Deck 16: Host-Microbe Interactions

Question 1

The connection between a particular organism and a specific disease was first made by

A) Jenner.
B) Pasteur.
C) Koch.
D) van Leeuwenhoek.
E) Hooke.

Answer 1

C

Question 2

A disease-causing microorganism or virus is referred to as a(n)

A) avirulent infection.
B) colony.
C) commensal.
D) pathogen.
E) virulent.

Answer 2

D

Question 3

The series of steps used to connect an organism to a disease are known as

A) Pasteur's postulates.
B) Lister's aseptics.
C) Linnaeus' taxonomics.
D) Koch's postulates.
E) Bergey's manual

Answer 3

D

Question 4

The microorganisms that are regularly found in or on the body, yet do no apparent harm are called

A) abnormal microbiota.
B) normal microbiota.
C) transient microbiota.
D) variant microbiota.
E) random biota.

Question 5

The infectious dose

A) is the same for all microorganisms.
B) may be 10-100 cells for Salmonella.
C) is defined as the number of microbes needed to cause infection.
D) is defined as the number of microbes needed to kill the host.
E) is the same for all bacteria but varies for viruses.

Question 6

Which of the following members of the normal microbiota inhibit the growth of Candida albicans?

A) E. coli
B) Lactobacillus species
C) Staphylococci species
D) Propionibacterium species
E) All of the answer choices are correct.

Question 7

The interaction of all organisms within a biological community with their environment is called a(n)

A) group.
B) cluster.
C) ecosystem.
D) network.
E) family.

Question 8

Opportunists or opportunistic pathogens

A) are usually saprophyte, like fungi.
B) take advantage of special circumstances.
C) are usually mutualistic.
D) always cause disease.
E) are never normal microbiota.

Question 9

Growth of a parasitic organism in or on the host is referred to as

A) colonization.
B) infection.
C) pathogenism.
D) mutualism.
E) commensalism.

Question 10

The suffix -emia means in the

A) body.
B) lymph.
C) interstitial fluid.
D) blood.
E) cerebrospinal fluid.

Question 11

Which of the following is NOT True about the role normal microbiota plays in maintaining host health?

A) They provide a surface that is incompatible for attachment of an invader.
B) They establish competition for nutrients and vitamins.
C) They produce antimicrobial substances.
D) They inhibit the innate immune system.
E) All of the choices are True.

Question 12

The symbiotic relationship wherein both partners benefit is termed

A) commensalism.
B) parasitism.
C) independence.
D) mutualism.
E) dysbiosis.

Question 13

Newborn babies acquire microbiota

A) when passing through the birth canal.
B) through breastfeeding.
C) by contact with the mother's skin.
D) from the environment.
E) All of the above are a source of microbiota.

Question 14

The composition of the normal microbiota may be affected by

A) hormonal changes.
B) use of antibiotics.
C) obesity level.
D) diet.
E) All of the choices are correct.

Question 15

A relationship in which one partner benefits and the other is harmed is termed

A) commensalism.
B) parasitism.
C) independence.
D) mutualism.
E) normal microbiota.

Question 16

The number of organisms necessary to cause infection is termed the

A) infectious dose.
B) fatal number.
C) minimum lethal dose.
D) pathogenic number.
E) incidence number.

Question 17

The microorganisms that are occasionally found in or on the body are called

A) abnormal microbiota.
B) transient microbiota.
C) variant microbiota.
D) normal microbiota.
E) random biota.

Question 18

The "hygiene hypothesis" proposes that

A) lack of exposure to microbes can lead to development of allergies.
B) good hygiene always prevents development of disease.
C) hand washing is the best preventative measure against infection.
D) the immune system develops best in a clean environment.
E) adaptive immunity only develops in a sterile environment.

Question 19

Organisms that are found together and interact on a more or less permanent basis are in a relationship termed

A) mutualism.
B) parasitism.
C) symbiosis.
D) transient microbiota.
E) variance.

Question 20

A relationship in which one partner benefits and the other is unaffected is termed

A) commensalism.
B) parasitism.
C) independence.
D) mutualism.
E) dysbiosis.

Question 21

Which of the following factors is not considered important for the establishment of an infection?

A) Adherence
B) Dose
C) Toxicity
D) Virulence factors
E) None of these is important

Question 22

Which of the following cause a foodborne intoxication?

A) Staphylococcus aureus AND E. coli O157:H7
B) E. coli O157:H7 AND Clostridium botulinum
C) Clostridium botulinum AND Mycobacterium tuberculosis
D) Mycobacterium tuberculosis AND Staphylococcus aureus
E) Staphylococcus aureus, E. coli O157:H7, AND Clostridium botulinum

Question 23

Which of the following would be considered a sign of a disease?

A) Severe headache
B) Throbbing pain
C) Intense nausea
D) Fever of 39°C
E) All of these are signs

Question 24

People who carry and may spread pathogenic organisms without any apparent signs or symptoms of illness are called

A) carriers.
B) primary infectors.
C) secondary infectors.
D) mutualists.
E) opportunists.

Question 25

Which of the following members of the normal microbiota inhibit the growth of Candida albicans?

A) E. coli
B) Lactobacillus species
C) Staphylococci species
D) Propionibacterium species
E) Neisseria species

Question 26

Which of the following would NOT be considered virulence factor(s)?

A) Adhesins
B) Capsules
C) Endotoxins
D) Proteases
E) Ribosomes

Question 27

Attributes of an organism that promote pathogenicity are called

A) disease factors.
B) colonization factors.
C) virulence factors.
D) mutualistic factors.
E) pathogenic factors.

Question 28

If a disease affects only a human and not an animal, then it would be difficult to fulfill Koch's postulate number ________.

A) 4
B) 3
C) 2
D) 1
E) 8

Question 29

Virulent pathogens are

A) more likely to cause disease.
B) more likely to cause severe disease.
C) unable to cause disease.
D) more likely to be opportunists.
E) most likely normal microbiota.

Question 30

The spread of toxin via circulation is called ________.

A) septicemia
B) bacteremia
C) toxemia
D) sepsis
E) viremia

Question 31

Colonization of the body is inhibited by

A) the shedding of skin cells.
B) the movement of mucus by cilia.
C) peristalsis in the digestive tract.
D) the flushing action of the urinary tract.
E) All of the choices are correct.

Question 32

Adhesins are

A) involved in the first step of the infectious process AND are endotoxins.
B) involved in the first step of the infectious process AND are often found at the tip of pili.
C) often found at the tip of pili AND are endotoxins.
D) exotoxins AND are involved in the first step of the infectious process.
E) are exotoxins OR are endotoxins.

Question 33

The first step in the establishment of infection is that the organism must

A) invade host tissues.
B) attach to host cells.
C) evade phagocytes.
D) produce toxins.
E) cause apoptosis.

Question 34

The process by which infectious agents are ingested by host cells is 

A) exocytosis.
B) pinocytosis.
C) endocytosis.
D) phagosome fusion.
E) endofusion.

Question 35

An example of genetic variation used in pathogen survival may be

A) preventing encounters with phagocytes.
B) avoid the killing effects of complement system proteins.
C) changing the pilus type.
D) surviving within a phagocyte.
E) protease production.

Question 36

The lack of susceptibility to diseases of other species in humans may be due to the

A) lack of any cytokine production.
B) presence of endotoxins.
C) lack of any cytokine production AND secretion of exotoxins.
D) presence of endotoxins AND secretion of exotoxins.
E) lack of receptors that are recognized by adherence factors.

Question 37

Bacteria that resist killing by complement proteins are termed

A) serum strong.
B) serum resistant.
C) balanced pathogens.
D) mutualistic.
E) mutualistic AND serum resistant.

Question 38

A more modern equivalent to Koch's postulates is termed

A) Pasteur's systematics.
B) Hoch's postulates.
C) atomic theory.
D) molecular postulates.
E) protein theory.

Question 39

Which of the following does S. pneumoniae use to survive in the host?

A) Plasmids
B) Capsule
C) Pili
D) Flagella
E) Spikes

Question 40

Species of both Shigella and Streptococcus

A) invade host cells AND cause a rash.
B) produce a toxin AND cause a rash.
C) cause diarrhea AND are delivered by flea bites.
D) are delivered via flea bites AND produce a toxin.
E) invade host cells AND produce a toxin.

Question 41

Which is/are True of viruses?

A) They may suppress the production of MHC class II molecules.
B) They may prevent induction of host cell apoptosis.
C) They may bind to MHC class II antigens.
D) They may produce an MHC class III mimic molecules.
E) They are facultative intracellular parasites.

Question 42

The damage caused by parasites may be due to all of the following EXCEPT

A) competition for nutrients.
B) the parasite's immune response.
C) the physical blocking of organs.
D) the direct digestion of host tissue.
E) the host's immune response.

Question 43

During incubation and convalescence a person may still spread infectious organisms.

Question 44

Disease(s) in which the causative agent becomes latent is/are

A) cold sores AND influenza.
B) genital herpes AND pneumonia.
C) chickenpox AND influenza.
D) shingles, genital herpes, AND cold sores.
E) shingles, genital herpes, AND common colds.

Question 45

The normal microbiota provides protection against potentially harmful organisms and stimulates the immune system. Why would the immune responses to members of the normal microbiota cross-react with pathogens?

A) Because one person's normal microbiota is another person's pathogen-when we pick up "normal" microbes from a different person, they will always cause infection within us.
B) Because pathogens are often more virulent strains of our own normal microbiota, so they will appear similar to those cells to our immune system, and may be acted upon by our immune responses.
C) Because the normal microbiota keeps the adaptive immune responses tuned up, active, and ready to respond to broad, general categories of microbes such as Gram-positive and Gram-negative bacteria and viruses.
D) Because if the immune system isn't used on a regular basis, it loses the ability to respond to pathogens. The normal microbiota keeps the system going so that it can be ready to respond to pathogens when we're exposed to them.
E) Because normal microbiota are often more virulent strains of our pathogens, so they will appear similar to those cells to our immune system, and may be acted upon by our immune responses.

Question 46

The chemical nature of endotoxins is that of a

A) protein.
B) lipopolysaccharide.
C) nucleic acid.
D) lipid.
E) carbohydrate.

Question 47

Infection always leads to disease.

Question 48

The infectious dose of most pathogens is about equal.

Question 49

A human fetus has no resident microbial population.

Question 50

An infectious disease is an infection that impairs the normal state of health.

Question 51

Which is True about superantigens?

A) They are a type of exotoxin AND they stimulate an abnormally high number of TC cells.
B) They bind to MHC class II molecules on T cells AND they are a type of endotoxin.
C) They bind to MHC class II molecules on T cells AND they enhance specific antibody production.
D) They are processed intracellularly AND they are a type of endotoxin.
E) They are a type of exotoxin AND they bind to MHC class II molecules on T cells.

Question 52

C5a peptidase

A) is a virulence factor.
B) synthesizes C5a.
C) is produced by the host cell in response to infection.
D) is a molecule promoting chemotaxis.
E) is a virulence factor AND is a molecule promoting chemotaxis.

Question 53

Which of the following is/are True about endotoxins?

A) Lipid A is the toxic portion of the molecule.
B) The toxic effects depend on the bacteria from which it came.
C) The lipid A portion is heat sensitive.
D) They are proteins.
E) The toxic effects depend on the bacteria from which it came AND they are proteins.

Question 54

High concentrations of some bacteria are necessary for successful invasion because their virulence genes are only expressed at high population densities.

Question 55

Obligate intracellular parasites may be grown in special synthetic media.

Question 56

The most successful parasites are the ones that live in harmony with their hosts.

Question 57

The chemical nature of exotoxins is that of a

A) protein.
B) carbohydrate.
C) lipid.
D) lipopolysaccharide.
E) carbohydrate.

Question 58

A strong attachment of a microorganism to a host cell automatically leads to disease.

Question 59

Only Gram-positive bacteria produce exotoxins.

Question 60

Bacteria may survive phagocytosis by

A) preventing fusion of the lysosome with the phagosome AND mimicking host molecules.
B) avoiding recognition and attachment of lymphocytes AND lysing the phagosome.
C) lysing the phagosome AND mimicking host molecules.
D) preventing encounters with phagocytes AND preventing fusion of two phagosomes.
E) preventing fusion of the lysosome with the phagosome AND lysing the phagosome.

Question 61

Please select the CORRECT definition regarding interactions between hosts and microbes.

A) Immunocompetent-having a weakness or defect in the innate or adaptive defenses.
B) Parasitism-relationship between two organisms in which one partner benefits and the other is unaffected.
C) Dysbiosis-an imbalance in the microbiome that may be caused by taking antimicrobial medications.
D) Secondary infection-infection in a previously healthy person, such as measles in a child who has not had measles before.
E) Fc receptors-molecule that binds the antigen-binding region of an antibody.

Question 62

In two of Koch's postulates (#2 and #3), a pure culture of the organism is required. Which of the following would NOT be a possible consequence of using a contaminated culture?

A) You can't necessarily attribute the illness directly to the microbe in question; it may in fact be caused by the contaminating microbe.
B) There's the possibility that the test animal might be acutely susceptible to the contaminating microbe, but completely resistant to the microbe you suspect causes the illness of interest. As such, when you introduce it into the test animal, it could confuse your final results.
C) Even though there's a contaminating microbe present, as long as the original suspect microbe is also present, the disease should still manifest in test animals and the organism should still be recoverable from test animals. As such, there's really no consequence to using a contaminated culture.
D) The problem is that one microbe may be toxic to the other. It may have killed all of your suspect microbe in the culture. Therefore, you can't be sure that you're infecting your test animals with the microbe you suspect is causing the illness, or if it's only the second (contaminating) microbe.
E) These would all be consequences of using contaminated cultures.

Question 63

Which of the following is NOT a likely reason why diseases caused by opportunists are becoming more frequent in the U.S. population? 

A) People with impaired immune systems such as those with HIV disease survive longer due to more effective therapies, but this gives them a longer period of time to be infected by opportunists.
B) People in the U.S. are living longer than ever before, but they're living with a number of chronic health issues that can impair the immune system. This leads to a greater likelihood of opportunistic infections.
C) Cancer treatments have improved significantly in the last 30 years, but they often suppress the immune system. This leads to a greater likelihood of opportunistic infections in people receiving these treatments.
D) Travel into and out of the U.S. has increased significantly. This has the potential to bring in many new pathogens that can cause infections, even in otherwise healthy and immunocompetent individuals.
E) People in the U.S. are living longer than ever before, but their immune systems decline with age. This leads to a greater likelihood of opportunistic infections, especially if they receive any kind of invasive procedure.

Question 64

Why is it not possible to use Koch's postulates to show that Treponema pallidum causes syphilis?

A) T. pallidum is a Gram-negative organism.
B) T. pallidum cannot be grown in pure culture.
C) T. pallidum causes different diseases in different hosts.
D) Syphilis is a polymicrobial disease; T. pallidum is only one of the causative agents involved in the disease.
E) T. pallidum does not contain a genome.

Question 65

Please select the correct definition of balanced pathogenicity.

A) A host-parasite relationship in which the parasite persists in the host, causing maximal harm. The pathogen becomes more virulent while the host becomes increasingly susceptible.
B) A generated balance in the microbiome that may be caused by taking antimicrobial medications. It generally helps the host maintain optimal health.
C) A mechanism that allows bacteria to transfer gene products directly into host cells, inducing changes such as altering the cell's cytoskeleton structure.
D) A situation in which an abnormally high number of TH cells (effector helper T cells) are stimulated, causing a massive release of cytokines (a "cytokine storm").
E) A host-parasite relationship in which the parasite persists in the host while causing minimal harm. The pathogen becomes less virulent while the host becomes less susceptible.

Question 66

A number of viruses often include a similar set of symptoms when they cause an infectious disease state (fever, headache, fatigue, runny nose). Why would they all cause the same symptoms if they're different viruses?

A) They all possess the same basic virulence genes and molecules, so they all trigger the same responses.
B) The symptoms are associated with the immune system's response, NOT the molecules from the pathogens themselves. Our responses against viruses are fairly similar, regardless of virus type, so the symptoms are similar.
C) Most viruses infect the upper respiratory tract. This leads to the common set of symptoms listed above. Only a few viruses infect areas away from this region.
D) Viruses specifically infect mainly epithelial membranes. As such, the virally induced reaction is similar in different areas of the body due to the same basic cell types (epithelial cells) being infected in each area.
E) All animal viruses must attach to and enter host cells. Since this step in the life cycle is identical in all viruses, the signs and symptoms that follow will also be identical.

Question 67

Jay tells you that he ate chicken for dinner, which you suspect is the source of his infection. You tell Jay that infectious disease progresses through several stages, and that he is in the 

A) incubation period.
B) prodromal period.
C) illness phase.
D) recovery phase.
E) convalescence stage.

Question 68

Select the correct sequence for proving Koch's postulates.
1) The microorganism must be recovered from the experimentally infected hosts.
2) The microorganism must be present in every case of the disease.
3) The same disease must be produced when a pure culture of the microorganism is introduced into susceptible hosts.
4) The microorganism must be grown in pure culture from diseased hosts.

A) 2, 4, 3, 1
B) 1, 2, 3, 4
C) 1, 3, 2, 4
D) 4, 3, 1, 2
E) 4, 1, 2, 3

Question 69

You think that Jay may have a Salmonella infection. Although a person's normal gastrointestinal microbiota protects them from pathogenic infections, in this case, Jay has contracted the disease. You explain to Jay the role his normal microbiota plays in excluding pathogens, including

A) covering binding sites that might otherwise be used for attachment by a pathogen
B) consuming available nutrients (thus "starving") the pathogen AND reducing water and oxygen availability in their immediate environment
C) producing compounds toxic to other bacteria AND phagocytizing any incoming pathogenic cells
D) producing compounds toxic to other bacteria, consuming available nutrients (thus "starving" the pathogen) AND covering binding sites that might otherwise be used for attachment by a pathogen.
E) producing compounds toxic to other bacteria, secreting carbohydrate "traps" that catch foreign bacteria AND phagocytizing any incoming pathogenic cells

Question 70

Is it a good strategy for a microbe to adhere to a receptor that plays a critical function for a host cell?

A) No, it ISN'T a good strategy. Host cells could use an alternative receptor and shut down production of the main receptor. The microbe would not have anything to attach to and the cell would thus prevent infection.
B) Yes, it IS a good strategy. If it's a receptor the cell MUST use, it doesn't have an alternative receptor to switch to, so even though that receptor makes the cell susceptible to infection, it HAS to put that target out there. This benefits the microbe.
C) No, it ISN'T a good strategy. Microbes need to evade detection and elimination by the immune system. If they adhere to a receptor that plays a critical function, they are less likely to trigger destructive immune responses. This would be similar to using a hostage as a shield in a police-standoff situation.
D) No, it ISN'T a good strategy. By binding to receptors, the microbes will be phagocytosed by cells and destroyed within them, thus failing to infect the host cell.
E) Yes, it IS a good strategy. If the microbe attaches to a critical receptor, the host cell will be forced to try to rid itself of the pathogen. One way it can do this is to phagocytose the pathogen, thereby taking it into its own nucleus, which benefits the pathogen.

Question 71

Please select the False statement regarding viral avoidance of the immune response.

A) Some viruses interfere with antigen presentation by MHC class I molecules.
B) Some viruses produce enzymes that, when activated, make holes in the phagocyte membrane, killing the cell.
C) Some viruses move directly from one cell to its immediate neighbors, thus avoiding antibodies.
D) Some viruses encode proteins that shut down expression of host genes such as those encoding IFNs and AVPs.
E) Some viruses display "fake" MHC class I molecules, tricking the immune system into believing that the cell is uninfected.

Question 72

Which of the following is NOT a mechanism for avoiding destruction by a phagocyte?

A) Some pathogens escape from the phagosome before it fuses with lysosomes.
B) Some pathogens prevent phagosome-lysosome fusion.
C) Some microbes can survive the destructive environment within the phagolysosome.
D) Some microbes produce IgA protease that cleaves IgA, the class of antibody found in mucus and other secretions.
E) These are all mechanisms for avoiding phagocytic destruction.

Question 73

Home-canned foods should be boiled before consumption to prevent botulism. Considering that this treatment does NOT destroy endospores, why would it be helpful in preventing the disease?

A) Because it would destroy the vegetative cells, and only the vegetative cells cause the disease.
B) Because it would at least weaken the endospores, making them more susceptible to elimination by our immune system.
C) Because the heat would denature the botulism endotoxin and inactivate it. The endotoxin is what leads to the disease symptoms, so this would make the food safer.
D) Because although botulism exotoxin is harmless, it has a bad odor and boiling removes this, making the food more appealing to eat.
E) Because the heat would denature the botulism exotoxin and inactivate it. The exotoxin is what leads to the disease symptoms, so this would make the food safer.

Question 74

What is the difference between a primary pathogen and an opportunistic pathogen?

A) A primary pathogen is a microbe that is able to cause disease in an otherwise healthy individual, while an opportunistic pathogen is a microbe that causes disease only when introduced into an unusual location or into an immunocompromised host.
B) An opportunistic pathogen is a microbe that is able to cause disease in an otherwise healthy individual, while a primary pathogen is a microbe that causes disease only when introduced into an unusual location or into an immunocompromised host.
C) A primary pathogen is an environmental microbe that is able to cause disease in an otherwise healthy individual, while an opportunistic pathogen is always a member of the normal microbiota and causes disease only when introduced into an unusual location.
D) A primary pathogen is an environmental microbe that is able to cause disease in an otherwise healthy individual, while an opportunistic pathogen is always a member of the normal microbiota and only causes disease in an immunocompromised host.
E) A primary pathogen is a microbe that is able to cause disease in an otherwise healthy individual, while opportunistic pathogens are the microorganisms routinely found growing in and on the body of a healthy individual. 

Question 75

The period of time between exposure to an agent and the onset of disease signs and symptoms is called the

A) prodromal phase.
B) decline phase.
C) incubation period.
D) lag phase.
E) carrier phase.

Question 76

Select the INCORRECT definition regarding the progression of an infectious disease.

A) Illness phase-period of time during which symptoms and signs of disease occur.
B) Incubation period-interval between the entrance of a pathogen into a susceptible host and the onset of illness caused by that pathogen.
C) Prodromal period-a period of early, vague symptoms indicating the onset of a disease.
D) Period of convalescence-period of recuperation and recovery from an illness.
E) Carrier phase-period in which a pathogen is harbored without noticeable ill effects, but may be transmitted to other hosts.

Question 77

The length of the incubation period depends on a variety of factors, including

A) the growth rate of the pathogen AND environmental conditions.
B) the host's condition AND the carrier's vaccination status.
C) number of infectious cells or virions encountered AND the host's condition.
D) number of infectious cells or virions encountered, the host's condition, AND the growth rate of the pathogen.
E) the growth rate of the pathogen only.

Question 78

You explain to Jay that infections and the associated diseases are often described according to the timing and duration of the symptoms. You define the different categories to him, telling him that he has

A) a chronic infection, which is an infection that develops slowly and may last for months or years.
B) a latent infection-the microbe causing Jay's illness will continue to exist in him, although likely without causing any symptoms.
C) a localized infection, in which the microbe is limited to a small area-in Jay's case the gastrointestinal tract.
D) an inopportunistic infection, because Salmonella species are part of a person's gastrointestinal normal microbiota.
E) an acute infection, characterized by symptoms that develop quickly but last only a short time.

Question 79

You describe to Jay the initial events that must have occurred in order for him to become ill. Which of the following statements is False? 

A) All pathogens must inject molecules into the host cell that induce a specific change in those cells; this is performed via structures called injectisomes.
B) Following adhesion, the pathogen must colonize the host, growing on the host cell surface.
C) Pathogens must adhere to host cells to initiate infection; bacteria use adhesins to attach to receptors on host cells.
D) In order to colonize, a pathogen must often compete with the normal microbiota, prevent binding of secretory IgA, and obtain iron.
E) All of these statements are correct.

Question 80

Would an antibody response against the B subunit of an A-B toxin protect against the effects of the toxin?

A) Yes. If antibodies bind to the B portion, the toxin can no longer bind to target cells and will thus not affect those cells.
B) No. Even if antibodies bind to the B portion of the toxin, it is the A portion that actually causes damage to the cell.
C) Yes. If antibodies bind to the B portion, that portion of the toxin does not become activated, and thus does not damage the host cell.
D) No. Even if antibodies bind to the B portion of the toxin, the toxin is still taken into the host cell by phagocytosis, damaging that cell.
E) This question cannot be answered. The immune system does not mount a strong response against proteins, so this situation is unlikely to occur.