Gut Ache Flashcards
(25 cards)
What bacteria causes typhoid fever?
Salmonella enterica serovar Typhi (S. Typhi)
How is typhoid fever transmitted?
Via faecal-oral route - contaminated food/H2O
How many global typhoid cases occur annually?
Over 27 million
What is the typical incubation period of typhoid fever?
6-30 days (commonly 8-14)
What are typical symptoms of typoid?
1) Gradual onset of fever (step-ladder pattern)
2) Cough
3) Constipation
How is typhoid diagnosed?
Through cultures of blood, stool and urine, repeated testing is often required
What is a carrier state in typhoid?
When an individual shows no symptoms but continues to shed the bacteria
What percent of typhoid cases become chronic carriers?
2-5%
Why are chronic carriers a public health concern?
They silently spread the infection without detected
Name the 3 main typhoid vaccines.
1) Ty21a (oral live)
2) Vi-PS (polysaccharide)
3) TCV (conjugate)
What are conjugate vaccines (TCV) more effective in children?
They elicit T-dependent immunity and work in children <2 years
What’s the downside of Vi-PS vaccines?
Poor immune response in young children and no memory response
What does NAR stand for in antibiotic resistance?
Nalidixic Acid Resistance
What is the Vi capsule?
A protective outer layer that prevent immune detection
What is Typhi toxin?
A cytolethal distending toxin (nuclease) that damages host DNA
What are SPI-1 and SPI-2?
Pathogenicity islands - gene clusters that help bacteria invade and evade host cells
What is the role of type III secretion systems in Salmonella?
To inject bacterial proteins into host cells for manipulation
How did S. Typi evolve from E. coli?
Through gene gain (virulence factors) and gene loss (environmental survival abilities)
Which foods commonly cause non-typhoidal Salmonella (NTS)?
1) Eggs
2) Poultry
3) Pork
4) Cheese
What’s the infectious dose for S. Typhi compared to NTS?
1) S. Typhi - around 100 organisms
2) NTS - around 1 million organisms
What’s the duration of illness for typhoid vs. NTS?
1) Typhoid - around 3 weeks
2) NTS - 3-10 days
Does NTS lead to chronic carrier state like S. Typhi?
No
Why is typhoid harder to detect than NTS?
Early typhoid shows minimal inflammation and has long incubation period
What does the gene loss in S. Typhi indicate about its evolution?
It became a human-adapted specialist pathogen
