Salmonella typhi as a Pathogenic Organism----A Mini Review

Abstract

Salmonella typhi is flagellated, rod shaped, gram negative, motile, facultative and anaerobic bacteria which have the size of 0.7-1.5 by 2.0-5.0 µm. The term was derived from the Greek word “typhus” which meant “smoky” and was used to describe the delirium that patients would exhibit with the disease. Salmonella typhi is a gram-negative bacterium that is responsible for typhoid fever and has been a burden on developing nations for generations. Typhoid fever is more common in children and young adults and is associated with low-income areas in which poor sanitation is prevalent. In 2000, typhoid fever was estimated to cause 21.7 million illnesses and 216,000 deaths globally, and the International Vaccine Institute estimated that there were 11.9 million cases of typhoid fever and 129,000 deaths in low to middle-income countries in 2010. Salmonella typhi is usually contracted by ingestion of food or water that is contaminated with the excrements of those that carry the organism and must survive the gastric pH barrier in the stomach prior to adherence in the small intestine. An infectious dose of Salmonella typhi in healthy individuals ranges between 1000 and 1 million organisms but can be related to the host’s defense mechanisms. Salmonella typhi serotype typhi enter the sub mucosal region of the small bowel by either direct penetration into the epithelial tissue mediated by the cystic fibrosis transmembrane conductance regulator (CFTR) or via the M-cell, a specialized lymphoid epithelial cell. Once within the submucosa, the bacterium causes hypertrophy of the Peyer’s patches. Classically, Salmonella typhi serotype typhi can be cultured from the bone marrow even after anti-microbial therapy has been initiated. Patients will typically present after a 7 to 14-day asymptomatic period after initial inoculation with Salmonella enterica serotype typhi.