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?

<p>Normochromic, normocytic anemia and leukopenia are commonly found.</p> Signup and view all the answers

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

<p>Immunologic methods using monoclonal antibodies have been attempted.</p> Signup and view all the answers

What serious hematological condition may develop during typhoid fever?

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

What bacterium is primarily responsible for causing typhoid fever?

<p>Salmonella enterica serovar Typhi.</p> Signup and view all the answers

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

<p>Over 21.7 million cases.</p> Signup and view all the answers

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

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

What are common gastrointestinal findings in patients with enteric fever?

<p>Fecal leukocytes and fecal blood are very common.</p> Signup and view all the answers

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

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

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

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

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

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

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

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

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

<p>Salmonella Paratyphi A.</p> Signup and view all the answers

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

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

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

<p>The ratio is about 10 to 1.</p> Signup and view all the answers

Which groups are especially vulnerable to typhoid fever?

<p>The elderly, infants, and immunocompromised patients.</p> Signup and view all the answers

How can typhoid fever be transmitted congenitally?

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

At what temperatures can Salmonella be killed effectively?

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

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

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

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

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

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

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

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

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

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

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

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

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

How does diarrhea manifest in the illness's progression?

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

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

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

What is the significance of culturing lesions in this context?

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

What clinical signs may indicate respiratory involvement in affected patients?

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

Flashcards

What is Typhoid Fever?

Typhoid fever is a severe bacterial infection caused by Salmonella Typhi.

How is Typhoid Fever spread?

The most common way typhoid fever spreads is by ingesting contaminated food or water.

What causes Typhoid Fever?

Salmonella Typhi, a gram-negative bacterium, causes Typhoid Fever.

Widal test for Typhoid Fever

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

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Limitations of Widal Test

Paired sera are difficult to obtain, and specific chemotherapy may be needed based on a single test.

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What's the incubation period for Typhoid?

The incubation period for typhoid fever is usually 7 to 14 days, but can range from 3 to 30 days.

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Why is Typhoid Fever a concern?

Typhoid fever is a serious health concern, especially in developing countries.

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False Positive Widal Test

These reactions can occur due to cross-reactivity with other Salmonella species.

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Urine Vi Antigen Detection in Typhoid

This method involves detecting specific antigens in the urine, often using monoclonal antibodies.

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What are typhoid carriers?

People who carry the bacteria but appear healthy can spread typhoid, posing a risk to public health.

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What are some symptoms of Typhoid Fever?

Typhoid Fever can cause a range of symptoms, including fever, headache, abdominal pain, and constipation.

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PCR for Typhoid

This technique amplifies specific genes of Salmonella Typhi in the blood, enabling rapid diagnosis.

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Pancytopenia in Typhoid

A common complication of Typhoid fever, characterized by a decrease in red blood cells, white blood cells, and platelets.

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How resistant is Salmonella Typhi?

Salmonella Typhi is highly resistant to many physical agents, but can be killed by heat.

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How can Typhoid Fever be prevented?

Typhoid fever can be prevented through vaccination, good hygiene practices, and access to clean water and sanitation.

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Normochromic Normocytic Anemia in Typhoid

This type of anemia is often present after several weeks of illness.

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What is Paratyphoid fever?

Paratyphoid fever is similar to Typhoid fever, but often less severe.

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Leukocyte Count in Typhoid

Leukocyte counts are frequently low in relation to fever and toxicity, but can vary widely.

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Thrombocytopenia in Typhoid

This is a common finding in Typhoid fever, often persisting for one week.

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Liver Function and Proteinuria in Typhoid

Typhoid fever can cause disturbances in liver function, and protein may be lost in the urine.

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What factors influence the severity of typhoid fever?

The severity of typhoid fever depends on factors like the duration of illness before treatment, the chosen antibiotic, age, past exposure, vaccine history, the virulence of the bacteria, the amount ingested, and other individual factors.

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What are the early symptoms of typhoid fever?

The initial symptoms of typhoid fever appear gradually over 2-3 days and include fever, fatigue, loss of appetite, muscle aches, headache, and abdominal pain.

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What is the characteristic bowel pattern in early typhoid?

Constipation, followed by diarrhea, becomes a more prominent symptom during the early stages of typhoid fever.

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What other symptoms can develop in early typhoid?

Cough and nosebleeds may occur as the typhoid fever progresses.

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Describe typhoid fever's progression in the second week.

During the second week of typhoid fever, the high fever persists, and fatigue, loss of appetite, cough, and abdominal symptoms worsen. Patients appear acutely ill, confused, and drowsy.

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What signs of mental confusion may appear in typhoid?

Delirium and stupor, a state of unresponsiveness, may develop during the second week of typhoid fever.

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What is Faget's sign and what does it indicate?

A relative bradycardia, which means a slower heart rate than expected for the high fever, known as Faget's sign, is a characteristic finding in typhoid fever.

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What are common physical exam findings in a person with typhoid?

An enlarged liver, an enlarged spleen, and a swollen abdomen with tenderness are common physical findings in typhoid fever.

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What characteristic rash may appear in typhoid?

A rash known as rose spots, characterized by small, flat, reddish-brown spots, appears on the body of about 50% of typhoid patients during the second week.

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What is the significance of nausea and vomiting in typhoid?

Nausea and vomiting occurring during the second or third weeks of typhoid fever suggest a complication.

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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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