Typhoid Fever: Pathogenesis (vectors, bacteria), Symptoms, Diagnosis, Treatment, Vaccine

Summary

This video discusses typhoid fever, its causes, transmission, symptoms, diagnosis, and treatment. Typhoid fever is caused by the bacteria *Salmonella enterica* serovar typhi or paratyphi and is transmitted through contaminated food or water, especially in areas with poor sanitation. Symptoms include fever, abdominal pain, and rose spots. Diagnosis is based on exposure history and symptoms, confirmed through tests like blood and stool cultures. Treatment involves antibiotics, though resistance patterns vary. Prevention focuses on sanitation, hygiene, and vaccination. The video also covers chronic carriage and relapse in some cases.

Takeaways

• 🦠 Typhoid fever is caused by Salmonella enterica serovar Typhi or Salmonella Paratyphi, with slight variations in clinical presentation, collectively known as enteric fever.
• 🤒 Typhoid fever is transmitted between humans via direct or indirect contact, often through contaminated food or water. Children, young adults, overcrowding, and poor sanitation increase the risk.
• 🧬 The bacteria survive gastric acids, penetrate the intestinal lining, and spread through lymphoid tissue, entering the bloodstream to cause systemic symptoms.
• 🌡️ Symptoms appear 5 to 21 days after ingestion, beginning with a 'stepwise' fever in the first week, followed by abdominal pain and rose spots in the second week, and potentially intestinal bleeding and splenomegaly in the third week.
• 🩺 Diagnosis of typhoid fever is based on clinical suspicion, especially after exposure to endemic areas. Blood and stool cultures can confirm the diagnosis, though sometimes empiric diagnosis is used.
• 💊 Treatment includes antibiotics like fluoroquinolones, azithromycin, and ceftriaxone. Treatment may vary based on local resistance patterns, with multi-drug-resistant strains being a concern.
• 🔄 Relapse can occur 2 to 3 weeks after resolution, with symptoms reappearing depending on the antibiotic used and local resistance patterns.
• 👩‍⚕️ Chronic carriage happens in 1-5% of cases, especially in adult women or those with biliary diseases. Carriers can excrete the bacteria for over 12 months, with gallstones acting as bacterial reservoirs.
• 💧 Prevention of typhoid fever includes access to clean water, proper sanitation, hygiene practices, and vaccination.
• 📚 Historical reference to 'Typhoid Mary' highlights the importance of identifying chronic carriers who can spread the disease without showing symptoms.

Q & A

What causes typhoid fever?

Typhoid fever is caused by an infection with a gram-negative bacterium called *Salmonella enterica* serovar Typhi, or related bacteria like *Salmonella paratyphi*, which has subtypes A, B, and C. These bacteria lead to different clinical presentations, but they all cause typhoid fever.

How is typhoid fever transmitted?

Typhoid fever is transmitted from human to human, either through direct contact or indirectly via contaminated food or water. Poor sanitation and overcrowding are risk factors that facilitate the transmission.

What are the main risk factors for contracting typhoid fever?

The main risk factors include being a child or young adult, overcrowding, and poor sanitation. These conditions increase the likelihood of direct or indirect contact with contaminated food or water.

How do Salmonella Typhi and Paratyphi bacteria infect humans?

These bacteria are ingested orally, survive stomach acids, and enter the duodenum. They penetrate the intestinal epithelium and invade lymphoid tissue through mechanisms like entering via M cells or using the CFTR chloride ion channel.

Why might patients with cystic fibrosis be less susceptible to typhoid fever?

Cystic fibrosis patients may be less susceptible because the bacteria use the cystic fibrosis transmembrane conductance regulator (CFTR) channel to enter cells. In cystic fibrosis patients, this channel is mutated, potentially preventing the bacteria from hijacking it to infect the intestines.

What are the early symptoms of typhoid fever?

The early symptoms include a stepwise fever, which shows a gradual increase in temperature over time. This occurs in the first week of infection, along with general discomfort.

What are rose spots, and when do they appear during typhoid fever?

Rose spots are small, blanchable papules (1-5 mm) that appear on the skin during the second week of typhoid fever. These spots are a characteristic symptom of the disease.

What are the potential complications in the third week of typhoid fever?

In the third week, complications include intestinal bleeding, hepatosplenomegaly (enlargement of the liver and spleen), and intestinal perforation. These are serious symptoms that require medical attention.

How is typhoid fever diagnosed?

Typhoid fever is diagnosed by suspecting it based on symptoms such as fever, abdominal pain, and GI issues, especially if the patient has been in an endemic area. Blood and stool cultures are typically used for confirmation.

What are the common treatments for typhoid fever?

The treatment depends on local resistance patterns but generally includes antibiotics like fluoroquinolones, azithromycin, ceftriaxone, or carbapenems. Severe cases might also require steroids like dexamethasone.