number of factors. It depends on which of these many different species of NTM we might be working with. It also depends on, perhaps, where the site of the infection is. So, if we talk about, again, individuals with lung disease, it can actually be a very stubborn problem to treat. We often will use two or three different antibiotics. We’re often talking about a period of a couple years of therapy. And that is to get what we think might be a success rate in actually eliminating this bacteria of, perhaps, only 50 percent.
So, oftentimes we end up on longer drug courses, repeated drug courses. Some of the medications we use have their own problems that patients encounter. It’s a real challenge. And, unfortunately, at this point, you know, it’s hard sometimes to pick out, in all situations, who needs to be treated; what, exactly, the benefit of treatment will be. These are all areas under active investigation. But there’s a lot we don’t know.
Dr. Linda Austin: You mentioned earlier that the disease has actually been around for a very long time, but is it a relatively new focus of research interest?
Dr. Preston Church: Yes, it is. I think for years there have really only been a few centers that have had a significant focus on dealing with NTM infections. I think, though, that the recognition about just how important this is as a contributor to lung disease in a variety of different individuals has lead to more and more people getting on board with trying to systematically look at these patients, study these patients, and also to form collaborations in order to do research, and really try to answer some of these questions.
Dr. Linda Austin: Just to give us an idea of the scope of the problem, cases per year in South Carolina, or in the United States, do you know those numbers offhand?
Dr. Preston Church: You know, it’s not a reportable illness, and so there is often not a good sense of exactly what those numbers may be.
Dr. Linda Austin: Well, let me ask you, then, this way. At our center, Medical University of South Carolina, how many cases might come, roughly, in the course of a year?
Dr. Preston Church: Probably, if I were to base it on the cases I believe I’m aware of, I would submit that we have about 50 or so patients who are probably in care at MUSC. There are, I believe, considerably more cases than that. In fact, I know there are considerably more than that in South Carolina. Again, a lot of these patients are, you know, a physician’s office may have a couple of these patients within the office. A specialist’s office may have only a small number. And so, they’re, really, dispersed across the state.
Dr. Linda Austin: So, it’s certainly not a wild epidemic, but it’s not that rare either, if we have 50 cases here.
Dr. Preston Church: No. It’s certainly not rare. And, again, I think that some of the issues are that there’s more out there than we know about, because of some of the difficulty is in diagnosis. And some of the problem is with actually thinking about the diagnosis in a timely fashion.
Dr. Linda Austin: Is it particularly contagious if a family member, for example, has it? Does the rest of the family have to be especially careful?
Dr. Preston Church: Interestingly, to the best of my knowledge, and the scientific literature, there’s no documentation of person-to-person spread. This is something that lives within our environment. And, identifying environmental sources is sometimes a bit of a challenge. One can raise suspicions. But we know a number of these live in wetland environments. And so, if one wanted to go look at one of the members of this group that we refer to as m-avium, brown water swamps are a favorite hangout of m-avium. Well, where are the brown water swamps in the U.S.? They’re in the Southeastern U.S.
A number of these things live in tap water, or public water supplies. They can live in pools. They can live in hot tubs. They are very hardy, and they’re very well adapted to living in the world around us.
Dr. Linda Austin: Dr. Church, thanks so much for talking with us today.
Dr. Preston Church: You’re welcome.
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