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40 Cards in this Set
- Front
- Back
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Parasite
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A life form that lives on or in another life form
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Saprophyte
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An organism which lives on dead organic matter
(ie. fungi on skin) |
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Pathogen
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An organism which has the capacity to cause disease
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Pathogenicity
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The ability of a microorganism to cause disease
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Virulence
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The degree of pathogenicity or likelihood of causing disease
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High virulence--->
(strict, principal or frank pathogens) |
Disease
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Low virulence + compromised host----->
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Disease
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Commensal
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An organism which lives on or within another organism from which it derives benefit but neither injures nor benefits
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Opportunist
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An organism which does not usually cause disease in individuals with intact host defense systems but which can cause disease in immunocompromised individuals or when conditions change
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Synergism
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*Positive interaction
*Produce substances utilized by other species *ie. lactic acid produced by streptococci utilized by veillonella |
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Antagonism
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*Inhibit other species
*ie: Bacteriocins |
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Bacteriocins
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Produced by bacteria that inhibit other organisms.
Organic acids- make environment acidic Hydrogen peroxide- toxic to anerobic organisms |
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Advantages of normal flora
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*Prevention of colonization by potential pathogens
*Release of substances which have metabolic value for host. (vitamins) *Antigenic stimulation important to normal development of the immune system *Provide as much as 10% of our energy requirements. |
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Disadvantages of indigenous flora
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*opportunistic infections
*immunosuppression |
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opportunistic infections
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*spread into sterile areas
*overgrowth with changes in local environmental conditions -antibiotics -pH changes |
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Virulence factors
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*Have intrinsic properties of pathogenic microbes which allow them to overcome the host defenses and establish an infection
*They enhance the ability of pathogenic microorganisms to cause disease. |
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Pathogenic properties of bacteria
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*Ability to produce toxic proteins (exotoxins)
*Endotoxin of gram negative cell walls *Cell-wall molecules (adhesins) and structures (pili) which enhance attachment of bacteria to surfaces *Capsules which allow bacteria to avoid phagocytes |
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Pathogenic properties of bacteria
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*Survival in phagocytic cells
*Ability to grow intracellularly *Ability to invade and spread -cytotoxins -enzymes |
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Microbial Adherance
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*Requires a receptor and an adhesin
*Receptors *Bacterial adhesins *viral attachment proteins |
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Bacterial Endotoxin
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Lipopolysaccharide
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Endotoxin
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*Lipopolysaccharide
*Cell wall component of gram negative bacteria *Less potent but stable to heating *clinical outcome: shock, death |
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Exotoxins
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*Protein
*Released extracellularly *Produced by both gram positive and gram negative bacteria *Highly toxic |
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Biologic Activity of Endotoxins
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fever, IVC (intravascular coagulation), leukopenia, activation of complement
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Biologic Activity of Exotoxcins
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inhibition of protein synthiesis, cytotoxic, neurotoxic, etc
ie: Clostridium botulinum (botulism) |
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Major kinds of Exotoxins
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Cytolytic
Bipartite Superantigens |
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Cytolytic
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exotoxins that lead to cell lysis
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Bipartite
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Exotoxins that have A and B subunits; B subunit binds to cell surface; A subunit enters cell. May activate adenylate cyclase, inhibit protein synthesis, inhibit release of cell products
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Superantigens
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stimulate T cells to release cytokines
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Cytotoxins
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Kills cells by:
*blocking protein sythesis *interfere with cellular functions *disrupt cell membranes |
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Examples of cytotoxic organisms
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Diptheria toxin- Cornyebacterium diptheriae
Exotoxin A- Pseidomonas aeruginosa Hemolysins- streptococci, staphylococci |
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Enterotoxins
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Intestinal inflammation
Loss of water/ions leads to diarrhea Salmonella, Shigella, enterotoxigenic Escherichia coli, Vibria cholerae |
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Prevention of Infectious Disease
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Increase resistance
Decrease dose |
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Endemic
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a disease that prevails continuously in a geographic region
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Epidemic
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a sudden and simultaneous outbreak or increase in the number of cases of disease in a community
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Pandemic
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a disease affecting an increased proportion of the population over a wide geographic area (often worldwide)
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Zoonosis
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a disease that is endemic to animal populations
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sign
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objective evidence of disease noted by an observer (observer notes these)
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symptom
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subjective evidence of disease as sensed by patient (patient feels these)
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Predominant cultivable oral flora in a healthy mouth
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*Gram positive cocci 45-50%
*Gram positive rods 20% *Gram negative cocci 16% *Gram negative rods 10-25% |
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Oral streptococci (gram +)
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mitis
mutans salivarius anginosus |
