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In a groundbreaking study, the Global Typhoid Genomics Consortium has analyzed over 13,000 genomes of Salmonella Typhi (Typhi) bacteria from 110 countries, shedding light on the concerning spread of drug-resistant strains of this bacterium. Typhi is the causative agent of typhoid fever, a potentially deadly disease that claims over 110,000 lives annually, with a significant impact in sub-Saharan Africa and South Asia, where access to safe water and sanitation is limited.
Health experts have long been concerned about the potential rise of antimicrobial-resistant Typhi strains, which could render conventional antibiotics ineffective in treating typhoid fever, ultimately leading to a surge in mortality rates.
The World Health Organization (WHO) has prequalified two vaccines that have demonstrated high efficacy in preventing typhoid fever. These vaccines not only offer a lifeline to regions with limited access to healthcare infrastructure but also present a promising strategy in curbing the emergence and spread of resistant Typhi strains.
However, implementing new vaccines in resource-constrained areas poses a challenge for public health officials. They must navigate complex decisions about vaccine introduction into an already crowded immunization schedule.
The Consortium’s comprehensive genetic analysis has revealed a striking diversity of Typhi strains between countries and regions. Notably, the H58 Typhi variant, often associated with drug resistance, has rapidly proliferated through Asia and Eastern and Southern Africa. Conversely, it is less prevalent in other parts of the world. However, other regions have seen the emergence of distinct drug-resistant Typhi strains.
Of particular concern is the widespread resistance to the antibiotic ciprofloxacin, which accounted for over 85% of cases in South Africa. In Pakistan, approximately 70% of Typhi cases exhibited extensive drug resistance in 2020, though these variants have not yet established themselves elsewhere.
Furthermore, variants resistant to both ciprofloxacin and ceftriaxone have been identified, alongside instances of azithromycin resistance cropping up in various variants across South Asia.
While the Consortium’s analysis provides invaluable insights into the global distribution and transmission patterns of drug-resistant Typhi, it is important to note that certain regions lacked sufficient genetic data. However, information gleaned from travel-associated cases has helped to fill in some of these gaps.
These findings serve as a crucial starting point for collaborative efforts to share and analyze genetic data, empowering local public health action. Continued support from funders will be essential to bridge global surveillance data gaps, ensuring a comprehensive and effective response to the growing threat of drug-resistant Typhi.
This study was published recently in https://elifesciences.org/articles/85867
