Anaerobes and Biofilm

Question 1

What two characteristics make an organism an anaerobe?

Answer 1

1-Do not require oxygen for life and reproduction

2-Oxygen’sdirect toxic effect may prohibit their growth

Question 2

What are 3 toxic or free radical oxygen products? Why are these toxic to anaerobes?

Answer 2

1-O2- (Superoxide)
2-H2O2 (Hydrogen Peroxide)
3-OH. (Hydroxyl Radical)

they are toxic because they lack protetive enzyme such as superoxide dismutases and eroxidases

Question 3

Why are anaerobes referred to as “Party Animals”?

Answer 3

Sites colonized with mixtures of organisms frequently provide conditions favorable to the growth of anaerobes.

*Volatile/foul smelling metabolic byproducts of anaerobes contribute as well

Question 4

What are the 2 main natural habitats for anaerobes?

Answer 4

1-Enivornmental/exogenous (ie. Clostridium tetanus and botulinum due to spores)
2-Endogenous (mouth, vagina, bowel, skin)

Question 5

Fusobacterium, Veilonella, actinomyces, pigmented porphyromonas and prevotella sp. are typical of what site?

Answer 5

Oral

Question 6

Propionibacterium are typical of what site?

Answer 6

Skin

Question 7

Lactobacillus and prevotella bivia are typical of what site?

Answer 7

Vagina

Question 8

Bacteroides fragilis and other bacteroides species are typical of what site?

Answer 8

Colon

Question 9

What are 4 main pre-disposing factors for anaerobic infection?

Answer 9

1-Trauma to mucous membranes or skin (trauma may also allow access to deeper tissues)
2-Vascular stasis (poor oxygenation)
3-Tissue necrosis
4-Decrease of redox potential of tissues

Question 10

Spore-forming gram-positive rods are which family of anaerobes?

Answer 10

Clostridium species

Question 11

What are the 4 most common clostridium species? What diseases do they cause?

Answer 11

1-C. tetani (tetanus)
2-C. perfringenes (gas gangrene)
3-C. botulinum (botulism)
4-C. difficile (pseudomembranous colitis)

Question 12

Which two main families of anaerobes are Non-spore forming gram positive rods?

Answer 12

1-Actinomyces

2-Propionibacterium

Question 13

Chronic granulomatous, infectious disease with sinus tracts and fistulae, which erupt to the surface and drain pus containing sulfur granules is typical of which anaerobe?

Answer 13

Actinomyces

Question 14

Which anaerobe is normal skin and respiratory flora, and causes similar infection to coagulate negative staph?

Answer 14

Propionibacterium

*P. acnes often found in acne pustules

Question 15

What two anaerobic genera are the gram-possitve cocci?

Answer 15

1-Peptostreptococcus (can go to brain or deep lung)

2-Anaerobic and microaerophillic streptococcus (do not respond to metronidazole)

Question 16

Which anaerobic genus is gram-negative cocci? Hint: they are the only anerobic genus of gram neg cocci usually implicated as pathogens

Answer 16

Veillonella species

*only gram-neg cocci anaerobes implicated as pathogenic. Found in mixed infections of oral origin

Question 17

What are the 3 main gram-negative rod anaerobes?

Answer 17

1-Bacteroides (70% of clinically significant bacteremia)
2-Prevotella and porphyromonas (mouth flora and dental abscesses)
3-Fusobacterium (mouth sometimes with actinomyces)

Question 18

What are 3 main ways to treat anaerobic infection?

Answer 18

1-Create an environment in which anaerobes cannot proliferate (drainage, debridement etc)
2-Arrest the spread of anaerobes into healthy tissue (antimicrobials)
3-Neutralize toxin

Question 19

What are the 3 main steps to biofilm formation?

Answer 19

1-attachment of cells to substrate
2-growth and aggregation of cells
3-maturation and maintenance of architecture

Question 20

What are the 5 stages of biofilm formation?

Answer 20

1-Attachment (seconds)
2-Irreversible binding (minutes, cells are sessile)
3-Layering/maturation (greater than 10 um thick)
4-Ultimate thickness/maturation (days, greater than 100 um thick)
5-Dispersion (several days, cells become planktonic)

Question 21

What are 3 construction characteristics of biofilms?

Answer 21

1-Stalks and mushroom-shaped microcolonies
2-Matrix of EPS, proteins and DNA
3-Fluid-filled channels

Question 22

What are the 3 layers of a mature biofilm?

Answer 22

1-Outer (most exposed to nutrients, most active, some become planktonic)
2-Intermediate (metabolism down-regulated, still using nutrients and exchanging genes)
3-Innermost (attached, earliest, least active, includes persister cells)

Question 23

What are the 3 cell types in biofilms?

Answer 23

1-Planktonic (free living)
2-Sessile (attached/participating in biofilm)
3-Persister (inert, in all biofilms)

Question 24

After the acquired pellicle made up of protein and glycopeptides, what two organisms typically colonize first in dental plaque?

Answer 24

1-Streptococcus mutans
2-Actinomyces

*Glucan polymer glycocalyx

Question 25

Which bacteria is an example of a bridge bacteria that cannot bind the pellicle but can bind to primary colonizers?

Answer 25

Fusobacterium

Question 26

What are 5 examples of late colonizers?

Answer 26

1-Streptococcus salivarius
2-Propionibacterium
3-Prevotella
4-Veillonella
5-Selenomonas

*generally considered non-pathogenic

Question 27

What are 4 pathogens that require late colonizers in order to attach?

Answer 27

1-Porphyromonas gingivalis
2-Bacteroides forsythia
3-Aggregatibacter actinomycetemcomitans
4-Treponema denticola

Question 28

Anaerobic streptococci do not respond to the classic anaerobe drug. Which drug is that?

Answer 28

metronidazole

Question 29

What is the most common anaerobic bacteria in the colon?

Answer 29

Bacteroides fragilis.