04 Gram-Positive Rods Flashcards Preview

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Flashcards in 04 Gram-Positive Rods Deck (10):
1

What are the two types of Gram-Positive Rods?

Spore-forming. Non-spore forming

2

What are the spore-forming Gram-Positive Rods?

Bacillus cereus (food poisoning). Clostridium botulinum (botulism). Clostridium perfringens (gas gangrene, food poisoning). Clostridium difficile (antibiotic-associated colitis)

3

What are the Non-spore forming Gram-Positive Rods?

Listeria monocytogenes (bacteremia, meningitis). Propionibacterium acnes (normal skin flora; acnes, shunt infections)

4

What are spores?

Structures that form inside the cell in response to adverse conditions - bacillus, clostridium sp. Contains bacterial DNA, a small amount of cytoplasm, cell membrane, peptidoglycan, very little water, AND a thick keratinlike coat that is resistant to heat, dehydration, radiation, and chemicals. No metabolic activity; can remain dormant for many years. Upon exposure to water and appropriate nutrients, germinate into reproducing bacterial cells. Sterilization cannot be achieved by boiling; requries steam heating at 121C for 30 minutes

5

Which Gram-Positive Rods can cause food poisoning?

B. cereus, C. perfringens. Spores contaminate grains, vegetables, and meats --> germinate under anaerobic conditions --> produce enterotoxins --> nausea/vomiting, diarrhea

6

What are some wound infection Gram-Positive Rods?

C. tetani, C. perfringens. Spores in soil --> enter wound sites --> germinate in traumatized tissues --> produce toxins --> tetanus (C. tetani) or gas gangrene (C. perfringens)

7

As soon as you hear "gas gangrene" what should you immediately be thinking?

C. perfringens

8

What is Clostridium difficile?

Normal flora of the GI tract in 3% of the general population (30% in hospitalized patents). Transmitted by fecal-oral route. Cause antibiotic-associated colitis. Exotoxin A --> watery diarrhea; Exotoxin B --> cytotoxin causing damage to colonic mucosa forming pseudomembranes. ID in the lab by detection of exotoxin in filtrates of stool samples on cultured cells by specific antibody or PCR

9

What is Listeria Monocytogenes?

Small tumbling GPR (non-spore forming); growth in 4 Celsius. "Food-borne" infection: transmitted to humans by contact with animals or their feces, unpasteurized milk, contaminated vegetables. Incubation period of invasive disease ~3 weeks. Intracellular; cell-mediated immunity

10

What is the spectrum of diseases from Listeria monocytogenes?

Newborns (meningitis, pneumonia). Immunocompromised (high dose steroids, malignancy): meningitis. Pregnant women (HA, "flu-like" symptoms, self-limited, choroamnionitis, septic abortion, stillbirth, premature birth)