Ch 15 study guide Microbial Mechanisms of Pathogenicity Flashcards
Pathogenicity
the ability to cause disease
Virulence
the severity or harmfulness of a disease
why is virulence important?
virulence is how dangerous/deadly a pathogen is
(the degree of pathogenicity)
How are capsules and cell wall components related to pathogenicity? Give specific examples.
Encapsulated bacteria can resist phagocytosis and continue growing.
Which of these is NOT how bacteria penetrate host defenses?
Capsule
Cell wall components
Enzymes
Myocotoxins
Myocotoxins
because its a fungi, not a bacteria
Describe how hemolysins might contribute to pathogenicity
Hemolysins lyse red blood cells; hemolysis might supply nutrients for bacterial growth
Describe how leukocidins might contribute to pathogenicity
Leukocidins destroy neutrophils and macrophages that are active in phagocytosis; this decreases host resistance to infection.
Describe how coagulase might contribute to pathogenicity
Coagulase causes fibrinogen in blood to clot;
the clot may protect the bacterium from phagocytosis and other host defenses.
Describe how kinases might contribute to pathogenicity
kinases break down fibrin;
kinases can destroy a clot that was made to isolate the bacteria, thus allowing the bacteria to spread.
Describe how hyaluronidase might contribute to pathogenicity
hydrolyses hyaluronic acid which holds together connective tissue, allowing for the organism to spread and also causes tissue blackening
Describe how siderophores might contribute to pathogenicity
Siderophores take iron from host iron-transport proteins, thus allowing bacteria to get iron for growth.
what is the effect of collagenase and how it assists with survival of pathogens within the human body?
breaks down collagen which allows for the spread of gas gangrene
Describe how IgA proteases might contribute to pathogenicity
destroys IgA antibodies which helps to inhibit immune response
Which of the following is not a portal of entry for pathogens?
- mucous membranes of the respiratory tract
- mucous membranes of the gastrointestinal tract
- skin
- blood
- parenteral route
Blood
An encapsulated bacterium can be virulent because the capsule
- resists phagocytosis
- is an endotoxin
- destroys host tissues
- kills host cells
- has no effect
resists phagocytosis
The earliest smallpox vaccines were infected tissue rubbed into the skin of a healthy person. The recipient of such a vaccine usually developed a mild case of smallpox, recovered, and was immune thereafter. What is the most likely reason this vaccine did not kill more people?
- skin is the wrong portal of entry for smallpox.
- The vaccine consisted of a mild form of the virus.
- Smallpox is normally transmitted by skin-to-skin contact.
- Smallpox is a virus.
- The virus mutated.
skin is the wrong portal of entry for smallpox
Tell me what you learned about horseshoe crabs and limulus amebocyte lysate assay? (LAL)
- Horseshoe crabs produce amebocytes that contain Factor C, which coagulates endotoxin found within Gram NEGATIVE bacteria
- Every vaccine was first tested with LAL
What are the major routes of microbial entry?
- Mucous membranes
- Skin
- Parenteral route
- Preferred portal of entry
What type of action exposes microbes to each specific mucous membrane? (Ex. Food/water for GI tract)
Why is the preferred route important?
certain bacteria cannot survive on/in some regions of the body but can flourish in other
ex, Salmonella typhi causes typhoid fever if swallowed (preferred route). If it is rubbed on skin, no problems occur.
What is the definition of ID50?
infectious dose for 50% of a sample population
Measures virulence of a microbe
What is the definition of LD50?
lethal dose for 50% of a sample population
Measures potency of a toxin
The lower the ID, the more or less virulent?
the lower the ID, the more virulent it is
How do capsules help bacteria evade the immune system?
Prevents phagocytic cell from adhering to
the bacterium
If a bacteria has a capsule, is it virulent or avirulent? Vice versa?
capsule = virulent
no capsule = avirulent
Know the examples of enzymes that facilitate microbial colonization of the human body * Both the direct effect and how it assists with survival.
Know the three ways by which bacteria can damage host cells
- Using host’s nutrients
- Causing direct damage in the immediate vicinity of the invasion
- Producing toxins, transported by blood and lymph, that damage sites far removed from infection
What is hemolysin?
Hemolysin is a membrane-disrupting toxin produced by certain bacteria that lyse red blood cells
kill erythrocytes by forming protein channels
What is the major reason why bacteria utilize hemolysin?
Bacteria utilize this toxin to help invade the host more while being able to steal the iron from RBCs
Why do bacteria kill red blood cells?
to better outcompete for iron nutrients
What is a siderophore?
proteins secreted by pathogens that bind iron more tightly than host cells
What is the only example of an endotoxin?
Lipid A is the only endotoxin, found in the Gram - Cell wall
Which type of bacteria produces endotoxin?
Gram negative bacteria
Which type of bacteria is most likely to secrete exotoxins?
Both Gram-negative and Gram-positive bacteria produce exotoxins
but Gram + is more likely to release exotoxins
Know the mechanisms of the three types of exotoxins without knowing specific examples
Type I: Superantigens
Type II: Membrane-Disrupting Toxins
Type III: A-B Toxins
A-B Toxins
contain an enzyme component (A part)
and a binding component (B part)
Most exotoxins are A-B
toxins
Membrane-Disrupting Toxins
lyse host cells by
disrupting plasma membranes
What are Superantigens?
what ailment do they cause?
cause an intense immune response due to
release of cytokines from host cells (T cells)
Cause symptoms of fever, nausea, vomiting, diarrhea,
shock, and death
Which 6 toxins were fungal instead of bacterial?
ergot
aflatoxin
mycotoxin
phalloidin
amanitin
lysergic acid diethlylamide(LSD)
Know what LAL is and why it is important to the pharmaceutical industry. (hint: horseshoe crabs)
Limulus amebocyte lysate (LAL) assay found in horseshoe crab blood
used to detect the presence and concentration of bacterial endotoxins in drugs and biological products
What is the most toxic bacterial exotoxin?
Botulinium toxin (AB toxin) reaslesed from Clostridium botulinium
What are the three major routes of microbial entry?
mucus membranes
skin
parenteral route
how can microbes gain entry through our mucus membranes?
through the respiratory tract (breathing)
gastrointestinal tract (swallowing)
genitourinary tract (urethra)
conjunctive (eyes)
how can microbes gain entry through our skin?
hair follicles
sweat glands
how can microbes gain entry through our parenteral route?
microbes get put directly into skin (via puncture wounds)
What is the number 1 portal of microbial entry?
mucus membranes
