Reply to Chen et al

TO THE EDITOR—We thank Chen et al for their interest and response to our brief report and appreciate the opportunity to clarify the most notable findings reported. We believe that our finding that a complex Mycobacterium tuberculosis infection (defined by multiple copy numbers in at least 1 mycobacterial interspersed repetitive units–variable number of tandem repeats [MIRU-VNTR] locus) was independently associated with a nearly 2-fold increase in the odds of a persistently positive sputum culture after 2 months of treatment is the most important novel result we report. While multidrug resistance was indeed the risk factor most strongly independently associated with an increased odds of persistent culture positivity, the relationship between multidrug resistance and poorer treatment response has been well documented by others and is an expected finding.