1-14 Anaerobic Bacteria Flashcards Preview

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Flashcards in 1-14 Anaerobic Bacteria Deck (24)

Metabolism/Oxygen tolerance of obligate anaerobes

derive all atp from fermentation (inefficient, produces organic acids/alcohols)

-lack enzymes to grow in oxygen (catalase, peroxidase, superoxide dismutase) and lack ability to regenerate oxidized enzymes

-cannot grow or quickly die in oxygen


metabolism/oxygen tolerance of obligate aerobes

some bacteria, similar to mammalian cells, rely on oxygen for their ATP producing ETC pathway

-cannot grow OR die without oxygen


metabolism/oxygen tolerance of facultative aerobes

bacteria that encode pathways for both fermentation and ETC to product ATP

use oxygen when available, ferment when not

grow FASTER with oxygen (more efficient metabolism), but can grow without


Strict anaerobe

killed in presence of oxygen


Aerotolerant Anaerobes

use fermentation but arenot killed by oxygen

possess enzymes necessary to detoxify oxygen radicals


describe anaerobic pathogenesis by normal flora.


-pathogenesis occurs when bacteria escape normal compartment

-forms absesses - swollen/painful, often flesh destroying to block off blood supply

-GNAB, actinomyces, c.diff


pathogenesis by environmental bacteria?

depend mainly on spore-forming ability to enter human body.

Wounds - spores enter skin wounds, germinate, produce exotoxins (tetanus)

Canning - spores germinate in canned foods (aerobic environment), begin releasing botulism toxin.
-bacteria killed once can opened
- botulism toxin already present


Importance of anaerobic endospore formation/exotoxin productin in pathogenesis?

-depends on spore forming ability to enter body

-virulence of anaerobes mainly determined by exotoxin expression


Anaerobic samples must be

handled anaerobically and labeled as such. Aspirate an absess and leave in needle, do not swab.


Simple anaerobic culture technique?

innoculate test tube of media and add reducing agant (thioglyconate) to eliminate dissolved oxygen

fill completely, stopper tightely, incubate

strict aerobes at top (pseudomoas), strict anaerobes at bottom (clostridium), faculatative anaerobes throughout (e.coli)


Streak plate technique

streak onto agar media and place in culture jar

add chemical envelope to remove oxygen (gas-pak) and color indicate when successful

airtight seal, incubate 48H

take jar to glovebox for handling/ID


What tests can be performed to identify anaerobic bacteria?

gram stain

chemical testing (able to ferment, hydrolyze?)

gas chrome of fermentation
products (waste)

nucleic acid sequencing


Genera of major anaerobic pathogens? compare contrast

clostridium, GNAB, antinomyces

clos and actin are gram +

GNAB, actin, and c.diff are normal flora

remainder of clostridia are soil organisms that depend on ability to form spores to enter human body


Clostridiums (C.diff, C.Tetani, C.Botulinum, etc.) are gram...



Some foodborne Clostridium infections can be treated without antibiotics. How?

Its all about exotoxins. The bacteria may have been killed off in the body or passed through without causing illness, but the toxin is what matters. Treat with antitoxin.


How could C.diff infection be spread via colonoscope?

C.diff forms spores and colonoscopes cannot be autoclaved.


clostridium tetani details

gram + spore forming rod

insertion beneath skin limits air contact. Spores germinate, vegetative cells release exotoxin (a-b subunit) tetnospasmin which circulates in blood, finds ends of peripheral motor neurons. Large B delivers A to receptor, opens up pore on end of neuron. Then inserts A inside which travels retrograde axonal transport as far as it can go. When it finds itself in CNS (2-14 days to spinal cord) – acts as protease, attacking synaptobrevin in inhibitory motor nerves of CNS. Wihout it, vesciles containing GABA and glycine release from effected neuron. Loss of central inhibitory activity on motor an autonomic nerves. Every impulse will cause dramatic muscle contraction. The AB and interference with singal transduction goes with common theme of exotoxin.


how is tetanus prevented?

ii. Prevention – universal vaccination with tetanus toxoid – live, treated with fermadelyde, unfolds, refolds, will illicit immune response.


c.diff details

gram(+) spore forming rod

causes colitis or associated diarreha

tramission - fecal oral

-typical patient has received ABX or cancer treatment

Germinating cells release exotoxin A – disrupts tight junctions of gut causing intestinal swelling and inflammation, leaking

Exotoxin B is the major toxin – disrupts cytoskeleton by depolymerizing actin and killing surrounding cells


diagnosis of c.diff?

sigmoidoscopy will show patches of dead and dying cells


c.diff treatments?

discontinuation of ABX, ABX for c.diff, surgical removal of entire colon or diseased areas


untreated c.diff can lead to?

Toxic megacolon (a colon which is dangerously swollen to the point of popping) or colonic perforation may occur (release flora into body cavity)


treatment of abcess vs toxigenic?

abscess - surgical care, drain and debride

toxigenic - antitoxin

in most cases, simultaneous antibiotic treatment


metabolism of c.tetani?

strict anaerobe.

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