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Terms in this set (39)
the ability to cause disease by overcoming host defenses
degree of pathogenicity
Portals of Entry: Mucous Membranes
Line the body cavities that are open to the environment
Provide a moist, warm environment hospitable to pathogens
Respiratory tract is the most common site of entry
Entry is through the nose, mouth, or eyes
Gastrointestinal tract may be route of entry
Must survive the acidic pH of the stomach
Respiratory tract- easiest and most frequent
Gastrointestinal- access through food, water, fingers
conjunctiva- membrane covering eyes and eyelids
portals of entry: Skin
• Largest organ in body, first line of defense
• Impenetrable by most organisms if unbroken
• Some organisms can infect through hair follicles or sweat gland ducts
• Few organisms can bore through skin (hookworm)
• Some fungi can grow in keratin layer or infect skin itself
Portals of Entry: Parenteral Route
a portal of entry for pathogens by deposition directly into tissues beneath the skin and mucous membranes
-punctures, injections, bites, cuts, wounds, surgery, and splitting of skin and membranes due to swelling or drying
infectious dose for 50% of sample population ID50
represents virulence (infectious capability) of organism- the lower the #, the more infectious the organisms to its host.
-does not indicate severity of disease
lethal dose for 50% of the population; LD50
represents potency of toxin
causes food poisoning that can lead to flaccid paralysis, often in canned food, but can be easily inactivated
Shigella, and E. coli O157:H7 Cleaves host cell rRNA (inactivates 60S ribosome) Enhances cytokine release, causing HUS
-causes food poisoning that leads to bloody diarrhea and blood in urine.
food poisoning that leads to nausea, vomiting, diarrhea
occurs between surface molecules on pathogen and host receptor (sugars)
-adhesins and ligans
surface molecules bind specifically to surface receptors on cells or certain host tissues
EX: glycocalyx, pili, fimbriae, flagella
Example of bacteria binding to other bacteria
Plaque on teeth is often started by Streptococcus mutans and other organisms can attach to them like bacteria that leads to periodontal disease.
Glycocalyx and sugar coat increases bacteria cell's virulence by blocking phagocytosis.
cell wall components that contribute to virulence
bacteria can contain chemical substances that can contribute to virulence
EX: M proteins on surface of Streptococcus pyogenes is heat resistance and acid resistant. mediates attachment, and resists phagocytosis.
Outer membrane protein in Neisseria gonorrhoeae that attaches to host and gets inside cell leading to infection
in acid fast bacteria like Mycobacterium tuberculosis, protects them from digestion in phagocytosis and allows bacteria to replicate inside cells.
extracellular enzymes that enhance virulence.
Pathogens alter their surface antigens to evade antibodies from immune system. (and antibodies are rendered ineffective)
penetration into host
microbes use host cytoskeleton protein actin to penetrate host cells and move through and between host cells.
-some microbes survive or can be dormant inside phagocytes.
-some microbes replicate in phagolysome
digestive structure that forms between phagosome containing bacteria from entry to the cell and lysosome organelle
resistant to phagocytosis. Can hide so antigens are not detected by immune system.
pathogens damage host cells: Using hosts nutrients:
bacteria require iron.
-can secrete proteins called siderophores to bind iron more tightly than hosts needs.
-some receptors bind directly to iron: transporting proteins and hemoglobin
at site of infection using hosts nutrients and producing waste products
-penetration into host cell
-cause cell lysis when multiply inside cell
-host cell destroyed
productuction of toxins: exotoxins
gram-positive: proteins produced inside some bacteria and secreted to outside
-harmful because they can act over and over
-soluble in body fluids so they can easily diffuse into the blood and rapidly transported
-altered toxins (toxoids) are used to cause the production of antitoxins.
EASILY DESTROYED BY HEAT
-altered toxins (toxoids) are used to
cause production of antitoxins.
gram negative bacteria
-lipid A portion of LPS(outer membrane of cell wall)
-released during replication and from lysis
-can lead to formation of blood clots, miscarriages, and even death.
-can cause septic shock from antibiotic treatment if enough bacteria is present.
-do not promote formation of effective antibodies
exotoxins with a non-toxic portion (B) that binds to a host cell and a toxic portion (A) that acts on the host cell to produce an effect
-2 polypeptide subunits
EX: Tetanus caused by clostridium tetani leading to uncontrollable muscle contractions (lock jaw and death)
EX: Clostridium difficile
Exotoxins that lyse host cells by disrupting plasma membranes
Exotoxin group (or class) which causes severe immune reactions
EX: staphylococcal food poisoning
carry pathogenicity genes
EX: tetanus, neurotoxin, staphylococcal enterotoxin
-change in characteristic of microbe due to prophage (bacteriophage DNA incorporated into bacterial chromosome) that can make them more harmful
-bacterial cell is more immune to infection
visible effects of viral infection
-cytocidal effects: results in cell death
-non-cytocidal effects: results in cell damage but not cell death
portal of exit
microbes leave the body related to the part of the body. that has been infected
-typically uses same entry for exit
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