SN1 SHORT NOTE 5M

Write a short note on typhoid (enteric) fever.

General Medicine · Final Professional

Aetiology

Enteric fever is a systemic illness caused by *Salmonella enterica* serotype Typhi (typhoid) and serotypes Paratyphi A, B and C (paratyphoid). It is a Gram-negative, flagellated, non-lactose-fermenting bacillus, and humans are the only reservoir — which makes eradication theoretically possible.

Transmission is faeco-oral, through contaminated water and food, and by chronic carriers handling food. It is endemic throughout India, with peaks in the monsoon, and reflects inadequate sanitation and unsafe water.

Pathogenesis

1. Ingested bacilli survive gastric acid (an infective dose of 10⁵–10⁹, lowered by achlorhydria and antacids) and invade the Peyer's patches of the terminal ileum via M cells.

2. They are taken up by macrophages but survive intracellularly, multiplying in mesenteric lymph nodes.

3. Primary bacteraemia seeds the liver, spleen and marrow (the incubation period, 7–14 days).

4. Secondary bacteraemia produces the clinical illness; bacilli re-enter the gut via the gall bladder and bile, causing hyperplasia, necrosis and ulceration of Peyer's patches — the basis of the intestinal complications in the third week.

Clinical Features — the Classic Weekly Progression

Week	Features
Week 1	"Step-ladder" fever rising progressively each day; headache, malaise, relative bradycardia (Faget's sign), dry cough, constipation more often than diarrhoea in adults, abdominal discomfort
Week 2	Sustained high fever; rose spots — sparse, blanching, 2–4 mm pink macules on the trunk (difficult to see in dark skin); hepatosplenomegaly; abdominal distension; coated tongue with clean red edges; "typhoid state" — apathy, delirium, muttering
Week 3 — the dangerous week	COMPLICATIONS: intestinal perforation and haemorrhage; toxaemia; myocarditis; shock
Week 4	Gradual defervescence and recovery, with weakness persisting for weeks

Complications

Intestinal perforation (1–3%) — classically in the third week, at the terminal ileum, from necrosis of Peyer's patches. Presents with sudden abdominal pain, guarding, rigidity, loss of liver dullness and free gas under the diaphragm. A surgical emergency with high mortality; in a toxic patient with abdominal pain the signs may be muted, so a high index of suspicion is essential.
Intestinal haemorrhage — melaena or fresh bleeding from ulcerated Peyer's patches.
Typhoid encephalopathy — delirium, stupor, coma; the "muttering delirium" of the typhoid state; typhoid meningitis is rare.
Myocarditis — a leading cause of death; ECG changes, arrhythmia, heart failure.
Hepatitis and cholecystitis; splenic abscess.
Osteomyelitis — with a particular association with sickle cell disease.
Relapse (5–10%) — 1–3 weeks after apparent recovery, usually milder.
Chronic carrier state (1–4%) — persistent excretion for over a year, usually from the gall bladder (often with gallstones); commoner in women and the elderly. Carriers are the reservoir that sustains transmission.

Investigations

Test	Timing / yield	Comments
Blood culture	Week 1 — highest yield (60–80%)	The gold standard. Take a large volume before antibiotics
Bone marrow culture	Any week; highest sensitivity (~90%)	Remains positive even after antibiotics; invasive, reserved for difficult cases
Stool and urine culture	Weeks 2–3 onwards	Also used to detect carriers
Widal test	From the end of week 1; paired samples	Poorly specific — false positives from previous infection, vaccination and other Salmonella; a single titre is of little value and it is over-relied upon in India. A fourfold rise in paired sera is required
Typhidot / rapid IgM tests	Early	Convenient but variable performance

Supporting findings: leucopenia with relative lymphocytosis and eosinopenia (leucocytosis suggests perforation or another diagnosis), anaemia, thrombocytopenia, and mildly raised transaminases. Erect abdominal X-ray or ultrasound/CT for suspected perforation.

Management

Antibiotics. Choice is dictated entirely by resistance patterns: classical multidrug-resistant strains (resistant to ampicillin, chloramphenicol and co-trimoxazole) are widespread, fluoroquinolone resistance is now very high in India, and extensively drug-resistant (XDR) strains resistant additionally to third-generation cephalosporins have emerged in the subcontinent. Third-generation cephalosporins (ceftriaxone, cefixime) and azithromycin are the current mainstays, guided by local susceptibility data.
Supportive care: hydration and electrolyte correction, antipyretics, adequate nutrition (a soft, low-residue diet), and monitoring for complications.
Corticosteroids (dexamethasone) — of proven benefit in severe typhoid with delirium, obtundation, stupor, coma or shock, where they reduce mortality substantially.
Surgical management of perforation — resuscitation, antibiotics and early laparotomy with closure or resection; delay markedly worsens outcome.
Chronic carriers: prolonged antibiotic course; cholecystectomy where there are gallstones and eradication fails. Exclude carriers from food handling.

Prevention

Safe water and sanitation — the definitive answer: chlorination, boiling, protected water supply, safe sewage disposal.
Food hygiene — hand washing, avoiding raw and street-vended food and untreated water and ice.
Vaccination — Vi polysaccharide and Vi conjugate vaccines (the conjugate vaccine is effective in young children and gives longer protection) and the oral live Ty21a vaccine; recommended for endemic populations, travellers and outbreak control.
Identify and treat carriers; notify and investigate outbreaks.

CLINICAL PEARL

Do not diagnose typhoid on a single Widal test — this is one of the most widespread diagnostic errors in Indian practice, leading to unnecessary antibiotics for what is often dengue, malaria, scrub typhus or a viral fever. Take blood cultures before antibiotics in every suspected case. Conversely, in a patient in the third week with sudden abdominal pain and a rigid abdomen, think perforation immediately, even if the fever appeared to be settling.

NEEDS VERIFICATION

Antibiotic choices and durations — resistance patterns in India have shifted substantially and vary regionally; confirm against current local antibiograms and national guidance.

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