New Global Mutation Guide Released, WHO Warns Drug-Resistant TB Remains a Threat

WHO's first tuberculosis mutation catalogue was published in 2021, followed by a second edition in 2023, establishing a growing international evidence base for genomic drug resistance testing.

Tuberculosis remains one of the world's deadliest infectious diseases, and treating it becomes increasingly difficult when the bacteria responsible for the infection develop resistance to medicines. The World Health Organization (WHO) has released the third edition of its Catalogue of mutations in Mycobacterium tuberculosis complex and their association with drug resistance, providing an expanded global reference for identifying genetic changes linked to drug-resistant tuberculosis (TB). The updated publication gives laboratories, researchers and healthcare programmes stronger scientific evidence to interpret genetic test results and support earlier decisions about effective treatment.

The new catalogue brings together information from more than 71,000 clinical tuberculosis isolates collected across over 75 countries, creating WHO's most comprehensive global reference for understanding genetic mutations associated with drug resistance. This represents a 37 per cent increase in the volume of data and a 12 per cent expansion in geographical coverage compared with the second edition published in 2023. The broader evidence base can help laboratories identify resistance-related genetic changes more consistently, making advanced molecular testing increasingly useful in countries working to improve tuberculosis diagnosis and treatment.

Drug-resistant tuberculosis continues to create serious challenges for healthcare systems, particularly in places where access to advanced diagnostic equipment and suitable medicines remains limited. WHO reports that fewer than half of people affected by drug-resistant TB receive treatment, highlighting the urgent need for faster detection and better connections between diagnosis and medical care. Better interpretation of genetic information could help healthcare professionals recognize resistance earlier and select treatments better suited to patients' infections.

Expanded Genetic Evidence Supports Better Drug Resistance Detection

The third edition includes more detailed scientific evidence on tuberculosis resistance to newer and repurposed medicines, including pretomanid and cycloserine, which are important considerations in treating difficult forms of the disease. Understanding the genetic changes associated with resistance to these medicines can help researchers and diagnostic specialists recognize patterns that may affect how well particular treatments work. WHO has also introduced updated bioinformatic and statistical methods to improve the classification of mutations, supporting more reliable interpretation of complex genetic findings.

Dr Tereza Kasaeva, Director of WHO's Department for HIV, TB, Hepatitis and Sexually Transmitted Infections, emphasized that detecting drug resistance quickly and accurately is essential for helping patients receive effective treatment without unnecessary delays. She explained that targeted next-generation sequencing technologies are becoming increasingly accessible, creating new opportunities to examine tuberculosis bacteria and identify genetic mutations associated with resistance. The updated catalogue provides stronger evidence for these technologies, including information on newer medicines and guidance that can help laboratories apply genomic findings consistently in everyday diagnostic practice.

Clearer Guidelines Help Laboratories Understand Genetic Test Results

Genetic testing can reveal mutations in tuberculosis bacteria, but interpreting their relationship with drug resistance requires carefully assessed evidence and consistent classification methods. WHO has strengthened its interpretation framework by combining the Graded Mutation List with additional grading rules and other criteria that help users evaluate the meaning of individual mutations. This approach is designed to reduce differences in interpretation between laboratories and improve confidence in the use of molecular and sequencing-based drug susceptibility testing.

The publication also includes expanded practical guidance and new frequently asked questions to help laboratory professionals, researchers and tuberculosis programmes understand how to use the catalogue correctly. These resources explain how genetic evidence can be interpreted and applied when assessing drug resistance, making the reference more useful for specialists working with increasingly advanced diagnostic technologies. Diagnostic developers can use the updated information to support the development and evaluation of molecular tests, strengthening efforts to make drug resistance detection more accurate and accessible.

Global Collaboration Strengthens the Fight Against Drug-Resistant Tuberculosis

The updated catalogue is expected to support tuberculosis control programmes by improving sequencing-based drug susceptibility testing and helping countries monitor the emergence and spread of resistance-related mutations. More consistent genetic interpretation can strengthen global drug resistance surveillance, giving public health authorities better information for understanding resistance patterns and planning appropriate responses. These improvements are particularly important as healthcare systems work to identify resistant infections earlier and help patients access suitable treatment before their conditions become more difficult to manage.

WHO's first tuberculosis mutation catalogue was published in 2021, followed by a second edition in 2023, establishing a growing international evidence base for genomic drug resistance testing. The third edition reflects continued cooperation among national tuberculosis programmes, international reference laboratories, academic institutions and technical partners contributing scientific findings and expertise. Their combined work has expanded the available genetic evidence, helping diagnostic developers, researchers and health professionals better understand the mutations that can influence tuberculosis treatment.

The growing availability of genetic testing offers opportunities to improve tuberculosis care, especially when diagnostic results can be translated into timely treatment decisions. WHO's expanded catalogue provides an important scientific resource for connecting advances in sequencing technology with practical improvements in drug resistance detection and surveillance. Its greatest value will come from helping healthcare systems identify resistant infections more reliably, guide appropriate treatment and improve care for people living with one of the world's most serious infectious diseases.