The Genomic Mystery of Shigella sonnei Revealed

The Genomic Mystery of Shigella sonnei Revealed

Dhaka November 1, 2013. In an article entitled, ‘Tracking the establishment of local endemic populations of an emergent enteric pathogen’ published in October 22, 2013, issue of PNAS (Vol. 110 no.43: 17522-17527), the lead author Kathryn E. Holt with twenty nine other associates from twelve different research Institutes including The Wellcome Trust Sanger Institute, UK have uncovered a high-resolution view of the genome of the dysentery bacterium Shigella sonnei . The researchers sequenced the genomes of 263 isolates of S. sonnei, a pathogen responsible for more than 160 million cases of dysentery and 1 million related deaths every year. Since emerging in Europe during the 1500s, S. sonnei has spawned a multi-drug resistant clade known as Global III that is now the dominant cause of dysentery in many endemic areas of the world. The authors obtained S. sonnei isolates from patients who had been treated at various hospitals in Vietnam during a 15-year period, with all but two of the isolates belonging to the pandemic Global III clade. The analysis revealed that S. sonnei went through several changes after its introduction to Vietnam in the 1980s. Bacterial populations in some areas of Vietnam accumulated pathogenesis-boosting mutations that were retained as the bacteria replicated and spread geographically, gradually becoming genetic fixtures in the local S. sonnei population. According to the authors, the study provides insight into the microevolution of a human pathogen during its establishment in a new human population. ([Summarized by Samsad Razzaque, Research Associate in Plant Bioth lab.DU. ]

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