evolution from monoresistance to pre-extensive drug resistance during a prolonged household outbreak.

Whole genome sequencing (WGS) is sensitive tool for the analysis of tuberculosis transmission and drug-resistance. We used WGS to analyze the evolution from isoniazid monoresistance to MDR/preXDR during a prolonged household outbreak. The outbreak started with a isoniazid resistant strain (katG S315T mutation) and evolve in two cases to pre-XDR phenotype (with mutations in katG, rpoB, embB, pncA and gyrA genes). Based on WGS data and epidemiological interview we proposed a possible chain of transmission an evolution of the strains. Similar intra-patient and inter-patient acquisition of variability was observed, making difficult to distinguish reinfection or reactivation. Analysis of WGS data together with epidemiological clinical history are discussed in order to distinguish between prolonged infections or transition from latency to reactivation. Classical interview and clinical history taking should be consider to fully understanding WGS data. With a still low incidence of TB cases, Uruguay could use universal WGS of all isolates to reduce time of diagnosis, detect outbreaks and perform public actions to reduce TB incidence.