Abstract
BackgroundThe incidence of non-tuberculous mycobacteria (NTM) isolation from humans is increasing worldwide. In England, Wales and Northern Ireland (EW&NI) the reported rate of NTM more than doubled between 1996 and 2006. Although NTM infection has traditionally been associated with immunosuppressed individuals or those with severe underlying lung damage, pulmonary NTM infection and disease may occur in people with no overt immune deficiency.Here we report the incidence of NTM isolation in EW&NI between 2007 and 2012 from both pulmonary and extra-pulmonary samples obtained at a population level.MethodsAll individuals with culture positive NTM isolates between 2007 and 2012 reported to Public Health England by the five mycobacterial reference laboratories serving EW&NI were included.ResultsBetween 2007 and 2012, 21,118 individuals had NTM culture positive isolates. Over the study period the incidence rose from 5.6/100,000 in 2007 to 7.6/100,000 in 2012 (p < 0.001). Of those with a known specimen type, 90 % were pulmonary, in whom incidence increased from 4.0/100,000 to 6.1/100,000 (p < 0.001). In extra-pulmonary specimens this fell from 0.6/100,000 to 0.4/100,000 (p < 0.001).The most frequently cultured organisms from individuals with pulmonary isolates were within the M. avium-intracellulare complex family (MAC). The incidence of pulmonary MAC increased from 1.3/100,000 to 2.2/100,000 (p < 0.001). The majority of these individuals were over 60 years old.ConclusionUsing a population-based approach, we find that the incidence of NTM has continued to rise since the last national analysis. Overall, this represents an almost ten-fold increase since 1995. Pulmonary MAC in older individuals is responsible for the majority of this change.We are limited to reporting NTM isolates and not clinical disease caused by these organisms. To determine whether the burden of NTM disease is genuinely increasing, a standardised approach to the collection of linked national microbiological and clinical data is required.
Highlights
The incidence of non-tuberculous mycobacteria (NTM) isolation from humans is increasing worldwide
It is not clear why this is so, and possible explanations include an increase in the number of individuals with structural lung damage making them more susceptible to mycobacterial infection, more mycobacteria in the environment, improved laboratory detection techniques, a greater awareness of their potential relevance - resulting in more frequent mycobacterial culture being performed, or the result of more investigation to exclude M. tuberculosis
We demonstrate that whilst there has been a significant increase in a number of NTM, the overall rise is largely explained by pulmonary Mycobacterium avium-intracellulare complex
Summary
The incidence of non-tuberculous mycobacteria (NTM) isolation from humans is increasing worldwide. In England, Wales and Northern Ireland (EW&NI), the incidence of NTM in all sample types was previously reported to have almost trebled between 1995 (0.9 per 100,000 population) and 2006 (2.9 per 100,000 population) [2]. NTM are isolated in immunocompetent individuals, with or without pre-existing structural lung damage [4]. It is not clear why this is so, and possible explanations include an increase in the number of individuals with structural lung damage making them more susceptible to mycobacterial infection, more mycobacteria in the environment, improved laboratory detection techniques, a greater awareness of their potential relevance - resulting in more frequent mycobacterial culture being performed, or the result of more investigation to exclude M. tuberculosis. We demonstrate that whilst there has been a significant increase in a number of NTM, the overall rise is largely explained by pulmonary Mycobacterium avium-intracellulare complex
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