Resistance to anti-TB drugs: evaluation of universal resistance surveillance implementation in Chile

TB remains a public health challenge in Chile, where all bacteriologically confirmed TB cases are tested for drug susceptibility at the National Reference Laboratory of the Instituto de Salud Pública (ISP).

We evaluated the impact of implementing universal surveillance for rifampicin and isoniazid resistance in Chile and described resistance profiles and epidemiological factors.

Retrospective analysis of drug susceptibility testing (DST) results from Mycobacterium tuberculosis cultures processed at the ISP between 2003 and 2020. DST was performed using line probe assays and mycobacteria growth indicator tube liquid culture. Demographic and clinical data were analysed, and a negative binomial regression model assessed changes before and after universal surveillance in 2014 (2003-2014 vs. 2015-2020).

Among 44,800 isolates analysed, 911 had first-line resistance to isoniazid or rifampicin: 377 showed isoniazid monoresistance, 155 rifampicin monoresistance, 378 multidrug resistance, and one extensively drug-resistant case. Detection of resistant cases increased after universal surveillance (incidence rate ratio = 3.592, P < 0.001). Resistance was most frequent in men aged 16-64 and in the central macrozone.

Universal surveillance improved detection of drug-resistant TB in Chile, supporting its value for timely treatment adaptation and targeted public health strategies, especially in high-risk demographic and geographic groups.