1-14 Anaerobic Bacteria

Question 1

Metabolism/Oxygen tolerance of obligate anaerobes

Answer 1

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

Question 2

metabolism/oxygen tolerance of obligate aerobes

Answer 2

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

-cannot grow OR die without oxygen

Question 3

metabolism/oxygen tolerance of facultative aerobes

Answer 3

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

Question 4

Strict anaerobe

Answer 4

killed in presence of oxygen

Question 5

Aerotolerant Anaerobes

Answer 5

use fermentation but arenot killed by oxygen

possess enzymes necessary to detoxify oxygen radicals

Question 6

describe anaerobic pathogenesis by normal flora.

examples?

Answer 6

• pathogenesis occurs when bacteria escape normal compartment
• forms absesses - swollen/painful, often flesh destroying to block off blood supply
• GNAB, actinomyces, c.diff

Question 7

pathogenesis by environmental bacteria?

Answer 7

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

Question 8

Importance of anaerobic endospore formation/exotoxin productin in pathogenesis?

Answer 8

• depends on spore forming ability to enter body

- virulence of anaerobes mainly determined by exotoxin expression

Question 9

Anaerobic samples must be

Answer 9

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

Question 10

Simple anaerobic culture technique?

Answer 10

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)

Question 11

Streak plate technique

Answer 11

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

Question 12

What tests can be performed to identify anaerobic bacteria?

Answer 12

gram stain

chemical testing (able to ferment, hydrolyze?)

gas chrome of fermentation
products (waste)

nucleic acid sequencing

Question 13

Genera of major anaerobic pathogens? compare contrast

Answer 13

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

Question 14

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

Answer 14

+

Question 15

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

Answer 15

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.

Question 16

How could C.diff infection be spread via colonoscope?

Answer 16

C.diff forms spores and colonoscopes cannot be autoclaved.

Question 17

clostridium tetani details

Answer 17

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.

Question 18

how is tetanus prevented?

Answer 18

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

Question 19

c.diff details

Answer 19

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

Question 20

diagnosis of c.diff?

Answer 20

sigmoidoscopy will show patches of dead and dying cells

Question 21

c.diff treatments?

Answer 21

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

Question 22

untreated c.diff can lead to?

Answer 22

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

Question 23

treatment of abcess vs toxigenic?

Answer 23

abscess - surgical care, drain and debride

toxigenic - antitoxin

in most cases, simultaneous antibiotic treatment

Question 24

metabolism of c.tetani?

Answer 24

strict anaerobe.