Question

Name the causative organism of typhoid and draw its diagram.

Answer 1

Hint: Typhoid is a waterborne disease that is caused by bacteria living as intestinal parasites.

Complete answer:
The causative agent of typhoid is ‘Salmonella typhimurium'. Salmonella typhimurium are gram-negative bacilli that possess peritrichous flagella for movement. They are aerobic and facultative anaerobic organisms. The bacteria was first isolated by Salmon and Smith in 1885 and they named it Salmonella.
Typhoid fever is acquired by the ingestion of contaminated food and water with the bacteria. On reaching the small intestine the bacteria attach to the epithelial cells of the intestinal villi and penetrate into the submucosa layer of the intestinal wall. The infection can also spread to liver, gallbladder, kidney, bone marrow, spleen, etc. They multiply abundantly in the gallbladder.

Additional Information:
1. The pathogenicity of Salmonella is due to its antigenic structure. It consists of three antigens-
- H-antigen- It is present in the flagella. It prevents the bacteria from destruction by chemicals like acids and alcohols.
- O-antigen- It is present on the cell wall. It makes the bacteria resistant to boiling, acids, and alcohols. It acts as a toxin.
- Vi-antigen- It is also present on the cell wall covering the O antigen.
2. Typhoid along with Parathyroid fever (caused by Salmonella paratyphi) is commonly known as ‘enteric fever'.
3. Human beings are the only natural host for Salmonella typhi and Salmonella paratyphi.
4. Mary Mallon, commonly known as Typhoid Mary was responsible for causing several outbreaks of typhoid for around 15 years by serving infected food in her restaurants.

Note:
1. Typhoid can be diagnosed by the Widal test. It detects the formation of natural antibodies against the structural antigens in our bodies.
2. It can also be diagnosed by ELISA and can easily be detected in feces and urine.
3. The ingested bacteria are discharged continuously into the Peyer's patches and lymphoid follicles of the ileum.