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32 Cards in this Set
- Front
- Back
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Define microaerophilic, capnophilic, and facultative bacteria. |
microaerophilic - require oxygen in reduce quantity Capnophilic - require carbon dioxide Facultative - can grow either with or without oxygen. |
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True/False: Anaerobic bacteria include both obligate and aerotolerant bacteria. |
True. |
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True/False: Anaerobic bacteria require cytochrome systems, superoxide dismutase, and catalase. |
False: The cytochrome system is absent and only some have superoxide dismutase and catalase. |
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For anaerobic bacteria, are pH and oxidation-reduction potential important for growth? |
Yes. |
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Where are some common places in the human body to find anaerobic bacteria? |
Colon, mouth, vagina. |
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What three things to anaerobic bacteria cause in the eye? |
Conjunctivitis, keratitis, and dacryocystitis. |
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What are some of the characteristics of anaerobic gram negative bacilli and where are they found? |
They are non-spore forming, pleomorphic rods found as normal flora in the upper respiratory tract, intestinal and female genital tract. Can also be found in the colon. |
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What is the common clinical disease from a gram-negative bacilli manifest as? |
Usually abscess formation with mixed anaerobic and facultative anaerobic bacteria. |
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What bacteria causes necrotizing fasciitis? |
Bacteroides fragilis whose capsule is antiphagocytic. |
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What are the 2 most important groups of gram-negative anaerobic bacilli? |
Bacteroides fragilis and Prevotella melaninogenica. |
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Why will you often find mixes of anaerobic bacteria with facultative bacteria? |
Because the facultative bacteria (such as enterobacteriaceae) can use up the oxygen and essentially protect the anaerobic bacteria. They can also produce beta-lacatamases and toxins to protect each other. |
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Describe fusobacterium. |
They are pleomorphic, non-spore forming gram negative bacilli. They are usually present in mixed infections, but can be sole agent. found in upper respiratory and intestinal tract. The major one is F. necrophorum which causes Lemierre's syndrome. |
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What is Lemierre's syndrome? |
Jugular vein thrombosis caused by F. necrophorum. |
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What are the characteristics of actinomyces? |
They are gram-positive bacilli that are slow growing and difficult to isolate. |
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What do actinomyces bacteria usually cause? Where are they found and what is the most common one? |
They can cause extensive soft tissue involvement crossing tissue plane and involving multiple organ systems, draining sinus tracts with 'sulfur granules', and are found in oral, respiratory, and female genital tract infections. The most common is Actinomyces israelii. |
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What are some of the anaerobic gram-positive bacilli? |
Actinomyces, propionibacterium: normal flora of skin. lactobacillus: normal flora of vagina. Also, eubacterium, bifidobacterium, and arachnia. |
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What is the only genus of anaerobes that form spores? |
Clostridium. |
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What are the major clostridium species? |
C. tetani C. botulinum C. perfringens C. septicum C. difficile |
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What is the disease and major toxin associated with C. tetani? |
Tetanus - the toxin is tetanospasmin which blocks inhibitory neurotransmitters. |
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What is the disease and major toxin associated with C. botulinum? |
Botulism - ingestion of preformed neurotoxin (except for wound and infant botulism) that blocks the release of acetylcholine. |
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What is the disease and major toxin associated with C. perfringens? |
Gas gangrene and food poisoning. The toxin is phospholipase C (alpha toxin) that destroys cell membranes (gas gangrene) and enterotoxin (food poisoning) |
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What is the disease associated with C. septicum and C. difficile? |
C. septicum - malignancy and neutropenia. C. difficile - pseudomembranous colitis, antibiotic associated diarrhea. |
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Both C. tetani and C. botulinum interfere with neurotransmitters. What is the difference? |
C. tetani blocks the inhibitory transmitters that would stop the continuous stimulation while C. botulinum inhibits the release of the neurotransmitter acetylcholine so no stimulation can occur. |
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What does Clostridium difficile cause and who is at risk? |
It causes antibiotic associated diarrhea and pseudomembranous colitis. It is a healthcare associated infection, so those in hospitals are at risk. |
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How is C. difficile diagnosed and treated? |
It is diagnosed by molecular methods and treated with broad spectrum antibiotics. |
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True/False. C. difficile always causes disease once in humans. |
False. It is part of the normal flora in about 3% of adults. |
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What are the clinical signs of anaerobic infections? |
Foul smelling discharge, proximity to a mucosal surface, gas in tissue, and abscess formation. |
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How would a gram stain help you in diagnosing and treating anaerobic infections? |
It can help establish that it is/isn't a mixed infection or the presence/absence of clostridia in wounds. |
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What are some of the important factors when trying to culture anaerobic infections? |
They must be collected and transported properly, grown on a complex medium supplemented with hemin, Vitamin K, and/or blood, also antibiotics (aminoglycosides) to supress facultative anaerobes. Their incubation and work up must be performed in CO2 in nitrogen/hydrogen mix. |
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What are some of the tools used in culturing anaerobic bacteria? |
Anaerobe chambers, anaerobic containers (CampyPak and BBL GasPak Plus or the newer/better Anoxomat), and the MALDI-TOF MS. |
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What is the MALDI-TOF MS and what does it require? |
It is matrix-assisted laser desorption ionization-time-of-flight mass spectrometry and requires a large database to compare the results to. |
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How do you treat anaerobic infections? |
Surgical drainage of closed abscess For mixed infections, cover for both aerobic and anaerobic component. Antibiotics: Metronidazole, clindamycin, and penicillin G (although resistance is common); aminoglycosides are not effective. For toxin mediated disease - antitoxin and antibiotics if active infection vs. intoxication. |
