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Typhoid fever is a life-threatening illness caused by S typhi.
In the United States about 400 cases occur each year
75% of these are acquired while traveling internationally.
Common in the developing world, where it affects about
21.5 million persons each year.
Epidemiology
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Salmonella
Gram negative bacteria
Motile except S gallinarum pullorum
MAC NLF colonies
Selective medium
Wilson & Blair bismuth sulphite
Jet black colonies due to H2S
S paratyphi A green colonies ( no H2S)
Enrichment media Selenite F & tetrathionate broth
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Pathogenesis
Source Carriers Cases
Transmission Ingestion of contaminated water or food
IP 7-14 days
Poultry, diary
Virulence factors
Invasiveness
Intracellular survival & multiplication
Endotoxin
High infectious dose (108 CFU)
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Salmonella are ingested in
contaminated food or water
Organisms reach the
terminal ileum
Enteritis
Organisms invade the gut wall
& cause ulcertion, perforation
& hemorrhage
Organisms spread to intestinal
lymphatics & are phagocytosed by
macrophages
Organisms disseminate to
bones, kidneys, lungs,liver,
brain & blood
Enteric fever or
typhoid fever
Infection pattern of Salmonella
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Salmonellosis = Generic term for disease
Enteric fever (prototype is typhoid fever and less severe
paratyphoid fever)
Septicemia (particularly S. choleraesuis, S. typhi, and S.
paratyphi)
Asymptomatic carriage (gall bladder is the reservoir for
Salmonella typhi)
Clinical Syndromes of Salmonella
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Clinical features
Nausea & vomiting
Bradycardia
Toxemia
Soft palpable spleen
Hepatomegaly ?
Rose spots on skin (2nd - 3rd week)
Fever (Step ladder)
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Lab diagnosis of Enteric fever
1st week Blood culture BHI broth
2nd week Antibody detection
(serum)
Widal test
3rd week Urine culture
4th week Stool culture Use selective & enrichment
medium
Specimens Blood, Bone marrow, urine, stool, pus, csf
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Specimens Blood, urine, stool,
Culture
MAC NLF colonies
AST Report & Interpretations
Lab Diagnosis of Enteric fever
TSI agar K-/ A +(H2S)
W & B Jet black colonies (Stool culture)
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Serology - Widal Test
Tube agglutination test To detect antibodies in patient serum
Test is performed after 2 wks
Antigens used TO
To diagnose Enteric / typhoid fever
O antigen of S typhi
TH H antigen of S typhi
AH H antigen of paratyphi A
BH H antigen of paratyphi B
CH H antigen of paratyphi C
O is group specific Enteric fever
H is species specific Typhoid or paratyphoid
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TO 1: 320
TH 1: 160
AH 1: 20
BH 1: 20
CH 1: 20
Widal test - interpretation
Test is carried by double dilution of serum
1/20 1/40 1/80 1/160 1/320 1/640
Demonstration of rise in titre
Anamnestic response with TAB vaccine
Cases treated early may show poor antibody response
Titre suggestive of Typhoid fever
12. Carriers
Food handlers & Cooks
Repeated stool cultures
Widal test no value in endemic countries
Vi agglutinins indicates carrier status
Sewer swab technique tracing carriers in cities
Vaccines
TAB Typhoral Typhim
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Treatment & drug resistance
1948 Availability of Chloramphenicol (choice)
1972 Chloramphenicol resistance
Epidemic in Mexico
Epidemic in Calicut (Kerala India)
Endemic & confined to Kerala till 1978
Alternative – ampicillin, co-trimoxazole
(ACOT), furazolidone
1980 late Multi-drug resistance (MDR-S typhi)
Resistance to ACCOT
Current choice Fluoroquinoles (ciprofloxacin) or 3 GCs
(Third-Generation Cephalosporins)
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If you know you are traveling to an at
risk location:
Avoid Ice
Drink Only Bottled Water
& pasteurised milk
Consume cooked food
Vaccination ?
