Medical Microbiology II: Non-Lactose Fermenters
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Questions and Answers

What is the characteristic shape of Salmonella bacteria?

  • Spiral
  • Cocci
  • Rod-shaped (correct)
  • Filamentous

    • Which of the following is NOT a mode of transmission of Salmonella?

  • Fecal-oral route
  • Vector transmission (correct)
  • Ingestion of contaminated food products
  • Direct person to person transmission

    • What is the preferred method of diagnosis in the first week of illness?

  • Stool culture
  • Blood culture (correct)
  • Sputum culture
  • Urine culture

    • What is the term for the bacterial infections caused by species of Salmonella?

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

    Which of the following Salmonella strains does not produce hydrogen sulfide?

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

    Which of the following groups of Salmonella is associated with Enteric fever?

    <p>Enteric fever group</p> Signup and view all the answers

    What is the function of the Type III secretion system (TTSS) encoded by SPI-1?

    <p>To translocate bacterial proteins into the host cell</p> Signup and view all the answers

    What is the term for individuals who have natural immunity to Salmonella and contract only mild or asymptomatic disease?

    <p>Chronic carriers</p> Signup and view all the answers

    What is the purpose of the Salmonella-containing vacuole?

    <p>To enclose the bacterium in a membrane-bound compartment</p> Signup and view all the answers

    Which of the following is a characteristic of Salmonella bacteria?

    <p>Facultatively anaerobic</p> Signup and view all the answers

    Which of the following is NOT a recommended treatment for Salmonella infection?

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

    What is the name of the oral live attenuated vaccine against S.Typhi?

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

    What is the primary mode of transmission of S.typhi and paratyphi?

    <p>Person to person transmission by fecal-oral route</p> Signup and view all the answers

    Which Salmonella serovar is the most common cause of food poisoning?

    <p>S.Typhimurium</p> Signup and view all the answers

    What is the term for the individuals who can be infected by chronic carriers, especially the elderly, infants, and immunocompromised patients?

    <p>Susceptible individuals</p> Signup and view all the answers

    What is the duration of Salmonella infection in immunocompetent individuals?

    <p>Up to 7 days</p> Signup and view all the answers

    What is the primary difference between S. Enteritidis and S. Typhimurium?

    <p>Their ability to cause disease in humans</p> Signup and view all the answers

    What happens when Salmonella infects chicken flocks?

    <p>The chickens are asymptomatic, but the disease spreads rapidly</p> Signup and view all the answers

    What is the function of the Vi antigen?

    <p>It protects the bacilli from phagocytosis and complement activity</p> Signup and view all the answers

    What is the basis of the Kauffmann-White scheme for Salmonella classification?

    <p>The O and H antigens</p> Signup and view all the answers

    What is the purpose of adding Poly-O antisera to the suspension in the Kauffmann-White scheme?

    <p>To observe agglutination</p> Signup and view all the answers

    What is the effect of boiling on the H antigen?

    <p>It destroys antigenicity</p> Signup and view all the answers

    What is the characteristic of the O antigen?

    <p>It is unaffected by boiling</p> Signup and view all the answers

    What is the purpose of repeating the process with O4 and O16 antisera in the Kauffmann-White scheme?

    <p>To determine the serotype of the organism</p> Signup and view all the answers

    What was the occupation of the person responsible for several typhoid outbreaks in New York in the early 1900s?

    <p>A cook</p> Signup and view all the answers

    How many people were infected with typhoid due to the actions of the cook in New York?

    <p>78</p> Signup and view all the answers

    What was the condition for the cook's release from the isolation center on North Brother Island in 1910?

    <p>She never accept employment involving food handling</p> Signup and view all the answers

    What is the correct taxonomic name for the organism that causes typhoid fever?

    <p>Salmonella enterica ssp.enterica, serovar typhi</p> Signup and view all the answers

    What is the incubation period of typhoid and paratyphoid infections?

    <p>6-30 days</p> Signup and view all the answers

    What is the primary reservoir for Salmonella typhi?

    <p>The gall bladder</p> Signup and view all the answers

    What is the term for the combined name of typhoid fever and paratyphoid fever?

    <p>Enteric fever</p> Signup and view all the answers

    What is the primary mode of transmission of Salmonella typhi?

    <p>Through contaminated food and water</p> Signup and view all the answers

    What method can be used to determine the serotype of an organism?

    <p>Kauffman &amp; White book</p> Signup and view all the answers

    What is the problem associated with Salmonella Typhimurium DT104?

    <p>Antibiotic resistance</p> Signup and view all the answers

    What is the role of marA in Salmonella?

    <p>Regulator of multidrug efflux pumps</p> Signup and view all the answers

    Why is Salmonellosis a reportable disease?

    <p>It is prevalent in countries with poor water supply and sanitation</p> Signup and view all the answers

    What is the role of food handlers in the spread of Salmonellosis?

    <p>They play a great role in its spread</p> Signup and view all the answers

    How many organisms of Shigella are required to cause disease?

    <p>100-200</p> Signup and view all the answers

    Where is Shigella typically found?

    <p>In the human GIT during infections</p> Signup and view all the answers

    How long can carriers of pathogenic Shigella strains excrete the organism?

    <p>Up to two weeks</p> Signup and view all the answers

    Study Notes

    Non-Lactose Fermenters (Salmonella, Shigella, Yersinia)

    Salmonella

    • Gram-negative, rod-shaped, facultatively anaerobic bacterium
    • Motile by peritrichous flagella
    • Zoonotic, causes economically important disease in humans and livestock
    • Causes:
      • Enteric fever (Typhoid fever)
      • Gastroenteritis
      • Septicemias
      • Carrier state
    • Divided into 2 groups:
      • Enteric fever group
      • Food-poisoning group
    • Habitat:
      • S.typhi and paratyphi: only found in humans, not part of normal flora of the bowel
      • Other Salmonella spp.: widely disseminated in nature, associated with various animals
    • Mode of transmission:
      • S.typhi and paratyphi: person-to-person spread by fecal-oral route, ingestion of contaminated food or water
      • Other Salmonella spp.: ingestion of contaminated food products, direct person-to-person transmission in healthcare settings
    • Carrier state: natural reservoir for the disease, "chronic carriers" contract only mild or asymptomatic disease, but still carry the bacteria in their body for a long time

    Typhoid Fever (Salmonella Typhi)

    • Caused by Salmonella enterica serovar Typhi
    • Incubation period: 6-30 days
    • Symptoms: nausea, vomiting, fever, and death
    • Can only infect humans, no other host identified
    • Septicemia (particularly S.choleraesuis, S.typhi, and S.paratyphi)
    • Asymptomatic carriage (gall bladder is the reservoir for Salmonella typhi)
    • Lab diagnosis: stool culture not usually positive during the first week of illness, so blood culture is preferred
    • S.Typhi: gas not produced during fermentation, K/A+
    • Virulence factors:
      • Type III secretion system (TTSS)
      • Acid resistance
      • Salmonella-containing vacuole

    Treatment and Prevention

    • Fluoroquinolones (such as ciprofloxacin), azithromycin, and ceftriaxone
    • Prevention: safe food and water precautions, vaccine (ViCPS, Typhim Vi, and Vivotif)

    Salmonella enterica serovar Typhimurium

    • Most common cause of food poisoning by Salmonella species
    • Causes diarrhea, abdominal cramps, vomiting, and nausea, generally lasting up to 7 days
    • Can be fatal in immunocompromised people if not treated with antibiotics

    Salmonella Antigenic Structure

    • H - Flagella Ag: heat-labile, boiling destroys antigenicity, strongly immunogenic
    • O - Somatic Ag: forms integral part of the cell wall, unaffected by boiling, less immunogenic than H Ag
    • Vi - Surface Ag (Capsular): covers the O Ag, destroyed by boiling at 60°C for 1 hour, a virulence factor

    Salmonella Serotyping

    • Classification based on the Kauffmann-White scheme using somatic (O) and flagellar (H) antigens
    • Method: using Poly-O and Poly-H antisera, and the Kauffman & White book to determine the serotype

    Pathogenesis and Clinical Disease

    • Molecular typing methods: phage typing, antibiotic-resistant typing, PCR-based methods, pulsed-field gel electrophoresis (PFGE), and plasmid typing
    • Antibiotic resistance: AcrAB, SoxRS, and MarAB implicated in chromosomal-based resistance
    • Epidemic measures: reportable disease, prevalent in countries with poor water supply and sanitation, food handlers play a great role in its spread

    Shigella

    • One of the most infectious bacteria, ingestion of as few as 100 to 200 organisms can cause disease
    • Habitat: only found in human GIT at times of infections, not part of normal bowel flora
    • Transmission: person-to-person via fecal-oral route, especially in overcrowded areas and areas with poor sanitary conditions
    • Carriers of pathogenic strains can excrete the organism up to two weeks after infection and occasionally for longer periods

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    Description

    This quiz covers non-lactose fermenters, specifically Salmonella, Shigella, and Yersinia, and their characteristics, including shape, motility, and disease causes.

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