Question
A 20-year-old woman came to the Medicine OPD with history of fever, fatigue and abdominal discomfort since 4 days. It did not resolve with antipyretics. Samples were collected for the common probable causes of this condition and was confirmed as typhoid fever. (
- (a) What are the common probable causes of the above case scenario. (
- (b) Which is the confirmatory test for typhoid fever. (
- (c) What is the most important instruction to be given for sample collection for the above test. (
- (d) How does one get this infection. (e) Who is a chronic carrier of typhoid. In whom is chronic carriage likely. (f) How to detect chronic carriers. Give details. (g) What is the public health importance of detecting a chronic carrier. (h) Define Multi drug resistant Salmonella Typhi. (i) How to prevent typhoid infection. (2+1+1+1+2+3+1+1+3) (PTO)
Answer
a) Common probable causes: Enteric (typhoid/paratyphoid) fever — caused by Salmonella enterica serovar Typhi (Paratyphi A/B/C causing the milder paratyphoid variant); other common causes of a similar prolonged, antipyretic-unresponsive febrile illness that would be part of the initial differential include malaria, dengue, and other enteric/bloodstream bacterial infections — but given the clinical picture and specimen work-up here, typhoid fever due to S. Typhi is the confirmed cause.
b) Confirmatory test: Blood culture (in the first week of illness) or, more sensitively at any stage, bone marrow culture — isolation of Salmonella Typhi is the definitive confirmatory test.
c) Most important instruction for sample collection: blood for culture should be collected before starting antibiotics (or, if already started, ideally just before the next dose), since prior antibiotic exposure can suppress bacterial growth and cause a false-negative culture — this is the single most critical instruction for accurate diagnosis.
d) Mode of acquisition: faecal-oral transmission — ingestion of food or water contaminated with S. Typhi from the faeces of an infected patient or (importantly) an asymptomatic chronic carrier.
e) Chronic carrier — definition and likely individuals: a chronic carrier is an individual who continues to excrete S. Typhi in stool (or urine) for more than one year after the acute infection has clinically resolved, without exhibiting ongoing symptoms — the organism persists, most classically, in the gallbladder (particularly in individuals with pre-existing gallstones, which provide a niche for chronic bacterial colonization) or, less commonly, the urinary tract (in the presence of concurrent urinary schistosomiasis in endemic areas). Chronic carriage is more common in middle-aged/older women and those with gallbladder disease/cholelithiasis.
f) Detection of chronic carriers: repeated stool and urine culture over an extended period (since shedding may be intermittent, multiple samples are needed); duodenal/bile aspirate culture or bile obtained via string test/duodenal intubation can directly demonstrate biliary carriage; serological screening (Vi antibody titre) — a persistently elevated antibody to the Vi (capsular) antigen supports chronic carriage, given continued antigenic stimulation from the persisting organism, and can be used as a screening tool to identify individuals warranting confirmatory stool/bile culture.
g) Public health importance of detecting a chronic carrier: chronic carriers serve as an important silent reservoir for continued community transmission of typhoid fever, since they shed the organism while remaining asymptomatic themselves; identification allows for treatment or exclusion from food-handling occupations (a well-recognized historical example being food handlers who, as chronic carriers, caused repeated outbreaks), thereby interrupting ongoing transmission chains that would otherwise persist despite successful treatment of acute cases.
h) Multidrug-resistant Salmonella Typhi (MDR typhoid): defined as S. Typhi resistance to the three classical first-line drugs — chloramphenicol, ampicillin, and co-trimoxazole (trimethoprim-sulfamethoxazole) simultaneously — requiring the use of alternative agents (fluoroquinolones or third-generation cephalosporins, though resistance to these is also increasingly reported, e.g., extensively drug-resistant/XDR typhoid).
i) Prevention of typhoid infection:
- Safe drinking water supply and proper sewage/excreta disposal.
- Food and personal hygiene, hand hygiene.
- Typhoid vaccination — Vi capsular polysaccharide vaccine, Vi-conjugate (typhoid conjugate) vaccine (WHO-preferred, usable in infants), or live attenuated oral Ty21a vaccine.
- Identification, treatment, and occupational exclusion of chronic carriers, especially those working as food handlers.
- Health education and community sanitation improvement programmes.