IS PROTECTION AGAINST SHIGELLOSIS INDUCED BY NATURAL INFECTION WITH PLESIOMONAS-SHIGELLOIDES

Shigellosis due to Shigella sonnei is rare among people growing up and living in developing countries; however, infections due to S sonnei b ecomes more common than those due to S flexneri as societies develop e conomically. The relation between risk of S sonnei infection and econo mic development may be explained by the exposure of developing-country populations to Plesiomonas shigelloides. P shigelloides is often foun d in surface water, and one serotype (serotype 17) possesses a cell-wa ll lipopolysaccharide identical to that of S sonnei. Thus, exposure to P shigelloides by drinking contaminated water may immunise population s to S sonnei. As economic development occurs, water quality improves and populations become susceptible to S sonnei. Although drinking pure water has many advantages, immunisation against S sonnei may be one b enefit of traditional water sources.