INTRODUCTION Acute diarrhoeal diseases, a major public-health problem in developing countries, are often associated with significant morbidity and mortality, especially among children (1-4). Of the pathogens causing diarrhoea, Shigella continues to play a major role in aetiology of inflammatory diarrhoea and dysentery, thus presenting a serious challenge to public-health authorities worldwide (5-7). A recent epidemiological report by Niyogi in 2005 (8) concluded that annually an estimated 165 million children and young adults worldwide suffer from shigellosis and that 99% occur in developing countries, and in developing countries, 69% of cases occur in children aged less then five years (9). These organisms belong to the Enterobacteriaceae family, with four serogroups described: Shigella dysenteriae, S. flexneri, S. sonnei, and S. boydii. S. dysenteriae, first described by Kiyoshi Shiga in 1897 (10), was a major cause of mortality during World War I, but decreased in prevalence after the war and was rapidly replaced by S. flexneri as the major serogroup, which caused a broader spectrum of diarrhoeal illnesses ranging from mild to very severe (6). After World War II, S. sonnei replaced S. flexneri as the dominant pathogen in most developed and some developing countries (6,11-13). Shigella species have been found in most surface-waters, sewage, food, and crops contaminated by human faeces used as fertilizer (14,15). Although recovered from these sources, Shigella species are most frequently transmitted via direct person-to-person contact, and 10-100 organisms are required to start an infection (16).
