BIOL 1353 - Exam 4 - Mastering - Ch 15
A Perfect Storm: Overcrowding, Poor Sanitation, and Vibrio cholerae Part E The physical symptoms of cholera present only after a specific series of events has taken place. What is the most likely sequence of events in the pathogenesis of V. cholerae? Place the following statements in the order that best reflects the chronology of events during V. cholerae infection.
1. V. cholerae is ingested via contaminated water, 2. V. cholerae survives passage through the stomach and enters the intestine, 3. V. cholerae attaches via pili, 4. V. cholerae produces cholera toxin, 5. The host intestinal cells are destroyed, resulting in a profuse watery diarrhea, 6. v. cholerae exits the host via the feces Correct You might reasonably think that elimination from the body in feces would not confer an advantage for the bacteria. However, this is quite advantageous for V. cholerae because it enables the pathogen to go on to infect another host. V. cholerae can also survive as an environmental organism, so it will be able to survive even if it is not immediately introduced into another host.
Multiple Choice Question 15.9 Part A Which of the following is NOT a membrane-disrupting toxin? A-B toxin streptolysin S streptolysin O leukocidin hemolysin
A-B toxin
Multiple Choice Question 15.20 Part A All of the following are used by bacteria to attach to host cells EXCEPT ligands. fimbriae. capsules. A-B toxins. M protein.
A-B toxins.
Chapter 15 - Reading Questions - Question 1 Part A Which of the following is NOT a cytopathic effect (CPE) of viruses? chromosomal changes in the host cell the formation of a syncytium formation of inclusion bodies All of the above are possible CPE.
All of the above are possible CPE.
Chapter 15 - Reading Questions - Question 3 Part A Which of the following would be an example of an infection initiated via the parenteral route? An individual contracts gonorrhea as a result of unprotected sex. An individual contracts hepatitis B from an accidental stick with a contaminated needle. An individual contracts a gastrointestinal infection by consuming contaminated water. An individual contracts a hookworm infection as a result of walking around outside barefoot.
An individual contracts hepatitis B from an accidental stick with a contaminated needle.
A Perfect Storm: Overcrowding, Poor Sanitation, and Vibrio cholerae Part F Although cholera can be treated with antibiotics, data suggest that antibiotic treatment alone is NOT the most effective therapy. Which of the following statements describes the most likely reason for supplementing antibiotic therapy? Because V. cholerae is a gram-negative organism, it is not very effectively treated with antibiotics. Antibiotic therapy addresses only the growth of V. cholerae; it doesn't address the extreme dehydration suffered by a person infected with V. cholerae. The production of cholera toxin helps V. cholerae resist antibiotic treatment. As with V. cholerae, the acidic environment of the stomach can have a negative impact on antibiotic activity.
Antibiotic therapy addresses only the growth of V. cholerae; it doesn't address the extreme dehydration suffered by a person infected with V. cholerae. Correct Antibiotics (particularly doxycycline) are commonly included in the treatment of cholera. However, rehydration therapy is considered more essential in the effective treatment of the disease. Rehydration therapy will replace the lost fluids and electrolytes that were lost with the watery diarrhea. This diarrhea is so profuse that patients can lose up to 20 liters of fluid a day! This extreme loss of fluid and electrolytes often has severe consequences, such as shock and death. However, with prompt rehydration treatment, patients can fully recover, even in areas of the world where the disease is endemic.
Microbiology Animation: Virulence Factors: Exotoxins Part B Which domain of the A-B toxin binds to cell surface receptors on the host cell? A domain B domain Both the A and B domains have the ability to bind to cell surface receptors. A-B toxins do not bind to cell surfaces.
B domain
Mechanisms of Exotoxins and Endotoxins - Foundation Figure 15.4 Part D Part D - Superantigens, Another Type of Exotoxin Considering the pathology of a cytokine storm, select possible strategies that would be likely to diminish the harmful effects of superantigen toxins. Select all of the strategies that would be likely to block or reduce the harmful effects of superantigen toxins. Blocking molecular determinants on superantigens that interacts with T cells Blocking the release of cytokines from T cells Blocking the synthesis of lipopolysaccharide in gram-negative bacteria Blocking host cell receptor-mediated endocytosis Blocking secretion of proteins by bacterial cells Blocking the separation of the A and B components of the exotoxin Neutralizing circulating cytokines
Blocking molecular determinants on superantigens that interacts with T cells Blocking the release of cytokines from T cells Blocking secretion of proteins by bacterial cells Neutralizing circulating cytokines Correct: You have correctly identified several possible strategies that might be applied to inhibit or diminish the harmful effects of superantigens. These strategies include preventing the secretion of superantigen toxins by bacterial cells, blocking the stimulation of T cells by superantigens, blocking the release of cytokines from T cells, or neutralizing circulating cytokines. This is an active area of physiological and pharmaceutical research. Another group of exotoxins are classified as membrane-disrupting toxins. These essentially result in the lysis of host cells. Some membrane-disrupting toxins specifically lyse leukocytes and are referred to as leukocidins. Others disrupt red blood cells and are referred to as hemolysins. Sometimes membrane-disrupting toxins are named for the bacterial species that produces them. For instance, streptolysin O and streptolysin S are both produced by Streptococcus pyogenes. These membrane-disrupting toxins lyse red and white blood cells, as well as other body cells.
Mechanisms of Exotoxins and Endotoxins - Foundation Figure 15.4 Part C - How Might the Action of an A-B Toxin Be Blocked? Which of the following strategies might be used to block the activity of an A-B toxin? Select all of the strategies below that might inhibit or block the action of an Interfering with lipopolysaccharide synthesis in gram-negative bacteria Blocking separation of the A and B components of the toxin Inhibiting cytokine release stimulated by endotoxin Blocking receptor-mediated endocytosis in cells targeted by the A-B toxin Blocking the binding sites on the B portion of an A-B toxin Blocking host cell receptors to which A-B toxins bind Inhibiting the secretion of proteins from a bacterial cell
Blocking separation of the A and B components of the toxin Blocking receptor-mediated endocytosis in cells targeted by the A-B toxin Blocking the binding sites on the B portion of an A-B toxin Blocking host cell receptors to which A-B toxins bind Inhibiting the secretion of proteins from a bacterial cell --------------------------------------------------------------- You have correctly identified several different strategies that may inhibit or block the action of an A-B exotoxin. Antibodies against exotoxins (also known as antitoxins) can often neutralize the effects of toxins by binding to and blocking those sites on the toxin molecule that would normally attach to the host cell. It is possible that monoclonal antibodies against host cell receptors may also prevent a toxin from binding to its specific host cell receptors. --------------------------------------------------------------- Superantigens are another type of exotoxin. This type of exotoxin brings about a very intense and nonspecific reaction from components of the cell-mediated immune response, particularly T cells and the cytokines they secrete. Superantigens nonspecifically activate T lymphocytes, which respond by secreting enormous amounts of cytokines. This intense cytokine response is often referred to as a cytokine storm, and these chemical messengers recruit and activate other components of the host immune response. The end result can be quite self-destructive, causing fever, nausea, vomiting, diarrhea, and sometimes even cardiovascular shock and death. Examples of toxin superantigens include staphylococcal enterotoxin and the toxin that causes toxic shock syndrome. Occasionally other infections not involving bacteria or exotoxins can invoke a cytokine storm; examples include infections from influenza and smallpox viruses.
Microbial Mechanisms of Pathogenicity - Foundation Part E - Factors that Influence a pathogen's ability to penetrate or evade host defenses Students will match factors that influence a pathogen's ability to penetrate or evade host defenses with its best description. Match each item related to the penetration or evasion of host defenses with its best description.
Capsules - this viscous outer covering found in certain microorganisms helps pathogens evade the host's defenses by impairing phagocytosis. Cell wall components - this structure contains substances that contribute to pathogen's virulence, for example, M protein mediates microbial attachment to epithelial cells. Enzymes - these proteins contribute to a pathogen's virulence, for example, by forming and breaking down fibrin clots, breaking down connective proteins, and countering certain types of antibodies. Antigenic variation - the process allows pathogens to alter their surface antigens to avoid attack by antibodies produced by the immune system. Invasins - these microbial surface proteins rearrange the host cell's actin filaments, allowing pathogens to enter and move in and between cells. Upon successful and entry and penetration of host tissues, pathogens can cause damage to host cells in many ways. For example, pathogens can use and deplete nutrients in the human body. To obtain free iron, a nutrient that is in limited quantities, some pathogens secrete proteins called siderophores that bind iron obtained from the host cell's iron-transport proteins, and transport this iron to bacteria through interactions with cell surface receptors. Pathogens can also cause direct damage to host cells by using host cell nutrients, producing waste products, and multiplying inside host cells, which can ultimately rupture cells. Some pathogens can also induce cells to engulf them, and later be extruded, which can damage these cells. Finally, some pathogens can penetrate, and often damage, host cells using bacterial motility structures. Toxins are responsible for causing most of the damage to host cells. These poisonous substances can be transported by the blood or lymph to produce far-reaching, sometimes fatal, effects. Fever, cardiovascular disturbances, diarrhea, spasms, and shock are just some of the possible effects. Toxins can also inhibit protein synthesis and destroy blood cells and vessels. When toxins are present in the blood, this is known as toxemia. Toxins can be placed in one of two broad categories: 1) Exotoxins - those that are produced and secreted by pathogens and 2) Endotoxins - toxins that are part of the outer portion of the cell wall of gram-negative bacteria. Exotoxins work by destroying parts of the host cell or inhibiting its metabolic functions, while endotoxins trigger an immune system response when lipid A is released from dead gram-negative bacteria. Some pathogens may themselves be infected with bacteriophages (viruses), which incorporated viral DNA into bacterial chromosomes to produce latent prophages. This does not cause lysis of the bacterium, but rather, may confer new properties due to the presence of viral genes. This process is called lysogenic conversion (a change in the characteristics of a microbe due to a prophage); in some cases, pathogenesis can be attributed to the prophages these bacteria contain. Diphtheria toxin Erythrogenic toxins Staphylococcal enterotoxin Pyrogenic toxin Botulinium neurotoxin The capsule of Streptococcus pneumoniae Shiga toxin in Escherichia coli O157 and Cholera toxin in Vibrio cholera are all encoded by phage genes. Finally, host cell infections with animal viruses can cause damage to these cells. Cytopathic effects describe the visible effects of viral infection, and these can vary with the virus.
Microbiology Animation: Virulence Factors: Inactivating Host Defenses Part E How can capsules enable bacteria to evade the immune system? Capsules can bind up IgA, rendering it inactive. Capsules block the complement biding sites on the surface of the pathogen. A capsule is a superantigen that distracts the immune system.
Capsules block the complement biding sites on the surface of the pathogen.
Multiple Choice Question 15.30 Part A All of the following bacteria release endotoxin EXCEPT Salmonella typhi. Clostridium botulinum. Proteus vulgaris. Neisseria meningitidis. Haemophilus influenzae.
Clostridium botulinum.
Multiple Choice Question 15.6 Part A Which of the following statements is FALSE? Leukocidins destroy neutrophils. Hemolysins lyse red blood cells. Kinase destroys fibrin clots. Hyaluronidase breaks down substances between cells. Coagulase destroys blood clots.
Coagulase destroys blood clots.
Mechanisms of Exotoxins and Endotoxins - Foundation Figure 15.4 Part B - Mechanism of Action of A-B Exotoxins The majority of exotoxins are A-B toxins, which are composed of two polypeptide subunits referred to as A and B. The B component functions to bind or attach to the host cell, whereas the A component exerts its toxic effects on the cell. This activity asks you to place the images in the correct order as they occur when an A-B toxin interacts with the host cell. Drag the images below into boxes to indicate the correct order of events illustrating the mechanism of action of an A-B exotoxin.
Correct You have correctly placed each of the steps in the mechanism of action of a typical A-B exotoxin. An understanding of this process may reveal possible strategies to block or inhibit it and potentially prevent or reduce toxin-mediated damage to the host.
Mechanisms of Exotoxins and Endotoxins - Foundation Figure 15.4 Part G - The Pyrogenic Response to Endotoxin Endotoxin is well known for its ability to produce a pyrogenic response (fever). Place in the correct order the steps by which gram-negative bacteria may bring about fever response. Drag the images into the labeled targets to reflect the correct order of steps by which gram-negative bacteria can bring about a fever response.
Correct You have correctly sequenced the images that reflect the development of fever in response to endotoxin. First, a gram-negative microbe is phagocytized and digested. In the process, endotoxin is released within the phagocyte; the phagocyte responds by releasing cytokines, primarily IL-1 and TNF-alpha. These cytokines are distributed throughout the body by the circulatory system. When they reach the brain, the hypothalamus responds by releasing prostaglandins, which ultimately raises the body's temperature set-point and causes a fever.
Mechanisms of Exotoxins and Endotoxins - Foundation Figure 15.4 Part E - Membrane-Disrupting Exotoxins Consider the structure of a plasma membrane. Select the mechanisms through which a toxin is likely to disrupt the plasma membrane of a host cell. Disruption of phospholipid bilayer Binding of the toxin to the peptidoglycan layer Binding of the toxin to the lipopolysaccharide layer Insertion of a protein channel in the host cell plasma membrane Blocking synthesis of transport proteins
Disruption of phospholipid bilayer Insertion of a protein channel in the host cell plasma membrane Correct You have correctly identified that a membrane-disrupting toxin is likely to either insert protein channels in the host cell membrane or disrupt the integrity of the phospholipid bilayer. Either process would cause the plasma membrane to become leaky, leading to lysis of the cell. Now that we have explored the three types of exotoxins, let's turn our attention to endotoxins. Endotoxin is produced exclusively by gram-negative bacteria. It is the lipid A portion of lipopolysaccharide that makes up the outer leaflet of the gram-negative outer membrane, the outermost layer of the gram-negative cell wall. Review the structure of the gram-negative cell wall.
Mechanisms of Exotoxins and Endotoxins - Foundation Figure 15.4 Part F - Characteristics of Endotoxin Select the statements that correctly describe endotoxins. Endotoxin causes a strong immune response and abundant antibody production in the host. Endotoxins may cause a life-threatening drop in blood pressure known as endotoxic shock. Drugs that neutralize endotoxin will kill gram-negative bacteria. Endotoxin can cause fever, chills, weakness, and fatigue. Endotoxin can be used to vaccinate individuals. Symptoms caused by endotoxin may actually worsen after treatment of an infection caused by gram-negative bacteria. Sterilized items may contain endotoxin and cause a reaction in a patient.
Endotoxins may cause a life-threatening drop in blood pressure known as endotoxic shock. Endotoxin can cause fever, chills, weakness, and fatigue. Symptoms caused by endotoxin may actually worsen after treatment of an infection caused by gram-negative bacteria. Sterilized items may contain endotoxin and cause a reaction in a patient. Correct You have correctly identified the statements that apply to endotoxin. Their lipid nature causes them to be very weak antigens, so they rarely provoke an antibody response in the host, and there is no vaccine against them. This lipid nature also enables them to retain their toxic properties after steam autoclaving. The symptoms of endotoxins are less specific than the symptoms of the various exotoxins. Endotoxins cause a fever response, general body aches, weakness, and potentially shock and death.
Chapter 15 - Reading Questions - Question 10 Part A Which of the following statements about lysogenic conversion is true? Lysogenic conversion is a result of the transfer of plasmids from one bacterium to another. Endotoxin production by bacteria is frequently the result of a lysogenic infection. Lysogenic bacteria are always less virulent than nonlysogenic bacteria because the viral infection weakens them. Exotoxin production by bacteria is frequently the result of a lysogenic infection.
Exotoxin production by bacteria is frequently the result of a lysogenic infection.
Mechanisms of Exotoxins and Endotoxins - Foundation Figure 15.4 Part A - Differences Between Exotoxins and Endotoxins Exotoxins and endotoxins are two fundamentally different types of bacterial toxins. In this activity, you will determine whether each of the following statements applies to exotoxins or endotoxins. Some statements may apply to both types of toxins. Drag each statement to the appropriate box, indicating whether the statement applies to exotoxin, or endotoxin, or both exotoxin and endotoxin.
Exotoxins are classified into different types based on their structure and function. The three basic types of exotoxins are A-B toxins, membrane-disrupting toxins, and superantigens. This next activity will focus on the structure and mechanism of A-B toxins.
A Perfect Storm: Overcrowding, Poor Sanitation, and Vibrio cholerae Part C Which of the following are properties of exotoxins? Select ALL that apply. Exotoxins target specific cellular structures or molecules. Exotoxins are protein molecules. Exotoxins are extremely heat stable. Exotoxins are released from the cell during death or replication. Exotoxins are produced primarily by gram-negative bacteria. Very small amounts of exotoxin can be lethal.
Exotoxins target specific cellular structures or molecules. Exotoxins are protein molecules. Very small amounts of exotoxin can be lethal.
Microbiology Animation: Virulence Factors: Endotoxins Part C Which of the following would be the first sign of an infection that resulted in the release of endotoxin? Weakness Nausea Fever Pain
Fever
Microbiology Animation: Virulence Factors: Enteric Pathogens Part A Which of the following features of Salmonella prevent it from being phagocytosed? Invasins Fimbriae Flagella
Flagella
Microbiology Animation: Virulence Factors: Penetrating Host Tissues Part B Which of the following enzymes breaks down the "glue" that holds cells together? Fibrinolysin Streptokinase Collagenase Hyaluronidase
Hyaluronidase
Microbiology Animation: Virulence Factors: Enteric Pathogens Part B Where do Salmonella pathogens grow and replicate in the infected host? Inside Shigella cells Inside intestinal epithelial cells Inside M cells Inside phagocytes
Inside phagocytes
Microbiology Animation: Virulence Factors: Hiding from Host Defenses Part D How does the protozoan Trypanosoma evade detection by the immune system? It can change the surface antigens frequently, preventing the immune system from tracking it. It prevents phagosome-lysosome fusion. It produces a capsule which is composed of polysaccharides similar to those found in the host. It can resist oxidation inside macrophages.
It can change the surface antigens frequently, preventing the immune system from tracking it.
Microbiology Animation: Virulence Factors: Endotoxins Part D Why is a release of endotoxin into the bloodstream potentially deadly? It results in dehydration of the patient. Endotoxin can quickly enter the brain from the bloodstream, causing brain damage. It causes necrosis of the liver. It can lower blood pressure and cause the patient to go into shock.
It can lower blood pressure and cause the patient to go into shock.
Multiple Choice Question 15.22 Part A Which of the following statements about staphylococcal enterotoxin is FALSE? It is an exotoxin. It causes diarrhea. It is produced by Staphylococcus aureus growing in the host's intestines. It is a superantigen. It causes vomiting.
It is produced by Staphylococcus aureus growing in the host's intestines.
Multiple Choice Question 15.26 Part A Which of the following statements about M protein is FALSE? It is found on fimbriae. It is heat- and acid-resistant. It is a protein. It is found on Streptococcus pyogenes. It is readily digested by phagocytes.
It is readily digested by phagocytes.
Microbial Mechanisms of Pathogenicity - Foundation Part D - The Role of Infectious Dose (ID50) in Causing Infection Students will view data related to infectious doses for a specific microorganism, and identify the best conclusion based on this data. Bacillus anthracis can cause infection via three different portals of entry. The ID50 of cutaneous anthrax is 10 to 50 endospores, while inhalation anthrax requires 10,000 to 20,000 endospores, and gastrointestinal anthrax requires 250,000 to 1,000,000 endospores. Which statement best describes a conclusion that can be drawn based on this information? Exposure to a small number of endospores (less than 1,000) is most likely to result in gastrointestinal anthrax. Equal numbers of cutaneous, inhalation, and gastrointestinal anthrax infections are observed in human hosts. It is significantly easier to be infected with cutaneous anthrax as compared to other forms of anthrax. Cutaneous anthrax is rarely observed when monitoring cases across the population. The portal of exit impacts the infectious dose needed to cause infection at the portal of entry.
It is significantly easier to be infected with cutaneous anthrax as compared to other forms of anthrax. Correct: This is correct. The ID50 through the skin is only 10 to 50 endospores, making it easier to acquire cutaneous anthrax as compared to other forms of anthrax. Pathogens can damage tissue surfaces, but most invade tissues in order to cause disease. Several factors contribute to the ability of a pathogen to penetrate tissues and evade host defenses. Capsules help pathogens evade host's defenses by impairing phagocytosis, the process in which specialized host's cells engulf and destroy foreign cells. In addition, the cells walls of certain bacteria contain substances that contribute to virulence. For example, M protein found on the cell surface and fimbriae mediates microbial attachment to epithelial cells and helps pathogens resist phagocytosis by white blood cells. Some microorganisms produce enzymes that contribute to its virulence. For example, coagulases can form fibrin clots in blood that protect the bacterium from host defenses; kinases break down fibrin clots formed by the body to isolate the infection; hyaluronidase and collagenase break down hyaluronic acid and collagen, respectively, allowing for the entry and spread of pathogenic bacteria in certain tissues; and, IgA proteases can counter certain types of antibodies produced by the host's defenses. A host's immune system develops acquired immunity through exposure to antigens present on the surface of pathogens. However, some pathogens can alter their surface antigens through a process called antigenic variation. By the time an immune response is mounted, the pathogen has altered its surface antigens and is unaffected by antibodies produced by the host's immune system. This process contributes to the pathogen's ability to evade host defenses. Finally, pathogens can penetrate and move between and through host cells by interacting with the host's cytoskeletal protein, actin. Some microbes produce surface proteins known as invasions that rearrange actin filaments, which disrupts a host cell's cytoskeleton and triggers the entry of pathogens. Once inside the cell, certain pathogens then use actin to transport itself through the cytoplasm and to move from one cell to another.
Multiple Choice Question 15.36 Part A Gram-negative septic shock results from the following events. What is the second step? Fever occurs. LPS is released from gram-negative bacteria. Body temperature is reset in the hypothalamus. IL-1 is released. Phagocytes ingest gram-negative bacteria.
LPS is released from gram-negative bacteria.
Microbial Mechanisms of Pathogenicity - Foundation Part G - Overall Factors Related to Microbial Mechanisms of Pathogenicity Students will view several scenarios and classify whether infection is likely or unlikely to occur. Reviewing the overall microbial mechanisms of pathogenicity (Figure 15.9), predict the ability of the pathogen to cause infection in each of the following scenarios. Drag the appropriate items to their respective bins.
Likely to cause infection: - a pathogen that causes gastrointestinal infections is accidentally ingested in contaminated food - a pathogen in quantities more than double its infectious dose is introduced at the appropriate portal of entry - a population of microbes less than its infectious dose is introduced in a compromised human host - droplets from a person infected with a respiratory virus are inhaled by a healthy individual Not likely to cause infection: - a pop. of microbes greater than its infectious dose is introduced to a healthy individual, but these microbes are unable to adhere to host tissues - a pathogen with multiple virulence factors is introduced in a healthy host, but in quantities far below its infectious dose - a pathogen that cause urinary tract infections is accidentally ingested in contaminated water
Microbiology Animation: Virulence Factors: Endotoxins Endotoxins are also known as interleukin-1. cytokines. Lipid A. prostaglandins.
Lipid A.
Microbiology Animation: Virulence Factors: Enteric Pathogens Part C Where is the site of Shigella attachment in the host? M cells Intestinal epithelial cells Leukocytes Phagocytes
M cells
Microbiology Animation: Virulence Factors: Inactivating Host Defenses Part A What are leukocidins? Molecules that destroy the complement proteins Molecules that are capable of destroying phagocytes Molecules that can degrade IgA
Molecules that are capable of destroying phagocytes
Chapter 15 - Reading Questions - Question 7 Part A Which of the following statements about adherence is true? Most bacterial adhesins are glycoproteins or lipoproteins. Most bacteria can adhere to any cell in the host. Adhesins are always located on the bacterium's cell membrane. The host cell receptors for bacterial adhesins are usually proteins.
Most bacterial adhesins are glycoproteins or lipoproteins.
Concept Map: Penetration of Host Defenses Part B According to your Concept Map, which of the following organisms exhibits antigenic variation? S. pneumoniae N. gonorrheae Mycobacterium tuberculosis H. influenzae
N. gonorrheae
Microbiology Animation: Virulence Factors: Inactivating Host Defenses Part C Meningitis and gonorrhea are caused by measles virus. Neisseria species. Pseudomonas species.
Neisseria species.
Chapter 15 - Reading Questions - Question 4 Part A Which statement regarding endotoxins is true? One consequence of endotoxins is the activation of blood-clotting proteins. Endotoxins are part of the outer portion of the cell wall of gram-positive bacteria. Endotoxins induce host cells to produce effective antitoxins that help to protect them against the toxin's effects. The effects of endotoxins vary greatly, depending on the specific bacterium the produces them.
One consequence of endotoxins is the activation of blood-clotting proteins.
Microbiology Animation: Virulence Factors: Enteric Pathogens Part E What is the etiologic agent of typhoid? E. coli Shigella Salmonella
Salmonella
Multiple Choice Question 15.18 Part A All of the following organisms produce exotoxins EXCEPT: Corynebacterium diphtheriae. Salmonella typhi. Clostridium botulinum. Staphylococcus aureus. Clostridium tetani.
Salmonella typhi.
Chapter 15 - Reading Questions - Question 2 Part A 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? More organisms of Staphylococcal bacteria must be ingested to cause infection, as compared Shigella bacteria. Shiga toxin is more lethal than staphylococcal enterotoxin. Staphylococcal enterotoxin is the more lethal of the two toxins. The parenteral route is the preferred portal entry for Shigella bacteria.
Shiga toxin is more lethal than staphylococcal enterotoxin.
Microbial Mechanisms of Pathogenicity - Foundation Part F - Factors that Lead to Damaged Host Cells Students will match factors that damage host cells with its best description. Match each item related to damage to host cells with its best description.
Siderophores - these bind up iron obtained from the host cell's iron-transport proteins and transport this iron to bacteria through intersections with cell surface receptor. Direct damage - this occurs during nutrient depletion, accumulation of waste products, pathogen entry and exit, and ruptured host cells. Toxins - these cause most of the damage to host cells; these poisonous substances can be transported by the blood or lymph and may produce far-reaching effects. Lysogenic conversion - this results in a change in microbe characteristics due to the presence of prophage genes that confer new properties. Cytopathic effects - these describe the visible effects of viral infections that results in host cell damage.
Microbiology Animation: Virulence Factors: Penetrating Host Tissues Part C Which of the following virulence factors would be found in Staphylococcus aureus? Staphylokinase Streptokinase Hyaluronidase Collagenase
Staphylokinase
Microbiology Animation: Virulence Factors: Exotoxins Part C How are superantigens different from other types of exotoxins? Superantigens must be endocytosed into a target cell before becoming active. Superantigens cause an overstimulation of the host immune system. Superantigens are comprised of two functional domains. Superantigens only act against host neurons.
Superantigens must be endocytosed into a target cell before becoming active.
Microbiology Animation: Virulence Factors: Hiding from Host Defenses Part B How does a capsule help certain bacteria evade detection by the immune system? 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. The capsule makes the bacterium too sticky to be phagocytosed by the immune cells. Capsules allow the bacteria to stick together, creating a larger mass that is too big for immune cells to engulf. Capsules have the ability to destroy antibodies secreted by the immune system.
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.
A Perfect Storm: Overcrowding, Poor Sanitation, and Vibrio cholerae Part G Disease research and epidemiology bring together many different facets to help us better understand disease pathology and spread. Which of the following statements are true? Select ALL that apply. The ID50 value refers to the number of microbes needed to cause half of an infected population to die. The interactions that occur between a microbe and host influence the evolution of both. The terms pathogenicity and virulence can be used interchangeably to describe the severity of an infection. Bacterial exotoxins can be altered to create toxoids, which can be used to produce protective immunity in a host. Some pathogens are able to cause disease within a host without penetrating the body. Intoxications result from a bacterial infection in which a large amount of bacterial toxin is produced.
The interactions that occur between a microbe and host influence the evolution of both. Bacterial exotoxins can be altered to create toxoids, which can be used to produce protective immunity in a host. Some pathogens are able to cause disease within a host without penetrating the body.
Microbial Mechanisms of Pathogenicity - Foundation Part B - Characterizing Portals of Entry and Exit Students will classify portals of entry based on whether it relates to the mucous membrane, skin, or parenteral route. Sort each item based on whether it best represents one of the following portals of entry: mucous membrane, skin, or parenteral route.
The number of invading microbes needed to cause infection in 50% of a sample population is known as the infectious dose (ID50). This number is determined based on pathogen and portal of entry. In general, if only a few microorganisms enter a host, the host's defense system is likely to overcome the virulence of this pathogen and prevent infection. However, if a large number of pathogens enter a host, this increases the chances that infection will occur. Once sufficient numbers have gained entry to a host, pathogens need a mechanism to attach to host tissues. Adherence (attachment) is accomplished by means of surface molecules called adhesions or ligands located on the pathogen. Adhesions bind specifically to complementary surface receptors on host tissue.
Microbiology Animation: Virulence Factors: Hiding from Host Defenses Part A How are immune cells able to detect foreign pathogens? They detect foreign, unfamiliar chemical substances released by the invading cells. They are able to detect structures on the surfaces of foreign cells that are not found in the host. They can compare the DNA sequences from the foreign cells to host DNA.
They are able to detect structures on the surfaces of foreign cells that are not found in the host.
Concept Map: Penetration of Host Defenses Part A What do hyaluronidase and kinase have in common? They are both critical components of microbial capsules. They both break down components of the extracellular matrix. They are both enzymes involved in evading host defense. They both directly prevent phagocytosis. All of the above are correct.
They are both enzymes involved in evading host defense.
Multiple Choice Question 15.7 Part A Which of the following statements about exotoxins is generally FALSE? They are produced by gram-positive bacteria. They have specific methods of action. They are more potent than endotoxins. They are composed of proteins. They are resistant to heat.
They are resistant to heat.
Microbiology Animation: Virulence Factors: Penetrating Host Tissues Part D How do fibrinolysins enhance a pathogen's virulence? They destroy the molecules that hold cells together. They break down fibrin proteins that are involved in clot formation, allowing the cells to penetrate deep into damaged skin. They destroy the fibers that are found at the base of superficial tissues, allowing for deeper penetration by the pathogen.
They break down fibrin proteins that are involved in clot formation, allowing the cells to penetrate deep into damaged skin.
Microbiology Animation: Virulence Factors: Enteric Pathogens Part D How do Shigella cells move between host cells? They are secreted directly into the epithelial cells from the M cells. They lyse the M cell, releasing thousands of new cells to infect other host cells. They can polymerize actin molecules from the epithelial cells into tail-like structures that propel them from one cell to another. They are secreted by phagocytes.
They can polymerize actin molecules from the epithelial cells into tail-like structures that propel them from one cell to another.
Microbiology Animation: Virulence Factors: Inactivating Host Defenses Part D How do superantigens enable pathogens to hide from the immune system if they actually stimulate the immune system? They cause the immune system to turn on itself. They cause the immune system to produce an exaggerated response, distracting it from the actual pathogen. They cause fever, which destroys the complement proteins. They cause the immune system to destroy IgA antibodies.
They cause the immune system to produce an exaggerated response, distracting it from the actual pathogen.
A Perfect Storm: Overcrowding, Poor Sanitation, and Vibrio cholerae Part B Some studies have indicated that the ID50 for Vibrio cholerae can be as high as 108 organisms. Which of the following most likely explains the requirement for this relatively high ID50? Because the major virulence factor of V. cholerae is cholera toxin, large numbers of bacteria are required to produce enough toxin to cause disease. V. cholerae does not produce enough virulence factors to overcome the host response and cause disease. To establish infection, V. cholerae must survive the host immune response and the acidic environment of the stomach. Because V. cholerae cells are relatively small compared to host cells, thousands of bacteria must infect each cell to cause disease.
To establish infection, V. cholerae must survive the host immune response and the acidic environment of the stomach. Correct The acidic environment of the stomach is extremely harsh on V. cholerae, and the microbe doesn't possess particular virulence factors to help it combat this environment. Therefore, the high infective dose is needed to ensure that enough bacteria make it through the acidic environment and into the intestine, where the pH is much higher than that of the stomach. Once in the intestine, V. cholerae is able to begin to establish infection. One of the virulence factors responsible for disease caused by V. cholerae is cholera toxin. This is an exotoxin produced by V. cholerae under specific environmental conditions found in the intestine.
Microbiology Animation: Virulence Factors: Hiding from Host Defenses Part C Which of the following microorganisms actually grows inside the macrophage? Leishmania Streptococcus pneumoniae Tuberculosis bacterium Legionella Shigella
Tuberculosis bacterium
Chapter 15 - Reading Questions - Question 8 Part A Which of the following toxins does NOT match the description? tetanus toxin: an A-B neurotoxin that causes uncontrollable muscle contractions streptococcal erythrogenic toxin: a superantigen that damages capillaries and results in a characteristic rash hemolysins: membrane-disrupting toxins that destroy erythrocytes Vibrio enterotoxin: a superantigen that destroys epithelial cells
Vibrio enterotoxin: a superantigen that destroys epithelial cells
Microbiology Animation: Virulence Factors: Endotoxins Part B When the cell attaches to a host cell in the human body During bacterial conjugation When the cell moves toward a energy source When the cell dies
When the cell dies
Multiple Choice Question 15.44 Part A In response to the presence of endotoxin, phagocytes secrete tumor necrosis factor. This causes: a decrease in blood pressure. the disease to subside. a gram-negative infection. a fever. an increase in red blood cells.
a decrease in blood pressure.
Multiple Choice Question 15.14 Part A The fimbriae of Neisseria gonorrhea and enteropathogenic E. coli are examples of adhesins. ligands. receptors. adhesins and ligands. adhesins, ligands, and receptors.
adhesins and ligands.
Concept Map: Penetration of Host Defenses Part C Which of the following virulence factors could directly prevent phagocytosis and/or phagocytic degradation? M proteins waxy lipids capsules all of the above none of the above
all of the above
Multiple Choice Question 15.2 Part A The ability of some microbes, such as Trypanosoma or Giardia to alter their surface molecules and evade destruction by the hosts antibodies is called antigenic variation. lysogenic conversion. cytocidal effect. virulence. cytopathic effect.
antigenic variation.
Multiple Choice Question 15.17 Part A Botulism is caused by ingestion of a proteinaceous exotoxin; therefore, it can easily be prevented by administering antibiotics to patients. filtering food. preventing fecal contamination of food. not eating canned food. boiling food prior to consumption.
boiling food prior to consumption.
Multiple Choice Question 15.11 Part A Which of the following does NOT contribute to the symptoms of a fungal disease? toxins capsules cell walls allergic response of the host metabolic products
cell walls
Chapter 15 - Reading Questions - Question 9 Part A Which disease would be potentially propagated in an environment without functional plumbing and in which drinking water is contaminated with sewage? influenza cholera ringworm yellow fever
cholera
Multiple Choice Question 15.16 Part A Superantigens produce intense immune responses by stimulating lymphocytes to produce leukocidins. cytokines. exotoxins. endotoxins. interferons.
cytokines.
Microbiology Animation: Virulence Factors: Exotoxins Part A An exotoxin that has the ability to kill or damage host cells is referred to as a(n) cytotoxin. enterotoxin. superantigen. neurotoxin. A-B toxin.
cytotoxin.
Multiple Choice Question 15.39 Part A Bacterium Portal of Entry ID50 Staphylococcus aureus Wound <10 Staphylococcus aureus Wound + Ampicillin 300 the table shows the ID50 for Staphylococcus aureus in wounds with and without the administration of ampicillin before surgery. Based on the data, the administration of ampicillin before surgery increases the risk of staphylococcal infection. decreases the risk of staphylococcal infection. replaces tetracycline. has no effect on risk of infection. The answer cannot be determined based on the information provided.
decreases the risk of staphylococcal infection.
Multiple Choice Question 15.45 Part A 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 exotoxin. bacterial infection. viral infection. endotoxin. The answer cannot be determined based on the information provided.
endotoxin.
Multiple Choice Question 15.32 Part A Bacteria such as E. coli and Salmonella produce invasins that bind host cells, thus causing the cells to produce iron-binding proteins. release cytokines. engulf the bacteria. destroy the bacteria. release TNF.
engulf the bacteria.
Multiple Choice Question 15.3 Part A Most pathogens that gain access through the skin just infect the skin itself. must adhere first while their invasive factors allow them to penetrate. can penetrate intact skin. enter through hair follicles and sweat ducts. must be injected.
enter through hair follicles and sweat ducts.
Chapter 15 - Reading Questions - Question 5 Part A Which type of bacterial enzyme helps spread Streptococcus pyogenes by digesting blood clots? collagenase coagulase fibrinolysin hyaluronidase
fibrinolysin
A Perfect Storm: Overcrowding, Poor Sanitation, and Vibrio cholerae In January 2010, a devastating earthquake struck Haiti about 15 miles west of the capital city of Port-au-Prince. The earthquake killed over 200,000 people and displaced over 1 million from their homes. Many of these people had nowhere to go other than displacement camps and shantytowns, where the sanitary conditions were less than ideal. It was not only private homes that were destroyed; hospitals, communication networks, land and air transport, and other important infrastructure were damaged. In October 2010, a cholera epidemic was reported in the Artibonite Department (Haitian departments are analogous to states). This was the first cholera epidemic in Haiti in over a century. Within 10 weeks, cholera had spread to all Haitian departments. By the end of the epidemic, more than 470,000 cases had been reported, and more than 6500 people were dead. Both during and after the epidemic, epidemiologists, doctors, and scientists were working to determine the source of the outbreak and its transmission patterns, identify the causative strains, and care for the infected. Part A The ability of Vibrio cholerae to cause disease depends on a number of factors. Which of the following are requirements for causing disease within a host? Select all that apply. production of exotoxins gaining access to the host via a portal of entry direct damage of host tissues adherence to host tissues depleting the host of nutrients at the site of infection evasion of host defenses
gaining access to the host via a portal of entry adherence to host tissues evasion of host defenses For an organism to establish an infection, it needs to gain entry to the host. Once inside a host, the organism will need to adhere to host tissues in order to invade cells and/or cause infection. Remember that from the moment that the bacteria enter the body, the immune system will be fighting them; therefore, bacteria need some mechanisms to help them evade this response so they are not eliminated. Disease also requires that the pathogen damage the host tissues, either directly (e.g., by lysing the cell) or indirectly (e.g., by producing toxins that circulate throughout the body). Gaining entry to the host is just part of the story. The number of organisms that enter the host is significant; enough bacteria must survive in order to establish the infection and cause disease. One measure of virulence is the ID50 value. It is important to note that this value is determined experimentally and can vary for each pathogen under different conditions.
Multiple Choice Question 15.24 Part A Lysogenic bacteriophages contribute to bacterial virulence because bacteriophages kill the bacteria, causing release of endotoxins. produce toxins. kill human cells. carry plasmids. give new gene sequences to the host bacteria.
give new gene sequences to the host bacteria.
Multiple Choice Question 15.37 Part A Antibiotics can lead to septic shock if used to treat gram-negative bacterial infections. gram-positive bacterial infections. protozoan infections. viral infections. helminth infestations.
gram-negative bacterial infections.
Multiple Choice Question 15.15 Part A All of the following are examples of entry via the parenteral route EXCEPT skin cut. injection. surgery. bite. hair follicle.
hair follicle.
Multiple Choice Question 15.33 Part A Which of the following mechanisms is used by gram-negative bacteria to cross the blood-brain barrier? antigenic variation inducing TNF inducing endocytosis producing toxins producing fimbriae
inducing TNF
Multiple Choice Question 15.12 Part A All of the following are methods of avoiding host antibodies EXCEPT IgA proteases. antigenic changes. membrane-disrupting toxins. invasins. inducing endocytosis.
membrane-disrupting toxins.
Multiple Choice Question 15.1 Part A The most frequently used portal of entry for pathogens is the: mucous membranes of the gastrointestinal tract. mucous membranes of the respiratory tract. parenteral route. skin. All of these portals are used equally.
mucous membranes of the respiratory tract.
Multiple Choice Question 15.29 Part A Polio is transmitted by ingestion of water contaminated with feces containing polio virus. What portal of entry does polio virus use? skin only parenteral only mucous membranes only skin and parenteral skin, parenteral, and mucous membranes
mucous membranes only
Microbiology Animation: Virulence Factors: Exotoxins Part E A patient who has been hospitalized with uncontrolled muscle spasms has probably been infected with bacteria that secrete a(n) superantigen. enterotoxin. membrane disrupting toxin. neurotoxin.
neurotoxin.
Multiple Choice Question 15.23 Part A Which of the following contributes to the virulence of a pathogen? numbers of microorganisms that gain access to a host evasion of host defenses toxin production numbers of microorganisms that gain access to a host and evasion of host defenses numbers of microorganisms that gain access to a host, evasion of host defenses, and toxin production
numbers of microorganisms that gain access to a host, evasion of host defenses, and toxin production
Multiple Choice Question 15.31 Part A Cholera toxin polypeptide A binds to surface gangliosides on target cells. If the gangliosides were removed, polypeptide A would enter the cells. polypeptide B would not be able to enter the cells. Vibrio would not produce cholera toxin. Vibrio would bind to target cells. polypeptide A would bind to target cells.
polypeptide B would not be able to enter the cells.
Multiple Choice Question 15.19 Part A Which of the following cytopathic effects is cytocidal? antigenic changes release of enzymes from lysosomes giant cells transformation inclusion bodies
release of enzymes from lysosomes
Multiple Choice Question 15.35 Part A Endotoxins in sterile injectable drugs could cause giant cell formation. nerve damage. no damage, because they are sterile. septic shock symptoms. infection.
septic shock symptoms.
Multiple Choice Question 15.42 Part A Bacteria that cause periodontal disease have adhesins for receptors on streptococci that colonize on teeth. This indicates that streptococci cause periodontal disease. bacteria that cause periodontal disease adhere to teeth. streptococcal colonization is necessary for periodontal disease. streptococci get bacterial infections. bacteria that cause periodontal disease adhere to gums and teeth.
streptococcal colonization is necessary for periodontal disease.
Microbiology Animation: Virulence Factors: Exotoxins Part D 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): cytotoxin. membrane disrupting toxin. superantigen. enterotoxin.
superantigen.
Multiple Choice Question 15.27 Part A Symptoms of intense inflammation and shock occur in some gram-positive bacterial infections due to A-B toxins. superantigens. lipid A. membrane-disrupting toxins. erythrogenic toxin.
superantigens.
Microbiology Animation: Virulence Factors: Inactivating Host Defenses Part B Measles viruses are capable of inactivating host defenses by destroying complement proteins. producing superantigens. suppressing the immune system. producing leukocidins.
suppressing the immune system.
Multiple Choice Question 15.4 Part A The ID50 is: the dose that will kill 50 percent of the test population. the dose that will cause an infection in 50 percent of the test population. the dose that will cause an infection in some of the test population. the dose that will kill some of the test population. a measure of pathogenicity.
the dose that will cause an infection in 50 percent of the test population.
Multiple Choice Question 15.28 Part A Which of the following is an example of direct damage due to bacterial infection? the excessive secretion of fluids in a Vibrio cholera infection the hemolysis of red blood cells in a staphylococcal infection the invasion and lysis of intestinal cells by E. coli the uncontrolled muscle contractions in Clostridium tetani infection the fever, nausea, and low blood pressure in a Salmonella infection
the invasion and lysis of intestinal cells by E. coli
Multiple Choice Question 15.21 Part A Symptoms of protozoan and helminthic diseases are due to: tissue damage due to growth of the parasite on the tissues. waste products excreted by the parasite. products released from damaged tissues. tissue damage due to growth of the parasite on the tissues and waste products excreted by the parasite. tissue damage due to growth of the parasite on the tissues, waste products excreted by the parasite, and products released from damaged tissues.
tissue damage due to growth of the parasite on the tissues, waste products excreted by the parasite, and products released from damaged tissues.
Chapter 15 - Reading Questions - Question 6 Part A In which of the following cases would the Limulus amebocyte lysate (LAL) assay be used? to check for enterotoxins to detect the presence of the botulinum toxin to confirm the diagnosis of gas gangrene to ensure that a sterilized medical device is free of endotoxin
to ensure that a sterilized medical device is free of endotoxin
Multiple Choice Question 15.38 Part A Which of the following is NOT a cytopathic effect of viruses? increased cell growth inclusion bodies forming in the cytoplasm or nucleus toxin production host cells fusing to form multinucleated syncytia cell death
toxin production
Multiple Choice Question 15.5 Part A All of the following contribute to a pathogens invasiveness EXCEPT hyaluronidase. capsules. toxins. coagulases. cell wall components.
toxins.
Multiple Choice Question 15.43 Part A Nonpathogenic Vibrio cholerae can acquire the cholera toxin gene by conjugation. phagocytosis. infecting a pathogenic Vibrio cholerae. transduction. transformation.
transduction.
Multiple Choice Question 15.10 Part A Cytopathic effects are changes in host cells due to bacterial infections. fungal infections. viral infections. helminthic infections. protozoan infections.
viral infections.
Microbiology Animation: Virulence Factors: Penetrating Host Tissues Part A Certain traits that allow pathogens to create infection and cause disease are termed hyaluronidases. virulence factors. collagenases. streptokinases.
virulence factors.