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Anaerobic Pathogens (Hull)


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Hallmark of these anaerobic infections especially when they are of our own flora is that they are (monomicrobial/polymicrobial), and why?
Polymicrobial, because can have synergistic effects together. Ie, facultative anaerobes like E. Coli can come in first, set up shop, use up all the oxygen, and once its gone, our anaerobes can come in and go into their growth phase
What is the most common cause of mouth infections? It is common in people who don't brush their teeth.
Actinomyces (A. israelii is the species that most commonly causes infection)
Actinomyces also forms "sinus tracts" and "sulfur granules." What are these?
*Sinus tracts, ie can have a hole on the side of face or on trunk where puss is draining out of
*Sulfur granules are clumps of the bacteria sticking together (have a sort of yellow color like sulfur)
True or False - Porphyromonas; Prevotella is both the same organism but with a changing name, and it is most commonly associated with poor oral hygiene, oral surgery, and human bites (ie a little kid biting other people at Daycare)
Bacteria can obtain energy from carbon sources (as ATP) via __________ or ___________ or both
respiration or fermentation
In respiration, compounds are oxidized completely to ______ and ______ and high amounts of ATP are generated from electron transport chains utilizing cytochromes. The ultimate electron acceptor is usually _________.
H2O, CO2 ... oxygen
Fermentations do not involve respoiratory chains and ATP is usually formed only by _________-__________ _______________.
substrate-level phosphorylation
What type of organisms require oxygen as a terminal electron acceptor, and DO NOT ferment?
Strict aerobes
What type of organisms grow well without oxygen, will preferentially utilize O2 when its around, and will ferment under anaerobic conditions?
facultative anaerobes
What typeof organisms cannot use oxygen, and fermentation is their only source of energy?
Anaerobes come in 3 types, what are they?
aerotolerant (not killed by exposure to air), moderate (killed by air, but not by small amounts of oxygen), and strict anaerobes (killed by less than 1% oxygen)
True or false - Even though something may be aerotolerant, it still CANNOT GROW in the presence of O2, just merely won't be killed by the O2
What type of organisms use oxygen as a terminal electron acceptor, but grow BEST if supplemented with CO2?
Why is it incorrect to refer to E. Coli as aerobic?
Because its a facultative anaerobe!!!
Oxygen reacts with flavins to generate __________ and ________. Many anaerobes lack ________ and ___________, enzymes that will protect against these toxic metabolites
hydrogen peroxide and superoxide anion... catalase and superoxide dismutase
Clostridium are all gram +/-
Gram +
The only way you can kill spores is by
What is the shape of Clostridium spores?
tennis racket shaped, drumstick shaped at the terminal spore
What is the causative agent of tetanus?
Clostridium tetani
If you have a deep flesh puncture wound from say a rusty nail, when you go to the ER they will give you 2 things...
antibiotics and a tetanus booster shot
Tetanus toxin is primarily a ________
Explain the mechanism of action of tetanus toxin
It's an (A-B toxin). It's B chain binds to gangliosides on the neuronal membrane, and its A chain is internalized into the cell and blocks the release of inhibitory transmitter (glycine). Therefore, neurons continue to fire (continually excited), and eventually every muscle in the body will start to fire off....this causes a rigid paralysis
What is the position of someone with tetanus?
The grimmace of tetanus, everything arched back, eventually die because of respiratory failure
Why is tetanus toxin such an excellent vaccine candidate?
Because tetanus toxin has NOOO VARIANTS, and its such a great immunogen its actually used in other vaccines to make the body's responses better
What populations are at risk of tetanus in the US? In the world?
US - elderly people whose immunity is waning (need to get boosters but haven't), and drug abusers (from all those dirty needles)
*World - neonates in countries whose vaccination program is not giving these kids vaccines for whatever reasons (economical, social, etc)
These anaerobic pathogens will strike what sense as most characteristic?
Smell, they have the worst smell ever from the biproducts of their fermentation (the organic acids)
What is very likely to be seen in home-canners, especially those who are canning root vegetables (ie potatoes, carrots, turnips, etc)
Clostridium botulinum
What are you at risk for if you make a huge stew (that has rooted veggies in it)that is supposed to last a week and just throw it into the fridge? What is the proper way to handle this?
Clostridium botulinum. Fill your sink with cold water and even ice cubes and put the pot in there to let it cool down (because the heat drove off all the oxygen). OPEN the lid to let oxygen back in, and stir it around for a while to air it all out and make sure oxygen has gotten back in to prevent the growth of the Clostridium botulinum
Infant botulism (floppy baby syndrome) has been implicated as a caus of ______, and more specifically what the moms had been feeding them was...
SIDS, herbal teas that they sweetened with raw, unpasteurized honey (raw, unpasteurized honey, and even spanish olives have been found to carry C. botulinum)
Why does the honey affect the baby but not an adult?
Because, there are only spores in the honey, and these spores cannot germinate in an adult intestine, but they ARE ABLE to germinate inside that of the baby's.
Explain the mechanism of botulinum toxin action?
(A-B) structure neurotoxin, heat-labile, B chain binds to gangliosides on neuronal membrane, and A chain enters cells, and BLOCKS THE RELEASE OF ACETYLCHOLINE (this causes a flaccid paralysis)
What is the causative agent of pseudomembranous colitus and antibiotic associated colitis?
Clostridium difficile
Explain the two toxins of Clostridium difficile...
*Exotoxin A - enterotoxin, causes the fluid loss (the diarrhea)
*Exotoxin B - cytotoxin, causes damage to cell walls and thus causes the pseudomembrane to form
Name the 4 components of the pseudomembrane in pseudomembranous colitis?
mucous, fibrin, dead necrotic epithelium, and lymphocytes
What causes antibiotic associated colitis?
Patient may have been on oral antibiotics for a long period of time that killed off the balance of his normal gut flora and allowed the once minor portion of Clostridium difficile to overgrow, resulting in a diarrhea that develops (caused by Exotoxin A)
What should you do if someone has an antibiotic associated colitis?
Stop the offending antimicrobial immediately, and switch to a more specific antibiotic (ie vancomycin that just targets gram + for example)
How do anaerobic bacteria live in an otherwise you'd assume oxygenated environment as your mouth?
Since they are so small, they can live in small patches of poorly oxygenated oral surfaces (ie between gums and teeth)
Explain how you can get an anaerobic pneumonia?
*There are some areas of the lung that become anoxic with damage to them, and these anaerobic bacteria can grow here
*Or if someone is fuckin drunk, and starts puking, some of the bile and acid can aspirate into the lungs and this is damaging to the lung and along with this you can have growth of anaerobic bacteria
Bacteriodes _____ is the most common gram ____ species associated with anaerobic infection
fragilis, negative
Why were amputations so common during wartime in the pre-antibiotic era?
Soldiers were getting gas gangrene on the battlefield, dirt was getting into their wounds
What is another situation where you get gas gangrene besides in warfare?
Autoaccidents, where a piece of the car may go through you, or you may get thrown out of the car scraping yourself and getting dirt in you
What is the most common site of Clostridium?
dirt, and there are some that live normally in our flora
What is the causative agent of gas gangrene and also diarrhea?
Claustridium perfringens
Claustridium perfringens can produce _____ exotoxins
>12, won't produce all of them at the same time though, depends on environment
Diarrhea from Clostridium perfringens is found in what situation?
Corned beef, pastrami, deli meats, improper handling during preparation, becomes contaminated with spores. During the cooking phase, the heat-labile enterotoxin is killed off, but not the spores (only autoclave can do that). Then, during the subsequent cooling down period, spores germinate and grow and reproduce their heat labile enterotoxin. Sooo, if you just heat up your meat before eating it in this case you'd be good and not get the diarrhea, but who heats up their deli meat anyways?
Why is surgery the main treatment of Clostridium perfringens infection if you weren't able to prevent it by prompt treatment of wounds?
Because in gas gangrene, you get a liquefactive necrosis of the muscles, and as a result it becomes very difficult to get antibiotics to those areas that are necrotic (not perfused)
Why do you grow Clostridium perfringens on egg yolk agar?
Because egg yolk is an excellet source of lecithin, which is broken up by the alpha toxin of the bacteria (a lecithinase enzyme)
Explain the 2 zones of hemolysis that form on the blood agar plate of Clostridium perfringens.
*theta toxin - small zone of clearing
*alpha toxin - larger zone that forms

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