Podcast
Questions and Answers
What characteristic morphology does the organism exhibit on a 5% Sheep’s Blood Agar?
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?
Which antimicrobial is the organism resistant to?
- Erythromycin
- Amoxicillin
- Cephalosporin (correct)
- Vancomycin
What type of oxygen environment does the organism thrive in?
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?
What is the expected result of a Gram stain of the organism?
Which culture medium is specifically mentioned for diagnosing the organism?
Which culture medium is specifically mentioned for diagnosing the organism?
Which of the following statements about the organism's ability to survive is accurate?
Which of the following statements about the organism's ability to survive is accurate?
What type of hemolysis is observed on Sheep’s Blood Agar?
What type of hemolysis is observed on Sheep’s Blood Agar?
What virulence factor allows Listeria to escape the phagolysosome?
What virulence factor allows Listeria to escape the phagolysosome?
At what temperature can motility be observed to differentiate L. monocytogenes from Corynebacterium?
At what temperature can motility be observed to differentiate L. monocytogenes from Corynebacterium?
Which of the following conditions can be caused by Listeria monocytogenes?
Which of the following conditions can be caused by Listeria monocytogenes?
What is the outcome of refrigeration of Listeria for several months?
What is the outcome of refrigeration of Listeria for several months?
What is the purpose of Loeffler’s Medium in the culture of Corynebacterium diphtheriae?
What is the purpose of Loeffler’s Medium in the culture of Corynebacterium diphtheriae?
How does the Reverse CAMP Test indicate the presence of Corynebacterium pseudotuberculosis?
How does the Reverse CAMP Test indicate the presence of Corynebacterium pseudotuberculosis?
What differentiates Listeria from other bacteria in laboratory cultures?
What differentiates Listeria from other bacteria in laboratory cultures?
What does Shick’s Test assess in relation to Corynebacterium diphtheriae?
What does Shick’s Test assess in relation to Corynebacterium diphtheriae?
Which factor contributes to the transmission of listeriosis in humans?
Which factor contributes to the transmission of listeriosis in humans?
Which serum is commonly used in thioglycollate broth to enhance the growth of lipophilic coryneform bacteria?
Which serum is commonly used in thioglycollate broth to enhance the growth of lipophilic coryneform bacteria?
What type of hemolysis is exhibited by Listeria monocytogenes?
What type of hemolysis is exhibited by Listeria monocytogenes?
What is indicated by a positive result in the in vivo toxigenicity test using guinea pigs?
What is indicated by a positive result in the in vivo toxigenicity test using guinea pigs?
Which of the following is considered a common consequence of listeriosis?
Which of the following is considered a common consequence of listeriosis?
Which method is utilized for in vitro toxigenicity testing of Corynebacterium species?
Which method is utilized for in vitro toxigenicity testing of Corynebacterium species?
What type of bacteria is primarily targeted through the culture process on CTBA after initial subculture?
What type of bacteria is primarily targeted through the culture process on CTBA after initial subculture?
In what conditions should the Reverse CAMP Test be incubated for accurate results?
In what conditions should the Reverse CAMP Test be incubated for accurate results?
What is a characteristic of the Corynebacterium diphtheriae's club-shaped appearance?
What is a characteristic of the Corynebacterium diphtheriae's club-shaped appearance?
Which biotype of Corynebacterium diphtheriae is associated with non-hemolytic characteristics?
Which biotype of Corynebacterium diphtheriae is associated with non-hemolytic characteristics?
What type of toxin does Corynebacterium diphtheriae produce?
What type of toxin does Corynebacterium diphtheriae produce?
What is the primary method of transmission for the respiratory form of diphtheria?
What is the primary method of transmission for the respiratory form of diphtheria?
Which medium is specifically used for enhancing the growth of Corynebacterium diphtheriae?
Which medium is specifically used for enhancing the growth of Corynebacterium diphtheriae?
How does the cutaneous form of diphtheria typically present itself?
How does the cutaneous form of diphtheria typically present itself?
What gram stain reaction does Corynebacterium diphtheriae exhibit?
What gram stain reaction does Corynebacterium diphtheriae exhibit?
What is the main pathogenic sign of Corynebacterium diphtheriae infection?
What is the main pathogenic sign of Corynebacterium diphtheriae infection?
Which of the following is a commonly used agar for identifying Corynebacterium diphtheriae?
Which of the following is a commonly used agar for identifying Corynebacterium diphtheriae?
What is the appearance of colonies on Cystine Tellurite Blood Agar for Corynebacterium diphtheriae?
What is the appearance of colonies on Cystine Tellurite Blood Agar for Corynebacterium diphtheriae?
What type of bacteria is Erysipelothrix rhusiopatiae?
What type of bacteria is Erysipelothrix rhusiopatiae?
Which of the following statements about Erysipelothrix rhusiopatiae is true?
Which of the following statements about Erysipelothrix rhusiopatiae is true?
What is the typical motility characteristic of Erysipelothrix rhusiopatiae?
What is the typical motility characteristic of Erysipelothrix rhusiopatiae?
In which test does Erysipelothrix rhusiopatiae show a positive result?
In which test does Erysipelothrix rhusiopatiae show a positive result?
How does Erysipelothrix rhusiopatiae typically grow on agar?
How does Erysipelothrix rhusiopatiae typically grow on agar?
Which of the following environments can Erysipelothrix rhusiopatiae survive in?
Which of the following environments can Erysipelothrix rhusiopatiae survive in?
What disease is commonly associated with Erysipelothrix rhusiopatiae?
What disease is commonly associated with Erysipelothrix rhusiopatiae?
What is the Gram stain result for Erysipelothrix rhusiopatiae?
What is the Gram stain result for Erysipelothrix rhusiopatiae?
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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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