Rifampicin-resistant tuberculosis in Singapore, 2005 to 2018

Abstract

Background: Globally, about 80% of rifampicin-resistant (RR) tuberculosis (TB) are also resistant to isoniazid. Thus, it is taken as a surrogate marker of multi-drug resistant (MDR) TB. Aim: The objective of this study is to determine the incidence of RR-TB in Singapore, the proportion of MDR TB in them and the treatment outcome of the non-MDR RR-TB patients. Method: All cases of TB are notifiable to the Singapore TB Elimination Programme. The TB registry captures results of all TB cultures, treatment progress and the final outcome of each case. Information of patients with RR-TB notified between 1.1.2005 to 31.12.2018 were extracted from the TB registry for analysis. Results: Between 2005 to 2018, there were 391 patients with phenotypic RR-TB, of whom 307 were MDR TB. 40.5% of the 84 local-born with rifampicin resistance were not due to MDR-TB, compared with 16.3% among the 307 foreign-born. While all foreign-born non-MDR RR TB were first episode TB, 29.4% of the local-born had a history of previous TB. There were 12 patients with HIV co-infection among the 54 with known results. 68 of the 84 RR-TB cases had fingerprinting done; 8 cases in 2 clusters had similar drug susceptibility result. Among the 43 residents, 65.1% had completed treatment, majority were given 18 months of the non-MDR TB treatment regimen; 16.3% died, 5 were still on treatment, 1 had left country and 1 with unknown outcome; only 1 patient had recurrent TB with a different drug susceptibility TB after 3 years. Conclusion: Among the local-born with rifampicin-resistant TB, 40.5% of them were not due to MDR-TB and there was a relatively high rate of HIV co-infection.