Chapter 7: Gram-positive Bacteria: Non-Spore-forming rods: Corynebacterium and Listeria Flashcards
Corynebacterium diphtheriae - Gram-stain?
Gram-positive
What are the two Gram-positive rods that do not form spores?
Corynebacterium diphtheria
Listeria monocytogenes
Corynebacterium - morphology?
rods, very pleomorphic and club-shaped, “Chinese-letter” arrangement
Corynebacterium - spore-forming?
No spores
Corynebacterium - motility?
non-motile
Corynebacterium diphtheriae - metabolism?
aerobic (or facultative anaerobic)
Which Gram-positive rods appear very pleomorphic and club-shaped, with random “Chinese-letter” arrangement?
Corynebacterium diphtheriae
Corynebacterium diphtheriae - catalase?
catalase positive
What special culture requirements are required for detection of Corynebacterium diphtheriae?
1) potassium tellurite agar
2) Loeffler’s coagulated blood serum agar
(“TELL yoUR InTErn not to loaf around”)
How does Corynebacterium diphtheria appear when grown on potassium tellurite agar?
turns from gray to dark black colonies
How does Corynebacterium diphtheria appear after 12 hours of growth in Loeffler’s medium and stained with methylene blue?
metachromatic (red and blue) Babes-Ernst granules
Black colonies on cystine tellurite agar and appearance of rod-shaped pleomorphic bacteria in Loeffler’s coagulated blood serum media is indicative of what microbe?
Corynebacterium diphtheriae
How is Corynebacterium diphtheriae transmitted? Where does it colonize?
respiratory droplets that colonize the nasopharynx, which serves as a base from where it secretes its toxin
How does infection with Corynebacterium diphtheriae typically present? What if left untreated? (4)
1) pseudomembranous pharyngitis (grayish-white membrane)
2) cervical lymphadenopathy (“Bull’s neck”)
3) cranial and peripheral nerve palsy; CNS effects (blurred vision, pharyngeal/diaphragmatic paralysis)
4) arrhythmia and myocarditis
What 2 organ systems are affected in infection with Corynebacterium diphtheriae?
1) cardiac (arrhythmia and myocarditis)
2) nervous (peripheral and cranial nerve palsies) (CNS effects: blurry vision and pharyngeal/diaphragmatic paralysis)
Infection with what microbe presents with the following features:
1) pseudomembrane in pharynx
2) cervical lymphadenopathy (“Bull’s neck”)
3) cranial and peripheral nerve palsy; CNS effects (blurred vision, pharyngeal/diaphragmatic paralysis)
4) arrhythmia and myocarditis
Corynebacterium diphtheriae
What is the pseudomembrane in oropharynx caused by Corynebacterium diphtheriae infection composed of? (4)
fibrin
leukocytes
necrotic epithelial cells
Corynebacterium diphtheriae cells
If you see a dark grayish inflammatory exudate on the pharynx, suggestive of Corynebacterium diphtheriae infection, should you try to scrape it off?
No!! It will cause bleeding, and the systemic absorption of the lethal exotoxin will be enhanced.