Drug resistance in Salmonella Typhi: implications for South Asia and travel.

PURPOSE OF REVIEW: Recent attempts at mapping Typhoid epidemiology have revealed an enormous burden of disease in developing countries. Countries hitherto believed to have a low incidence, such as the African subcontinent, on accurate mapping were found to have a significant burden of disease. Drug resistance, because of rampant overuse of antibiotics, has driven selection pressure to extensively drug-resistant typhoid becoming a reality in the Indian subcontinent. With widespread travel, importation of this variety of typhoid to nonendemic countries is likely to lead to outbreaks in a nonimmune population.

RECENT FINDINGS: A strain of extensively drug-resistant Salmonella Typhi isolated in Pakistan in 2016 has been responsible for multiple outbreaks in Pakistan and multiple travel-related cases all over the world in United States, UK, and Australia. This novel strain belongs to H58 lineage harbouring a plasmid encoding additional resistance elements like blaCTX-M-15 and a qnrS fluoroquinolone resistance gene. This resistance pattern has rendered many therapeutic options like Ceftriaxone and Fluoroquinolones clinically inactive impacting care in endemic and traveller populations alike.

SUMMARY: Changing epidemiology and drug resistance in typhoid indicates that it may be prudent to vaccinate nonimmune travellers travelling to typhoid endemic areas, especially the Indian subcontinent.