TYPHOID

• Typhoid fever is caused by Salmonella typhi.
• Paratyphoid fever is caused by Salmonella paratyphi A, B & C.
• The term “Enteric fever” encompasses both typhoid & paratyphoid fevers.
• Infection acquired by ingestion of faecally contaminated food/water
• Man – Only known reservoir.
  • Most common among males
• Incubation period: 7 – 14 days, but ranges from 3 days to 3 weeks.

• Coated tongue
• Stepladder pyrexia
• Relative bradycardia
• Soft palpable spleen
• Rose spots (appears at 2nd week on trunk).
  • Are bacterial emboli to skin & occur in 1/3 of typhoid fever cases.
• Marked constipation in early stage or “pea-soup diarrhea”
• Typhoid ulcers:
• Longitudinal & without subsequent strictures formation.
• Note: Tuberculous ulcers are transverse that lead to stricture formations.

• Multiple ulcers found in terminal ileum.
• Ulcer margins – Slightly raised.
• Ulcer base – Black due to sloughed mucosa.
• Microscopically ulcers show erythrophagia & mononuclear cell infiltration.

• Perforation appears clinically as Pyrexia for
• Acute pain in peri-umbilical region spreading all over abdomen.

• Paratyphoid fever caused by S.paratyphi C more often leads to septicemia with suppurative complications
• Infection spread prevented by isolating patient till three bacteriologically negative stools.
• Urine reports are obtained on three separate days.

COMPLICATIONS:

• GI bleeding -Most common complication.

Neurologic manifestations: 

• Meningitis
• Guillain-Barre syndrome
• Neuritis

Neuropsychiatric symptoms:

• Muttering delirium or Coma vigil, with picking at bedclothes or imaginary objects.
• Commonest complications in 3rd or 4th week – 
• Intestinal perforation (less common in children below 5yrs) & hemorrhage.
• Cholangiocarcinoma
• Splenomegaly
• Leucopenia with neutropenia.

CARRIERS

• Carrier state occurs due to persistence of bacilli in gallbladder resulting in passage of organism in feces & via urine.
• Fecal carriers – Most common
• Healthy carriers – Emerge from subclinical cases
• Urinary carriers – More dangerous, common in patients with calculi or schistosomiasis.
• More common in women, infants, older age groups (> 40 years) and biliary abnormalities.

Convalescent carriers: 

• Shed bacilli in feces for 3 weeks to 2 months after clinical cure.

Temporary carriers: 

• Shed bacilli for more than 3 months but less than 1 year.

Chronic carriers: 

• Shed bacilli for more than a year
• This state associated with bacilli presence in gall-bladder.
• 2 – 4% become chronic carriers at end of 1 year.

Pseudo-carriers:

• Carriers of avirulent organisms in typhoid.
• In breastfed infant less chance of enteric infection – 
• Due to Ig & nutrients in breast milk

LAB DIAGNOSIS

• Blood culture (gold standard) – 90% positive in first week.
• Clot culture – Higher rate of isolation.
• Urine culture – Positive in 2nd & 3rd week.
• Bile culture – detection of carriers.
• Bile – Good culture medium for Bacillus.
• Fecal & bone marrow culture – Valuable in patients on antibiotics.
• Typhoid perforation diagnosed by plain X-ray abdomen in erect posture.
• Vi antibody – Used for detecting carrier.
• Demonstrated of circulating antigen – staphylococcal agglutination test (Staph.aureus-Cowan I strain).

New diagnostic tests:

• IDL tubex test – Detects IgM09 antibodies in few minutes.
• Typhidot test – Detects IgM & IgG antibodies.
• Leukopenia & neutropenia in 25% cases
• Leukocytosis – Children during first 10 days of illness, cases complicated by intestinal perforation or secondary infection.

WIDAL REACTION:

• Widal test – Investigation of choice in 3rd week.

• Dreyer’s tube – Conical bottom, H agglutinationDCH.
• Felix tube – Round bottom, O agglutination FOR.

• H & O antigens of S.typhi and H antigens of S.paratyphi are employed.
• Paratyphoid 0 antigens not used.
• Most immunogenic in typhoid is H antigen.
• H-antigen titre remains positive for several months after infection.
• Usually positive at end of 1st week, titre increases till 4th week & then declines.
• Demonstration of rise in titers is more meaningful than a single test.
• Significant titres > 1/320 for O; 1/640 for H is considered positive.
• Widal positive should not be taken as proof of typhoid fever.
• As agglutinins may be present due to prior disease, inapparent infection or immunization.
• Those who had prior infection or immunization develop anamnestic response (transient rise in antibody titers) during an unrelated fever.

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