Persistent Transmission of Shigellosis in England Is Associated with a Recently Emerged Multidrug-Resistant Strain of Shigella sonnei.

Whole-genome sequencing has enhanced surveillance and facilitated detailed monitoring of the transmission of species in England. We undertook an epidemiological and phylogenetic analysis of isolates from all cases of shigellosis referred to Public Health England between 2015 and 2018 to explore recent strain characteristics and the transmission dynamics of species. Of the 4,950 confirmed cases of shigellosis identified during this period, the highest proportion of isolates was (54.4%), followed by (39.2%), (4.1%), and (2.2%). Most cases were adults (82.9%) and male (59.5%), and 34.9% cases reported recent travel outside the United Kingdom. Throughout the study period, diagnoses of and infections were most common in men with no history of recent travel abroad. The species prevalence was not static, with cases of infection in men decreasing between 2015 and 2016 and the number of cases of infection increasing from 2017. Phylogenetic analysis showed this recent increase in infections was attributed to a novel clade that emerged from a Central Asia sublineage exhibiting resistance to ciprofloxacin and azithromycin. Despite changes in species prevalence, diagnoses of infections in England are persistently most common in adult males without a reported travel history, consistent with sexual transmission among men who have sex with men. The trend toward increasing rates of ciprofloxacin resistance in , in addition to plasmid-mediated azithromycin resistance, is of significant public health concern with respect to the transmission of multidrug-resistant gastrointestinal pathogens and the risk of treatment failures.