Typhoid fever Flashcards
Define typhoid fever.
Typhoid and paratyphoid fevers are collectively known as enteric fevers and they are caused respectively by the organisms Salmonella typhi and Salmonella paratyphi (types A, B and C).
What are the hosts of salmonella typhi/paratyphi?
Both of these organisms are primarily human pathogens, though S. paratyphi type B has been known to infect cattle
What type of bacteria are salmonella species?
Gram -ve rods
NOT normally present as commensals in the gut
How is typhoid transmitted?
Consumption of contaminated food and drink handled by people who shed the organism from stool or, less commonly, urine
Sewage
Shellfish
NB: food needs to be heavily contaminated for infection to occur
What are the risk factors for typhoid?
- Disease-related or iatrogenic achlorhydria
- Recent antibiotic use
- Immunosuppression
- Other infections
- Extremes of age
- Haemoglobinopathies e.g. SCD
What are the clinical features of typhoid?
- initially systemic upset as above
- relative bradycardia
- abdominal pain, distension
- constipation: although Salmonella is a recognised cause of diarrhoea, constipation is more common in typhoid
- rose spots: present on the trunk in 40% of patients, and are more common in paratyphoid
What are the complications of typhoid fever?
- osteomyelitis (especially in sickle cell disease where Salmonella is one of the most common pathogens)
- GI bleed/perforation
- meningitis
- cholecystitis
- chronic carriage (1%, more likely if adult females)
How do you diagnose typhoid fever?
Blood culture - 1 or more must be positive; positive in 61% of cases
Stool or urine culture - usually become positive in second week of onset of symptoms
Serology - Widal’s test of agglutination against flagellar (H) and somatic (O) antigens of S. typhi. Only used in developing countries now. Replaced by ELISA in developed countries.
What is the incubation period of typhoid?
10-20days in typhoid
1-10days in paratyphoid
What is the prognosis with typhoid fever?
Case fatality rate is less than 1% with prompt antibiotic therapy, but may be as high as 20% in untreated cases
What is the management of typhoid fever?
Notifiable disease
Empirical antibiotics e.g. azithromycin - for many decades, antibiotics such as chloramphenicol, ampicillin, and cotrimoxazole were used for treating enteric fever but MDR strains have emerged.
+/- Dexamethasone - for severe infection e.g. shock, delirium, coma
+/- Surgery - in ileal perforation
Non-typhi - ciprofloxacin
How do you prevent typhoid?
- Food and water safety
- Vaccination - although none offer complete protection
