Primary transmission of multidrug-resistant and extensively drug-resistant tuberculosis among HIV-infected persons: what does the future hold in store?

The article by Andrews et al. demonstrating exogenous reinfection as a cause of multidrug-resistant (MDR) and extensively drug resistant (XDR) tuberculosis (TB) in South Africa in the current issue of the Journal brings chilling news [1]. The authors report that all of the MDR and XDR TB that occurred in patients previously treated for TB was the result of primary transmission, rather than emerging as a result of inappropriate or inadequate treatment. All 17 of the subjects who they identified with MDR and/or XDR TB after an episode of drug-susceptible TB had been reinfected, and none of the cases were relapses with acquired drug resistance. This striking preponderance of reinfection suggests that exposure to and primary infection with MDR and/or XDR TB is the predominant mode of acquiring MDR and/or XDR TB in this population. This finding indicates that efforts to strengthen