Typhoid in detail

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 Typhoid Fever — Overview for Medical Students


Definition:

Typhoid fever is an acute, systemic infection caused by the bacterium Salmonella enterica serotype Typhi (S. Typhi). It is transmitted primarily via the fecal-oral route and is common in areas with poor sanitation. If untreated, it can be life-threatening

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Etiology (Cause)


Causative organism: Salmonella Typhi (gram-negative bacillus, motile, non-spore forming).


Source: Humans are the only reservoir.


Transmission: Contaminated food or water, direct contact with an infected person or chronic carrier.


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Pathophysiology


1. Ingestion of S. Typhi → survives gastric acid → reaches small intestine.


2. Invades intestinal mucosa → enters lymphatics → bloodstream.


3. Disseminates to liver, spleen, bone marrow → causes systemic infection.


4. Organisms re-enter intestine via bile → can cause intestinal ulceration.



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Incubation Period


Usually 7–14 days (range: 3–60 days depending on dose of bacteria).


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Clinical Features


Week-wise presentation:


1st Week: Step-ladder fever (gradually rising), malaise, headache, dry cough, abdominal discomfort, bradycardia (Faget sign).


2nd Week: High sustained fever (39–40°C), relative bradycardia, rose spots (faint salmon-colored macules on trunk), hepatosplenomegaly.


3rd Week: Intestinal ulceration → possible complications like intestinal hemorrhage, perforation, encephalopathy.


4th Week: Gradual defervescence and recovery (if treated).


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Diagnosis


Blood culture: Most sensitive in first week.


Widal test: Detects antibodies (useful after 1st week; not specific).


Stool/urine culture: Positive in later stages.


CBC: Leukopenia with relative lymphocytosis.



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Complications


Intestinal hemorrhage

Intestinal perforation (especially ileum)

Myocarditis

Encephalopathy

Chronic carrier state (e.g., gallbladder colonization)


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Treatment


Antibiotics:


First-line: Azithromycin, Ceftriaxone, or Ciprofloxacin (resistance-dependent).


Supportive: Adequate hydration, nutrition, antipyretics.



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Prevention


Safe water and food hygiene


Sanitation improvement


Typhoid vaccines (Vi polysaccharide, Ty21a oral vaccine)




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Quick Summary Table:


Feature Typhoid Fever


Causative Agent Salmonella Typhi

Incubation 7–14 days

Transmission Fecal-oral route

Hallmark Signs Step-ladder fever, relative bradycardia, rose spots

Diagnosis Blood culture, Widal test

Treatment Antibiotics + supportive care

Prevention Hygiene, vaccination




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from graphviz import Digraph


# Create a flowchart for Typhoid Pathophysiology

dot = Digraph(comment="Typhoid Pathophysiology", format='png')


# Nodes

dot.node('A', 'Ingestion of S. Typhi\n(contaminated food/water)')

dot.node('B', 'Survives gastric acid')

dot.node('C', 'Small intestine\n(invasion of mucosa)')

dot.node('D', 'Enters lymphatics → bloodstream')

dot.node('E', 'Dissemination to\nliver, spleen, bone marrow')

dot.node('F', 'Bacteria re-enter intestine\nvia bile')

dot.node('G', 'Intestinal ulceration')

dot.node('H', 'Complications:\nHemorrhage, perforation')


# Edges

dot.edges(['AB', 'BC', 'CD', 'DE', 'EF', 'FG', 'GH'])


# Render

path = '/mnt/data/typhoid_pathophysiology'

dot.render(path, cleanup=True)


path + '.png'

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