9. Enteric fever Flashcards
What is an alternative name for enteric fever?
Typhoid and paratyphoid (generally milder)
Where is enteric fever endemic?
Mainly Asia
also Africa and S America
What is the causative agent of enteric fever?
Salmonella enterica serovar Typhi / Parathyphi A B or C
What type of bacteria is S. enterica? What is its gram stain appearance?
Enterobacteriaceae
Aerobic gram-negatie rod
Name 3 S. enterica virulence factors.
- gram-negative endotoxin, VI antigen
- invasin - allows intracellular growth
- fimbriae - adhere to epithelium over ileal lymphoid tissue (Peyer’s patches), allowing entry into blood and lymph
How is S. enterica transmitted?
faecal-oral route from contaminated food/water (human pathogen only)
What is the incubation period of S. enterica?
7-14 days
What are the signs and symptoms of enteric fever?
Symptoms:
- headache
- abdominal discomfort, constipation or diarrhoea
- dry cough
Signs:
- fever
- relative bradychardia
What type of disease is enteric fever?
systemic (bacteraemia)
What are the possible complications of enteric fever? What is the mortality rate if untreated?
- intestinal haemorrhage and perforation
- 10% mortality
What investigations are indicative of enteric fever?
- FBC: moderate anaemia, relative lymphopenia
- LFTs: raised transaminase and bilirubin
- Blood (and faeces) culture
(serology not reliable)
What is the treatment strategy for enteric fever?
CEFTRIAXONE or AZITHROMYCIN (7-14 days)
Why is treatment of S. enterica difficult?
rapidly develops resistance (e.g. to chloramphenicol, ampicillin, ciprofloxacin…)
How can enteric fever be prevented?
- food and water hygiene precautions
- typhoid vaccine (modest protective effect 50-75%)
- Vi capsular polysaccharide antigen
- live attenuated vaccine
