Shigellosis

Abstract

The acute diarrhea caused by Shigella spp. is called bacillary dysentery or shigellosis, which is a most effective contagious agent, facilitated by a very low inoculum of organisms, and can easily spread directly and result into cluster infection. It rarely occur in non-human primates other than humans. There are four Shigella species, mainly S. sonnei'm developed countries, S. flexneri'm developing countries, and S. dysenteriae causing most severe infection in young children with mortality rate of nearly 30%. The estimated annual global incidence of shigellosis is 165 million per year and it is the leading cause of infant diarrhea and related deaths in developing countries. The major routes of transmission are oral-fecal spread via exposure to contaminated food or water, or exposure to infected objects or sexual contact. Vulnerable populations include: day care center children and their care-givers, international travelers, men-sex-men, and HIV infected groups. The incubation period is about 1-3 days. Symptoms are usually sudden onset of severe abdominal cramping pain, high fever, vomiting, anorexia, and watery diarrhea; later followed by abdominal pain, tenesmus, urgency, fecal incontinence, small amounts of mucoid diarrhea, and bloody stools. Dehydration is the most common complication of shigellosis and can be associated with central nervous system disorders, such as drowsiness, delirium, and epilepsy; rare severe complications include hemolytic uremic syndrome associated with Shiga-toxin producing strains, post-infection arthritis, rectal prolapse, and toxic megacolon. Laboratory diagnosis mainly bases on bacterial culture and identification of stool, but also can be made by enzyme immunoassay, probe or PCR to directly detect bacteria or virulence genes. Selection of antibiotic therapy is available based on local antimicrobial resistance profiles. Antibiotics, such as tetracyclines, ampicillin, and TMP-SMX, are no longer recommended as initial empirical choice for global emergence of antimicrobial resistance. Even without treatment, most infected patients recover within 5 to 7 days. Preventive measures focus on hand hygiene and food and drinking water hygiene.