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Flashcards in microbiology stack Deck (8)
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actinomyces israelli

non-spore forming GPR
* anaerobic, branching, slow-growing, filamentous
* normal flora of GI tract (mouth to rectum)
* cervicofacial (head & neck) infections most common, usually due to poor dental hygiene, trauma, dental procedures
***** disruption of mucosal barrier or aspiration
* slow progress, chronic if untreated
* large inflammatory mess with draining sinuses
* fibrosis of tissue may result in deformity
* diagnosis: pus culture, gram stain of S-granules
* therapy: penicillin; high doses & long term therapy



a bacterium that fails to grow on the surface of solid medium in air containing 10% oxygen


mechanism of O2 toxicity (*speculative)

1. anaerobic possess flavoproteins so in the presence of O2 may form H2O2 and/or toxic radicals (superoxide anion; hydroxyl radical; or singlet oxygen)

2. many lack catalase (CAT, peroxidase) and super-oxide dismutase (SOD) enzymes that are in most aerobes & facultative anaerobes
2O2- + 2H+ -SOD-> O2 + H2O2
H2O2 + H2O2 -CAT-> 2H2O + O2

3. certain metabolic enzymes must be in the reduced state for activity (fumarate reductase), therefore, aerobic conditions induce a metabolic block

4. anearobes not equally intolerant of O2

5. single mechanism not applicable to all anaerobes and different mechanism may also apply under different environmental conditions



* predisposing factors usually present
* surgery (especially bowel)
* vascular disease
* impaired host defenses
* prolonged antibiotic therapy
* chronic underlying disease
* growth of facultative anaerobes in mixed wound infection
* necrosis
* not always evident


virulence factors

* antibiotic resistance (especially bacteroides)
* exotoxins / exoenzymes
- neurotoxins:


Yersinia, what (symptoms, tx)

Gram negative rod


Pseudomonas, what



Serratia, what