Evaluation of the impact of Shigella virulence genes on the basis of clinical features observed in patients with shigellosis.

Abstract

Shigella continues to cause significant morbidity and mortality each year, mostly in under-five children living in developing countries. We investigated the association between Shigella virulence genes and shigellosis. We randomly selected 61 S. flexneri strains isolated from patients in Bangladesh between 2009 and 2013, and evaluated the presence of 140 MDa large-virulence-plasmid (p140), and 22 virulence genes including ipaH, ial, toxin, and T3SS-related genes. We found p140 in 79% (n = 48) and ipaBCD in 90% (n = 55) strains, while seven strains were missing the p140. The prevalence of ial was 89%, ipgC and ipgE was 85%, and the prevalence for the remaining genes was < 85%. During the multivariate analysis, we found that instead of sen, the Shigella enterotoxin gene set along with several other virulence genes such as ipgA, icsB, ipgB1, spa15, and mxiC, were significantly influencing multiple clinical features relevant to shigellosis, including bloody stool, mucoid stool, and rectal straining. We believe our model will help to determine the actual disease burden by directly looking for the genetic material in clinically suggestive patients, especially when detecting the causative organisms by traditional means is difficult.