Introduction Non-Tuberculous Mycobacteria (NTM) are ubiquitous in the environment meaning clinical, radiological and microbiological criteria are important in diagnosing NTM lung disease. A multicentre, retrospective review was performed to characterise NTM disease within our region and describe the outcomes of current management.

Methods All NTM positive sputum samples received by the National Mycobacterium Reference Laboratory (NMRL) from Imperial College NHS Healthcare and North West London Hospitals NHS Trusts between 2010–2014 were extracted. HIV-negative individuals with ≥2 positive sputum samples or ≥1 positive bronchoalveolar lavage were included. Demographic, clinical, radiological, microbiological, management and outcome data was obtained from electronic records.

Results 1190 NTM sputum samples were identified from 822 individuals. 152 individual patients met inclusion criteria for analysis. Table 1 describes cohort demographics.

Within the cohort 48/152 (32%) were treated for NTM disease. All treated subjects and 74/104 (71%) non-treated subjects met international guidelines for diagnosis of NTM infection, which included positive clinical, radiological (cavities or bronchiectasis +/- nodules or infiltrates) and microbiological criteria. Mycobacterium avium complex (MAC) was the most commonly isolated (68/152; 45%) and treated organism (21/48; 44%) followed by Mycobacterium kansasii (11/48; 23%). 19/48 (40%) completed treatment (median duration: 17 months [IQR: 12–24]). 10/48 (21%) remain on treatment (median duration: 18 months [IQR: 11–36]), 11/48 (23%) stopped treatment due to side effects and 13/48 (27%) were either lost to follow up or treated for Mycobacterium tuberculosis.

Of those treated, 29/48 (60%) culture converted; 23/29 (79%) remain negative at 12 months post culture conversion. Of 19/48 who completed treatment, 5/19 (26%) had symptomatic or radiological disease progression compared to 11/28 (39%) who did not complete treatment. 11/48 (23%) patients died within the treatment group. Within the untreated subjects who met international guidelines for NTM infection (74/104), mortality was 19/74 (26%) (p = 0.83).

Discussion NTM is a challenging disease with only 39% of eligible subjects receiving treatment and a high associated mortality. Furthermore, only 40% starting treatment completed it and the 21% who remain on treatment have been treated for a median duration of 18 months to date. Unlike similar HIV-negative UK cohorts, MAC pulmonary disease is the most prevalent.