Exam 3 Ch 15
which type of toxin can kill phagocytic leukocytes (WBCs) and macrophages, and how do they accomplish this?
*leukocidins* (membrane-disrupting exotoxins) -they form protein channels -most produced by staphylococci and streptococci
How does the portal of entry relate to the occurrence of disease?
*pathogens have a preferred portal of entry that is a pre-requisite for them being able to cause disease.* For ex, Salmonella typhi causes typhoid fever if swallowed (preferred route). If it is rubbed on skin, no problems occur.
What is coagulase and what is its relationship to virulence? Who makes it?
-bacterial enzyme that clots fibrinogen in blood into fibrin. The firbin clot may protect bacteria from phagocytosis, and isolate it from other defenses of the host. *S. aureus*
Most pathogens must penetrate tissues to cause disease. Which factors contribute to the ability of bacteria to invade a host?
-capsules: phagocytes don't recognize the bacteria and they can't adhere to it -cell wall components (such as M proteins, Fimbraie, OPA, Mycolic acid): lets bacteria attach to host -enzymes (such as coagulase, kinase, hyaluronidase, collagenase): facilitate clotting or unclotting or spreading -antigenic variation: so antibodies can't recognize the pathogen
What is M Protein?
-cell wall component -a protein produced by Streptococcus pyogenes that helps with attachment to epithelial cells of host and virulence by resisting phagocytosis -heat/acid resistant -found on cell surface and fimbriae -mediates attachment of the bacterium to epithelial cells of the host (in the resp tract) -helps bacterium resist phagocytosis by white blood cells
The cell walls of certain bacteria contain chemical substances that contribute to its ability to invade a host/virulance. These cell wall components include:
1. *M protein*(helps mediate attachment/allow pathogen to resist phagocytosis) *S.Pyogenes* 2. *fimbriae* and outer membrane protein *OPA*(can attach to host cell which then takes in the bacteria) *Neisseria gonorrhea* 3. *mycolic acid*(helps pathogen resist digestion by phagocytes which take pathogen in, but pathogen can multiply inside the whale!) *Mycobacterium tb*
Exotoxins are divided into three principal types on the basis of their structure and function...
1. A-B toxins 2. membrane-disrupting toxins 3. superantigens
3 key factors in entrance?
1. portal of entry where microbe can colonize (mucous membrane/skin/parenteral routes) 2. attachment btw microbes and the host cell (adhesins/ligands) 3. the # of microbes; the more the merrier
What are IgA proteases? Who makes these?
enzymes that can destroy IgA antibodies which are produced by the body as a defense against adherence of pathogens to mucosal surfaces. -produced by some pathogens such as *S. pneumoniae which causes meningitis and otitis media, and Haemophilus influenza, N. gonorrhoeae and N. meningitidis.*
the majority of adhesins on the microorganisms studied so far are ___________ or _________. The majority of receptors on host cells are _________
glycoproteins or lipoproteins majority of receptors on host cells are sugars such as mannose.
A sudden drop in blood pressure induced by bacterial toxins. Prev
septic shock
__________ is an enzyme secreted by certain bacteria, such as streptococci. It hydrolyzes hyaluronic acid (polysach that holds together certain cells of the body, particuarly cells in connective tissue). This digesting action helps the microorg spread from its initial site of infection.
Hyaluronidase
What cell structure does Neisseria gonorrhoeae use to attach and enter host epithelial cells? M proteins fimbriae capsules cell wall waxes flagella
fimbriae
An enzyme that lyses red blood cells. Prev
hemolysin
Bacterial iron-binding proteins. Prev
siderophore
type of exotoxin/bacterial protein/antigen - provokes a very intense immune response due to release of cytokines from host cells, leading to fever/nausea/vomiting/diarrhea/shock/death
superantigens!
What are invasins?
surface proteins produced by some microbes such as Salmonella and E. Coli -rearranges nearby actin filaments of the cytoskeleton, (a dramatic change in membrane at point of contact) -the mechanism by which the microbe gets into the cell is provided by the host cell's cytoskeleton.
How would microbes exit the body via the RESPIRATORY TRACT portal of exit?
Droplets (colds, diphtheria & influenza) Sputum (TB)
Diptheria toxin is an example of an...
AB toxin (exotoxin)
Can endotoxins be neutralized by antitoxin?
no..only exotoxins
What are superantigens?
type of exotoxin/bacterial protein/antigen - provokes a very intense immune response due to release of cytokines from host cells, leading to fever/nausea/vomiting/diarrhea/shock/death (more specifically, the superantivens stimulate proliferation of immune cells called T cells (types of WBCS called lymphocytes) which release the cytokines)
Cystitis is caused by _______ through the ____________ portal of entry
E. Coli, genitourinary tract
A component of the gram-negative outer membrane; endotoxin. Prev
Lipid A
Which bacterial protein can take iron from human lactoferrin?
siderophore
Which of these substances does NOT protect a bacterium from phagocytosis? M protein siderophore leukocidin capsule
siderophore
Endotoxins exert their effects by ....
stimulating macrophages to release cytokines in high concentrations. At these levels, cytokines are toxic.
A blood-clot dissolving enzyme, produced by beta-hemolytic streptococci. Prev
streptokinase Prev
A hemolytic enzyme, produced by streptococci. Prev
streptolysin Prev
Virulence can be expressed as....
*ID50 (infectious dose for 50% of the inoculated hosts)*....recall that *potency* can be expressed as LD50 (lethal dose for 50% of the inoculated hosts)
__________ are enzymes that can destroy antibodies; defense against adherence of pathogens to mucosal surfaces. They are made by ____ ______ ______
*IgA proteases* produced by organisms such as Neisseria (N. gonorrhoeae, N. meningitidis) Streptococcus pneumoniae, Haemophilus influenzae
what are toxoids?
*altered exotoxins* When exotoxins are inactivated by heat/formaldehyde/iodine/other chemicals, they no longer cause disease but can still stimulate the body to produce antitoxins(antibodies against exotoxins). They are now called toxoids. -toxoids are injected into the body as a vaccine because they can stimulate you to produce immunity. Ex: tetanus shot!
What are the signs and symptoms produced by endotoxins?
*chills, fever, weakness, generalized aches, and in some cases shock and death*. -also can induce miscarriage -also can activate *blood clotting proteins*, causing formation of clots that can obstruct capillaries causing DIC (disseminated intravascular coagulation)
A kinase produced by streptococci. Prev
fibrinolysin
Local infections can be protected in a fibrin clot caused by the bacterial enzyme ________ produced by ______
*coagulase enzyme*. (the clot may protect the bacterium from phagocytosis and isolate it form other defenses of the host.) produced by *S. aureus*
___________are bacterial enzymes that clot the fibrinogen in blood. Who makes this?
*coagulases*. the fibrin clot may protect the bacterium from phagocytosis and isolate it from other defenses of the host. -produced by some members of the genus S. aureus
which type of toxins destroy erythrocytes (rbcs) and how do they accomplish this
*hemolysins* (membrane-disrupting exotoxins) -form protein channels -produced by staphylococci/streptococci (when hemolysins are produced by streptococci they are called streptolysins.
__________ are bacterial enzymes that break down fibrin and thus digest clots formed by the body to isolate the infection.
*kinases* ex: fibrinolysin (streptokinase) which is produced by streptococci pyogenes
bacteria can spread from a focal infection by means of ___________ (which destroys blood clots), ______________ (which destroys a mucopolysachharide that holds cells together)
*kinases* destroy clots formed by the body to isolate the infection. *hyaluronidase* hydrolyzes hyaluronic acid, a type of polysach that holds together certain cells of the body, particularly in connective tissue. this helps microorg spread from initial site of infection.
cytokines are __________ produced by _________ that regulate _______________ and mediate ____________. Cytokines are released in response to ___________. High levels of cytokines enter the blood stream and give rise to ______________.
*small protein molecules* produced by *various body cells, esp T cells*, that regulate *immune responses* and mediate *cell-to-cell communication. * excessively high levels of cytokines released by T cells * in response to superantigens* enter bloodstream and give rise to *symptoms like fever, nausea, vomiting, diarrhea..shock or death*
What are adhesins or ligands?
*surface molecules on pathogen that bind specifically to complementary surface receptors of the cells of certain host tissues.* (allow for adherence to occur, i.e. attachment of pathogen to host at portal of entry, which is usually a necessary step in pathogenicity)
Compare the LD50 of exo and endo toxins
Exotoxins are lethal in small amounts, but LD50 for endotoxins would have to be relatively large
Please explain the different parts of the A-B toxin and how it works
-type of exoenzyme Both part A and B are polypeptides. A= active (enzyme) component. B= binding component Bacterium produces/releases AB toxin. B component attaches to host cell receptor. It enters cell via receptor-mediated endocytosis, then enclosed by pinched off portion of membrane during pinocytosis. AB components separate. A alters function of host (may inhibit protein synthesis), B is released
Learning the mechanisms of microbial pathogenicity is fundamental to understanding how pathogens are able to overcome the host's defenses.....these include
1. Portal of entry 2. Penetration or evasion of host defenses 3. damage to host cells 4. portals of exit 1. Portal of entry (mucous membranes/skin/parenteral routes) ----# of invading microbes/adherence-------- 2. Penetration or evasion of host defenses (capsules, cell wall components, enzymes, antigenic variation, invasins, intracellular growth) 3. damage to host cells(siderophores, direct dammage via endo and exo toxins) 4. portals of exit (mucous membranes, skin, parenteral route)
in order to cause disease, pathogens must do what?
1. access host via portal of entry or adhering to host tissue 2. penetrate host/evade host defenses 3. damage host cells, either directly or via accumulation of microbial waste products
If a pathogen overcomes the host's defense, it can cause damage to host cells in the following ways:
1. by using host's nutrients 2. by causing direct damage in the immediate vicinity of the invasion 3. by producing toxins, txped by blood and lymph 4. by inducing hypersensitivity reactions (discussed in a later chapter)
What are the five tasks of pathogenic bacteria listed on the slide
1. encounter and entry 2. establish an infectious niche 3. evasion of host defenses or penetration 4. damage to host cells or tissues 5. transmission to a new host
How do endotoxins cause fever?
1. macrophage ingests a gram-neg bacterium 2. bacterium is degraded in a vacuole, releasing endotoxins that induce macrophage to produce cytokines 3. cytokines are released into bloodstream by macrophages...they travel through blood to hypothalamus of the brain 4. cytokines induce hypothalamus to produce prostaglandins which reset body's thermostat to a higher temp, producing fever.
Bacterial exotoxins consisting of two polypeptides. Prev
A-B toxin
How do microbes use actin in their favor?
Actin is a protein/major component of host cell cytoskeleton. -Salmonella and E. Coli produce invasin proteins which make actin rearrange so as to let microbes into cell. -Shigella and Listeria use actin to propel themselves through the host cell cytoplasm and from one host to the next.
Which of these statements is not true for bacterial capsules? Pathogenic and nonpathogenic bacteria can produce capsules. Capsules related to virulence are produced by the causative agents of anthrax and bubonic plague. Antibodies produced against a capsule cannot affect whether disease will occur. The importance of the capsule to virulence for Streptococcus pneumoniae can be determined because there are strains both with and without the capsule. For Streptococcus pneumoniae, the encapsulated strain is more virulent.
Antibodies produced against a capsule cannot affect whether disease will occur.
How can pathogens cause direct damage to a host?
As pathogens metabolize and multiply in cells, the cells usually rupture. OR they produce toxins that damage the host (most damage is done this way)
Tetanus is caused when __________ enters through ___________
Clostridium tetani enters through a cut (parenteral)
Which statement is not true of endotoxins? They can induce chills, fever, aches, clotting, shock, and miscarriage. They are eliminated from the body as a result of antitoxin production. Endotoxins are produced by Neisseria meningitidis and E. coli. They are more heat-resistant than exotoxins are. They can lyse amoebocytes found in crab hemolymph.
Correct Answer: They are eliminated from the body as a result of antitoxin production.
Discuss the differences in how endotoxins and the various types of exotoxins exert their effects. Endotoxins stimulate ________________. AB toxins alter ____________. Membrane disrupting toxins cause __________Superantigens stimulate ________________
Endotoxins: stimulate macrophages to release cytokines in very high concentrations. At these levels, cytokines are toxic Exotoxins: - A-B toxins: enter host via endocytosis and A piece can alter cell functions like inhibiting protein synth. -Membrane-disrupting toxins cause lysis of host cells by disrupting plasma membranes by forming protein channels through it or by disrupting phospholipid portion of the membrane -Superantigens which stimulate proliferation of T cells which release cytokines)
What are membrane-disrupting toxins and how do they work? Examples of these include...
Exotoxins that cause lysis of host cells by disrupting their plasma membranes. -either by forming protein channels through it, or by disrupting the phospholipid bilayer portion of the membrane. Ex: leukocidin: S. aureus, streptococci hemolysins: staph/streptococci tracheal toxin: B. pertussis, injures the cells in your trachea
Compare the source of Exotoxins and Endotoxins
Exotoxins= proteins produced inside pathogenic bacteria (usually gram pos, but can be gram neg), as part of their growth and metabolism. -Exotoxins are secreted into surrounding medium during log phase Endotoxins= lipid portions of lipopolysachharides (LPS) that are part of the outer membrane of the cell wall of gram neg bacteria (LIPID A). -Endotoxins are liberated when the bacteria die and the cell wall breaks apart
How would microbes exit the body via the DIGESTIVE TRACT portal of exit?
Feces (hep A, cholera and salmonellosis, typhoid fever, shigellosis) Saliva (rabies, mumps, mono)
Neisseria gonorrhoeae grows inside human epithelial cells and leukocytes. These bacteria use _________ and _______ to attach to host cells, after which, the host cells take in the bacteria
Fimbriae and OPA (outer membrane protein)
How can you express the virulence of a microbe?
ID50 "infectious dose for 50% of a sample population" (the 50 isn't an absoulte value, but it is used to compare relative cirulence under experimental conditions) For ex, the ID 50 for cutaneous anthrax is 10-50 endospores; for inhalation anthrax it is 10,000-20,000 endospores, so cutaneous is more virulent recall that LD50 is how you express potency of a toxin
How can you express the potency of a toxin?
LD50 "lethal dose for 50% of a sample population" ex, LD50 for botulinum toxin in mice = 0.03 ng/kg
I am a cell wall component. I am a protein found on cell surface and fimbriae of Streptococcus pyogenes. I am heat/acid resistant. I mediate attachment of bacteria to epithelial cells of host. I help resist phagocytosis by WBC/s. I contribute to virulence
M Protein
Endotoxin is another name for __________________. lipid A. cytokine. interleukin-1. cell wall.
LIPID A!
A heat- and acid-resistant protein of streptococcal cell walls and fibrils. Prev
M protein, S. pyogenes has this, it prevents complement from binding, it mediates attachment of bacterium to epithelial cells of host, it helps bacterium resist phagocytosis
Immunity to S. pyogenes depends on the body's production of an antibody specific to __________
M. protein.
I am the type of exotoxin that causes lysis of host cells by forming protein channels or by disrupting phospholipid bilayer
Membrane disrupting toxins..cuase lysis of host cells by disrupting their plasma membranes...either by forming protein channels in plasma membrane or by disrupting phospholipid bilayer portion of membrane
How would microbes exit the body via the GENITAL TRACT portal of exit?
Semen and vaginal secretions (AIDS, Syphilis) Urine (brucellosis, typhoid fever, Hep B)
Rabies is caused when ________ enters via ___________
Rhabdovirus enters via dog bite
toxic shock syndrome is a result of?
S. aureus makes superantigens, cause release of cytokines which cause fever, nausea and other symptoms
Salmonella and strains of E. coli use ________to help with penetration of host cells because it can rearrange ______ filaments. Once inside the host cell, Shigella and Listeria use ______to propel themselves through cytoplasm, evading phagocytosis.
Salmonella and E. coli contact cells plasma membrane and produce INVASIN protein, which can rearrange actin filaments in the host's cytoskeleton.....Shigella and listeria use ACTIN to propel themselves through cytoplasm.
True or False? Adhesin molecules can vary in structure among strains of a given bacterial species.
TRUE recall that pathogen has adhesins or ligands that bind specifically to complementary surface repceptors on cells of certain host tissue. adhesins may be located on microbe's glycocalyx or pili, fimbriae, flagella
What are leukocidins and hemolysins?
These are types of membrane-disrupting exotoxins produced by staphylococci and streptococci. They act by forming protein channels *Leukocidins* kill phagocytic leukocytes (white blood cells) and macrophages (in tissue) *Hemolysins* kill erythrocytes (red blood cells)
What do Streptococcus pneumoniae, Haemophilus influenzae and Bacillus anthracis and Bordetella, E. Coli and P. aeuroginosa all have in common?
They all can produce a capsule to evade phagocytosis. helps with their virulence!
Bacterial pathogens penetrate host defenses with....
Via...capsules, cell wall components, enzymes, antigenic variation, penetration into cytoskeleton of host
What is antigenic variation? Who does this?
a process by which some pathogens can alter their surface antigens. thus, by the time the body mounts an immune response against the pathogen, its altered its antigens and is unaffected by the antibodies, which are supposed to bind to the antigens and inactivate/destroy them. For ex: N. gonorrhoeae has several copies of the Opa-encoding gene, resulting in cells with different antigens and cells that can express different antigens over time. Who: *N. gonorrhea, Influenzas, Trypanosome bruceigambence which causes african sleeping syndrome*
Which virulence factor is specifically involved in helping an organism to physically spread throughout the body?
Your Answer: hyaluronidase
surface projections on a pathogen called ____________ adhere to complementary receptors on the host cells
adhesins (ligands)
the attachment between pathogen and host is accomplished by means of ___________
adhesins or ligands, which are surface molecules on the pathogen that bind specifically to complementary surface receptors on cells of certain host tissues.
A carbohydrate-specific binding protein that projects from prokaryotic cells; used for adherence Prev
adhesion/ligand
When the balance between host and microbe is tipped in favor of the microbe ____________ results
an infectious disease
__________ is the process by which some pathogens can alter their surface antigens, so when the body mounts its immune response against the pathogen, the antigens are already altered and thus it is unaffected by antibodies
antigenic variation!
A specific antibody produced by the body in response to a bacterial exotoxin or its toxoid. Prev
antitoxin
Antibodies produced against exotoxins are called ____________
antitoxins
Almost all pathogens can _______ to host tissues at their portal of entry.
attach themselves i.e. "adherence" or "adhesion"
what are kinases and what are their relation to virulence? Who makes these?
bacterial enzymes that break down fibrin and thus digest clots formed by body to isolate infection. *staphylococcus makes staphylokinase, streptococcus makes streptokinase (fibrolysin)
microbes have the ability to come together in masses, cling to surfaces, and take in/share available nutrients. These communities, which constitute masses of microbes and their extracellular products that can attach to living and non living surfaces are called _________________
biofilms. For ex, dental plaque on teeth, algae on pool walls, shower scum
______ is an enzyme produced by several species of Clostridium and facilitates spread of gas gangrene. It breaks down the protein that forms the connective tissue of muscles and other body organs and tissues.
collagenase
What do Collagenase, Hyaluronidase and Invasins have in common?
components that help entering host cell/penetration........(recall that invasins are surface proteins that rearrange actin filaments in cytoskeleton of host cell like a drop of liquid hitting a solid surface, the microbe sinks into a ruffle on the host cell and is engulfed)
A bacterial toxin that kills host cells or alters their functions. Prev
cytotoxin
What happens when microbes overpower the host defenses?
disease results!
Cytokines are responsible for _________________. drop of blood pressure. drop of blood pressure AND blood clotting. directly killing the pathogen. drop of blood pressure AND directly killing the pathogen. blood clotting.
drop in BP and clotting. endotoxins can activate blood clotting proteins that obstruct capillaries
Part of the outer portion of the cell wall (lipid A) of most gram- negative bacteria; released on destruction of the cell. Prev
endotoxin
All _________produce the same signs and symptoms regardless of the species of microogranism, although not to the same degree
endotoxins
_________ are lipid portions of lipopolysachharides (LPS) that are part of the outer membrane of the cell wall of gram neg bacteria (LIPID A). they are liberated when the bacteria die and the cell wall breaks apart
endotoxins
________ exert their effects by stimulating macrophages to release cytokines in very high concentrations. At these levels, cytokines are toxic
endotoxins (as opposed to exotoxins... - A-B toxins: enter host via endocytosis and alter cell function like inhibiting protein synth. -Membrane-disrupting toxins cause lysis of host cells by disrupting plasma membranes by forming protein channels through it or by disrupting phospholipid portion of the membrane -Superantigens which stimulate proliferation of T cells which release cytokines)
__________ cause fever and shock
endotoxins cause fever by inducing release of interleukin and shock because of a decrease in BP
bacterial cell death, antibiotics, and antibodies may cause the release of __________
endotoxins, which are lipopolysaccharides (the Lipid A component of gram neg outer membrane)
because of the ____________ nature of most exotoxins, even small amounts are quite harmful
enzymatic nature. remember, exotoxins are proteins, many are enzymes that catalyze certain biochemical rxns, and they can act over and over again.
What does collagenase do?
enzyme produced by several species of clostridum -breaks down collagen protein (which forms connective tissue of body organs/muscles/tissues) - facilitates spread of gas gangrene caused by clostridia
What is Hyaluronidase?
enzyme secreted by certain bacteria such as streptococcus and staphylococcus. -hydrolyzes hyaluronic acid (poly sach that holds together certain cells of the body, particularly cells in connective tissue) -digestion action helps the microorg spread from its initial site of infection. -can also be involved in blackening of tissue at infected wound sites -is produced by some clostridia that causes gas gangrene.
A protein toxin released from living, mostly gram-positive bacterial cells.
exotoxin
______________ are produced by bacteria and released into the surrounding medium
exotoxins
______________ are proteins produced inside pathogenic bacteria (usually gram pos, but can be gram neg), as part of their growth and metabolism. They are secreted into surrounding medium during log phase
exotoxins
Exotoxins are produced by bacteria and released into surrounding medium. What causes disease symptoms?
exotoxins, not the bacteria itself
Enteropathogenic strains of E. coli have adhesins on __________
fimbria; these adhere to specific kinds of cells in certain regions of the small intestine.
An appendage on a bacterial cell used for attachment. Prev
fimbriae
what is the portal of entry for pathogens contracted sexually?
genitourinary tract
Capsules are formed out of _____________
glycocalyx material
Where on a microbe may adhesions be located?
glycocalyx, pili, fimbriae, flagella
Streptococcus mutans attaches to the surface of teeth via _________
glycocalyx. An enzyme produced by S. mutans converts glucose into a sticky polysach which forms the glycocalyx. causes tooth decay.
When bacteria get iron from the host using siderophores, this is an example of ___________
how bacterial cells can damage host cells by using the host's nutrition
An enzyme secreted by certain bacteria that hydrolyzes hyaluronic acid and helps spread microorganisms from their initial site of infection. Prev
hyaluronidase
A surface protein produced by Salmonella typhimurium and Escherichia coli that rearranges nearby actin filaments in the cytoskeletonof a host cell. Prev
invasin
What is the function of a capsule?
it increases virulence because the chemical nature of the capsules appears to prevent the phagocytic cell from adhering to the bacterium. This impairs phagocytosis.
(1) An enzyme that removes a P from ATP and attaches it to another molecule. (2) A bacterial enzyme that breaks down fibrin (blood clots). Prev
kinase
Substances produced by some bacteria that can destroy neutrophils and macrophages. Prev
leukocidins Prev
__________ is the most common receptor for adheesins
mannose
Microbes leave the body via__________
microbes leave the body via *portals of exit* in secretions, exretions, discharges, or tissue that has been shed. -in general, portals of exit are related to the part of the body that has been infected. (i.e. microbe usually uses same portal for entry and exit)
most pathogens enter through the ____________
mucous membranes of the GI and respiratory tracts
What does Mycobacterium tuberculosis have that can increase its virulence?
mycolic acid (waxy lipid) helps resist digestion by phagocytes. phagosome can engulf it and bring it into the cell but the lysosome can't destroy.. M tuberculosis can even multiply when inside the whale
An exotoxin that interferes with normal nerve impulse conduction. Prev
neurotoxin
Are capsules the only cause of a pathogens virulence?
no. there are many causes of virulence.
Where are the genes for most exotoxins carried?.
on bacterial plasmids or phages.
One way a pathogen can cause damage to a host is by using its nutrients. Explain!
pathogenic bacteria need iron, but it isn't just roaming freely around host. -As such, some pathogens secrete *siderophore* which takes iron away from iron txp proteins by binding to it more tightly, and makes it available to the bacteria -Some pathogens have receptors that bind directly to iron txp proteins and take the iron that way -OR bacteria can just kill the host with toxins to release the iron and make it available
_________ is the ability to cause disease (by overcoming defenses of host)
pathogeniticy
Malaria is caused when ____________ enters body via _________
plasmodium (protozoa) enters body via biological transmission through parenteral route (mosquito bite)
pathogens can gain entrance to the human body and other hosts through several avenues which are called ____________. Name some of the avenues....
portals of entry (mucous membranes, skin, parenteral route aka direct deposition beneath skin/membranes)
What are siderophores?
proteins secreted by some pathogens that can bind to iron-txp proteins/hemoglobin in the host and take the iron. Then the bacteria uses its siderophore receptors to take it up. this is an example of the pathogen using the host's nutrition to damage it
How would microbes exit the body via a SKIN portal of exit?
pus and lesion exudate Ex: S. aureus and chicken pox (virus)
An attachment for a pathogen on a host cell. Prev
receptor
the __________ is the easiest and most frequent traveled portal of entry for infectious microorganisms
respiratory tract (TB, cold, pneumonia, *flu*, measles)
An antigen that activates many different T cells, thereby eliciting a large immune response. Prev
superantigen Prev
Toxins that stimulate proliferation of T cells nonspecifically and provoke intense immune responses are called __________.
superantigens ....these guys are antigens/bacterial proteins that nonspecifically stimulate proliferation of T cells, which are WBCs that can stimulate relase of cytokines. Ex: toxic shock syndrome toxin by S. aureus, enterotoxin by S. aureus , exotoxin A by S. pyogenes causing necrotizing faciitis. don't confuse with endotoxins, which exert effect by stimulating macrophages to release cytokines in high concentrations producing chills/fever/weakness/shock AND may activate blood clotting as well which obstructs capillaries.
pathogenicity is ___________
the ability to cause disease (by overcoming defenses of host)
What part of gram neg cell is the endotoxin?
the lipid portion of the Lipopolysachharide *Lipid A*
How does the # of invading microorganisms relate to the likelihood of disease?
the more the merrier...more pathogens means increased likelihood of disease
Some microorganisms can gain access to the body when they are deposited directly into the tissues beneath the skin or into mucous membranes when these barriers are penetrated or injured. This route is called _________
the parenteral route ex, tetanus, gangrene
some pathogens have capsules that prevent __________. Which pathogens have this?
the pathogens from being phagocytized. Streptococcus (S. pyogenes for sure), pseudomonas, Escherichia, bordetella, Haemophilus influenzae, Bacillus anthrasis
The most common portals of exit are....
the respiratory and gastrointestinal tracts.
What do capsules/IgA proteases/antigenic variation/coagulase/M protein/Mycolic acid all have in common?
they are components that help microorganisms escape phagocytosis by the host cell
What is the portal of entry for Giardiasis which causes Giardia lamblia?
through the GI tract..dirty water
___________ refers to the presence of toxins in the blood
toxemia
The capacity of a microorganism to produce a toxin. Prev
toxigenicity
the capacity of microorganisms to produce toxins is called ___________
toxigenicity
Any poisonous substance produced by a microorganism. Prev
toxin
___________ are poisonous substances that are produced by certain microorganisms
toxins
How do microorganisms gain access to the GI tract?
via food and water and contaminated fingers
_________ is the degree of pathogenicity
virulence is the degree of pathogenicity, which is the ability of a pathogen to produce a disease by overcoming defenses of the host.
When are endotoxins released? What about exotoxins?
when gram-neg bacteria die and their cell walls undergo lysis, thus liberating the endotoxin OR also released during bacterial multiplication (compare to exotoxins, produced inside some bacteria as part of their growth and metabolism and secreted into surrounding medium or released following lysis)
Can non pathogenic bacteria produce capsules?
yes
