Typhoid fever Flashcards
Basis of serotyping
- Somatic O antigen (LPS cell wall components)
- Surface Vi antigen (restricted to S. typhi and S. paratyphi C)
- Flagellar H antigen
Characteristic of salmonella
produce acid on glucose fermentation, reduce nitrates, and do not produce cytochrome oxidase
a systemic disease characterized by fever and abdominal pain caused by dissemination of S. typhi and S. paratyphi
Enteric (typhoid) fever
Risk factor for typhoid fever
- contaminated water/ice
- flooding
- food & drinks purchased from street vendors
- raw fruits and vegetables grown in fields fertilized with sewage
- ill household contacts
- lack of hand washing and toilet access
- evidence of prior H.pylori infection
Multi-drug resistant (MDR) strains of S. typhi
contain plasmids encoding resistance to chloramphenicol, ampicillin, and trimethoprim
incubation period of S. typhi
10-14 days but ranges from 5-21 days
Most prominent symptom of typhoid fever
prolonged fever (38.5-40.5) which can continue up to 4 weeks if untreated
Early physical findings of enteric fever
RAsh (“rose spots”), hepatosplenomegaly, epistaxis and relative bradycardia at the peak of high fever
faint , salmon-colored, blanching maculopapular rash located primarily on the trunk and chest
Rose spots
Timeline when GI bleeding and intestinal perforation occur in typhoid fever
3rd-4th week
Neurologic manifestations of typhoid fever
meningitis, GBS, neuritis, and neuropsychiatric symptoms (“muttering delirium” or “coma vigil”)
Relapse
within 2-3 weeks of fever resolution
Chronic asymptomatic carriage
shed S. typhi in either urine or stool for >1 year
- common among women, infants, and persons who have biliary abnormalities or concurrent bladder infection with Schistosoma hematobium
- increased risk fo gallbladder cancer
Definitive diagnosis of typhoid fever
isolation of S. typhi or S. paratyphi from blood, bone marrow, other sterile sites, rose spots, stool, or intestinal secretions
yield not reduced by up to 5 days of prior antibiotic therapy
Bone marrow culture
can be positive despite a negative bone marrow culture
Intestinal secretions
can be come positive during the 3rd week of infection in untreated patients
Stool cultures
most effective in the treatment of drug-susceptible typhoid fever
Fluoroquinolones (Ciprofloxacin)
Treatment of drug-resistant strains of typhoid fever
Ceftriaxone, cefotaxime, and oral cefixime, oral azithromycin
Duration of treatment of typhoid fever
at least 10 days or for 5 days after fever resolution
Role of glucocorticoids
administration of dexamethasone (an initial dose of 3 mg/kg followed by eight doses of 1 mg/kg every 6h) with chloramphenicol was associated with substantially lower mortality rate than was treatment with chloramphenicol alone
-indicated in severe enteric fever
Treatment of chronic carriage stage
4 weeks with oral ciprofloxacin or other fluoroquinolones
Treatment in cases of anatomic abnormality (biliary or kidney stones)
eradication often requires both antibiotic therapy and surgical correction
Antibiotic therapy for enteric fever in adults
Rose spots
Role of typhoid vaccines
should be considered for persons planning to travel to high risk areas
Commercially available
1. Ty21a - oral live attenuated S. typhi vaccine (days 1,3,5, and 7, with revaccination of full 4-dose series every 5 years)
- Vi CPS - a parenteral vaccine consisting of purified Vi polysaccharide from the bacterial capsule (single dose,, booster every 2 years)
