chapter 15

exotoxin work by

destroying particular parts of the host cells or inhibiting certain metabolic functions -most lethal substances known

saxitoxin

dinoflagellates such as, Alexandrium, medically important because they produce _________________ mollusk feed on dinoflagellates, show no symptoms of disease, people who eat mollusks develop paralytic shellfish poisoning

exotoxins are

disease specific example; botulismis usually due to ingestion of _______________ not to bacterial infection disease caused by bacteria that produce exotoxins are often caused by minute amounts of exotoxins, not by bacteria themsleves

fungi

do not have well defined set of virulence factors -toxic metabolic products -provoke allergic response -some toxins inhibit protein synthesis proteases= modify host cell membranes, allow attachment of fungus to host cell -capsules prevent phagocytosis example; Trichothecenes fungal toxins inhibit protein synthesis Trichophyton = secrete proteases

mycotoxins

few mushrooms produce toxin called _____________ -produced by fungi example; phalloidin and amanitin ingestion of amanitin mushroom can cause death

gastrointestinal tract

gain access in food and water, via contaminated fingers -most microbes that enter the body this way are destroyed by hydrochloric acid (HCI) and enzymes in the stomach -those that survive cause disease, such as hepatitis A, thyphoid fever

toxins

poisonous substances that are produced by certain microorganisms -produce fever, cardiovascular problems, diarrhea, and shock -transported by blood or lymph can cause serious, sometimes fatal effects 2 types: endotoxin and exotoxin

genitourinary tract

portal of entry for pathogens contracted sexually -sexually transmitted infections (STIs) -may penetrate unbroken mucous membrane -cut or abrasion example; HIV, genital warts, herpes

intoxication

presence of toxin without microbial growth

toxemia

presence of toxins in host blood

exotoxin

produced inside some bacteria as part of their growth and metabolism, secreted by bacterium into the surrounding medium or released following lysis -proteins -many are enzymes that catalyze certain biochemical reactions -small amounts are harmful -carried on bacterial plasmids or phages can be gram + or -

Opa

protein allows attachment to host cells outermembrane protein example; Neisseria gonorrhoeae grows inside himan epithelial cells and leukocytes bacteria use fimbriae and _________ to attach to host cell

viral mechanisms (of evading host defenses)

-viruses can penetrate and grow inside host cell (where components of immune system cannot reach) -attachment sites, use receptors on host cells to attach -attachment site can mimic substances useful to host cells (example; attachment sites of rabies virus can mimic neurotransmitter acetylcholine) HIV = hides attachment sites from immune response, attacks components of immune system directly variation in attachment sites makes them unrecognizable by immune system -destroy immune cells

cytopathic variation (of effects)

1. macromolecular synthesis within host cell to stop 2. cells lysosome to release enzyme, results in destruction of intracellular contents and host cell death 3. creating inclusion bodies in cell cytoplasm 4.fusing cells to create syncytium 5.changing host cell function or inducing chromosomal changes with no visible changes 6. produce interferons to protect uninfected cells 7. induce antigenic changes on surface of infected cell 8. loss of contact inhibition in cell, leading to cancer

endotoxins and the pyrogenic response

1. macrophage ingest gram negative bacterium 2. bacterium is degraded in vacuole, releasing endotoxins that induce the macrophage to produce cytokines, IL-1 and TNF-a 3. cytokines are released into blood stream by macrophages, travel to hypothalamus of brain 4. cytokines induce hypothalamus to release lipids called prostaglandins, which reset the thermostat in hypothalamus at higher temperature, results in fever

exotoxins are divided into

3 principal types based on structure and function 1. A-B toxins 2. membrane disrupting toxins 3. superantigens

D. toxin (diphtheria toxin)

C. diphtheriae produces ___________________ when infected by lysogenic phage carrying tox gene -cytotoxin inhibits protein synthesis in eukaryotic cells does this using A-B toxin mechanism

toxigenicity

ability of microorganism to produce toxin

another consequence of endotoxins

activation of blood clotting proteins causing formation of small blood clots -blood clots obstruct capillaries and resulting decreased blood supply induces death of tissues (condition referred to as DIC

syncytium

adjacent infected cells fuse to form large multinucleate cell common cold, measles, mumps

toxoids

altered exotoxins inactivated exotoxins used in vaccines they simulate antitoxin production so immunity is produced

adhesins (or ligands)

attachment between pathogen and host accomplished by means of surface molecules on pathogen called ___________ bind specifically to complementary surface receptors on cells of certain host tissues -are glycoproteins or lipoproteins found on... -glycocalyx -fimbriae, pili, flagella

kinases

bacterial enzyme that break down fibrin and digest clots formed by the body to isolate infection -better known is fibrinolysin produced by streptococci

coagulases

bacterial enzymes that coagulate (clot) by fibrinogen in blood -fibrin clot may protect the bacterium from phagocytosis and isolate it from other defenses of the host some members of genus Staphyloccus

TNF

binds to many tissues of the body and alters metabolism in number of ways

antitoxins

body produces antibodies called ______________ provide immunity to exotoxins -antibodies against specific exotoxins

superantigens

cause intense immune response -bacterial proteins T cells are simulated to release enormous amounts of chemicals called cytokines cause symptoms of fever, nausea, vomiting, diarrhea, shock, and death include staphylococcal toxins

membrane disrupting toxin

cause lysis of host cell by disrupting plasma membrane -some do this by forming protein channels in plasma membrane -others disrupt phospholipid portion of membrane example; S. aureus = cell lysing exotoxon, forms protein channels C. perfringens = exotoxin that disrupts phospholipids

lysogenic conversion

change in characteristics of microbe due to prophage -as a result bacterial cell is immune to infection by same type of phage example; Virbrio cholerae, pathogenic strains carry lysogenic phages these phages can transmit cholera toxin gene to nonpathogenic V. cholerae strains, increasing number of pathogenic bacteria

A-B toxins

consist of 2 parts designated A and B both are polypeptides A part = active (enzyme) component B part = binding component example; diphtheria toxin

respiratory tract

easiest and most frequently traveled portal of entry for infectious microorganisms -inhaled into the nose or mouth in drops of moisture and dust particles example; common cold, pneumonia, influenza,

collagenase

enzyme produced by several species of clostridium -facilitates the spread of gas gangrene colagenase breaks down protein collagen, which forms connective tissue of muscles and other body organs and tissues

hyaluronidase

enzyme secreted by certain bacteria such as streptococci -digest polysaccharides that hold cells together spreading infection -hydrolyzes hyaluronic acid, type of polysaccharide that holds together certain cells of the body, particularly cells in connective tissue, helps microorganism spread from its initial site

the parenteral route

gain access to body when deposited directly into the tissues beneath the skin or into mucous membrane when barriers are penetrated or injured -punctures, injections, bites, cuts, wounds, surgery, and splitting of skin or mucous membrane example; HIV, hepatitis virus

portals of entry

gain entrance to the human body and other hosts through several avenues -mucous membrane gastrointestinal respiratory conjuctiva genitourinary -skin -parenteral route (direct deposition, beneath skin or membrane)

inclusion bodies

granules found in cytoplasm or nucleus of some infected cells sometimes viral parts nucleic acids or proteins in process of being assembled into virions characterized by ability to stain with acidic (acidophilic) or basic (basophilic)

sclerotia

highly resistant portions of mycelia of fungus that can detach toxin is contained in ______________

ID50

infectious dose for 50% of sample population -compare relative virulence under experimental conditions (measures virulence of a microbe) ______ through skin (cutaneous anthrax) is 10 to 50 endospores inhalation of anthrax is 10,000 to 20,000 endospores gastrointestinal anthrax is 250,000 to 1,000,000 endospores data shows that cutaneous anthrax is significantly easier to acquire than the gas. or inhalation

skin

largest organ of body in terms of surface area -some microbes gain access to body through openings in the skin, such as hair follicles and sweat glands example; some fungi grow on keratin in skin or infect the skin itself

LD50

lethal dose for 50% of sample population potency of toxin expressed (measures potency of a toxin) ____ for botulinum toxin in mice 0.03 ng/kg for shiga toxin, 250 ng/kg staphylococcal enterotoxin 1350 ng/kg compared to other two toxins a smaller dose of butulinum toxin is needed to cause symptoms

shock

life threatening decrease in blood pressure

mucous membrane

many bacteria and viruses gain access to body by penetrating ___________, lining of respiratory tract, gastrointestinal tract, genitourinary tract and conjunctiva (delicate membrane that covers eyeballs and lines eyelids)

preferred portal of entry

many pathogens have a preferred portal of entry that is required for them to be able to cause disease example; Salmonella typhi = produces all symptoms of disease when swallowed (preferred route) , although if rubbed on skin there would be no reaction streptococci that are inhaled caused pneumonia

plasmid

may carry genes for... toxins = neurotoxin resistance to antibiotics (R factors)= B-lactamase enzymes = dextransucrase small circular DNA molecules capable of independent multiplication

biofilm

microbes form ____________ (communities that share nutrients) -communities that constitute masses of microbes and extracellular products that can attach to living and nonliving surfaces -adheres to surface, typically moist and contains organic matter -dental plaque, stents, catheters, heart valves, hip replacements

invasins

microbes produce surface proteins called _______________________ -rearrange nearby actin filaments of the cytoskeleton example; S. tryphimurium makes contact with host cell, _______________ of the microbe cause appearance of host cell plasma membrane to resemble splash of a drop of liquid hitting solid surface this effect is called membrane ruffling, disruption in cytoskeleton of host cell

contact inhibition

most normal cell cease growing in vitro when they come close to another cell leading to cancer

iron is required for

most pathogenic bacteria

adherence (or adhesion)

most pathogens attach to host tissues in process called _______________ necessary step in pathogenicity

waxy lipid

mycolic acid resist digestion by phagocytosis makes up wall of Mycobacterium tuberculosis, also increases virulence by resisting digestion by phagocytes and can multiply inside phagocytes

endotoxin

outer portion of cell wall of gram negative bacteria -lipopolysaccharide -released when gram negative bacteria die, cell wall undergo lysis (also released during bacterial multiplication) -simulate macrophages to release cytokines in very high concentrations (at this level cytokines are toxic) -produce same signs and symptoms regardless of species of microorganism, but not same degree

direct damage

pathogens use host for nutrients and produce waste products -multiply host cells and cause ruptures -disrupt host cell function -penetrate host cell by excreting enzymes and by own motility -done by toxins

IgA proteases

pathogens with the ability to produce enzyme -destroy IgA antibodies example; N. gonorrhoeae has this ability

capsules

resist the host defenses by impairing phagocytosis (process by which certain cells of body engluf and destroy microbes) strains with capsules are virulent, but strains without capsules are avirulent, since they are susceptible to phagocytosis (many nonpathogentic bacteria HAVE capsules and many pathogenic bacteria DO NOT have capsules)

M protein

resists phagocytosis Streptococcus pyogenes, produce heat resistant and acid resistant protein called _________ -mediates attachment of bacterium to epithelial cells of host and helps the bacterium resist phagocytosis by white blood cells (protein increases virulence of microorganism) immunity of S. pyogenes depends on bodys production of antibody specific to _________________

membrane ruffling

result of disruption in cytoskeleton of host cell cell of plasma membrane to resemble drop of liquid

portals of exit

secretions, discharges, excretions or tissue that has been shed ______________________________ are related to part of body that has been infected common are respiratory and gastrointestinal tract example; respiratory tract= coughing and sneezing gastrointestinal tract= feces and saliva genitourinary tract= urine, secretions from penis and vagina (usually sexually transmitted infections) skin

septic shock

shock caused by bacteria gram negative bacteria cause endotoxic shock

antigenic variation

some pathogens can alter their surface antigens by the time body mounts an immune system response against pathogen, pathogen already altered its antigens and is unaffected by the antibodies

algae

some species produces neurotoxins called saxitoxin genera dinoflagellates, such as Alexandrium, medically important because they produce saxitoxin

aflatoxin

toxin that has carcinogenic properties -produced by growth of the mold, Aspergillus flavus -when ingested, toxin might be altered in human body to mutagenic compound

pathogenicity

the ability to cause disease

virulence

the degree of pathogenicity

siderophores

to obtain free iron, some pathogens secrete proteins called _________________ -released into the medium, where they take iron away from iron transport proteins by binding iron even more tightly (pathogens that bind iron more tightly than host proteins -some bacteria bind to iron transport proteins such as hemoglobin and internalize them

ergot

toxin itself alkaloid -can cause hallucinations resembling those produced by LSD -natural source of LSD -constricts capillaries -cause gangrene of limbs by preventing proper blood circulation

protozoa (evade host defenses)

use antigenic variation to stay one step ahead of host immune system example; Trypanosoma = produces and displays specific antigen. In response body produces antibodies against antigen. Within 2 weeks microbe displays different antigen microbe can make up to 1,000 different antigens

helminths

use host tissue for own growth or produce large parasitic masses resulting in cellular damage evokes symptoms

interferons

virus infected cells produce __________________ host DNA actually codes for ______________. This protects neighboring uninfected cells from viral infection

cytopathic effects (CPE)

visible effects of viral infection -cytocidal effects =result in cell death -noncytocidal effects = result in cell damage but not cell death

protozoa

waste products often produces disease symptoms in the host plasmodium= causes rupture toxoplasma= gains entry by phagocytosis, parasite prevents normal acidification and digestion, can grow in phagocytic vacuole Giardia lamblia= attach to host cells by sucking disc, digest cells and tissue fluid