Impact of resistance to first-line and injectable drugs on treatment outcomes in MDR-TB.

Recently, resistance to additional first-line and injectable drugs was reported to be an independent risk factor for adverse outcomes in multidrug-resistant (MDR) tuberculosis (TB) patients. The aim of the present study was to confirm these observations in MDR-TB patients without HIV infection. MDR-TB patients treated at a tertiary referral hospital in South Korea between January 1996 and December 2005 were included. The unadjusted and adjusted odds ratios of adverse treatment outcome were calculated for resistance to each drug and combination of drugs using simple or multiple logistic regressions. None of the resistance to additional first-line or injectable drugs was associated with higher odds for adverse treatment outcome in 155 MDR but nonextensively drug-resistant (non-XDR) TB patients. However, streptomycin resistance was associated with 12 times the odds for adverse treatment outcome in 42 extensively drug-resistant (XDR) TB patients. Neither combinations of first-line drugs nor those of injectable drugs were associated with increased odds for adverse treatment outcomes in non-XDR MDR-TB patients or XDR-TB patients. Only streptomycin resistance among the first-line or injectable drugs was associated with adverse treatment outcomes in extensively drug-resistant tuberculosis patients without HIV infection.