Isolation Prevalence of Pulmonary Nontuberculous Mycobacteria in Ontario in 2007

Mohammed Al Houqani,Pamela Chedore,Kevin May,Theodore K Marras,Frances Jamieson,Mauli Mehta

doi:10.1155/2011/865831

Abstract

The reported prevalence of pulmonary nontuberculous mycobacteria (NTM) infections is increasing. To determine the 'isolation prevalence' of NTM in 2007 and compare it with previously published research that examined the increasing rates of isolation of NTM from clinical pulmonary specimens between 1997 and 2003. Isolation prevalence was investigated retrospectively by reviewing a cohort of all positive pulmonary NTM culture results from the Tuberculosis and Mycobacteriology Laboratory, Public Health Laboratory (Toronto, Ontario) in 2007, which identifies at least 95% of NTM isolates in Ontario. Isolation prevalence was calculated as the number of persons with a pulmonary isolate in a calendar year divided by the contemporary population and expressed per 100,000 population. Changes in isolation prevalence from previous years were assessed for statistical significance using generalized linear models with a negative binomial distribution. In 2007, 4160 pulmonary isolates of NTM were collected from 2463 patients. The isolation prevalence of all species (excluding Mycobacterium gordonae) was 19 per 100,000 population in 2007 - an increase from previous observations reported for Ontario - corresponding to an average annual increase of 8.5% from 1997 to 2007 (P<0.0001). Average annual increases in isolation prevalence of Mycobacterium avium complex (8.8%, P<0.0001) and Mycobacterium xenopi (7.3%, P=0.0005) were largely responsible for the overall increase, while prevalence rates of rapidly growing mycobacteria remained relatively stable. The isolation prevalence of pulmonary NTM continues to increase significantly in Ontario, supporting the belief that pulmonary NTM disease is increasingly common.

Highlights

BACKgROund: The reported prevalence of pulmonary nontuberculous mycobacteria (NTM) infections is increasing
COnClusIOn : La prévalence d’isolement d’infections pulmonaires mycobactériennes non tuberculeuses (MBN) continue d’augmenter considérablement en Ontario, ce qui étaye la conviction que la maladie pulmonaire MBN est de plus en plus courante
Because there were no changes in the laboratory techniques used to detect mycobacteria in Ontario between 2003 and 2007, it was reasoned that a general increase in awareness of pulmonary NTM would have led to an increase in the number of mycobacterial culture requests, but not necessarily an increase in the measured isolation prevalence

Summary

OrIgInal artIcle

Isolation prevalence of pulmonary nontuberculous mycobacteria in Ontario in 2007. Mohammed Al Houqani MBBS FRCPC1, Frances Jamieson MD FRCPC2,3, Pamela Chedore MLT4, Mauli Mehta, Kevin May MLT4, Theodore K Marras MD FRCPC5. Because there were no changes in the laboratory techniques used to detect mycobacteria in Ontario between 2003 and 2007, it was reasoned that a general increase in awareness of pulmonary NTM would have led to an increase in the number of mycobacterial culture requests, but not necessarily an increase in the measured isolation prevalence. To investigate whether the increase in isolation prevalence was due to a surveillance bias, the annual change in the number of respiratory specimens submitted for mycobacterial culture between 1997 and 2007, and differences in the fraction that were positive for NTM were examined. The annual number of respiratory specimens submitted for mycobacterial culture generally increased throughout the study period, with the Nontuberculous mycobacteria in Ontario

Avium complex

Findings

Pulmonary isolates