WHO publishes the third edition of its tuberculosis mutation catalogue
· BehindLines newsroom
On 30 October 2026, the World Health Organization posted the third edition of its catalogue of Mycobacterium tuberculosis complex mutations associated with drug resistance. This 86-page technical document serves as a reference for interpreting genetic sequencing results from the bacteria that cause tuberculosis.
According to the WHO record, the catalogue is meant to support sequencing-based drug susceptibility testing, diagnostic development, surveillance and research. It draws on paired whole-genome sequencing and phenotypic testing data covering more than 71,000 clinical isolates from more than 75 countries. The evidence is expanded for five drugs: bedaquiline, linezolid, delamanid, pretomanid and cycloserine. WHO also mentions updated bioinformatic and statistical methods, a strengthened interpretation framework and more practical guidance.
For context, an analysis of the first edition, published in 2022 in Lancet Microbe and available on PubMed Central, describes a set of 41,137 isolates from 45 countries, of which 38,215 passed quality control. The authors counted 1,149 mutations classified as associated with resistance out of 13,211 unique mutations examined. These figures concern the earlier version, not the new one.
WHO stresses limits on use. Some mutations depend on genomic context: the graded list is not enough by itself and must be used with the catalogue's additional grading rules. The organization recommends validated bioinformatic workflows to interpret resistance at the level of a sample. The authors of the 2022 analysis noted for their part that the evaluation at the time was carried out on the data used to build the catalogue, which could overestimate performance.
What is still unknown: the page consulted does not give the total number of mutations listed, nor the performance of this edition for each drug. The full document will have to be read, and independent evaluations awaited, to measure its effect on laboratories.