LAUSR

In May 2016, the WHO recommended a 9-12 month MDR-TB treatment regimen for pulmonary MDR-TB patients without confirmed resistance to a medicine in this regimen (excluding isoniazid resistance). The majority of MDR pulmonary TB (PTB) cases in Singapore originate from South-east Asian countries where capacity for full drug susceptibility testing (DST) is not widely available. We report the phenotypic drug susceptibility pattern of these cases to detemine their eligibility for the WHO shorter MDR-TB regimen. From 2002 to 2016, there were 214 foreign-born MDR PTB cases diagnosed in Singapore. These originated from Indonesia (n=76), Myanmar (n=54), China (n=37), Philiippines (n=18), Vietnam (n=15), India (n-7), Bangladesh (n=4) and others (n=3). Nine (4.2%) were XDR and 28 (13.1%) pre-XDR cases. Phenotypic DST showed 16.7% (35/209) resistance to ofloxacin, 5.2% (11/213) resistance to kanamycin, 23% (49/213) resistance to ethionamide, 47.2% (101/214) resistance to ethambutol, 56.7% (68/120) resistance to pyrazinamide and 5.4% (4/74) resistance to clofazimine. 151 (70.5%) of the 214 cases were resistant to at least one of these six constituent drugs of the WHO shorter MDR-TB treatment regimen, and only 15 (7%) showed confirmed susceptibility to all six drugs. The WHO shorter MDR-TB treatment regimen is not applicable in at least 70% of MDR-TB patients in South-east Asia if the patients in our study are representative of those in their countries.