Li Y, et al. - Researchers performed a retrospective observational study in which 144 cycloserine-treated and 181 cycloserine-nontreated patients were consecutively enrolled in Zhejiang Province, China, to evaluate cycloserine for its efficacy and safety as well as to elucidate its role for treatment of simple multidrug-resistant tuberculosis (MDR-TB), pre-extensively drug-resistant tuberculosis (pre-XDR-TB), and extensively drug-resistant tuberculosis (XDR-TB). Successful completion of treatment was observed in 69.4% of patients in the cycloserine group. Upon subgroup analysis, they noted that simple MDR-TB cases, but not pre-XDR-TB or XDR-TB cases, could benefit from cycloserine, reducing the risk of unfavorable treatment outcomes. For the treatment of MDR-TB, cycloserine appeared to be an attractive agent. The investigators suggested that its safety profile may justify its use in most MDR-TB cases. Odds of favorable outcomes were significantly improved with cycloserine in patients with simple MDR-TB but not pre-XDR-TB and XDR-TB, suggesting the necessity for more aggressive regimens for pre-XDR-TB or XDR-TB patients.