1-14 Anaerobic Bacteria Flashcards
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.
examples?
- 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.
