Dikhyaa Mohanty 
Bacteria causing typhoid fever are becoming increasingly resistant to some of the most important antibiotics for human health. The largest genome analysis of Salmonella enterica serovar Typhi (S. Typhi) also reveals those resistant strains almost all originating in South Asia have spread to other countries nearly 200 times since 1990.
According to the reports, Typhoid fever is a global public health concern, causing 11 million infections and more than 100,000 deaths per year. While it is most prevalent in South Asia which accounts for 70 per cent of the global disease burden it also has significant impacts in sub-Saharan Africa, Southeast Asia, and Oceania, highlighting the need for a global response. Antibiotics can be used to successfully treat typhoid fever infections, but their effectiveness is threatened by the emergence of resistant S. Typhi strains.
Researchers from Stanford University in the US performed whole-genome sequencing on 3,489 S. Typhi isolates obtained from blood samples collected between 2014 and 2019 from people in Bangladesh, India, Nepal, and Pakistan with confirmed cases of typhoid fever. A collection of 4,169 S. Typhi samples isolated from more than 70 countries between 1905 and 2018 was also sequenced and included in the analysis.
Resistance-conferring genes in the 7,658 sequenced genomes were identified using genetic databases. Strains were classified as multidrug-resistant (MDR) if they contained genes giving resistance to classical front-line antibiotics ampicillin, chloramphenicol, and trimethoprim/sulfamethoxazole. The team also traced the presence of genes conferring resistance to macrolides and quinolones, which are among the most critically important antibiotics for human health.
