Enterobacteriaceae and Salmonella Overview
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Questions and Answers

Which characteristic is true regarding Salmonella species?

  • They typically display black centers on HE or XLD agar. (correct)
  • They cannot produce H2S.
  • They are always lactose fermenters on MAC agar.
  • They are obligate anaerobes.

    • What is a primary means of transmission for Shigella spp.?

  • Contaminated water. (correct)
  • Direct contact with infected animals.
  • Inhalation of respiratory droplets.
  • Consumption of undercooked meat.

    • Which of the following is a key virulence factor for Salmonella?

  • Capsule for evasion.
  • Endotoxin-mediated shock.
  • Fimbriae for adhesion. (correct)
  • Spores formation.

    • What distinguishes Salmonella enterica serotype Typhi from other Salmonella species?

    <p>It is a major human pathogen.</p> Signup and view all the answers

    The O antigen of Salmonella is best described as:

    <p>Heat-stable and part of the cell wall.</p> Signup and view all the answers

    Which of the following is true regarding Yersinia species?

    <p>They are transmitted by a wide variety of animals.</p> Signup and view all the answers

    Identifying Salmonella positive tests includes which of the following?

    <p>Negative for indole.</p> Signup and view all the answers

    What is the best description of the primary human pathogens in the Enterobacteriaceae family?

    <p>They are not normal biota of the intestinal tract.</p> Signup and view all the answers

    Which Salmonella serotype is most commonly associated with typhoid fever?

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

    What is a primary source of Salmonella infections linked to gastroenteritis?

    <p>Poultry and eggs</p> Signup and view all the answers

    What are common clinical symptoms of acute gastroenteritis caused by Salmonella?

    <p>Nausea, vomiting, fever, and watery diarrhea</p> Signup and view all the answers

    What differentiates enteric fever from typical gastroenteritis caused by Salmonella?

    <p>Enteric fever commonly occurs without diarrhea</p> Signup and view all the answers

    What role does the reticuloendothelial system (RES) play in the pathogenesis of enteric fever?

    <p>It is responsible for disseminating bacteria to multiple organs</p> Signup and view all the answers

    Which of the following is NOT a common factor contributing to outbreaks of typhoid fever?

    <p>Good sanitation practices</p> Signup and view all the answers

    What is the typical incubation period for symptoms of Salmonella gastroenteritis to appear after ingestion?

    <p>8 to 36 hours</p> Signup and view all the answers

    Which of the following statements about the Vi antigen is accurate?

    <p>It helps identify Salmonella serotype Typhi.</p> Signup and view all the answers

    What symptoms do patients typically develop during the first week of Salmonella typhoid fever?

    <p>Fever, malaise, anorexia, lethargy, myalgia, and a dull headache</p> Signup and view all the answers

    During which weeks of Salmonella typhoid fever do 'rose spots' typically appear?

    <p>Weeks 2 and 3</p> Signup and view all the answers

    What is the incubation period for the symptoms of Salmonella typhoid fever to appear?

    <p>9 to 14 days after ingestion</p> Signup and view all the answers

    Which organ is primarily affected by Salmonella typhoid fever during prolonged infections?

    <p>Gallbladder</p> Signup and view all the answers

    What is the consequence of prolonged bacteremia due to Salmonella typhoid fever?

    <p>Seed the bloodstream with bacteria</p> Signup and view all the answers

    Which laboratory sample is most likely to be positive during the 2nd week of Salmonella typhoid fever?

    <p>Blood culture</p> Signup and view all the answers

    What complication is NOT typically associated with prolonged Salmonella typhoid fever infection?

    <p>Appendicitis</p> Signup and view all the answers

    What feature significantly indicates the invasion of Salmonella organisms during weeks 2 and 3?

    <p>Sustained fever and bacteremia</p> Signup and view all the answers

    What is the primary route of transmission for Shigella?

    <p>Direct person-to-person</p> Signup and view all the answers

    Which group is particularly at risk for Shigella infections?

    <p>Children in daycare centers</p> Signup and view all the answers

    What is a common symptom associated with Shigellosis?

    <p>High fever and chills</p> Signup and view all the answers

    Which of the following is NOT a feature of Shigella?

    <p>Heat stable</p> Signup and view all the answers

    What type of infection is primarily caused by Shigella?

    <p>Shigellosis or Bacillary Dysentery</p> Signup and view all the answers

    What treatment is usually recommended for Shigellosis?

    <p>Antimicrobial drug therapy</p> Signup and view all the answers

    Which bacterium is responsible for the plague?

    <p>Yersinia pestis</p> Signup and view all the answers

    Which demographic factor contributes to Shigella spread?

    <p>Practice of anal-oral sexual activity</p> Signup and view all the answers

    What is the causative agent of plague?

    <p>Yersinia pestis</p> Signup and view all the answers

    Which of the following is NOT a form of plague caused by Yersinia pestis?

    <p>Gastrointestinal plague</p> Signup and view all the answers

    How is Yersinia pestis primarily transmitted?

    <p>Bite of infected fleas</p> Signup and view all the answers

    What symptom is characteristic of bubonic plague?

    <p>Painful swollen lymph nodes</p> Signup and view all the answers

    Which age group is most commonly affected by acute gastroenteritis caused by Yersinia enterocolitica?

    <p>Infants and young children (1-5 years)</p> Signup and view all the answers

    What cultural characteristic is true for Yersinia enterocolitica?

    <p>Survives in cold temperatures</p> Signup and view all the answers

    What is a common symptom of appendicitis-like syndrome caused by Yersinia enterocolitica?

    <p>Right lower quadrant abdominal pain</p> Signup and view all the answers

    What type of staining characteristic is observed in Yersinia species?

    <p>Bipolar staining</p> Signup and view all the answers

    Study Notes

    Enterobacteriaceae

    • Enterobacteriaceae are primarily human intestinal pathogens that are not part of the normal intestinal biota.
    • These bacteria are Gram-negative rods, facultatively anaerobic.
    • Enterobacteriaceae can be differentiated on media such as MacConkey agar (MAC), Hektoen Enteric agar (HE), and Xylose Lysine Deoxycholate agar (XLD).

    Salmonella

    • Salmonella is a common human pathogen that inhabits the gastrointestinal tracts of animals.
    • Human infection primarily occurs through contaminated or undercooked animal food products.
    • Salmonella species are identified through serological testing, as they are negative for indole, VP, urease, and PAD, and most produce H2S.
    • There are six subspecies in the species Salmonella enterica, and all other Salmonella species are serotypes of S. enterica.
    • Salmonella enterica serotype Typhi is a specific serotype that causes Typhoid fever. It is important to remember that Typhi is not a species, but a serotype.

    Salmonella Virulence Factors

    • Fimbriae assist in initiating intestinal infection.
    • Salmonella has the ability to traverse the intestinal mucosa.
    • An enterotoxin is involved in causing gastroenteritis.

    Salmonella Antigenic Structures

    • Salmonella possess three main antigenic structures:
      • O antigen: Heat-stable lipopolysaccharide responsible for the cell wall antigen.
      • H antigen: Heat-labile flagellar antigen. These antigens appear in two phases (Phase I and Phase II). Phase I can identify particular serotypes while Phase II is nonspecific.
      • Vi antigen: Heat-labile capsular antigen similar to a K capsule antigen. It acts as a key identifier for Salmonella serotype Typhi.

    ### Salmonella Infections

    • Salmonella infection can manifest as acute gastroenteritis/food poisoning, enteric fever, or nontyphoid bacteremia.

    Salmonella Gastroenteritis

    • Salmonella gastroenteritis, also known as food poisoning, is associated with Salmonella enterica serotype enterica.
    • Sources of infection include poultry, eggs, milk, egg products, pets, and contaminated food contact surfaces.
    • Symptoms appear 8 to 36 hours after ingestion of contaminated food.

    Salmonella Enteric Fever

    • Enteric fever is a serious fever disease that can be caused by various Salmonella strains.
    • Salmonella Typhi causes typhoid fever.
    • Symptoms include prolonged fever, bacteremia, involvement of the reticuloendothelial system (RES), and possible dissemination of bacteria to multiple organs.
    • Enteric fever is more common in tropical and subtropical areas.
    • Poor sanitation and lack of a modern potable water system contribute to outbreaks.

    Salmonella Typhoid Fever Timeline

    • Symptoms usually develop 9 to 14 days after ingestion of the organism.
    • The amount of ingested organism affects incubation time.
    • The first week consists of flu-like symptoms and bacteremia.
    • During weeks 2 and 3, the patient experiences sustained fever with prolonged bacteremia.
    • "Rose spots" appear on the skin during week 2 of the fever.

    Salmonella Typhoid Fever Diagnosis

    • Blood cultures may be positive in the first week of the disease but are rarely reliable in weeks 3 and 4.
    • Urine cultures may be positive during week 2.
    • Salmonella Typhi is a non-motile Salmonella serotype, and lacks H antigens.

    Shigella Species

    • Shigella is a human pathogen that is transmitted through the fecal-oral route, typically from carriers.
    • Individuals in daycare centers, crowded housing, and those who practice anal–oral sexual activity are at higher risk.

    ### Shigella Infection

    • Shigella causes a disease known as Shigellosis or Bacillary dysentery.
    • The infection begins with the attachment of bacteria to the mucosal surfaces.
    • Bacteria then penetrate the intestinal epithelial cells causing inflammation and ulceration.

    Shigella Infection Symptoms

    • Symptoms of Shigella infection range from asymptomatic to severe.
    • Fever, chills, abdominal cramps, tenesmus and watery diarrhea are common.
    • Blood and leukocytes are present in the stool.

    Shigella Treatment

    • Treatment involves oral rehydration and may include antimicrobial drug therapy.

    Yersinia Species

    • Yersinia is a genus that includes two main pathogens:
      • Yersinia pestis: Causes plague.
      • Yersinia enterocolitica: Causes gastroenteritis.

    ### Yersinia pestis

    • It's the causative agent of plague.
    • Infection occurs through the bite of an infected flea.
    • Pneumonic plague can be transmitted through respiratory droplets.
    • Classified as a Class A bioterrorism agent.

    Yersinia pestis Infection

    • Symptoms of bubonic plague include high fever and painful regional lymph nodes (buboes).
    • The septicemic form develops when the bacteria spreads to the bloodstream.
    • Pneumonic plague may occur due to secondary infection from bubonic or septicemic plague.

    Yersinia enterocolitica

    • Infections are acquired through contact with swine, cats, dogs, or contaminated food.
    • Yersinia enterocolitica survives in cold temperatures.
    • Infections commonly cause acute gastroenteritis, mimicking appendicitis, arthritis, and erythema nodosum.

    Yersinia enterocolitica Infections

    • The most common form of infection is acute gastroenteritis, often affecting infants and young children.
    • Symptoms include fever, headache, abdominal pain, nausea, and diarrhea.
    • Diarrhea may be bloody.
    • Appendicitis-like symptoms usually occur in older children and adults.

    Yersinia Cellular Morphology

    • Both Yersinia pestis and Yersinia enterocolitica are gram-negative coccobacilli with a characteristic safety pin appearance.
    • They are motile at 25° C.

    Yersinia Cultural Characteristics

    • Both species grow on blood agar and MacConkey agar (NLF).
    • They have a preferred growth range of 25 to 30° C.
    • Cold enrichment can be used to enhance recovery from fecal samples.
    • Yersinia enterocolitica is motile at 25° C but not at 35° C.
    • Yersinia pestis is motile.

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    BIOL 2010 Lecture 10 - Enterobacteriaceae Lecture Notes PDF

    Description

    This quiz explores the characteristics and identification of Enterobacteriaceae and Salmonella, two significant groups of pathogens. You'll learn about their clinical significance, testing methods, and their roles in human infections. Test your knowledge and understanding of these important bacteria!

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