lecture 13
Attenuated vaccines cause a weaker immune response than killed vaccines. T or F?
False
Virulence genes may be located on mobile genetic elements. T or F?
True
An attenuated strain of a pathogen a) has lost its virulence, but may be used to create a vaccine. b) has changed its antigens to avoid an adaptive immune response. c) is more virulent than the regular strains and may cause septic shock. d) is an extracellular pathogen that will be cleared by innate immunity.
a)
Clostridium perfringens causes gas gangrene, a serious infection of the muscle tissues that can lead to amputation. Clostridium are Gram-positive endospore-formers and obligate anaerobes that are killed when exposed to oxygen. Which of the following virulence factors would be most helpful to this organism in establishing an infection? a) collagenase, an enzyme that destroys collagen, which is a major protein of connective tissues b) endotoxin c) nuclease, an enzyme that breaks down nucleic acids d) a neurotoxin
a)
Staphylococcus aureus produces ________, leading to fibrin clots that protect them from attack by host cells. a) coagulase b) collagenase c) lipase d) amylase
a)
What is the difference between adherence and colonization? a) Colonization occurs when a microbe begins to grow in host tissues whereas adherence occurs when the microbe initially attaches. b) Colonization occurs when microbes begin to spread in host tissues, whereas adherence occurs when microbes first begin to reproduce in the host tissues. c) Colonization occurs when transient microbes are on a tissue, whereas adherence is a more permanent attachment to cells. d) Colonization occurs when microbes begin to spread in host tissues, whereas adherence occurs when microbes initially attach.
a)
When a person has previously been vaccinated against a viral pathogen, which cells are activated if that same pathogen re-enters the host's cells months or years later? a) Memory cytotoxic T cells b) Helper T cells c) Memory B cells
a)
Which of the following is a major growth-limiting micronutrient that influences microbial growth? a) iron b) water c) vitamin K d) sugar
a)
Which of the following is a reason that specific pathogens tend to infect specific tissues? a) There are chemical and physical differences between tissues. b) Tissues with neutral pH are colonized but those with acidic or alkaline pH are not. c) Microbes preferentially target external tissues, such as skin, as the environment is more favorable for their growth than inside the body. d) Some tissues have receptors for microbes, but others do not.
a)
Which of the following microorganisms actually grows inside the macrophage? a) Tuberculosis bacterium b) Leishmania c) Shigella d) Streptococcus pneumoniae e) Legionella
a)
________ in saliva cleaves glycosidic linkages in the peptidoglycan that is present in bacterial cell walls, weakening the wall and potentially causing cell lysis. a) Lysozyme b) Fibrin c) Lipid A d) Mucus
a)
Cytolytic toxins a) are extracellular proteins. b) are extracellular proteins that cause cell lysis and death by damaging the host cytoplasmic membrane. c) damage host cytoplasmic membrane. d) cause cell lysis and death.
b)
The condition that results when some bacteria are shed in the bloodstream and distributed to distant parts of the body but do not reproduce in the blood is called a) erythemia. b) bacteremia. c) septicemia. d) uremia.
b)
A pathogen must __________ in order for it to cause disease. a) enter a host b) secrete a toxin c) attach and multiply d) attach
c)
endotoxin
A toxic component of the outer membrane of certain gram-negative bacteria that is released only when the bacteria die. Lipid A portion of LPS triggers release of IL-1 by hypothalamus. causes fever dangerous if concentration of endotoxin is high in the bloodstream. lowers blood pressure to dangerous level
T or F: A toxoid is an attenuated form of a toxin that retains both its antigenicity and toxicity.
False
how does diphtheria toxin work?
It is an A-B toxin and enterotoxin 1. B part binding to cell membrane 2. B is cleaved and A is internalized 3. A catalyzes ADP-ribosylation of EF-2 into EF-2+(irregular form) which no longer polymerizes amino acids.
superantigens
cause excessive immune response- proliferation of T cells T cells release excessive amount of cytokines which cause fever, shock stephylococcus aureus and food poisoning
Cytolytic toxins
form protein pores in cytoplasmic membrane or disrupt phospholipid portion of membrane the cell dies
toxoid
inactivated toxin used in a vaccine
exotoxin classification by location
neurotoxin: effect neurons enterotoxin: enter intestines cytotoxin: generally cause severe damage (ex. inhibit protein synthesis)
The ability to cause disease is called _____.
pathogenicity
how does streptococcus pyogenes able to penetrate into tissue?
streptococcus pyogenes produce hyaluronidase hyaluronidase dissolves the hyaluronic acid that adheres epithelial cells they penetrate deeper into the tissue
Which disease CANNOT be prevented via the use of a vaccine generated from an attenuated pathogen? a) malaria b) measles c) mumps d) rubella
a)
how does cholera entertoxin work?
1. normal ion movement, Na+ from lumen to bloodm not net Cl- movement 2. infection and toxin production by V. cholerae 3. activation of epithelial adenylate cyclase by cholera toxin 4. elevated cAMP blocks Na+; net anion movement to intestinal lumen 5. massive water movement to the lumen and ion loss trigger cholera symptoms.
exotoxin classification by function and structure
AB toxin membrane disruption superantigen
AB toxin
An exotoxin composed of two subunits. The toxic A subunit is delivered to the host cell by the B subunit. B domain attaches to the cell receptor inhibit protein synthesis or interfere with host cytoskeleton
HIV infection causes immunosuppression because it causes the destruction of CD4 lymphocytes. a) True b) False
True
T or F: DNA vaccines are bacterial plasmids that contain cloned DNA with an antigen of interest are unlike attenuated vaccines because there is no chance of causing disease.
True
A patient is brought to the hospital with severe gastrointestinal distress, including cramps, dehydration and diarrhea. Which of the following symptoms would indicate that the pathogen is Vibrio cholerae? a) bloody, foul smelling diarrhea b) voluminous watery diarrhea c) frequent vomiting d) occasional diarrhea but no blood in the stool
b)
Epithelial cells lining the respiratory tract form a a) impenetrable barrier to infection. b) mucous membrane. c) dry and rigid barrier with tight junctions between cells. d) connective tissue layer.
b)
How does a capsule help certain bacteria evade detection by the immune system? a) The capsule makes the bacterium too sticky to be phagocytosed by the immune cells. b) The capsule is composed of polysaccharides that are similar to those found in the host; thus, the immune system does not recognize it as foreign. c) Capsules have the ability to destroy antibodies secreted by the immune system. d) Capsules allow the bacteria to stick together, creating a larger mass that is too big for immune cells to engulf.
b)
How does the protozoan Trypanosoma evade detection by the immune system? a) It can resist oxidation inside macrophages. b) It can change the surface antigens frequently, preventing the immune system from tracking it. c) It prevents phagosome-lysosome fusion. d) It produces a capsule which is composed of polysaccharides similar to those found in the host.
b)
It is thought that attenuation occurs especially in a laboratory setting because a) pathogens lose virulence with age and survive longer in laboratory cultures. b) nonvirulent or weakly virulent mutants grow faster in laboratory media when there is no selective advantage to virulence. c) there is selection for more virulent strains in the laboratory. d) patients can be treated with drugs that induce attenuation.
b)
Shiga toxin is an enterotoxin that is produced by a) Vibrio cholerae. b) Shigella dysenteriae. c) Clostridium tetani. d) Escherichia coli O157:H7.
b)
The diphtheria exotoxin is an A-B toxin that __________. a) causes host cell lysis b) is found only in Corynebacterium diphtheriae cells that have been infected with lysogenic bacteriophage β c) is found in all Corynebacterium diphtheriae cells d) is encoded for by genes in the chromosome of Corynebacterium diphtheriae cells
b)
What is the etiologic agent of typhoid? a) Shigella b) Salmonella c) E. coli
b)
Which of the following is NOT an example of an AB toxin? a) shiga-like toxin b) hemolysins c) tetanus toxin d) botulinum toxin
b)
R plasmids help prevent the spread of virulence factors. a) True b) False
b) R plasmids often contain Resistance genes
The macromolecules responsible for bacterial adherence that are NOT covalently attached to bacteria are collectively called a) biofilms. b) glycocalyx. c) capsules. d) lipid A.
b) glycocalyx: carbohydrate-enriched coating that covers eukaryotic and prokaryotic cells. on eukaryotic cells, glycocalyx is used for recognition of the cell. on bacterial cells, it provides a protective coat.________ are toxic proteins released from the pathogen during normal growth.
A patient admitted to the hospital with muscle weakness and paralysis is put on a ventilator because of breathing difficulties. It is determined that the symptoms are the result of a bacterial exotoxin. Which of the following is the most likely source of this toxin? a) airborne bacteria b) canned food c) contaminated water d) a puncture wound
b) correct incorrect answer reasons: a) This disease can be acquired by ingesting the toxin alone, and the bacteria are generally found in the soil. c) The organism causing this disease is generally found in soil, not in water. d) Tetanus is usually the result of a puncture wound. What are the symptoms of tetanus?
Compared with an endotoxin, would a bacterial exotoxin generally be more likely to function after it had been significantly heated? a) No, because exotoxins are carbohydrates and endotoxins are proteins. b) Yes, because exotoxins are proteins and non-living but endotoxins are part of the bacterial cell wall. c) No, because exotoxins are heat-labile and less resistant to heating than endotoxins. d) Yes, because exotoxins are very heat stable compared to endotoxins.
c)
How can capsules enable bacteria to evade the immune system? a) A capsule is a superantigen that distracts the immune system. b) Capsules can bind up IgA, rendering it inactive. c) Capsules block the complement biding sites on the surface of the pathogen.
c)
How do superantigens enable pathogens to hide from the immune system if they actually stimulate the immune system? a) They cause fever, which destroys the complement proteins. b) They cause the immune system to destroy IgA antibodies. c) They cause the immune system to produce an exaggerated response, distracting it from the actual pathogen. d) They cause the immune system to turn on itself.
c)
Pathogenicity and virulence differ in that a) virulence only refers to pathogens, whereas pathogenicity refers to any microbe that can cause an infection. b) pathogenicity only refers to pathogens, whereas virulence refers to any microbe that can cause an infection. c) pathogenicity refers to the overall ability of a microbe to cause disease, whereas virulence refers to the ability of one microbe to cause disease relative to another. d) virulence refers to the overall ability of a microbe to cause disease, whereas pathogenicity refers to the ability of one microbe to cause disease relative to another.
c)
Pathogenicity is the ability a) of the host to resist damage by the pathogen. b) of the host to inflict damage on the pathogen. c) of the pathogen to inflict damage on the host. d) None of these are correct.
c)
Staphylococcus aureus and Streptococcus pyogenes strains can produce ________ that cause the severe and sometimes life-threatening symptoms of toxic shock syndrome. a) cytolytic b) AB toxins c) superantigen toxins d) endotoxin
c)
Why are secondary or booster reimmunizations given? a) Secondary reimmunizations produce a phagocytic immune response that is longer lasting than the primary immune response. b) Secondary immunizations are necessary for an innate immune response. c) Secondary reimmunizations produce a secondary immune response and boost antibody titers. d) Frequent secondary reimmunizations are needed because the immune system doesnt remember antigens for more than a few years.
c)
________ are toxic proteins released from the pathogen during normal growth. a) Microtoxins b) Endotoxins c) Exotoxins d) Macrotoxins
c)
One way to test if someone has immunity to a particular pathogen is to measure the antibody titer. What does it mean if someone has a positive antibody titer? a) They must not have been exposed to the pathogen previously, meaning that they were able to rapidly produce antibodies. b) Previous exposure to the pathogen has caused T cells to attack the pathogen, leading to a more rapid response by T cells upon repeat exposure. c) Previous exposure to the pathogen (or through a vaccination) has caused B cells to produce memory B cells. When re-exposed to the pathogen, they rapidly produce antibodies against the antigen (resulting in a positive antibody titer). d) They must not have been exposed to the pathogen previously, meaning that they were not able to rapidly produce antibodies.
correct: c) incorrect answers reason b) antibody titer is based on looking at antibody-antigen reactions, not at T cell response
A researcher wanted to determine the LD50 (lethal dose that kills 50% of the infected hosts) for a newly isolated bacterial pathogen. Mice were inoculated with diluted cultures containing between 101 and 107 cells. After two days, all of the mice had died EXCEPT for the uninoculated controls. Which of the following is the most likely explanation? a) The pathogen has become attenuated. b) The pathogen has a very high LD50. c) Mice are not good model animals for this pathogen. d) This pathogen is highly virulent in mice.
d)
An exotoxin that has the ability to kill or damage host cells is referred to as a(n) a) neurotoxin. b) A-B toxin. c) enterotoxin. d) cytotoxin. e)superantigen.
d)
Diptheria toxin is a a) cytolytic toxin. b) type of endotoxin. c) superantigen toxin. d) AB toxin.
d)
Exotoxins are ________, but endotoxins are ________. a) lipids / proteins b) lipopolysaccharide-lipoprotein complexes / proteins c) carbohydrates / proteins d) proteins / lipopolysaccharide-lipoprotein complexes
d)
Measles viruses are capable of inactivating host defenses by a) producing superantigens. b) destroying complement proteins. c) producing leukocidins. d) suppressing the immune system.
d)
Septicemia is an example of a a) autoimmune infection. b) transient infection. c) localized infection. d) systemic infection.
d)
Tetanus toxin causes a) severe diarrhea. b) muscles to be unable to contract. c) hemolytic uremic syndrome. d) muscles to be unable to relax.
d)
Where is the site of Shigella attachment in the host? a) Leukocytes b) Intestinal epithelial cells c) Phagocytes d) M cells
d)
