(exam 2) ch 15 microbial mechanisms of pathogenicity Flashcards
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.
_________ is the ability to cause disease (by overcoming defenses of host)
pathogeniticy
pathogenicity is ___________
the ability to cause disease (by overcoming defenses of host)
_____________ is the degree of pathogenicity
virulence
What happens when microbes overpower the host defenses?
disease results!
in order to cause disease, pathogens must do what 5 things?
- gain access to host
- adhere to host tissue
- penetrate or evade host defenses
- damage host tissues
- accumulate waste products
pathogens can gain entrance to the human body and other hosts through several avenues which are called ____________.
portals of entry
what are three portals of entry in which pathogens can enter a host?
1) Mucous membranes= typically through respiratory and gastrointestinal tract
2) Skin
3) Parenteral route= deposited directly into tissues when barriers are penetrated
(Punctures, injections, bites, etc.)
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.
How does the # of invading microorganisms relate to the likelihood of disease?
the more the merrier…more pathogens means increased likelihood of disease
How can you express the virulence of a microbe?
ID50 “infectious dose for 50% of a sample population”
How can you express the potency of a toxin?
LD50 “lethal dose for 50% of a sample population”
Almost all pathogens can _______ to host tissues at their portal of entry.
attach themselves i.e. “adherence” or “adhesion”
the attachment between pathogen and host is accomplished by means of ___________.
adhesins or ligands, which are surface molecules (either on Glycocalyx or Fimbriae) on the pathogen that bind specifically to complementary surface receptors on cells of certain host tissues.
What are adhesins or ligands?
surface molecules on pathogen that bind to a host cell and allow for adherence to occur, i.e. attachment of pathogen to host at portal of entry, which is usually a necessary step in pathogenicity)
Where on a microbe may adhesions be located?
mainly on the glycocalyx and fimbriae
this property of adherence and adhesions allow for the formation of what?
biofilms
Capsules are formed out of _____________.
glycocalyx material which surround the cell wall
what is the main function of capsules?
they impair phagocytosis
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!
3 key factors in entrance?
- portal of entry where microbe can colonize (mucous membrane/skin/parenteral routes)
- attachment btw microbes and the host cell (adhesins/ligands)
- the # of microbes; the more the merrier
The cell walls of certain bacteria contain components that contribute to its ability to invade a host/virulance. These 3 cell wall components include:
- M protein
- Opa protein and fimbriae
- waxy lipids (mycolic acid)
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. I contribute to virulence. What am I?
M Protein
Immunity to S. pyogenes depends on the body’s production of an antibody specific to __________
M Protein
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
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)
what is the purpose of the cell wall component Opa protein and fimbriae?
found specifically on Neisseria gonorrhoeae (which is found in humans) and allows for attachment to host cells
What does Mycobacterium tuberculosis have that can increase its virulence?
waxy lipids (mycolic acid) helps resist digestion by phagocytes
___________are bacterial enzymes that clot the fibrinogen in blood.
coagulases
What is coagulase and what is its relationship to virulence?
It is a 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
__________ are bacterial enzymes that break down fibrin and thus digest clots formed by the body to isolate the infection.
kinases
what are kinases and what are their relation to virulence?
they are bacterial enzymes that break down fibrin and thus digest clots formed by body to isolate infection
__________ is an enzyme that digests polysaccharides that holds cells together- this digestion is associated with blackening tissue in wounds.
Hyaluronidase
What is Hyaluronidase?
enzyme secreted that hydrolyzes (breaks down) polysaccharides; this digestion action helps the microorganism spread from its initial site of infection.
-can also be involved in blackening of tissue at infected wound sites
______ is an enzyme produced that breaks down collagen which is one of the main structural proteins in connective tissues.
collagenase
What does collagenase do?
enzyme produced that
breaks down collagen protein (which forms connective tissue of body organs/muscles/tissues)
__________ are enzymes that can destroy antibodies; defense against adherence of pathogens to mucosal surfaces.
IgA proteases
What are IgA proteases?
enzymes that can destroy IgA antibodies which are produced by the body as a defense against adherence of pathogens to mucosal surfaces (saves bacterial adherence process from immune system of host)
What is antigenic variation? Who does this?
a process by which some pathogens can alter their surface antigens, so by the time the body mounts an immune response against the pathogen, it has already altered its antigens and is unaffected by the antibodies (because the antibodies do not recognize the different surface antigens), which are supposed to bind to the antigens and inactivate/destroy them
__________ 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!
why are biofilm bacteria more resistant to phagocytosis?
because they are shielded by extracellular polymeric substance (EPS) of biofilm- and phagocytes (cells of the immune system) have difficulty moving throug EPS
What are invasins?
What are invasins?
bacterial surface proteins that rearrange actin filaments of the cytoskeleton which cause membrane ruffling
invasins use actin to move from one cell to the next
Explain one way a pathogen can cause damage to a host is by using its nutrients.
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
What are siderophores?
Iron is required for most pathogenic bacteria. So siderophores are proteins secreted by pathogens that bind to iron more tightly than host cells (steals iron from host cell)
What are four ways that pathogens can cause direct damage to a host?
1) disrupts host cell function
2) uses host cell nutrients
3) produces waste products
4) multiplies in host cells and causes ruptures
the ability of microorganisms to produce toxins is called ___________.
toxigenicity
___________ refers to the presence of toxins in the host’s blood.
toxemia
__________ are poisonous substances that are produced by certain microorganisms.
toxins
____________ are presence of toxin without microbial growth.
intoxications
what signs and symptoms do toxins commonly produce?
fever, cardiovascular problems, diarrhea and toxic shock
what are two main types of toxins?
1) exotoxins
2) endotoxins
______________ are proteins produced inside pathogenic bacteria (commonly gram positive as part of their growth and metabolism); soluble in bodily fluids so they are easy to diffuse into the blood and spread.
exotoxins
_________ are lipid portions of lipopolysachharides (LPS) that are part of the outer membrane of the cell wall of gram negative bacteria (LIPID A).
they are released during bacterial multiplication and when the gram negative bacteria die.
endotoxins
because of the ____________ nature of most exotoxins, even small amounts are quite harmful (most lethal substances known)
enzymatic nature.
remember, exotoxins are proteins, many are enzymes that catalyze certain biochemical rxns- so these exotoxins can function again and again.
Where are the genes for most exotoxins carried?
on bacterial plasmids or phages
what are toxoids?
Inactivated exotoxins used in vaccines (they no longer cause disease but can still stimulate the body to produce antitoxins)
Ex: Diphtheria and tetanus vaccines!
Diseases are often caused by _________________ and not bacterial infection.
toxins. signs and symptoms experiences are directly due to toxin
what are antitoxins?
antibodies against specific exotoxins
Exotoxins are divided into three main types on the basis of their structure and function…
- A-B toxins
- Membrane-disrupting toxins
- Superantigens
what are A-B toxins and what is one type we are discussing?
(type of exotoxin)
contains an enzyme component (A part) and a binding component (B part)
Ex: Genotoxins
What are genotoxins?
(type of exotoxins; A-B toxins) which damage DNA (causing mutations, disrupting cell division, leading to cancer)
what are membrane disrupting toxins and what do they do?
(type of exotoxin) that lyse host cells by disrupting plasma membranes
what are three kinds of membrane disrupting toxins?
1) Leukocidins
2) Hemolysins
3) Streptolysins
what are Leukocidins?
(type of exotoxins; membrane disrupting toxins) kill phagocytic leukocytes
what are Hemolysins?
(type of exotoxins; membrane disrupting toxins) kill erythrocytes by forming protein channels
what are streptolysins?
(type of exotoxins; membrane disrupting toxins) hemolysis produced by streptococci
What are superantigens?
type of exotoxin that causes an intense immune response due to release of cytokines from host (T cells)
cause symptoms of fever, nausea, vomiting, diarrhea, shock, and death
What part of gram neg cell is the endotoxin?
the lipid portion of the Lipopolysachharide Lipid A
when are endotoxins released?
released during bacterial multiplication and when gram negative bacteria die
what symptoms do endotoxins cause?
chills, fever, aches, and weakness
productions of endotoxins can cause shock, which is?
life threatening decrease in blood pressure
what causes septic shock?
caused by bacteria / endotoxic shock
what is used to test for endotoxins?
Limulus amebocyte lysate (LAL) assay which uses blood of horseshoe crabs which contains anebocytes which can lyse in the presence of endotoxin, producing a clot
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)
The two most common portals of exit are….
the respiratory and gastrointestinal tracts
When the balance between host and microbe is tipped in favor of the microbe ____________ results.
an infectious disease
how do plasmids damage host cells?
plasmids carry genes for toxins (R factors), production of antibiotics, and enzymes
how does lysogeny damage host cells?
lysogenic conversion changes characteristics of a microbe due to incorporation of prophage
what is the main viral mechanism for evading host defenses?
grow inside the host cells so that the immune cells cannot reach them
what are cytopathic effects of viruses (CPE)?
visible effects of infection; used to diagnose infections; these effects vary depending on the virus (key different is point in infection when these effects occur)
what are cytocidal effects do?
kill cells
how is creating inclusion bodies in the cell cytoplasm a cytopathic effect of viruses (CPE)?
these inclusion bodies (Nergi body) are very diagnostic and can help identify causative agent
how is fusing cells to create a syncytium a cytopathic effect of viruses (CPE)?
the cytoplasmic mass (syncytium) shows cells mashed together into one massive cell
how are inducing antigenic changes on cell surface a cytopathic effect of viruses (CPE)?
this often leads to the destruction of the host cell
how is changing cell function or inducing chromosomal changes a cytopathic effect of viruses (CPE)?
this can often lead to the activation of oncogenes which can be cancer causing
how is loss of contact inhibition in the cell a cytopathic effect of viruses (CPE)?
because loss of contact inhibition in the cell is tumorigenic (massive, uncontrolled cell growth) which leads to cancer
how is the ability of pathogens to block alpha and beta interferons a cytopathic effect of viruses (CPE)?
alpha and beta interferons are produced by virally-infected cells and protect neighboring cells from viral infection (inhibit synthesis of viral proteins and host cell proteins and kill virus infected host cells by apoptosis; many viruses are able to BLOCK their protection
Exotoxins are produced by bacteria and released into surrounding medium. What causes disease symptoms?
exotoxins, not the bacteria itself
Antibodies produced against exotoxins are called ____________.
antitoxins
toxic shock syndrome is a result of?
S. aureus makes superantigens, cause release of cytokines which cause fever, nausea and other symptoms
what structure in fungi give it pathogenic properties to prevent phagocytosis?
capsules
what are some toxic metabolic products of fungi?
mushrooms produce mycotoxins which are neurotoxic
I am a mycotoxin of fungi and I inhibit protein synthesis, which toxin am I?
Trichothecene
I am a mycotoxin of fungi and I am an alkaloid toxin that cause hallucinations, which toxin am I?
Ergot
I am a mycotoxin of fungi and I am a carcinogenic toxin produced by Aspergillus, which toxin am I?
Aflatoxin
what are three ways that protozoa avoid host defenses?
1) Digesting cells and tissue fluids
2) growing in phagocytes
3) antigenic variation
I use host tissues for growth, produce large masses and cause cellular damage; And produce waste products that cause symptoms. What am I?
Helminths (parasitic worms)
__________________ is the neurotoxin produced by some algae which causes paralytic shellfish poisoning.
saxitoxin
coughing and sneezing are examples of pathogens leaving which portal of exit?
the respiratory tract
feces and saliva are examples of pathogens leaving which portal of exit?
gastrointestinal tract
urine and secretions from the penis and vagina are examples of pathogens leaving which portal of exit?
genitourinary tract
pus and skin secretions are examples of pathogens leaving which portal of exit?
the skin
through arthropods that bite; needles or syringes - are examples of pathogens leaving which portal of exit?
through the blood
