EXAM 3 Anaerobes

Question 1

describe anaerobes

Answer 1

• do not require oxygen for life and reproduction
• oxygen’s direct toxic effect may prohibit their growth

Question 2

why is oxygen toxic?

Answer 2

it reacts with organic matter to produce free radicals

Question 3

what are 3 toxic products and free radicals?

Answer 3

• O₂^- (superoxide)
• H₂O₂ (hydrogen peroxide)
• OH^• (hydroxyl radical)

Question 4

lack of ___, such as superoxide dismutases and peroxidases helps explain the toxic effects of oxygen, but some ___ can produce them in varying quantities

Answer 4

• protective enzymes
• anaerobes

Question 5

in vivo, bacteria tend to ___ the redox potential at their site of growth. sites colonized with ___ of organisms frequently provide conditions favorable to the growth of anaerobes. ___ and ___ of other anaerobes contribute to this balanced environment

Answer 5

• lower
• mixtures
• volatile and foul-smelling metabolic byproducts

Question 6

describe the two natural habitats of anaerobes

Answer 6

• environmental (exogenous) - clostridium species are notorious in the environment due to survival of their spores
• endogenous - most other anaerobic infections, including many clostridia are seeded from normal endogenous flora: mouth, vagina, bowel, skin

Question 7

what is the significance of some anaerobe species being so specific to their normal site?

Answer 7

they can offer clues to the physician of a hidden locus of infection when they are recovered elsewhere in the body

Question 8

what are the 4 anaerobic bacteria specific to the oral cavity?

Answer 8

• fusobacterium
• veilonella
• actinomyces
• pigmented porphyromonas and prevotella sp.

Question 9

what is the anaerobic bacteria specific to the skin?

Answer 9

propionibacterium

Question 10

what are the 2 anaerobic bacteria specific to the vagina?

Answer 10

lactobacillus and prevotella bivia

Question 11

what are the 2 anaerobic bacteria specific to the colon?

Answer 11

bacteroides fragilis and bacteroides sp.

Question 12

what are some predisposing factors of anaerobic infections?

Answer 12

• trauma to mucous membranes or skin
  
  • vascular stasis
  • tissue necrosis
  • decrease of redox potential of tissues
• trauma allows anaerobes of the indigenous microflora or soil to gain access to deeper tissues

Question 13

oxygen is ___ to anaerobic bacteria

Answer 13

toxic

Question 14

there are degrees of anaerobiasis, from ___ to ___

Answer 14

strict anaerobes to aerotolerant anaerobes

Question 15

anaerobes generally require ___ incubation periods in the laboratory

Answer 15

longer

Question 16

anaerobic infections are usually ___, and often smell ___

Answer 16

• mixed
• bad

Question 17

what are the 4 important anaerobic spore-forming gram positive rods?

Answer 17

clostridium species:

• tetanus - c. tetani
• gas gangrene - c. perfringenes
• botulism - c. botulinum
• antibiotic associated diarrhea and pseudomembranous colitis - c. difficile

Question 18

what are the main important anaerobic species of non-spore forming gram positive rods, and how are they manifested?

Answer 18

• actinomyces species
  
  • chronic granulomatous, infectious disease with sinus tracts and fistulae, which erupt to the surface and drain pus containing “sulfur granules”
• proprionibacterium species
  
  • normal skin and respiratory flora
  • scope of infection similar to coagulase negative staph species
• mobiluncus species
  
  • act synergistically with organisms including gardnerella vaginosis to cause bacterial vaginosis

Question 19

what are the 2 important anaerobic gram positive cocci species, and how are they manifested?

Answer 19

• peptostreptococcus species
  
  • usually found in abscess that arise from misplaced oral flora: brain or deep lung abscess
• anaerobic and microaerophillic streptococcus species
  
  • habitat and appearance similar to peptostreptococcus species

Question 20

what is the important anaerobic gram negative cocci, and how is it manifested?

Answer 20

• veillonella species
• the only anaerobic genus of gram negative cocci usually implicated as pathogens
• found in mixed infections of oral origin

Question 21

what are the 3 important anaerobic gram negative rods, and how are they manifested?

Answer 21

• bacteroides species
  
  • b. fragilis group account for about 70% of clinically significant anaerobic bacteremias
    
    • outnumbers e. coli in the colon by approximately 1000:1
• prevotella and porphyromonas species
  
  • include former pigmented bacteroides species
  • common in mouth flora and dental abscess
• fusobacterium species
  
  • also mouth associated; can occasionally be found mixed with actinomyces

Question 22

what are the 3 main treatment options for anaerobic infections?

Answer 22

• create an environment in which anaerobes cannot proliferate
• arrest the spread of anaerobes into healthy tissue
• neutralize toxins

Question 23

describe creating an environment in which anaerobes cannot proliferate as a treatment option for anaerobic infections

Answer 23

• useful measures include removing dead tissue (debridement), draining pus, eliminating obstructions, decompressing tissues, releasing trapped gas, and improving circulation in and oxygenation of tissues
• in lesser infections, surgical therapy may be all that is required

Question 24

describe arresting the spread of anaerobes into healthy tissue as a treatment option for anaerobic infections

Answer 24

antimicrobial agents play an important role here

Question 25

describe neutralizing toxins as a treatment option for anaerobic infections

Answer 25

* toxins are produced by the anaerobes when such toxins are present * specific anti-toxins can be used

Question 26

\_\_\_ are communities of microorganisms attached to a solid surface

Answer 26

biofilms

Question 27

the biofilm community is usually composed of numerous ___ species with intricate ___ communication (quorum sensing/pheromones)

Answer 27

* microbial * inter-species

Question 28

can biofilms be composed of a single species?

Answer 28

yes

Question 29

biofilm formation is a ___ mechanism

Answer 29

survival

Question 30

the biofilm surface can be ___ or ___ tissue

Answer 30

living or non-living (abiotic)

Question 31

describe the formation of biofilms

Answer 31

* attachment of cells to substrate * growth and aggregation of cells into microcolonies * maturation and maintenance of architecture

Question 32

what are the 5 stages of biofilm formation?

Answer 32

1. attachment (seconds) 2. irreversible binding (minutes) 3. layering/maturation 1 4. ultimate thickness/maturation 2 (days) 5. dispersion (several days)

Question 33

describe the attachment stage of biofilm formation

Answer 33

* stage 1, seconds * reversible binding * logarithimic growth * pili and bacterial adhesion molecules * changes in gene expression: decrease flagella, increase adhesion molecules

Question 34

describe the irreversible binding stage of biofilm formation

Answer 34

* stage 2 (minutes) * exopolysaccharides (EPS) trap nutrients and planktonic bacteria * cells are sessile

Question 35

describe the layering/maturation 1 stage of biofilm formation

Answer 35

* stage 3 * greater than 10 micrometer thickness

Question 36

describe the ultimate thickness/maturation 2 stage of biofilm formation

Answer 36

* stage 4 (days) * greater than 100 micrometer thickness * some cells released from substrate, but trapped in the EPS

Question 37

describe the dispersion phase of biofilm formation

Answer 37

* stage 5, several days * cells leaving * as nutrtiion becomes scarce, there are changes in gene expression * cells again become planktonic

Question 38

describe the construction of biofilms

Answer 38

* stalks and mushroom-shaped microcolonies attached to the substratum * matrix contains EPS, proteins, and DNA * viable? but non-culturable organisms * fluid-filled channels * exchange nutrients, dispose of wastes, some motile organisms

Question 39

describe the 3 layers fo mature biofilm

Answer 39

* outer - most exposure to nutrients, most active organisms, some become planktonic * intermediate - metabolism is down-regulated, but still using nutrients and exchanging genes * innermost - attached, earliest and least active, includes the persister cells

Question 40

what are some examples of the variety of environments where biofilms are found?

Answer 40

* ship hulls, rocks in rivers and streams, sludge in potable water supplies, lungs of cystic fibrosis patients, dental plaque * variety of environments, but interplay of biofilm and planktonic phenotypes and 3D architecture are universal

Question 41

which cell types are free living?

Answer 41

planktonic

Question 42

which cell types are attached/participating in the biofilm community?

Answer 42

sessile

Question 43

which cell types are metabolically inert, present in all biofilms, potential for maintenance of gene pool, resist environmental stress (including antibiotics), and are possibly able to disable apoptosis?

Answer 43

persister

Question 44

what are the advantages to living in a biofilm?

Answer 44

* protection from host defenses - including protection from oxygen-reactive molecules * physical barrier to PMNs and phagocytes * potential to outcompete normal biota * gene transfer spread resistance in community * provide protective enzymes * perform as organic polymers - creeping like a lava flow on inanimate surface without detachment

Question 45

as a biofilm forms, streamers of cells extend from the surface and break away to form what?

Answer 45

new biofilms elsewhere

Question 46

\_\_\_ can transmit already up-regulated resistant aggregates of organisms to other body sites

Answer 46

disaggregation

Question 47

what are the most well-studied natural human biofilms?

Answer 47

dental biofilms aka plaque

Question 48

what can happen to anaerobic bacteria if you have poor oral hygiene?

Answer 48

poor oral hygiene → blood stream → heart valves (cardiovascular disease)

Question 49

poor oral hygiene is a sequelae to \_\_\_

Answer 49

periodontitis * intimate relationship with ulcerated gums * likely hematogenous spread of adherant bacteria * heart valves, prosthetic joints * immune mimicry leading to atherosclerosis

Question 50

after teeth cleaning, the pellicle forms almost immediately. what is the pellicle?

Answer 50

coating of proteins and glycopeptides of host origin

Question 51

what are the primary colonizers of dental plaque?

Answer 51

* s. mutans and actinomyces * pili and adhesion molecules * glucan polymer glycocalyx (EPS)

Question 52

what are the bridge bacteria in the formation of dental plaque?

Answer 52

* glucan-binding proteins * fusobacterium

Question 53

bridge bacteria can't bind to the \_\_\_, but can bind to \_\_\_

Answer 53

* pellicle * primary colonizers

Question 54

the late colonizers in the development of dental plaque are generally considered \_\_\_, and consist of what bacteria?

Answer 54

* non-pathogenic * s. salivarius, propionibacterium, prevotella, veillonella, selenomonas

Question 55

the development of dental plaque with good oral hygiene is not usually associated with ___ due to a balance between ___ and \_\_\_. this mostly consists of gram ___ organisms.

Answer 55

* disease * host defenses * bacterial growth * positive

Question 56

describe the changes of the microbiota if dental plaque remains undisturbed on teeth for several days

Answer 56

mainly anaerobic and facultative gram negative bacilli and spirochetes

Question 57

if plaque remains undisturbed on teeth for several days, the microbiota are now considered pathogens. what are the 4 main pathogenic bacteria, and what do they require in order to attach?

Answer 57

* porphyromonas gingivalis * bacteroides forsythia * aggregatibacter actinomycetemcomitans (aa) * treponema denticola * they require the late colonizers (strep salivarius, proprionibacterium, prevotella, veillonella, selenomonas) to attach

Question 58

what are the virulence factors of **pathogenic** bacteria that result from undisturbed dental plaque?

Answer 58

* adhere to the gingival epithelium * invade tissue * initiate an inflammatory response

Question 59

pathogenic bacteria that result from undisturbed dental plaque primarily cause \_\_\_, but with continued poor hygiene, inflammation extends to ___ and can lead to eventual \_\_\_

Answer 59

* reversible, relatively mild gingivitis * periodontal support structures * tooth loss