Salmonella Subspecies Classification

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Questions and Answers

What is the primary route of infection for typhoidal salmonella?

Ingestion through the faecal-oral route (correct)

Direct contact with infected individuals

Consumption of contaminated water

Inhalation of contaminated air

Which of the following best describes the role of macrophages in the pathogenesis of enteric fever?

They destroy the bacteria immediately upon ingestion.

They inhibit bacterial multiplication.

They facilitate reinfection of the intestinal tract.

They ingest the bacteria and transport them to lymph nodes. (correct)

What occurs after the bacteria multiply in the mesenteric lymph nodes during enteric fever?

They are expelled through vomit.

They remain dormant in the lymph nodes.

They enter the bloodstream causing primary bacteraemia. (correct)

They travel to the lungs to cause pneumonia.

Which type of Salmonella primarily causes typhoidal infections in humans?

Salmonella typhi Signup and view all the answers

Which organs are primarily invaded by salmonella typhi after entering the bloodstream?

Liver, gall bladder, spleen, and bone marrow Signup and view all the answers

What complication can occur due to the reinfection from the gallbladder during enteric fever?

Necrosis of Peyer’s patches with associated bleeding Signup and view all the answers

What characteristic of Salmonella enterica allows it to survive in both anaerobic and aerobic environments?

Facultative anaerobe status Signup and view all the answers

Which of the following Salmonella subspecies is responsible for most human and animal infections?

Salmonella enterica Signup and view all the answers

What type of salmonellosis is characterized by gastroenteritis?

Non-typhoidal Salmonella infection Signup and view all the answers

Which of the following is NOT a subspecies of Salmonella enterica?

Salmonella choleraesuis Signup and view all the answers

What is a typical duration for gastroenteritis caused by non-typhoidal Salmonellae?

3-7 days Signup and view all the answers

Which of the following factors can increase prolonged excretion of non-typhoidal Salmonellae?

HIV infection Signup and view all the answers

Which complication is more likely in cases of acute gastroenteritis with certain virulent strains of Salmonella?

Bloodstream infection Signup and view all the answers

In what situation are antibiotics indicated for treating non-typhoidal Salmonellae gastroenteritis?

Only if there is severe illness and high risk of invasive disease Signup and view all the answers

What is the recommended treatment for the majority of cases of Salmonella gastroenteritis?

Fluid and electrolyte replacement Signup and view all the answers

What is a primary difference between Paratyphoid A and Paratyphoid B?

Paratyphoid B rarely shows rose spots. Signup and view all the answers

In which week of illness would blood cultures typically show the highest positivity for enteric fever?

First week Signup and view all the answers

What is the recommended first-line empiric treatment for enteric fever?

Ceftriaxone Signup and view all the answers

What challenge faces the use of Ciprofloxacin in treating enteric fever?

Increasing resistance to the drug. Signup and view all the answers

What is one of the key methods for preventing enteric fever?

Vaccination for high-risk areas. Signup and view all the answers

What type of vaccine is WHO recommended for those traveling to high-risk areas for enteric fever?

Live attenuated oral vaccine Signup and view all the answers

What percentage of patients with enteric fever may become chronic carriers after symptoms resolve?

5% Signup and view all the answers

Which of the following is NOT a common precaution for preventing enteric fever?

Consuming untreated water. Signup and view all the answers

What characterizes the incubation period for paratyphi A, B, and C infections?

7-21 days Signup and view all the answers

Which symptom is NOT typically associated with the first week of enteric fever?

Abdominal distension Signup and view all the answers

What is the treatment recommended for chronic carriers of Salmonella Typhi?

Ciprofloxacin for at least 1 month Signup and view all the answers

What percentage of untreated patients experience a relapse of enteric fever?

10-15% Signup and view all the answers

Which symptom is specifically noted in the second week of enteric fever?

Rose spots Signup and view all the answers

What severe complication can occur in untreated enteric fever by the third week?

Osteomyelitis Signup and view all the answers

In which contexts are most cases of enteric fever reported?

Underdeveloped areas with poor sanitation Signup and view all the answers

What should chronic carriers of Salmonella Typhi refrain from doing?

Working in the food industry Signup and view all the answers

Study Notes

Salmonella Overview

Salmonella is categorized into multiple subspecies, notably Salmonella enterica and Salmonella bongori.
Enterica subspecies includes various serovars responsible for 99% of human and animal infections.
Two main classifications: Typhoidal (affecting humans only) and Non-typhoidal (affecting both humans and animals).

Typhoidal Salmonella

Key serovars:
- Salmonella Typhi (causes typhoid fever)
- Salmonella Paratyphi A, B, C (cause paratyphoid fever, milder than typhoid).
Transmission via fecal-oral route through contaminated food or water.
Incubation period ranges from 7 to 21 days (up to 30 days).

Pathogenesis of Typhoidal Fever

Initial ingestion leads to bacterial adherence and penetration of intestinal epithelium, particularly in the distal ileum.
Bacteria taken up by macrophages can survive and proliferate, leading to bacteremia.
Hematogenous spread to organs like the liver, spleen, and bone marrow occurs.
Reinfection of intestinal tract via the gallbladder results in a vicious cycle of infection.

Clinical Features of Typhoidal Fever

Week 1: Gradual rise in temperature, headache, constipation or diarrhea, and possible relative bradycardia.
Week 2: High persistent fever (39-40°C), abdominal pain, "pea-soup" diarrhea, possible mental confusion, and rose spots appearing on the skin.
Week 3: Risk of severe complications like abdominal perforation and secondary bacteremia; relapse occurs in 10-15% of cases if inadequately treated.
Week 4: Improvement in symptoms, but risks of long-term complications remain.

Chronic Carrier Status

Approximately up to 6% of individuals can become chronic carriers post-recovery, shedding bacteria indefinitely.
Chronic carriers are usually asymptomatic but can pose transmission risk and have an increased risk of gallbladder cancer.

Diagnosis of Enteric Fever

Culture and PCR are essential diagnostic methods:
- Blood cultures have a higher yield in the first week.
- Stool cultures are positive from the second week onward.
The Widal test, once common, is now seldom used due to low sensitivity and specificity.

Treatment of Enteric Fever

Supportive care includes fluid and electrolyte replacement.
First-line antibiotics: Ceftriaxone recommended, with increasing resistance noted for other agents like Ciprofloxacin.
Treatment duration typically lasts 10-14 days.

Non-Typhoidal Salmonella and Gastroenteritis

Characterized by a sudden onset of symptoms including diarrhea, headache, and malaise, typically self-limiting within 3-7 days.
Severe dehydration risk is higher in vulnerable populations, such as the very young and immunocompromised.
Long-term chronic excretion of bacteria can occur, especially in individuals with weakened immune systems or underlying gastrointestinal conditions.

Complications of Non-Typhoidal Salmonella

Possible bloodstream infections (4% probability in acute gastroenteritis cases).
Systemic diseases may arise, including osteomyelitis and meningitis.
Reactive arthritis can occur following infection.

Management of Salmonella Gastroenteritis

Fluid and electrolyte replacement serves as the primary treatment for most cases.
Antibiotic therapy is only recommended in severe illnesses with a high risk of complications.

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Description

This quiz focuses on the classification of various Salmonella subspecies, including both typhoidal and non-typhoidal types. Learn about the characteristics and infection rates associated with each subspecies relevant to human and animal health.