Salmonella typhi: characteristics and transmission

• Salmonella enterica has approximately 2,500 serotypes or serovars.
• Salmonella typhi and typhimurium are clinically significant serotypes.
• Salmonella typhi causes gastroenteritis and enteric fever.
• Salmonella typhi is a gram-negative, rod-shaped bacterium and a facultative intracellular pathogen.
• It contains a capsule and flagella.
• Lactose is not fermented, but glucose is fermented, producing acid and gas.
• Hydrogen sulfide (H2S) is produced.
• Salmonella typhi is an exclusively human pathogen.
• Fecal-oral transmission and contaminated hands/objects spread it.
• It is mostly endemic in Asia, Africa, Latin America, and the Caribbean.
• Pet turtles have also been implicated as a source of infection.
• Young children and older adults are particularly susceptible.
• Individuals in crowded institutions may also be involved in salmonella readings.
• The capsular polysaccharide antigen prevents tagging with antibodies and phagocytosis by neutrophils, but macrophages can engulf the bacteria.
• Salmonella-secreted invasion proteins, inputted by pathogens in one, are virulence factors.
• Type three secretion system injects these salmonella-secreted invasion proteins into the host cell.
• Salmonella is ingested via the fecal-oral route, making its way to the distal ileum of the small intestine.
• It targets the epithelial layer of the mucosa lining.
• Salmonella invades the epithelial cells of the small intestine.
• Macrophages in the submucosa engulf Salmonella typhi.
• Salmonella typhi uses the host macrophage to enter nearby lymphatic vessels that break into local mesentery lymph nodes.
• Macrophages continue to flow through the parasite into the systemic lymphatic separation, where they enter the clinical endothelial tissues in the liver, spleen, bone marrow, gallbladder, and additional areas.
• Salmonella typhi can induce macrophage apoptosis, releasing the bacteria into the bloodstream, which can procure sexes.
• Another complication can arise in individuals with spleen issues because the spleen plays an important role in immunity against encapsulated bacteria.
• Salmonella typhus can cause osteomyelitis in clinically infected patients.
• Salmonella typhi remains in the gallbladder.

Clinical Diseases

• Enterocolitis or gastroenteritis, or salmonellosis, is a localized disease caused primarily by zeros, including typhi and typhimurium.
• Over 85% of cases of salmonella infection are foodborne.
• Salmonellosis is characterized by nausea, vomiting, and non-bloody diarrhea within 48 hours of ingesting contaminated food or water.
• Fever and abdominal cramping are common in normal immunocompromised patients.
• It is generally self-injury and lasts for 48 to 72 hours.
• Salmonella accounts for about 30% of deaths resulting from foodborne illnesses in the United States.
• Enteric or typhoid fever is primarily caused by serotype typhi.
• The inpatient period varies from 5 to 21 days.
• This is a severe, life-threatening systemic illness characterized by fever and frequently abdominal symptoms.
• Non-specific symptoms may include chills, sweats, headache, anorexia, weakness, sore throat, cough, myalgia, and either diarrhea or constipation.
• About 30% of patients have a faint and transient maculopapular rash on the trunk, called low spots.
• If untreated, mortality is approximately 15%.
• Complications can include intestinal hemorrhage and/or perforation, and rarely focal infections and endocarditis.
• A small percentage of patients become chronic carriers in the United States.
• Alfred fever has become less prevalent and is now primarily a disease of travelers and immigrants.
• Sustained bacteremia is often associated with vascular salmonella infections.
• Salmonella can also cause abdominal infections, osteomyelitis, septic arthritis, and infections of other tissues/organs when bacteria sit on either sclerotin plaques.

Laboratory Diagnosis

• Stool or blood samples are commonly used for diagnosis.
• Blood culture is most likely limited in the diagnosis of enterocolitis.
• Bone marrow culture is often positive.
• Stool culture is positive, especially in chronic carriers.
• Salmonella forms non-lactose-fermenting colonies on MacConkey's or EMB agar.
• On TSI, both gas and H2S are frequently produced.
• Salmonella typhi is urease negative, whereas proteus is urease positive and produces similar reactions on TSI agar.
• If the organism is urease negative, the salmonella can be identified and grouped by the slide elimination test.

Treatment

• The treatment of choice for entering fever, such as typhoid fever and septicemia with metastatic infection, is either ceftriaxone or ciprofloxacin.
• Ampicillin or Ciprofloxacin should be used in patients who are chronic carriers of Salmonella typhi.
• Cholecystectomy may be necessary to abolish the chronic carrier state.