1-13 Anaerobic Bacteria Flashcards
1
Q
What are three sources of anaerobic pathogenesis?
A
-
Normal flora run amok escape from their normal compartment and form abscesses.
ex) actinomyces in mouth, B. fragilis in colon - Spore-forming bacteria in soil enter wounds and germinate if tissue is deep enough to be low-oxygen.
ex) Clostridium tetani in tetanus, C. perfringens in gas gangrene -
Entry through food when spores survive sterilization and germinate after vacuum-packing. Their exotoxins can cause disease even after they are dead.
ex) foodborne botulism, C. perfringens food poisoning
2
Q
What are some special techniques that are either necessary or useful for anaerobic cultures?
A
- Sample must be stored under anaerobic conditions and transported very quickly to lab.
- After exposure to a reducing agent, liquid cultures must be stoppered quickly and intubated WITHOUT shaking.
- Agar plates should be streaked promptly and quickly, and then placed in an anaerobic culture jar.
- Working with an anaerobic glovebox may be necessary.
3
Q
What techniques can we use to identify anaerobic bacteria?
A
- Anaerobic cultures
- Gram stain
- Gas chromatography to analyze organic acids produced by fermentation pathways
- Shotgun sequencing is beginning to replace GC in medical diagnostics
4
Q
How do we treat anaerobic infections?
A
- If there’s an abscess, surgical care: drain and debride.
- If toxigenic, administer antitoxin.
- Generally, simultaenous antibiotic treatment as well.
5
Q
What are the three major pathogenic anaerobes?
A
-
Clostridia: Gram(+) soil organisms that depend on their spores to jump into humans.
* C. difficile*, however, is a normal flora. - GNAB: Gram(-) Anaerobic Bacilli that are normal flora who run amok.
- Actinomyces: Gram(+) normal flora.
6
Q
What is the primary determinant of anaerobic virulence?
A
Exotoxins!
Neuro-toxin production –> tetanus, botulism
Tissue-degrading enzymes –> gas gangrene, abscess formation
