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the enhanced ability of a microorganism to attach to a cell or surface
a decrease or loss of virulence
the presence of microorganisms in the blood
a dense, well-defined polysaccharide or protein layer closely surrounding a cell
the growth of a microorganism after it has gained access to host tissues
Define: Dental caries
tooth decay resulting from bacterial infection
Define: Dental plaque
bacterial cells encased in a matrix of extracellular polymers and salivary products, found on the teeth
an injury to a host organism, caused by a pathogen or other factor, that affects host function
the lipopolysaccharide portion of the cell envelope of most gram-negative Bacteria, which is a toxin when solubilized
a protein released extracellularly by a microorganism as it grows that produces immediate damage to the small intestine of the host
a protein released extracellularly by a microorganism as it grows that produces immediate host cell damage
polymer secreted by a microorganism that coats the surface of the microorganism
an organism that can harbor a pathogen
refers to any situation in which a microorganism is established and growing in or on a host, regardless of whether or not the host is harmed
the ability of a pathogen to enter into host cells or tissues, spread, and cause infection
grow in large numbers and may spread throughout host body
Define: Lower respiratory tract
the trachea, bronchi, and lungs
Define: Mucous membrane
ayer of mucus-covered epithelial cells that interact with the external environment
a liquid secretion that contains water-soluble glycoproteins and proteins that retain moisture and aid in resistance to microbial invasion on mucosal surfaces
Define: Normal microflora
microorganisms that are usually found associated with healthy body tissue
Define: Opportunistic pathogen
an organism that causes disease in the absence of normal host resistance
an organism, usually a microorganism, that grows in or on a host and causes disease
the ability of a pathogen to cause disease
a live microorganism that, when administered to a host, may confer a health benefit
a bloodborne systemic infection
Define: Slime layer
a diffuse layer of polymer fibers, typically polysaccharides, that forms an outer surface layer on the cell
the ability of an organism to cause disease by means of a preformed toxin that inhibits host cell function or kills host. Also, referred to as toxigenicity
toxins that inhibit host cell function or kill host cells.
Two types: Exotoxins & Endotoxins
Define: Upper respiratory tract
the nasopharynx, oral cavity, and throat
the relative ability of a pathogen to cause disease
both host and microbe benefit
microbe causes no damage to host
microbe (parasite causes damage to host)
Define: Pathogenic relationship
microbe causes damage to host (pathogen) thus, pathogen is name given to microbial parasite
Define: Normal Flora
microorganisms normally found in or on the body that typically do not cause disease
capable of working together; two microorganisms are synergistic if they are able to produce a host response greater than the sum of the effects they produce when acting alone
able to be transmitted between hosts
Define: Disease reservoir
a natural source of disease agent. Reservoirs may include sick patients, asymptomatic carriers, animals, recovered patients, environmental sources, etc
Define: Genitourinary Tract-upper
- healthy kidney, ureters, & urinary bladder
- free of microbes. However, distal urethra and its external opening harbour bacteria.
Define: Latent Infections
Give an example(s)
An infection that goes from being symptomatic to asymptomatic. Later they reappear as symptomatic.
Examples: Cold sores (Herpes virus infections) and shingles (Herpes varicella): person who had chickenpox as child still harbors virus. Later in adulthood, the individual develops shingles.
Characterise the difference between Primary (1o versus Secondary (2o) Infection
Give an example
An infection caused by one pathogen (1o) is followed by a 2o infection caused by second pathogen.
Ex: Mild respiratory caused by virus may be followed by bacterial pneumonia.
Asymptomatic Diseases (aka _______) means what?
Give an example
Asymptomatic Diseases (aka subclinical) mean that the patient is unaware of the disease because they do not present symptoms
Carriers: person colonized but does not have disease: Mary Mallon
Inanimate objects capable of transmitting microbe are called _____.
Inanimate objects capable of transmitting microbe are called Fomtie
Ex: Hospital equipment; patient’s bedding and gowns; latex gloves; eating and drinking utensils
Organisms that live on or in a host organism, causing damage to the host, are called ______. Microbial parasites are called _______.
Organisms that live on or in a host organism, causing damage to the host, are called parasites. Microbial parasites are called pathogens
What does the outcome of a host-parasite relationship depend on?
The outcome of a host-parasite relationship depends on the pathogenicity (virulence) of the parasite; that is, on the ability of the parasite to cause damage on the host, and on the resistance or susceptibility of the host to the parasite.
*(virulence = degree of pathogenicity)
True of False: The host-parasite relationship is static
The host-parasite relationship is dynamic and the virulence of the pathogen and the resistance of the host are constantly changing
What is the causative agent of Strep Throat?
Streptococcus pyogenes is the causative agent of Strep Throat; is considered a pathogen.
Candida albicans is normally what type of bacteria?
Candida albicans is normally a commensal bacteria (causes no damage to host). But, if host defense mechanisms are weakened, it becomes an opportunistic pathogen. (Ex. Thrush in children)
Neisseria meningitidis often resides benignly where? Where can it be pathogenic?
Neisseria meningitidis often resides benignly in respiratory tract but can cause meningitis in brain and spinal cord.
Streptococcus pneumoniae normally resides where?
Streptococcus pneumoniae is a normal resident of the nose and throat. Can cause pneumonia in the lungs
We now immunize the elderly against it
True or False: "Infection" is synonymous with "disease"
Infection is not synonymous with disease; even though the public and even physicians often use the terms synonymously.
True of False: The normal flora of the human body can never cause disease, only new bacteria can cause disease
Normal flora can sometimes cause disease if the host resistance is compromised
What are the 6 Steps to Disease
Exposure and Entry:
- I. Portals of Entry
- II. Adherence
- III. Invasion
- IV. Colonization & Growth
- V. Virulence factors produce damage
- A. Toxins
- B. Invasive factors
- VI. Disease
How do most microbes enter the human body?
Most microbes enter through breaks or wounds in skin or invasion of mucous membranes of respiratory, digestive, or genitourinary tract
How do bacteria or viruses usually initiate infection?
Bacteria or viruses usually initiate infection by adhering specifically to epithelial cells through interactions between macromolecules on surfaces of the pathogen and host.
Where do infections often begin?
Infections often begin at sites in mucous membranes, which consist of single or multilayers of epithelial cells, tightly packed cells that interface with environment
Define: Host Selectivity
a microorganism that normally infects humans binds to human epithelial cells better than those of a rat
What structures of a bacteria may be involved with adherence?
- Capsules (well defined layer), glycocalyx, or slime layers (loose network of polymer fibers) may be involved in adherence. (also resist phagocytosis).
- Fimbriae & Pili are bacterial surface protein structures that also function in attachment (bind host cell glycoproteins)
When does Disease result?
Disease results when anatomical and/or physiological damage occurs due to Virulence of microbe
Humoral Immunity is mediated by _____, whereas Cellular Immunity is mediated by _____
Humoral Immunity is mediated by antibodies, whereas Cellular Immunity is mediated by cells (T cells)
Describe the secreted enzyme, Hyaluronidase
Hyaluronidase is also called the spreading factor because it catalyzes the breakdown of hyaluronic acid, the substance that cements the human cells in tissues together. This allows the bacterial cells to spread through tissue causing a condition known as cellulitis. [Staphyloccus,Streptococcus,Clostridia]
Describe the secreted enzyme, Coagulase
This enzyme catalyzes the conversion of fibrinogen to fibrin with resultant clot formation. Present in pathogenic Staphyloccus. (clot prevents them being phagocytized.
Describe the secreted enzyme, Fibrinolysin
This catalyzes the conversion of plasminogen to the fibrinolytic enzyme plasmin. Thus it acts opposite of coagulase. In Staphylococcus aureus, the gene for fibrinolysin is on a bacteriophage and is expressed during lysogeny.
Describe the secreted enzyme, Lipase
Production of excessive amounts of lipase allow bacteria to penetrate fatty tissue with the consequent formation of abscesses.
Describe the secreted enzyme, Collagenase
This enzyme catalyzes the degradation of collagen, a protein found in tendons, ligaments, cartilage, nails and hair.
Describe the enzyme, Leukocidins
cause lysis of white blood cells; Staphyloccus aureus (pyogenic: pus producing).
Streptokinase and Streptodornase: actually fibrinolytic enzymes
Describe the enzyme, Lecithinase
destroys red blood cells & other tissue cells.
Describe the enzyme, Hemolysins
lyse red blood cells
What are the three general types of Exotoxins?
- Cytolytic toxins (include hemolysins): damage cell membranes, causing cell lysis & death (also are cytotoxins).
- A-B toxins: B promotes specific binding of toxin to host cell receptor (allows transfer of A (toxic part) across targeted cell membrane).
- Superantigen toxins: Stimulate large numbers of immune lymphocytes and causes systemic as well as inflammatory responses. Extensive inflammation & tissue damage.
What is the LD50? What bacterial characteristic(s) can you estimate from it?
- The LD50 (Lethal Dose 50) is the dose of an agent that kills 50% of the animals in a test group
- The virulence of a pathogen can be estimated from experimental studies of the LD50
What do Cytotoxins cause?
Inhibit a cell function or cause cell death
Cytolysins (Cytolytic toxins) are cytotoxins that cause cell death by lysis): Ex alpha toxin of Staph.
What do Neurotoxins cause?
inhibit nerve transmission
What do Enterotoxins cause?
alter permeability of intestinal epithelium
Examples: Cholera and Staph aureus food poisoning enterotoxin (also superantigen)
What type of toxin is Diptheria?
Diptheria toxin is an A-B toxin that inhibits a cell function: protein synthesis
Describe what Diptheria does (in detail)? How much of this toxin is needed to kill a cell? How is it formed?
- 1. B promotes binding of toxin to cell membrane
- 2. When it binds to cell membrane, it is cleaved and A is internalized.
- 3. A catalyzes ADP-ribosylation of elongation factor 2 (EF-2) and it no longer aids the transfer of amino acids to growing polypeptide chain. Ends protein synthesis
How much of Diptheria is needed to kill a cell? How is it formed?
Only a single toxin molecule is needed to kill a cell.
How is Diptheria formed?
Diptheria toxin is formed only by strains of Corynebacterium diptheriae cells that are lysogenized by phage beta.