41- Anaerobic Gram-Negative Bacilli Flashcards
What is the difference between Bacteroides, Porphyromonas, Prevotella and Fusobacterium?
• Bacteroids growth is stimulated by 20% bile. In contrast, bile-susceptible species are classified as Porphyomonas and Prevotella. Prevotella is a very small rod, but Fusobacterium is an elongated rod. Bacteroides grow rapidly in culture, but the rest can be incubated for 3 or more days before detection. Bacteroides have a capsule and although they are gram negative, do not have endotoxin activity. Fusobacterium however, does have endotoxin activity.
What is the role of the adhesins in Bacteroides fragilis?
it can adhere to peritoneal surfaces effectively because it is covered with a polysaccharide capsule. It can attach to epithelial cells and extracellular molecules by means of fimbriae
What is the role of the capsule in B. fragilis?
Protection form phagocytosis
What is the role of catalase in B. fragilis?
protection against oxygen toxicity. inactivates H2O2 and ROS
What are the role of the cytotoxic enzymes (BFT) in B. fragilis?
change intestinal epithelium and result in stimulation of chloride secretion and fluid loss
Why is it hard to Dx anaerobic bacteria?
• Specimens must be collected and transported in an oxygen free system, and incubated in an anaerobic environment. Sometimes specimens are contaminated with the normal bacterial population present on the adjacent mucosal surface because they are so close to each other. Using bile media is useful in growing anaerobes.
What organisms produce brain acesses?
Prevotella, Porphyomonas and Fusobacterium
What organism produces intraabdominal infections?
B. fragilis
What organism produces bacteremia?
B. fragilis
B. fragilis- lab tests
- Gram Stain (gram negative) and colonial morphology
- Resistance to kanamycin, vancomycin and colistin
- Stimulated growth in 20% bile
