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.

BACTERIAL WGS AND HOST GENOME-WIDE SNP ANALYSIS OF TUBERCULOSIS PATIENTS IN THAILAND

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Use of network analysis multidrug-resistant tuberculosis contact investigation in Kanchanaburi, Thailand

OBJECTIVE

To characterise MDR-TB outbreak and incorporate social network analysis with contact investigation to detect case-contact linkages and clusters.

METHODS

MDR-TB cases registered in the district hospital between October 2012 and September 2015 were interviewed and their contacts were investigated. A relationship-based weighted network was constructed.

RESULTS

Among 43 interviewed MDR-TB cases, 20 (47%) were male, five (12%) were asymptomatic (and discovered incidentally) and 22 (51%) had underlying diseases. From the documented 115 contacts, 61 (53%) were household contacts and 49 (43%) were close (non-household) contacts; 70 (61%) were screened for TB using various tests. In this network, we prioritised 37 contacts connected with more than one MDR-TB patient. The largest cluster was identified in the pharmacy unit of the hospital.

CONCLUSION

This investigation yielded a significant number of MDR-TB contacts, and social network analysis facilitated the prioritisation for screening. Social network analysis is useful and feasible in this program setting and complements MDR-TB contact investigation.

Association analysis of susceptibility candidate region on chromosome 5q31 for tuberculosis

Chromosome 5q31 spans the T helper (Th) 2-related cytokine gene cluster, which is potentially important in Th1/Th2 immune responses. The chromosome 5q23.2-31.3 has been recently identified as a region with suggestive evidence of linkage to tuberculosis in the Asian population. With the aim of fine-mapping a putative tuberculosis susceptibility locus, we investigated a family-based association test between the dense single nucleotide polymorphism (SNP) markers within chromosome 5q31 and tuberculosis in 205 Thai trio families. Of these, 75 SNPs located within candidate genes covering SLC22A4, SLC22A5, IRF1, IL5, RAD50, IL13, IL4, KIF3A and SEPT8 were genotyped using the DigiTag2 assay. Association analysis revealed the most significant association with tuberculosis in haplotypes comprising SNPs rs274559, rs274554 and rs274553 of SLC22A5 gene (P(Global)=2.02 x 10(-6)), which remained significant after multiple testing correction. In addition, two haplotypes within the SLC22A4 and KIF3A region were associated with tuberculosis. Haplotypes of SLC22A5 were significantly associated with the expression levels of RAD50 and IL13. The results show that the variants carried by the haplotypes of SLC22A4, SLC22A5 and KIF3A region potentially contribute to tuberculosis susceptibility among the Thai population.

Genome-wide SNP-based linkage analysis of tuberculosis in Thais

Tuberculosis, a potentially fatal infectious disease, affects millions of individuals annually worldwide. Human protective immunity that contains tuberculosis after infection has not been clearly defined. To gain insight into host genetic factors, nonparametric linkage analysis was performed using high-throughput microarray-based single nucleotide polymorphism (SNP) genotyping platform, a GeneChip array comprised 59 860 bi-allelic markers, in 93 Thai families with multiple siblings, 195 individuals affected with tuberculosis. Genotyping revealed a region on chromosome 5q showing suggestive evidence of linkage with tuberculosis (Z(lr) statistics=3.01, logarithm of odds (LOD) score=2.29, empirical P-value=0.0005), and two candidate regions on chromosomes 17p and 20p by an ordered subset analysis using minimum age at onset of tuberculosis as the covariate (maximum LOD score=2.57 and 3.33, permutation P-value=0.0187 and 0.0183, respectively). These results imply a new evidence of genetic risk factors for tuberculosis in the Asian population. The significance of these ordered subset results supports a clinicopathological concept that immunological impairment in the disease differs between young and old tuberculosis patients. The linkage information from a specific ethnicity may provide unique candidate regions for the identification of the susceptibility genes and further help elucidate the immunopathogenesis of tuberculosis.