It is a systemic infection caused by salmonella bacillus. S. typhi causes typhoid fever and S.paratyphi A & B cause paratyphoid fever.

Mode of Infection

Humans are the only natural reservoirs of S. typhi. Ingestion of food or water contaminated with human faeces is the most common mode of transmission. The salmonella organisms after ingestion attack the microvilli of the ileal brush borders and invade the intestinal epithelium through the Peyer's patches. These enter the thoracic duct causing transient bacteremia. These organisms then seed the reticuloendothelial organs (bone-marrow, liver, spleen) and other organs. The bacteremia recurs and the bacilli again reach the intestine through the bile by local multiplication in the walls of gall bladder. Circulating endotoxin (a lipopolysaccharide of the bacterial cell wall) is thought to be the cause of prolonged fever and toxic symptoms. Carrier state is found when individuals excrete S. typhi for three months or longer after infection.

Clinical features

Onset: Gradual onset step ladder fever, anorexia, malaise, diarrhea in early stages and then constipation 2^nd week: High fever, toxic child, delirium, relative bradycardia, hepatomegaly, splenomegaly, diffuse abdominal tenderness. Rose spots may be seen around 7th to 10th day (Maculopapular erythematous rash) on the chest and the abdomen. The fever usually resolves within 2-4 weeks but malaise and lethargy persist for a longer time.

Complications

1. Severe intestinal hemorrhage and intestinal perforation - seen usually in 1st week of illness. Perforations occur in distal ileum and lead to acute peritonitis.
2. Myocarditis - Seen as arrhythmias, Cardiogenic shock.
3. CNS psychosis - also seen as transverse myelitis, cerebellar ataxia and deafness.
4. Rare complications - Hepatitis, Cholecystitis, pancreatitis, pneumonia, bone marrow necrosis, pyelonephritis, meningitis, orchitis and lymphadenitis. Septic arthritis and osteomyelitis may be seen in children with hemoglobinopathies.

Diagnosis

1. Blood /Clot culture - positive early in course of diseases.
2. Stool / Urine culture - becomes positive after 1st week of disease.
3. Bone marrow cultures are often positive even when blood cultures are sterile and are less influenced by prior antibiotic therapy.
4. Widal test - It measures antibodies against 'O' and 'H' antigens of typhi. It becomes positive only in the 2nd week of illness.

Treatment

Due to multidrug resistance to chloramphenicol, ampicillin and TMP-SMX, 3rd generation cephalosporins and fluoroquinolones are drugs of choice.
Ciprofloxacin (10-15 mg/kg/d) for 7-10 days is effective and has a low recurrence rate.
Cefotaxime (200mg/kg/d) intravenously in 3-4 divided doses or ceftriaxone (100mg/kg/d IV in 1 or 2 divided doses) for 7-10 days have also been successful in treating enteric fever caused by resistant strains. Cefixime (8mg/kg/d PO in BD doses) for 7-10 days have also been successful.

Other antimicrobial agents useful are-

1. Chloramphenicol (50 mg/kg/d PO or 75 mg/kg/d IV in 4 equal doses) for at least 14 days.
   
2. Ampicillin (200mg/kg/d IV in 3-4 doses) for 14 days.
3. Amoxicillin (100mg/kg/d PO in 3 doses) for 14 days.
4. MP- SMX (10mg of TMP/kg/d PO in 2 doses) for 14 days.

In children with malnutrition, antibiotic therapy can be extended for 21 days to reduce the rate of complications. In patients with shock, obtundation, stupor or coma a short course of dexamethasone (3mg/kg initial dose followed by 1mg/kg every 6 hours for 48 hours) improves the survival.

To eradicate chronic carrier stage: High dose ampicillin or TMP-SMX for 4-6 weeks is required.

Prevention : Vaccines-

Oral Ty21a strain S.typhi - A live attenuated preparation. Recommended in children more than 6 years of age. Four enteric coated capsules on alternate days are given.
Vi Capsular polysaccharide vaccine - It is given intramuscular in children less than 2 yrs of age.


Booster is required every 3 yrs.

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Last created on 23-02-2001
Last updated on 14-05-2007