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Non-tuberculous mycobacterial (NTM) infections

Non-tuberculous mycobacterial (NTM) infections - What it is

​It is an infection caused by a group of bacteria collectively known as non-tuberculous mycobacteria (NTM). Majority of infections by NTM involve the lung but involvement of other parts of the body such as the lymph nodes, skin and soft tissue, bone and joint are also seen. Hospital acquired infections from NTM such as surgical wound infections and bloodstream infections are also increasingly recognised. 

Non-tuberculous mycobacterial (NTM) infections - Symptoms

​Similar to tuberculosis, NTM infections generally progress in a slower, gradual manner compared to the usual bacterial infections. NTM lung infection typically presents with chronic symptoms of prolonged cough, breathlessness, fatigue and non-specific chest pains. Patients with NTM lung infection commonly have associated chronic lung conditions (e.g bronchiectasis) that causes dilation of the airways and permanent scarring of the lungs. In instances where it involves blood vessels in the lungs, it may cause patient to cough out blood, called hemoptysis in medical terms. Constitutional symptoms such as prolonged fevers and weight loss are also common symptoms. 

Non-tuberculous mycobacterial (NTM) infections - How to prevent?

​There are no established measures that would prevent this infection. NTM organisms are readily found in our environment and could even be found on our bodies, such as in the airways leading to the lungs. In majority of cases, this situation would not result in infection. Rather, NTM infection usually happens in predisposed patients (see below), such as those with poor immunity or underlying chronic lung diseases. In these cases, the organism is able to overcome the patient’s body defences resulting in clinical infection. 

Non-tuberculous mycobacterial (NTM) infections - Causes and Risk Factors

NTM lung infections usually affect patients who have pre-existing chronic lung conditions. Examples of these conditions include chronic obstructive pulmonary disease (COPD), bronchiectasis (scarring of lung tissue and dilated airways) and previous tuberculosis infection of the lungs. 

Those with hospital acquired NTM infections are usually related to recent procedures or presence of indwelling medical devices in the body. For example, a patient who had recent surgery done may be complicated by NTM infection of the surgical wound. Or a patient undergoing dialysis via a catheter may have NTM infection of the device resulting in a bloodstream infection. 

As these are organisms readily found in the environment, exposure to non-medical procedures with unhygienic practices can also cause infection. An example would be a skin infection following tattooing from using ink contaminated with NTM.

Any underlying condition that causes a person’s immunity to be affected can also predispose to NTM infections. In those situations, there is a possibility of more severe infection or NTM infection involving more than 1 area of the body. 

Non-tuberculous mycobacterial (NTM) infections - Diagnosis

NTM infections are usually diagnosed by a combination of findings. Firstly, there has to be a positive culture result relevant to the area of infection that is positive for growth of NTM. Secondly, the clinical findings should be consistent with NTM infection. Thus, an inflamed post-surgical wound with pus expressed and positive culture of NTM from the pus itself would give us the clinical diagnosis of NTM post-surgical wound infection. 

The diagnosis of lung NTM infection on the other hand is more complex and would require a combination of positive respiratory sample cultures, compatible symptoms and compatible lung imaging findings suggestive of NTM infection. 

Non-tuberculous mycobacterial (NTM) infections - Treatments

Treatment of NTM infections is complex and depends of a variety of factors such as the specific organism, site and severity of infection. However, a couple of general principles would apply universally for NTM infections. Firstly, treatment requires a combination of 2 or more different antibiotic agents. Secondly, the treatment course is expected to be prolonged, generally in terms of weeks and months. If there are surgical options available, this should be exercised to optimise cure. 

With regards to NTM lung infections, the current practice in our institution would be to give a combination of 3-4 antibiotics including intravenous antibiotics in the first 4-6 weeks of treatment. This would be followed by a combination of 2-3 oral antibiotics for 6-12 months. Improvement of symptoms is expected during the course of treatment in most cases but relapses and incomplete resolution are the norm. Treatment progress will be closely monitored by the physician with regular follow ups to ensure treatment response as well as early detection and prevention of side effects of prolonged antibiotic treatment. 

Non-tuberculous mycobacterial (NTM) infections - Preparing for surgery

Non-tuberculous mycobacterial (NTM) infections - Post-surgery care

Non-tuberculous mycobacterial (NTM) infections - Other Information

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