04 Gram-Positive Rods Flashcards
What are the two types of Gram-Positive Rods?
Spore-forming. Non-spore forming
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)
What are the Non-spore forming Gram-Positive Rods?
Listeria monocytogenes (bacteremia, meningitis). Propionibacterium acnes (normal skin flora; acnes, shunt infections)
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
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
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)
As soon as you hear “gas gangrene” what should you immediately be thinking?
C. perfringens
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
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
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)
