Anaerobes Flashcards
What gram-negative anaerobic bacillus is involved in most intra-abdominal infections?
Bacteriodes fragilis (often isolated in mixed bacterial infections)
Sites of infection of anaerobic gram-negative bacteria
Colon, mouth and skin
What is the virulence factor of Bacteriodes fragilis?
Polysaccharide capsule - anti-phagocytic
What are metabolic properties of Bacteroides fragilis that are used to differentiate it in culture?
- stimulated by bile
- resistant to gentamicin
- hydrolyzes esculin to a black precipitate
What is a gram positive, anaerobic, spore-forming bacillus whose pathogenesis is primarily due to production of its toxin?
Clostridia
What are the 4 groups of clostridia?
C. dificile
C. perfringens
C. tetani
C. botulinum
- Which group of clostridia causes antibiotic associated diarrhea?
- What is the mechanism of action of its toxins?
- How do you treat it?
- C. dificile
- Toxins A and B glucosylate Rho GTPases –> disrupt GI epithelium causing diarrhea
- Metronidazole, Vancomycin or a subset of fluoroquinolones
- What causes the majority of clostridial-mediated myonecrosis?
- What predisposes someone to this pathogen?
- What causes the host cell death?
- C. perfringens
- Deep wound to the muscles
- Loss of tissue reduction potential
What types of paralysis are caused by C. tetanus and C. botulinum respectively?
C. tetanus causes spastic paralysis and C. botulinum causes flaccid paralysis
Explain the similarities and differences between the tetanus and botulinum toxins.
Similarity: Both are proteases that cleave SNARE proteins to inhibit synaptic vesicle fusion.
Difference: TeNT is transported to the CNS to inhibit and interneuron resulting in the spastic paralysis. BoNT inhibits the release of ACh from peripheral neurons resulting in the flaccid paralysis.
Which one has a vaccine: tetanus and/or botulinum?
Tetanus
Which serotypes of C. botulinum are the most common forms for humans?
A, B, and E
What are the 3 natural intoxications and infections with BoNT?
- Food-borne intoxication - toxin ingested
- Infant botulism - infection - spores are ingested
- Wound botulism - infection - spores in the wound
Besides for cosmetic purposes, what is a medical therapy for BoNT?
Blepharospasm - an abnormal contraction of the eyelids causing a functional blindness
-useful because BoNT has a long half-life
- Do gram negative or gram positive bacteria form spores?
2. What are the three bacteria that do? - state which ones are aerobic and anaerobic
- Gram positive
2. Bacillus (aerobe), Clostridium (anaerobe) and Sporosarcina (aerobe)
