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Open Access Research article

A spatial epidemiological analysis of nontuberculous mycobacterial infections in Queensland, Australia

Michael P Chou14*, Archie CA Clements1 and Rachel M Thomson23

Author Affiliations

1 University of Queensland, Infectious Disease Epidemiology Unit, School of Population Health, Brisbane, Australia

2 Gallipoli Medical Research Centre, Greenslopes Private Hospital, Brisbane, Australia

3 CHRISP-TB, Queensland Health, Brisbane, Australia

4 School of Population Health, University of Queensland, Level 2, Public Health Building, Herston Road, Herston, QLD 4006, Australia

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BMC Infectious Diseases 2014, 14:279  doi:10.1186/1471-2334-14-279

Published: 21 May 2014

Abstract

Background

The epidemiology of infections with nontuberculous mycobacteria (NTM) has been changing and the incidence has been increasing in some settings. The main route of transmission to humans is considered to be from the environment. We aimed to describe spatial clusters of cases of NTM infections and to identify associated climatic, environmental and socio-economic variables.

Methods

NTM data were obtained from the Queensland Mycobacterial Reference Laboratory for the period 2001–2011. A Bayesian spatial conditional autoregressive model was constructed at the postcode level, with covariates including soil variables, maximum, mean and minimum rainfall and temperature, income (proportion of population earning < $32,000 and < $52,000) and land use category.

Results

Significant clusters of NTM infection were identified in the central Queensland region overlying the Surat sub-division of the Great Artesian Basin, as well as in the lower North Queensland Local Government Area known as the Whitsunday region. Our models estimated an expected increase of 21% per percentage increase of population earning < $52,000 (95% CI 9–34%) and an expected decrease of 13% for every metre increase of average topsoil depth for risk of Mycobacterium intracellulare infection (95% CI -3 – -22%). There was an estimated increase of 79% per mg/m3 increase of soil bulk density (95% CI 26–156%) and 19% decrease for every percentage increase in population earning < $32,000 for risk of M. kansasii infection (95% CI -3 – -49%).

Conclusions

There were distinct spatial clusters of M. kansasii, M. intracellulare and M. abscessus infections in Queensland, and a number of socio-ecological, economic and environmental factors were found to be associated with NTM infection risk.

Keywords:
Nontuberculous mycobacteria (NTM); Mycobacterium intracellulare; Mycobacterium kansasii; Mycobacterium abscessus; Spatial epidemiology