***Microbiology Chapter 15***

25 July 2022
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question
What do hyaluronidase and kinase have in common?
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They are both enzymes involved in evading host defense.
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According to your Concept Map, which of the following organisms exhibits antigenic variation?
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N. gonorrheae
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Which of the following virulence factors could directly prevent phagocytosis and/or phagocytic degradation?
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all of the above
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How are immune cells able to detect foreign pathogens?
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They are able to detect structures on the surfaces of foreign cells that are not found in the host.
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How does a capsule help certain bacteria evade detection by the immune system?
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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.
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Which of the following microorganisms actually grows inside the macrophage?
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Tuberculosis bacterium
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How does the protozoan Trypanosoma evade detection by the immune system?
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It can change the surface antigens frequently, preventing the immune system from tracking it.
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What are leukocidins?
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Molecules that are capable of destroying phagocytes
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Measles viruses are capable of inactivating host defenses by
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suppressing the immune system.
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Meningitis and gonorrhea are caused by
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Neisseria species.
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How do superantigens enable pathogens to hide from the immune system if they actually stimulate the immune system?
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They cause the immune system to produce an exaggerated response, distracting it from the actual pathogen.
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How can capsules enable bacteria to evade the immune system?
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Capsules block the complement biding sites on the surface of the pathogen.
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Endotoxins are also known as
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Lipid A.
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When would endotoxins be released from a bacterial cell?
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When the cell dies
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Which of the following would be the first sign of an infection that resulted in the release of endotoxin?
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Fever
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Why is a release of endotoxin into the bloodstream potentially deadly?
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It can lower blood pressure and cause the patient to go into shock.
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An exotoxin that has the ability to kill or damage host cells is referred to as a(n)
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cytotoxin.
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Which domain of the A-B toxin binds to cell surface receptors on the host cell?
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B domain
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How are superantigens different from other types of exotoxins?
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Superantigens cause an overstimulation of the host immune system.
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A person who attended a picnic early in the day develops a very high fever and is unresponsive by the evening. This person most likely has been exposed to a(n)
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superantigen.
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A patient who has been hospitalized with uncontrolled muscle spasms has probably been infected with bacteria that secrete a(n)
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neurotoxin.
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In mice, the LD50 for staphylococcal enterotoxin is 1350 ng/kg, and the LD50 for Shiga toxin is 250 ng/kg. Which of the following statements is true?
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Shiga toxin is more lethal than staphylococcal enterotoxin.
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Which of the following would be an example of an infection initiated via the parenteral route?
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An individual contracts hepatitis B from an accidental stick with a contaminated needle.
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Which statement regarding endotoxins is true?
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One consequence of endotoxins is the activation of blood-clotting proteins.
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Which type of bacterial enzyme helps spread Streptococcus pyogenes by digesting blood clots?
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fibrinolysin
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In which of the following cases would the Limulus amebocyte lysate (LAL) assay be used?
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to ensure that a sterilized medical device is free of endotoxin
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Which of the following statements about adherence is true?
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Most bacterial adhesins are glycoproteins or lipoproteins.
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Which of the following toxins and does NOT match the description?
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Vibrio enterotoxin: a superantigen that destroys epithelial cells
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Which disease would be potentially propagated in an environment without functional plumbing and in which drinking water is contaminated with sewage?
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cholera
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Which of the following statements about lysogenic conversion is true?
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Exotoxin production by bacteria is frequently the result of a lysogenic infection.
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Which of the following features of Salmonella prevent it from being phagocytosed?
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Flagella
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Where do Salmonella pathogens grow and replicate in the infected host?
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Inside phagocytes
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Where is the site of Shigella attachment in the host?
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M cells
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How do Shigella cells move between host cells?
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They can polymerize actin molecules from the epithelial cells into tail-like structures that propel them from one cell to another.
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What is the etiologic agent of typhoid?
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Salmonella
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Certain traits that allow pathogens to create infection and cause disease are termed
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virulence factors.
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Which of the following enzymes breaks down the "glue" that holds cells together?
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Hyaluronidase
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Which of the following virulence factors would be found in Staphylococcus aureus?
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Staphylokinase
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How do fibrinolysins enhance a pathogen's virulence?
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They break down fibrin proteins that are involved in clot formation, allowing the cells to penetrate deep into damaged skin.
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Which of the following is NOT a cytopathic effect (CPE) of viruses?
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All of the above are possible CPE.
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The most frequently used portal of entry for pathogens is the
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mucous membranes of the respiratory tract.
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The ability of some microbes, such as Trypanosoma or Giardia to alter their surface molecules and evade destruction by the hosts antibodies is called
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antigenic variation.
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Most pathogens that gain access through the skin
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enter through hair follicles and sweat ducts.
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All of the following contribute to a pathogens invasiveness EXCEPT
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toxins
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The ID50 is
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the dose that will cause an infection in 50 percent of the test population.
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Which of the following statements is FALSE?
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Coagulase destroys blood clots.
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Which of the following is NOT a membrane-disrupting toxin?
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A-B toxin
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Which of the following statements about exotoxins is generally FALSE?
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They are resistant to heat.
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Endotoxins are
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part of the gram-negative cell wall.
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Cytopathic effects are changes in host cells due to
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viral infections.
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Which of the following does NOT contribute to the symptoms of a fungal disease?
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cell walls
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All of the following are methods of avoiding host antibodies EXCEPT
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membrane-disrupting toxins.
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Siderophores are bacterial proteins that compete with the host's
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iron-transport proteins.
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The fimbriae of Neisseria gonorrhea and enteropathogenic E. coli are examples of
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adhesins and ligands.
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All of the following are examples of entry via the parenteral route EXCEPT
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hair follicle.
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Superantigens produce intense immune responses by stimulating lymphocytes to produce
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cytokines
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Botulism is caused by ingestion of a proteinaceous exotoxin; therefore, it can easily be prevented by
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boiling food prior to consumption.
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All of the following organisms produce exotoxins EXCEPT
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Salmonella typhi.
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Which of the following cytopathic effects is cytocidal?
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release of enzymes from lysosomes
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All of the following are used by bacteria to attach to host cells EXCEPT
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A-B toxins.
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Symptoms of protozoan and helminthic diseases are due to
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tissue damage due to growth of the parasite on the tissues, waste products excreted by the parasite, and products released from damaged tissues.
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Which of the following statements about staphylococcal enterotoxin is FALSE?
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It is produced by Staphylococcus aureus growing in the host's intestines.
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Which of the following contributes to the virulence of a pathogen?
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numbers of microorganisms that gain access to a host, evasion of host defenses, and toxin production
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Lysogenic bacteriophages contribute to bacterial virulence because bacteriophages
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give new gene sequences to the host bacteria.
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Twenty-five people developed symptoms of nausea, vomiting, and diarrhea three to six hours after attending a church picnic where they ate a ham and green bean casserole with cream sauce. The most likely cause of this case of food intoxication is
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erythrogenic toxin.
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Which of the following statements about M protein is FALSE?
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It is readily digested by phagocytes.
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Symptoms of intense inflammation and shock occur in some gram-positive bacterial infections due to
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superantigens.
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Which of the following is an example of direct damage due to bacterial infection?
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the invasion and lysis of intestinal cells by E. coli
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Polio is transmitted by ingestion of water contaminated with feces containing polio virus. What portal of entry does polio virus use?
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mucous membranes only
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All of the following bacteria release endotoxin EXCEPT
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Clostridium botulinum.
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Cholera toxin polypeptide A binds to surface gangliosides on target cells. If the gangliosides were removed,
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polypeptide B would not be able to enter the cells.
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Bacteria such as E. coli and Salmonella produce invasins that bind host cells, thus causing the cells to
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engulf the bacteria.
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Which of the following mechanisms is used by gram-negative bacteria to cross the blood-brain barrier?
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inducing TNF
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Injectable drugs are tested for endotoxins by
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the Limulus amoebocyte lysate test.
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Endotoxins in sterile injectable drugs could cause
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septic shock symptoms.
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Gram-negative septic shock results from the following events. What is the second step?
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LPS is released from gram-negative bacteria.
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Antibiotics can lead to septic shock if used to treat
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gram-negative bacterial infections.
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Which of the following is NOT a cytopathic effect of viruses?
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toxin production
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Bacteria that cause periodontal disease have adhesins for receptors on streptococci that colonize on teeth. This indicates that
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streptococcal colonization is necessary for periodontal disease.
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Nonpathogenic Vibrio cholerae can acquire the cholera toxin gene by
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transduction.
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In response to the presence of endotoxin, phagocytes secrete tumor necrosis factor. This causes
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a decrease in blood pressure.
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Patients developed inflammation a few hours following eye surgery. Instruments and solutions were sterile, and the Limulus assay was positive. The patients inflammation was due to
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endotoxin.