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Nontuberculous disease, colonization rates increasing in Taiwan
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Over a 13-year period, the annual prevalence of tuberculosis in Taiwan decreased; however, the prevalence of nontuberculosis mycobacteria disease and colonization increased, according to a cross-sectional analysis conducted at the National Taiwan University Hospital.
“In Taiwan, the rate of nontuberculous mycobacteria (NTM) isolation among cultures positive for mycobacteria increased significantly during the period 2000-2012, whereas the rate of M. tuberculosis isolation decreased,” Jung-Yien Chien, MD, and colleagues wrote in their study. “Moreover, the prevalence of NTM pulmonary infection and colonization rapidly increased with time. This phenomenon was more evident among patients of advanced age and among male patients.”
For this study, the authors analyzed samples from 13,652 patients who were registered in the hospital’s Mycobacterial Laboratory database. Analysis showed that 56.9% of these patients were positive for NTM, while 43.1% were positive for M. tuberculosis. In addition, there was a significant downward trend in M. tuberculosis isolation among positive mycobacteria cultures and a significant upward trend in NTM isolation (P<.01 for both).
“These findings suggest that, although the rates of NTM pulmonary infection have gradually increased in Taiwan, more than half of NTM isolates caused colonization only,” the authors wrote.
Age may be a factor in the increasing prevalence. The rate of NTM isolation and the risk for developing NTM disease increased significantly with age. In patients aged 85 years or older, isolation rates for M. tuberculosis were 40.7% and 59.3% for NTM. Half of the NTM disease and colonization cases were found in patients who were aged 65 years or older.
Gender may also play a role in acquiring mycobacterial infections. The researchers found that men were more likely to have M. tuberculosis infections, NTM pulmonary infections and NTM colonization than women. Among patients aged older than 45 years, the male-to-female ratio was significantly higher in patients with TB than in patients with NTM disease or colonization.
“This finding might indicate that older women are more resistant to TB than NTM infection/colonization,” the authors wrote.
Disclosure: Infectious Disease News could not verify financial disclosures at the time of publication.
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