A recent study of TB endemic province of Khyber Pakhtunkhwa (North West Pakistan) found that known mutations in rpoB (e.g. S405L), katG (e.g. S315T), or inhA promoter loci explain the majority of MDR-TB, but there was evidence of complex mixed infections and heteroresistance, which may reflect the high transmission nature of the setting13. This evidence concerns the gene INHA and tuberculosis.