Enteric Fever and Salmonella Characteristics

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Questions and Answers

What is considered diagnostic of typhoid fever in a Widal test?

A four-fold rise of antibody in paired sera is considered diagnostic.

What complications can arise from the Widal test?

False positive reactions may occur due to non-typhoid salmonella and poorly standardized antigens.

How long does it typically take for symptoms of typhoid fever to resolve without complications?

Symptoms and physical findings usually resolve within 2-4 weeks.

What laboratory findings are common during enteric fever?

Normochromic, normocytic anemia and leukopenia are commonly found. Signup and view all the answers

What diagnostic method has been used to detect S. ser. Typhi specific antigens in urine?

Immunologic methods using monoclonal antibodies have been attempted. Signup and view all the answers

What serious hematological condition may develop during typhoid fever?

Thrombocytopenia may occur and can last for about one week. Signup and view all the answers

What bacterium is primarily responsible for causing typhoid fever?

Salmonella enterica serovar Typhi. Signup and view all the answers

What is the estimated annual incidence of typhoid fever cases worldwide according to WHO?

Over 21.7 million cases. Signup and view all the answers

What laboratory test can amplify specific genes of S. ser. Typhi?

Polymerase chain reaction (PCR) can be used to amplify specific genes. Signup and view all the answers

What are common gastrointestinal findings in patients with enteric fever?

Fecal leukocytes and fecal blood are very common. Signup and view all the answers

Who was 'Typhoid Mary' and what was her impact on public health?

Typhoid Mary Mallon was a food handler who infected at least 78 people, killing 5. Signup and view all the answers

What is the most common mode of transmission for typhoid fever?

Ingestion of foods or water contaminated with human feces. Signup and view all the answers

What can be observed in blood leukocyte counts during enteric fever?

Leukocyte counts may be low; leukopenia is frequently found after the 1st or 2nd week. Signup and view all the answers

How is the diagnostic significance increased when testing for raised antibodies?

Testing paired samples for raised antibodies carries greater diagnostic significance. Signup and view all the answers

Name a less severe disease caused by a closely related bacterium to S. Typhi.

Salmonella Paratyphi A. Signup and view all the answers

What are the dominant clinical features of typhoid fever regarding the incubation period?

The incubation period is usually 7-14 days but can vary from 3 to 30 days. Signup and view all the answers

What is the relative pathogenicity ratio of S. Typhi to S. Paratyphi?

The ratio is about 10 to 1. Signup and view all the answers

Which groups are especially vulnerable to typhoid fever?

The elderly, infants, and immunocompromised patients. Signup and view all the answers

How can typhoid fever be transmitted congenitally?

Through transplacental infection from a bacteremic mother to her fetus. Signup and view all the answers

At what temperatures can Salmonella be killed effectively?

At 54.4°C for 1 hour or 60°C for 15 minutes. Signup and view all the answers

What are the initial symptoms that develop over 2-3 days in children with this illness?

Initial symptoms include fever, malaise, anorexia, myalgia, headache, and abdominal pain. Signup and view all the answers

What potential severe symptoms may develop during the second week of illness?

Severe lethargy, sustained high fever, increased abdominal symptoms, and potential delirium or stupor may occur. Signup and view all the answers

What does the Faget sign indicate in patients with this infection?

The Faget sign indicates relative bradycardia, or a slower heart rate despite a high fever. Signup and view all the answers

What factors can influence the severity and clinical outcome of the infection?

Factors include the duration of illness before therapy, choice of treatment, age, vaccination history, and virulence of the bacterial strain. Signup and view all the answers

What type of rash may appear in about 50% of patients, and when does it typically occur?

A maculopapular rash known as rose spots may appear around the 7th-10th day of illness. Signup and view all the answers

What are some common physical findings in patients with this condition?

Common findings include hepatomegaly, splenomegaly, abdominal tenderness, and a distended abdomen. Signup and view all the answers

How does diarrhea manifest in the illness's progression?

Diarrhea may follow a period of constipation and become a more prominent symptom. Signup and view all the answers

What does the appearance of nausea and vomiting in the 2nd or 3rd week suggest?

The occurrence of nausea and vomiting suggests the possibility of a complication. Signup and view all the answers

What is the significance of culturing lesions in this context?

Cultures of the lesions have a 60% yield for detecting Salmonella organisms. Signup and view all the answers

What clinical signs may indicate respiratory involvement in affected patients?

Rhonchi and scattered rales may be heard upon auscultation of the chest. Signup and view all the answers

Study Notes

Enteric Fever (Typhoid Fever)

Typhoid fever is a significant health problem in developing countries
The World Health Organization (WHO) estimates over 21.7 million cases annually, with the majority in Asia, resulting in over 200,000 deaths
Typhoid Mary Mallon, a food handler, was responsible for infecting at least 78 people, with 5 fatalities. She highlights the risk of infectious carriers to public health

Etiology

Enteric fever is caused by Salmonella enterica serovar Typhi (S. Typhi), a gram-negative bacterium
Similar, but often less severe, illnesses are caused by S. Paratyphi A, B, and C
The ratio of illnesses caused by S. Typhi to S. Paratyphi is approximately 10:1

Salmonellae characteristics

Salmonellae are motile, non-spore-forming, non-encapsulated, gram-negative rods that grow aerobically
They are resistant to many physical agents, but susceptible to heating to 54.4°C for 1 hour or 60°C for 15 minutes
The bacteria can survive for weeks in sewage, dried foods, and feces

Mode of Transmission

Direct or indirect contact with an infected person (either sick or a carrier) is necessary for infection
Ingestion of contaminated food or water (fecal-oral route) is the most common method of transmission
Waterborne outbreaks, due to sanitation issues and poor personal hygiene, are common in developing nations
Transplacental infection from an infected mother to her fetus is possible.

Who Can Be Infected?

Anyone can be infected, but the elderly, infants, and immunocompromised individuals (e.g., those with AIDS or sickle cell anemia) are at higher risk

Clinical Features

Incubation period typically ranges from 7-14 days, but can vary depending on the infecting dose (3-30 days)
Clinical presentation can range from mild (low-grade fever, malaise, slight cough) to severe (abdominal discomfort, complications)
Factors influencing the severity include the duration of illness before treatment, type of antimicrobial treatment, age, prior exposure/vaccination, virulence of the bacteria, quantity ingested, and other host factors..

Clinical Features in Children

Onset is insidious (gradual)
Initial symptoms (fever, malaise, anorexia, myalgia, headache and abdominal pain) can develop over 2-3 days
Diarrhoea with subsequent constipation can be a prominent symptom
Cough and epistaxis may occur
Severe lethargy may develop in some children
Temperature often reaches 40°C
During the second week of illness, fever persists, fatigue, anorexia, cough, and abdominal symptoms worsen
Patients can appear acutely ill, disoriented, and lethargic; delirium and stupor may be observed

Physical Findings

Relative bradycardia, hepatomegaly, splenomegaly, and a distended abdomen with diffuse tenderness are common
Macular- or maculopapular rash (rose spots) on the 7th-10th day in about 50% of patients; culture from the spots yields Salmonella in 60% of cases
Auscultation may reveal rhonchi and scattered rales
Nausea and vomiting during the 2nd or 3rd week may suggest complications
Without complications, symptoms and findings resolve within 2-4 weeks

Infants and Young Children (<5 Years)

Enteric fever is relatively rare in this age group
Even though clinical sepsis may occur the presentation is typically mild, making diagnosis difficult
Diarrhea is a more frequent symptom in this age group compared to adults, potentially misdiagnosed as a viral syndrome

Neonates

Enteric fever during late pregnancy can be transmitted vertically (from the mother to the newborn)
Neonatal disease usually begins within 3 days of delivery
Symptoms may include vomiting, diarrhea, abdominal distention, fever (up to 40.5°C), seizures, hepatomegaly, jaundice, anorexia, and weight loss.

Common Clinical Features in Children

High-grade fever, coated tongue, anorexia, vomiting, hepatomegaly, diarrhea, toxicity, abdominal pain, pallor, splenomegaly, constipation, headache, jaundice, obtundation, ileus, perforation

Complications

Untreated enteric fever can lead to complications such as severe diarrhea, intestinal bleeding, perforation, persistent high fever, becoming a carrier, weight loss, delirium, hallucinations, meningitis, encephalopathy, hepatitis, cholecystitis, endocarditis, myocarditis, heart failure, shock, pneumonia, anemia, osteomyelitis, or septic arthritis

Diagnosis

Mainstay is a positive culture from blood or other site
Blood cultures positive 40-60% of the time, while stool and urine cultures become positive after 1 week
Bone marrow cultures can confirm diagnosis (85-90% positive) but are invasive.
Stool or urine cultures become positive after the first week

Widal Test

Significant antibody titers can aid in diagnosis
A rise in antibody levels in a paired sample (taken at different times) is more significant than a single sample. A four-fold increase in paired tests is the standard.
Non-typhoid Salmonella infections can cause false positives
Widal tests are not always standardized, hence can be unreliable

Direct Detection of Salmonella

Detecting specific antigens in the urine (e.g., S. Typhi Vi antigen) can aid in diagnosis
Polymerase Chain Reaction (PCR) amplifies specific genes in patient blood, enabling quick diagnosis (within hours)

Laboratory Investigations

Normochromic, normocytic anemia often develops weeks after fever
Leukocyte counts are often low (leukopenia) but can vary widely
Thrombocytopenia may occur for a week or more
Liver function tests are often disturbed.
Proteinuria.
Fecal leukocytes and fecal blood are common

Differential Diagnosis

During the initial stage, enteric fever can be mistaken for gastroenteritis, viral syndromes, bronchitis, or bronchopneumonia.
Other differential diagnoses in later stages include sepsis with other bacteria, intracellular infections (tuberculosis, brucellosis), and viral infections (infectious mononucleosis).

Treatment

General principles: adequate rest, hydration, attention to fluid-electrolyte balance
Antipyretic therapy (e.g., acetaminophen) as needed
Soft, easily digestible diet, unless the patient exhibits abdominal distention or ileus
Antibiotic therapy is crucial to reduce complications
Examples of antibiotics that have been useful in many cases include ampicillin, amoxicillin, trimethoprim-sulfamethoxazole (TMP-SMZ), cefixime, ceftriaxone, and ofloxacin. Doses and duration are varied
Short courses of antibiotics may be adequate in many cases

Treatment Duration

Most children become afebrile within 7 days, but treatment of uncomplicated cases should continue for at least 14 days.
Resistant strains are usually susceptible to third-generation cephalosporins.
Other considerations for treatment of severe sepsis, shock, or coma (including dexamethasone) are indicated when appropriate

Eradication of Chronic Carriage

A prolonged course (4-6 weeks) of high-dose ampicillin (or amoxicillin), possibly combined with probenecid or TMP-SMZ, can help eradicate the infection.
Cholecystectomy might be an option alongside antibiotics, if gallstones exist
Cholecystectomy would be considered if biliary tract problems are suspected

Prognosis

Mortality rate is low (<1%) in developed countries, but higher (>10%) in developing countries, particular in children and young infants
Patients with underlying conditions are at a higher risk
Relapses after stopping antibiotics are possible, with symptoms similar to an initial infection
Risk of prolonged shedding of pathogen (becoming a carrier) is lower in children but raises with age

Prevention

Improved sanitation and clean water are crucial in preventing the disease.
Good personal hygiene (handwashing) and food preparation practices are essential
Preventing carriers from food- or water-handling jobs is worthwhile

Vaccine

Two types exist: Oral (Ty21a; live-attenuated) and Intramuscular (Vi capsular)
The oral vaccine is for people over 2 years old, and is given over time
The IM vaccine is for individuals 2 years or older. One intramuscular injection, plus every 2 years for a booster is typical.

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Description

This quiz explores the critical aspects of enteric fever, particularly typhoid fever, including its prevalence, causes, and associated health risks. It also delves into the characteristics of Salmonella bacteria that lead to these illnesses. Test your knowledge on this significant health issue and its implications.