Bacteriology Lecture: Gram + Bacilli Part 2
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Bacteriology Lecture: Gram + Bacilli Part 2

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Questions and Answers

What characteristic morphology does the organism exhibit on a 5% Sheep’s Blood Agar?

  • Flat, brown colonies
  • Large, mucoid colonies
  • Small, white, translucent colonies (correct)
  • Small, red colonies

    • Which antimicrobial is the organism resistant to?

  • Erythromycin
  • Amoxicillin
  • Cephalosporin (correct)
  • Vancomycin

    • What type of oxygen environment does the organism thrive in?

  • Microaerophilic (correct)
  • Facultative anaerobic
  • Aerobic
  • Obligate anaerobic

    • What is the expected result of a Gram stain of the organism?

    <p>Gram-positive bacilli</p> Signup and view all the answers

    Which culture medium is specifically mentioned for diagnosing the organism?

    <p>McBride Agar</p> Signup and view all the answers

    Which of the following statements about the organism's ability to survive is accurate?

    <p>It can survive within phagocytes</p> Signup and view all the answers

    What type of hemolysis is observed on Sheep’s Blood Agar?

    <p>Narrow band of beta hemolysis</p> Signup and view all the answers

    What virulence factor allows Listeria to escape the phagolysosome?

    <p>Listeriolysin O</p> Signup and view all the answers

    At what temperature can motility be observed to differentiate L. monocytogenes from Corynebacterium?

    <p>25 degrees C</p> Signup and view all the answers

    Which of the following conditions can be caused by Listeria monocytogenes?

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

    What is the outcome of refrigeration of Listeria for several months?

    <p>Enhanced virulence</p> Signup and view all the answers

    What is the purpose of Loeffler’s Medium in the culture of Corynebacterium diphtheriae?

    <p>To stimulate the growth of C. diphtheriae &amp; production of metachromatic granules</p> Signup and view all the answers

    How does the Reverse CAMP Test indicate the presence of Corynebacterium pseudotuberculosis?

    <p>Through the formation of a bowtie appearance</p> Signup and view all the answers

    What differentiates Listeria from other bacteria in laboratory cultures?

    <p>Growth on Tomato Juice Agar</p> Signup and view all the answers

    What does Shick’s Test assess in relation to Corynebacterium diphtheriae?

    <p>The susceptibility of the individual to diphtheria</p> Signup and view all the answers

    Which factor contributes to the transmission of listeriosis in humans?

    <p>Ingestion of contaminated food</p> Signup and view all the answers

    Which serum is commonly used in thioglycollate broth to enhance the growth of lipophilic coryneform bacteria?

    <p>Rabbit serum</p> Signup and view all the answers

    What type of hemolysis is exhibited by Listeria monocytogenes?

    <p>Beta hemolysis</p> Signup and view all the answers

    What is indicated by a positive result in the in vivo toxigenicity test using guinea pigs?

    <p>Indication of high virulence potential</p> Signup and view all the answers

    Which of the following is considered a common consequence of listeriosis?

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

    Which method is utilized for in vitro toxigenicity testing of Corynebacterium species?

    <p>Modified Elek’s Test</p> Signup and view all the answers

    What type of bacteria is primarily targeted through the culture process on CTBA after initial subculture?

    <p>Corynebacterium diphtheriae</p> Signup and view all the answers

    In what conditions should the Reverse CAMP Test be incubated for accurate results?

    <p>At 37 degrees Celsius for 24-48 hours in aerobic conditions</p> Signup and view all the answers

    What is a characteristic of the Corynebacterium diphtheriae's club-shaped appearance?

    <p>Swollen one end</p> Signup and view all the answers

    Which biotype of Corynebacterium diphtheriae is associated with non-hemolytic characteristics?

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

    What type of toxin does Corynebacterium diphtheriae produce?

    <p>Heat-labile exotoxin</p> Signup and view all the answers

    What is the primary method of transmission for the respiratory form of diphtheria?

    <p>Droplet infection</p> Signup and view all the answers

    Which medium is specifically used for enhancing the growth of Corynebacterium diphtheriae?

    <p>Reco medium</p> Signup and view all the answers

    How does the cutaneous form of diphtheria typically present itself?

    <p>Slow healing ulcers and membranous formation</p> Signup and view all the answers

    What gram stain reaction does Corynebacterium diphtheriae exhibit?

    <p>Gram-positive bacilli</p> Signup and view all the answers

    What is the main pathogenic sign of Corynebacterium diphtheriae infection?

    <p>Pseudomembrane formation in tonsils</p> Signup and view all the answers

    Which of the following is a commonly used agar for identifying Corynebacterium diphtheriae?

    <p>Tinsdale Medium</p> Signup and view all the answers

    What is the appearance of colonies on Cystine Tellurite Blood Agar for Corynebacterium diphtheriae?

    <p>Gun metal black colonies</p> Signup and view all the answers

    What type of bacteria is Erysipelothrix rhusiopatiae?

    <p>Gram + bacilli</p> Signup and view all the answers

    Which of the following statements about Erysipelothrix rhusiopatiae is true?

    <p>It can cross the placenta.</p> Signup and view all the answers

    What is the typical motility characteristic of Erysipelothrix rhusiopatiae?

    <p>Tumbling motility</p> Signup and view all the answers

    In which test does Erysipelothrix rhusiopatiae show a positive result?

    <p>CAMP test</p> Signup and view all the answers

    How does Erysipelothrix rhusiopatiae typically grow on agar?

    <p>Umbrella-like growth</p> Signup and view all the answers

    Which of the following environments can Erysipelothrix rhusiopatiae survive in?

    <p>High salt concentrations</p> Signup and view all the answers

    What disease is commonly associated with Erysipelothrix rhusiopatiae?

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

    What is the Gram stain result for Erysipelothrix rhusiopatiae?

    <p>Gram + bacilli</p> Signup and view all the answers

    Study Notes

    Bacteriology Overview

    • Hemolytic and starch/glycogen tests yield negative results with a bleach-like odor.

    Corynebacterium diphtheriae

    • Gram-positive bacilli, highly pleomorphic; often club and rod-shaped.
    • Ferments dextrose and glucose; utilizes starch/glycogen (+).
    • Metachromatic granules (Babes-Ernst granules) are distinctive.
    • Biotypes include:
      • Intermedius: small, dry gray/black colonies with a gray border.
      • Gravis: largest colonies with a daisy head appearance, non-hemolytic.
      • Belfanti: most frequently recovered, associated with severe infections.
    • Toxigenic strains produce diphtheria exotoxin (heat labile A and B components).
    • Clinical infections include:
      • Respiratory form: pharyngitis with pseudomembranous covering and systemic effects on heart and nerves.
      • Cutaneous form: characterized by slow healing ulcers and membranous formations.
    • Culture media:
      • Tinsdale Medium for black colonies with brown halos.
      • Loeffler's Serum Slant for poached-egg colonies.
      • Cystine Tellurite Blood Agar (CTBA) for gray-black colonies.

    Laboratory Diagnosis

    • Nasopharyngeal and throat swabs are collected using Dacron Tipped Swab or Calcium Alginate.
    • Cultures are performed on 5% Sheep’s Blood Agar, Chocolate Agar, and anaerobic BAP.
    • Tests for motility, Gram stain, and various ferments (glucose, maltose, sucrose, mannitol) provide identification.
    • Toxigenicity testing includes:
      • In Vivo Toxigenicity (guinea pig lethality test).
      • In Vitro (Modified Elek’s Test for immunodiffusion).

    Erysipelothrix rhusiopathiae

    • Small Gram-positive coccobacilli, not part of normal flora (NF), and animal pathogens.
    • Possesses tumbling motility and resistant to salty, pickled conditions.
    • Associated with erysipeloid infections, especially in handlers or farmers.
    • Gram stain shows alpha hemolytic characteristics on BAP.
    • Can grow in refrigerated conditions for extended periods; isolated from crustaceans, ticks, and fleas.

    Other Bacterial Infections

    • Differential tests for Listeria monocytogenes, significant for foodborne illnesses and meningitis:
      • Motility at 25°C and unique salicin fermentation test.
    • Listeria virulence factors include Listeriolysin O and superoxide dismutase for survival and evasion mechanisms.
    • Lactobacillus acidophilus is a non-pathogenic resident of the GI tract, produces lactic acid to combat urogenital infections.
    • Notable for fermentation properties and importance in food products (e.g., yogurt).

    Diagnostic Features

    • Shick’s Test assesses susceptibility to diphtheria.
    • Reverse CAMP test clarifies distinctions between bacterial species.
    • Cultures and biochemical tests reveal significant traits for identification and environmental survival.

    Summary

    • Understanding the characteristics and laboratory diagnostics of Corynebacterium diphtheriae and Erysipelothrix rhusiopathiae is essential in clinical microbiology, particularly for differentiating pathogenic bacteria and managing infections.

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    GRAM+PT.2 (1).pdf

    Description

    This quiz covers key concepts in bacteriology, focusing on Gram-positive bacilli and specific characteristics of Corynebacterium diphtheriae. Test your understanding of colony morphology, hemolytic properties, and identifying features of bacteria. Ideal for students studying microbiology or related fields.

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