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Host and Defense > EXAM 3 Anaerobes > Flashcards

EXAM 3 Anaerobes Flashcards

1
Q

describe anaerobes

A
  • do not require oxygen for life and reproduction
  • oxygen’s direct toxic effect may prohibit their growth
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2
Q

why is oxygen toxic?

A

it reacts with organic matter to produce free radicals

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3
Q

what are 3 toxic products and free radicals?

A
  • O2- (superoxide)
  • H2O2 (hydrogen peroxide)
  • OH• (hydroxyl radical)
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4
Q

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

A
  • protective enzymes
  • anaerobes
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5
Q

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

A
  • lower
  • mixtures
  • volatile and foul-smelling metabolic byproducts
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6
Q

describe the two natural habitats of anaerobes

A
  • 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
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7
Q

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

A

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

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8
Q

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

A
  • fusobacterium
  • veilonella
  • actinomyces
  • pigmented porphyromonas and prevotella sp.
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9
Q

what is the anaerobic bacteria specific to the skin?

A

propionibacterium

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10
Q

what are the 2 anaerobic bacteria specific to the vagina?

A

lactobacillus and prevotella bivia

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11
Q

what are the 2 anaerobic bacteria specific to the colon?

A

bacteroides fragilis and bacteroides sp.

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12
Q

what are some predisposing factors of anaerobic infections?

A
  • 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
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13
Q

oxygen is ___ to anaerobic bacteria

A

toxic

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14
Q

there are degrees of anaerobiasis, from ___ to ___

A

strict anaerobes to aerotolerant anaerobes

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15
Q

anaerobes generally require ___ incubation periods in the laboratory

A

longer

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16
Q

anaerobic infections are usually ___, and often smell ___

A
  • mixed
  • bad
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17
Q

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

A

clostridium species:

  • tetanus - c. tetani
  • gas gangrene - c. perfringenes
  • botulism - c. botulinum
  • antibiotic associated diarrhea and pseudomembranous colitis - c. difficile
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18
Q

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

A
  • 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
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19
Q

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

A
  • 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
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20
Q

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

A
  • veillonella species
  • the only anaerobic genus of gram negative cocci usually implicated as pathogens
  • found in mixed infections of oral origin
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21
Q

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

A
  • 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
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22
Q

what are the 3 main treatment options for anaerobic infections?

A
  • create an environment in which anaerobes cannot proliferate
  • arrest the spread of anaerobes into healthy tissue
  • neutralize toxins
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23
Q

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

A
  • 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
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24
Q

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

A

antimicrobial agents play an important role here

25
Q

describe neutralizing toxins as a treatment option for anaerobic infections

A
  • toxins are produced by the anaerobes when such toxins are present
  • specific anti-toxins can be used
26
Q

___ are communities of microorganisms attached to a solid surface

A

biofilms

27
Q

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

A
  • microbial
  • inter-species
28
Q

can biofilms be composed of a single species?

A

yes

29
Q

biofilm formation is a ___ mechanism

A

survival

30
Q

the biofilm surface can be ___ or ___ tissue

A

living or non-living (abiotic)

31
Q

describe the formation of biofilms

A
  • attachment of cells to substrate
  • growth and aggregation of cells into microcolonies
  • maturation and maintenance of architecture
32
Q

what are the 5 stages of biofilm formation?

A
  1. attachment (seconds)
  2. irreversible binding (minutes)
  3. layering/maturation 1
  4. ultimate thickness/maturation 2 (days)
  5. dispersion (several days)
33
Q

describe the attachment stage of biofilm formation

A
  • stage 1, seconds
  • reversible binding
  • logarithimic growth
  • pili and bacterial adhesion molecules
  • changes in gene expression: decrease flagella, increase adhesion molecules
34
Q

describe the irreversible binding stage of biofilm formation

A
  • stage 2 (minutes)
  • exopolysaccharides (EPS) trap nutrients and planktonic bacteria
  • cells are sessile
35
Q

describe the layering/maturation 1 stage of biofilm formation

A
  • stage 3
  • greater than 10 micrometer thickness
36
Q

describe the ultimate thickness/maturation 2 stage of biofilm formation

A
  • stage 4 (days)
  • greater than 100 micrometer thickness
  • some cells released from substrate, but trapped in the EPS
37
Q

describe the dispersion phase of biofilm formation

A
  • stage 5, several days
  • cells leaving
  • as nutrtiion becomes scarce, there are changes in gene expression
  • cells again become planktonic
38
Q

describe the construction of biofilms

A
  • 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
39
Q

describe the 3 layers fo mature biofilm

A
  • 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
40
Q

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

A
  • 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
41
Q

which cell types are free living?

A

planktonic

42
Q

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

A

sessile

43
Q

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?

A

persister

44
Q

what are the advantages to living in a biofilm?

A
  • 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
45
Q

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

A

new biofilms elsewhere

46
Q

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

A

disaggregation

47
Q

what are the most well-studied natural human biofilms?

A

dental biofilms aka plaque

48
Q

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

A

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

49
Q

poor oral hygiene is a sequelae to ___

A

periodontitis

  • intimate relationship with ulcerated gums
  • likely hematogenous spread of adherant bacteria
    • heart valves, prosthetic joints
  • immune mimicry leading to atherosclerosis
50
Q

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

A

coating of proteins and glycopeptides of host origin

51
Q

what are the primary colonizers of dental plaque?

A
  • s. mutans and actinomyces
  • pili and adhesion molecules
  • glucan polymer glycocalyx (EPS)
52
Q

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

A
  • glucan-binding proteins
  • fusobacterium
53
Q

bridge bacteria can’t bind to the ___, but can bind to ___

A
  • pellicle
  • primary colonizers
54
Q

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

A
  • non-pathogenic
  • s. salivarius, propionibacterium, prevotella, veillonella, selenomonas
55
Q

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.

A
  • disease
  • host defenses
  • bacterial growth
  • positive
56
Q

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

A

mainly anaerobic and facultative gram negative bacilli and spirochetes

57
Q

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?

A
  • porphyromonas gingivalis
  • bacteroides forsythia
  • aggregatibacter actinomycetemcomitans (aa)
  • treponema denticola
  • they require the late colonizers (strep salivarius, proprionibacterium, prevotella, veillonella, selenomonas) to attach
58
Q

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

A
  • adhere to the gingival epithelium
  • invade tissue
  • initiate an inflammatory response
59
Q

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

A
  • reversible, relatively mild gingivitis
  • periodontal support structures
  • tooth loss

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