Enteric fever: Resurrecting the epidemiologic footprints

Yatish Agarwal, Dipendra K Gupta, Ravindra S Sethi

Astrocyte 2016 3(3):153-161

A genetically monomorphic, human-restricted bacterial pathogen that causes 21 million cases of typhoid fever and 200,000 deaths each year, predominantly in southern Asia, Africa, and South America, Salmonella enterica subspecies serovar Typhi has a long and colored evolutionary history. Based on studies relating to the population genetic structure of Typhi by mutation discovery within 200 gene fragments from a globally representative strain collection of 105 strains, researchers have drawn up a phylogenetic tree for Salmonella typhi. It is surmised that the first ancestral strains of the bacteria appeared somewhere in Indonesia between 43000 and 10000BC. That despite the passage of millennia of years since the setting up of its first footprints on Mother Earth, Salmonella typhi has persisted as a highly homogeneous tribe, may have much to do with the asymptomatic carrier state in humans that they can dig into to survive. This process of neutral evolution and genetic buffering in Typhi coupled with the relatively more recent adaptive evolution, a sequel of rapid transmission of phenotypic changes through acute infections, has led to production of its antibiotic-resistant strains has made the task of public health physicians even more daunting and complex. These chronicles dwell on the historical truths and multihued accounts relating to the epidemiology of a disease that once changed the course of European history, battles, and wars, and, narrates, how, over time, the bacteriologists, pharmacologists, and physicians of the times came up trumps against the slayer bacteria.

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