Bacteria Associated with Typhoid Fever
Typhoid fever is primarily caused by Salmonella enterica subspecies enterica serovar Typhi (Salmonella Typhi), but other bacteria including Salmonella Paratyphi A, B, and C can cause a clinically similar disease known as paratyphoid fever. 1
Primary Causative Organisms
Salmonella Typhi: The main causative agent of typhoid fever, a severe systemic infection characterized by sustained fever, headache, abdominal pain, and hepatosplenomegaly 1
Salmonella Paratyphi: Causes paratyphoid fever, an attenuated form of typhoid fever with similar but often less severe clinical presentation 2
- Salmonella Paratyphi A
- Salmonella Paratyphi B
- Salmonella Paratyphi C
Clinical Presentation and Diagnosis
Typhoid and paratyphoid fever typically present with:
- Insidious onset of sustained high fever (39-40°C)
- Headache, lethargy, malaise
- Relative bradycardia
- Abdominal pain
- Hepatosplenomegaly
- Constipation or diarrhea 1
Diagnostic approaches include:
- Blood cultures (sensitivity 40-80%) - gold standard and should be collected before antibiotics 1
- Bone marrow culture - highest sensitivity, especially valuable if antibiotics have been administered 1
- Stool culture (sensitivity 35-65%) 1
- Molecular diagnostic tests when available 1
Complications and Manifestations
Typhoid fever can lead to serious complications including:
- Intestinal perforation, most commonly in the ileum or jejunum 3
- Gastrointestinal bleeding
- Typhoid encephalopathy
- Hepatitis
- Myocarditis 1
Treatment Considerations
First-line treatment for typhoid fever:
- Ceftriaxone 2g IV every 24 hours for 10-14 days, especially for patients returning from Asia due to increasing fluoroquinolone resistance 1
- Azithromycin for uncomplicated cases or step-down therapy 1
- Ciprofloxacin can be used for typhoid fever if the organism is confirmed sensitive 4
Prevention
Preventive measures include:
- Hand hygiene
- Consumption of potable or treated water
- Proper cooking of food
- Vaccination for travelers to endemic areas 1
- Oral live-attenuated Ty21a vaccine (efficacy 50-70%)
- Parenteral polysaccharide capsular Vi vaccine
Epidemiology
- Highest incidence in South and Southeast Asia, particularly the Indian subcontinent 1, 5
- Also endemic in parts of Africa, Central and South America 1
- Travelers to endemic regions are at risk, particularly those visiting friends and relatives 1, 5
Common Pitfalls in Management
- Relying solely on serologic tests like the Widal test for diagnosis 1
- Failing to collect blood cultures before starting antibiotics 1
- Using fluoroquinolones empirically without considering regional resistance patterns 1
- Overlooking typhoid fever in patients with fever but without diarrhea 1
Future Directions
Research is ongoing for improved vaccines that would provide:
- Better protection against Salmonella Typhi
- Cross-protection against Salmonella Paratyphi strains
- Coverage against non-typhoidal Salmonella serovars 6
Understanding the full spectrum of bacteria associated with typhoid and paratyphoid fever is essential for accurate diagnosis, appropriate treatment, and effective prevention strategies, particularly in the context of increasing antimicrobial resistance.