Question
A young adult female presented with headache, fever and abdominal discomfort for the past 5 days. On examination, she was toxic with a temperature of 1010 F, coated tongue and mild splenomegaly were also present.
- (a) What is the most probable diagnosis. Name the etiological agents 3 mark(s)
- (b) Describe the pathogenesis of this disease 2 mark(s)
- (c) Describe the laboratory diagnosis in detail 3 mark(s)
- (d) Add a note on the treatment and vaccines available for this condition 2 mark(s)
Answer
a) Most probable diagnosis and etiological agents: Enteric (typhoid) fever — headache, prolonged fever, abdominal discomfort, toxic look, coated tongue, and mild splenomegaly are classical. Etiological agents: Salmonella enterica serovar Typhi (Paratyphi A/B/C cause the milder paratyphoid variant).
b) Pathogenesis Ingested bacilli survive gastric acidity and invade ileal mucosa via M cells overlying Peyer’s patches; taken up by macrophages, in which the facultative intracellular organism survives and multiplies, it spreads to mesenteric lymph nodes and then via the thoracic duct into blood (primary bacteraemia, usually asymptomatic). The organism seeds the reticuloendothelial system (liver, spleen, bone marrow, gallbladder), multiplies during the incubation period, and re-enters the blood (secondary bacteraemia), producing the clinical illness. Peyer’s patch hyperplasia can progress to necrosis and ulceration, risking haemorrhage/perforation; the gallbladder may harbour the organism chronically (carrier state).
c) Laboratory diagnosis
- Blood culture — best yield in the first week; bile broth neutralises antibacterial serum activity.
- Bone marrow culture — most sensitive at any stage, even after antibiotics.
- Stool and urine culture — positive from the second/third week.
- Widal test — rising titre of O and H agglutinating antibody in paired sera; limited by cross-reactions and background titres.
- Newer methods — Typhidot/IgM dot-EIA, PCR where available.
d) Treatment and vaccines Treatment: ceftriaxone (third-generation cephalosporin, current first-line for uncomplicated typhoid), azithromycin, or fluoroquinolones (resistance increasingly common). Vaccines: Vi capsular polysaccharide vaccine (injectable, ~3 years’ protection); Vi-conjugate (typhoid conjugate) vaccine (improved immunogenicity, usable in infants from 6 months, WHO-preferred); live attenuated oral Ty21a vaccine (not for immunocompromised individuals or young children).