Prevalence and associated risk factors of drug-resistant tuberculosis in Thailand: results from the fifth national anti-tuberculosis drug resistance survey

OBJECTIVE

To assess the prevalence and risk factors of drug-resistant tuberculosis (TB), the fifth national anti-TB drug resistance survey was conducted in Thailand.

METHODS

A cross-sectional study was conducted by stratified cluster sampling with probability proportional to size of TB cases from public health facilities in 100 clusters throughout Thailand from August 2017 to August 2018. Susceptibility testing of TB isolates to first- and second-line anti-TB drugs was performed on Löwenstein-Jensen medium using the indirect proportion method. Multiple imputation was done for handling missing data using Stata 16. The proportion of TB cases with drug resistance was determined. The odds ratio was used to evaluate risk factors associated with drug-resistant TB.

RESULTS

Among 1501 new TB and 69 previously treated TB cases, 14.0% [95% confidence interval (CI): 12.1-16.1] and 33.4% (95% CI: 23.6-44.8), respectively, had resistance to any anti-TB drug. Multidrug-resistant TB accounted for 0.8% (95% CI: 0.5-1.4) of new TB cases and 13.0% (95% CI: 6.5-24.4) of previously treated TB cases. Drug-resistant TB was associated with prior TB treatment [odds ratio (OR), 2.9; 95% CI: 1.6-5.0], age at 45-54 years (OR, 1.6; 95% CI: 1.0-2.4), male (OR, 1.5; 95% CI: 1.0-2.1) and human immunodeficiency virus (HIV) infection (OR, 1.6; 95% CI: 1.0-2.4).

CONCLUSIONS

The burden of drug-resistant TB remains high in Thailand. Intensified prevention and control measures should be implemented to reduce the risks of drug-resistant TB in high-risk groups previously treated, especially individuals of late middle age, males and those with coinfection of TB and HIV.

Indo-Oceanic Mycobacterium tuberculosis strains from Thailand associated with higher mortality

SETTING: This study was conducted among tuberculosis (TB) patients in a highly endemic Thai province.OBJECTIVE: To evaluate the association between different Mycobacterium tuberculosis lineages and clinical characteristics, especially mortality.DESIGN: We enrolled 1,304 TB patients registered from 2002-2011 with culture isolates whose lineages were identified by specific regions of deletion. Data on mortality within 1 year of follow-up were extracted from the registration system and hospital records. Mortality-associated risk factors, including bacterial lineages, as independent variables were analysed using Cox regression models.RESULTS: Of 1,304 isolates, 521 (40.0%) and 582 (44.6%) belonged to Indo-Oceanic and East-Asian lineages, respectively. Indo-Oceanic strains significantly increased the mortality risk compared with East-Asian strains (adjusted hazard ratio [aHR] 1.42, 95%CI 1.02-1.99) or modern lineages (aHR 1.49, 95%CI 1.08-2.06) in the 172 patients who died within 1 year after TB diagnosis. The former also caused significantly higher mortality than modern lineages among patients who died within 6 months after TB diagnosis (aHR 1.62, 95%CI 1.12-2.35). No significant association was found between drug resistance and death.CONCLUSION: In Thailand, the Indo-Oceanic lineage of M. tuberculosis increased mortality risk compared with modern lineages or the East-Asian lineage, the latter being considered highly virulent in previous studies.