Question
A male patient aged 20 years came with a history of fever for 15 days duration with coated tongue and soft palpable spleen. Answer the following:
- (a) Mention the probable diagnosis and source of infection 1 mark(s)
- (b) List the specimens to be sent for lab. diagnosis in this case 1 mark(s)
- (c) How will you proceed with lab. diagnosis in this case . 4 mark(s)
- (d) What is anamnestic reaction 2 mark(s)
- (e) How the disease can be prevented 2 mark(s)
Answer
a) Probable diagnosis and source of infection Enteric (typhoid) fever — prolonged fever (15 days) with coated tongue and soft, palpable splenomegaly is classical. Source: ingestion of food/water contaminated with Salmonella Typhi, typically from a chronic human carrier (faecal-oral transmission).
b) Specimens for laboratory diagnosis Blood (for culture, in the first week); bone marrow aspirate (most sensitive at any stage); stool and urine (from the second/third week); serum (for Widal test, from the second week onward).
c) Laboratory diagnosis
- Blood culture — highest yield in the first week of illness (bacteraemic phase); use bile broth to neutralize any antibacterial activity in the patient’s serum.
- Bone marrow culture — most sensitive test at any stage of illness, even after antibiotics have been started, since the organism concentrates in the reticuloendothelial system.
- Stool and urine culture — become positive later (2nd–3rd week) as the organism is excreted via the gut/gallbladder and kidneys.
- Widal test — demonstrates a rising titre of agglutinating antibody against Salmonella O and H antigens in paired (acute and convalescent) sera, ideally taken 7–10 days apart; a single high titre is only suggestive due to background titres in endemic populations and cross-reactivity.
- Newer methods: Typhidot/IgM dot-EIA for rapid diagnosis; PCR where available.
d) Anamnestic reaction A non-specific rise in antibody titre against an unrelated or previously encountered antigen, occurring when the immune system is stimulated by a current, different infection or immunization — the current stimulus non-specifically boosts memory-cell-mediated antibody production against a past antigen. In the context of Widal testing, an anamnestic reaction can cause a falsely elevated O/H titre in a patient who had a prior Salmonella infection or TAB vaccination but is now suffering from an unrelated febrile illness — an important cause of false-positive Widal results, limiting the test’s specificity.
e) Prevention Safe drinking water and sanitation, proper sewage disposal, food hygiene, and hand hygiene; typhoid vaccination (Vi capsular polysaccharide vaccine, Vi-conjugate vaccine, or live attenuated oral Ty21a vaccine); identification and treatment/occupational exclusion of chronic carriers, especially food handlers.