Distinguishing Between Tuberculosis and NTM: A Patient's Guide

Is it tuberculosis or NTM (non-tuberculous mycobacterial infection)?

Hello Doctor: My father had contact with an open tuberculosis patient for a period of time, and he has been coughing with sputum lately.
Last month, a CT scan was performed, and the doctor suspected tuberculosis.
Three sputum smears were negative, but three cultures were positive for Nontuberculous Mycobacteria (NTM), and the specific strain has not yet been identified.
Is it possible that the sputum collection method was incorrect, leading to a failure to detect the tuberculosis bacteria? Or could the NTM be a contaminant or a normal respiratory tract inhabitant that was misidentified as a pathogenic organism? Is there a standard in the laboratory for differentiation? Since tuberculosis was suspected, he has already started medication; what should we do now that he is halfway through the treatment? Is it NTM, tuberculosis, or could it be both? How should he continue his medication? I am very concerned that if the tuberculosis treatment is interrupted, it could lead to drug resistance.
Does the anti-tuberculosis medication have any effect on NTM? I am very anxious about what we should do next.
Please help clarify these concerns.

A-Nan, 50~59 year old female. Ask Date: 2015/10/22

Dr. Huang Yiwen reply Pulmonology

Dear Anan,
Hello, this is a profound topic regarding the issues of tuberculosis (TB) and nontuberculous mycobacteria (NTM).
It indeed poses challenges for many physicians.
The coexistence of TB and NTM is possible because when a laboratory cultures NTM, they may not continue to check for the presence of TB, as NTM cultures generally grow faster and can obscure the detection of TB bacteria.
NTM originates from the environment, including water and soil, and is a type of opportunistic pathogen (in Taiwan, half of the laboratory cultures are NTM).
Individuals with immunocompromised conditions require more treatment.
NTM is not transmitted from person to person, unless there are three or more NTM strains present along with clinical symptoms and chest X-ray (CXR) abnormalities, in which case treatment for NTM may be initiated.
However, it is essential to perform NTM typing (commercial products can differentiate 15 types) to determine the appropriate medication.

In contrast, TB treatment is relatively straightforward.
If TB medication does not lead to clinical improvement or changes in X-ray findings, TB treatment can be discontinued, and the diagnosis can be adjusted to NTM (considering whether NTM treatment is necessary).
If there is improvement, treatment can continue even without strain evidence.
The emergence of drug resistance is more complex, but it does not occur simply from stopping medication; irregular adherence to the treatment regimen is more likely to lead to resistance.
Next, I would like to hear your thoughts on this matter.
I see that you have a solid understanding of medical knowledge, so I believe you will have no issues.
Changhua Hospital cares about you.

Reply Date: 2015/10/22

More Info

Distinguishing between tuberculosis (TB) and non-tuberculous mycobacteria (NTM) infections can be quite challenging, especially given the overlapping symptoms and diagnostic complexities. Your father's situation, where he has been diagnosed with NTM after multiple tests, raises several important questions regarding the accuracy of the diagnosis and the appropriate treatment moving forward.

Firstly, it is essential to understand that NTM, which includes various species of mycobacteria that are not classified as TB, can be found in the environment, particularly in soil and water. These organisms can cause lung infections, especially in individuals with underlying lung conditions or compromised immune systems. In your father's case, the fact that he has been in contact with an open TB patient does raise concerns, but the negative smear tests and positive cultures for NTM suggest that he may not have TB.

Regarding your question about the possibility of not collecting the correct sputum sample, it is indeed possible. Sputum collection techniques are crucial for accurate diagnosis. If the sample is not collected properly, it may not contain the bacteria being tested for, leading to false-negative results for TB. However, the laboratory typically follows strict protocols to minimize such errors, and multiple negative smear tests alongside positive cultures for NTM strengthen the likelihood that TB is not present.

As for the concern about NTM being a contaminant or a normal inhabitant of the respiratory tract, it is important to note that while NTM can be part of the normal flora, they can also cause disease, particularly in susceptible individuals. The laboratory will have specific criteria to determine whether the NTM isolated is clinically significant, which usually includes the presence of symptoms and radiographic evidence of disease.

Now, regarding the treatment dilemma, it is crucial to continue the anti-TB medications until a definitive diagnosis is made. Stopping TB treatment prematurely could lead to the development of drug-resistant TB if it is indeed present. Anti-TB medications are not effective against NTM, and the treatment for NTM is typically more prolonged and involves a combination of antibiotics for at least 12 months, depending on the specific species and the patient's clinical response.

Given that your father has already started anti-TB treatment, it is advisable to consult with a specialist in infectious diseases or a pulmonologist who can evaluate his case comprehensively. They may recommend further testing, such as molecular testing or additional cultures, to confirm the presence of NTM and rule out TB definitively. If NTM is confirmed as the primary pathogen, the doctor will guide you on transitioning to the appropriate NTM treatment regimen.

In summary, the key steps moving forward include:
1. Consult a Specialist: Seek a referral to an infectious disease specialist or pulmonologist for a thorough evaluation and management plan.

2. Continue Current Treatment: Do not stop anti-TB medications until a definitive diagnosis is made, as this could lead to complications.

3. Further Testing: Discuss the possibility of additional tests to confirm the NTM species and assess the need for specific treatment.

4. Monitor Symptoms: Keep track of any changes in symptoms and report them to the healthcare provider.

5. Educate Yourself: Understanding both TB and NTM can empower you and your family to make informed decisions regarding treatment and management.

Navigating the complexities of these infections can be daunting, but with the right medical guidance and support, you can ensure that your father receives the appropriate care.

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