Deck 10: Host-Microbe Interactions and Pathogenesis

Question 1

Which statement shows an example of a commensal species in one host becoming a pathogenic species in another host?

A) C. difficile flourishes in the large intestine after antibiotic therapy.
B) New infectious diseases are due to increases in host tropism.
C) Shigella flexneri preferably infects the tissues of humans and other primates.
D) E. coli lives harmlessly in the appendix but will be attacked by the immune system if it invades the abdominal cavity.
E) Up to 30% of pregnant women harbor Group B streptococci in the vagina to no ill effect, but when transmitted to their newborns, a proportion of babies develop serious infection.

Answer 1

Up to 30% of pregnant women harbor Group B streptococci in the vagina to no ill effect, but when transmitted to their newborns, a proportion of babies develop serious infection.

Question 2

Host- microbe interactions

A) are generally commensal.
B) are always harmful.
C) involve a dynamic give- and- take between the microbe and the host.
D) do not involve host factors.
E) never result in the normal species of the microbiota causing disease.

Answer 2

involve a dynamic give- and- take between the microbe and the host.

Question 3

ID50 describes

A) the number of cells or virions which will kill 50 individuals.
B) the number of cells or virions needed to establish an infection in 50 percent of exposed hosts.
C) the amount of toxin lethal to a 50- pound human or other animal.
D) the number of cells or virions which will kill 50% of exposed hosts.
E) the percentage of individuals which will develop an infection after exposure to 50 cells or virions.

Answer 3

the number of cells or virions needed to establish an infection in 50 percent of exposed hosts.

Question 4

Which is not a category of virulence factors?

A) immune system evasion
B) adhesion
C) toxins
D) attenuation
E) nutrient acquisition

Question 5

Examples of healthy host- microbe interactions with our normal microbiota include all except

A) microbiota disruption.
B) moderation of immune attack against microbiota species while in their normal tissues.
C) competition with pathogens.
D) vitamin manufacture.
E) immune system maturation.

Question 6

Which type of toxin is pictured?

A) endotoxin
B) type 1 exotoxin
C) type 2 exotoxin
D) type 3 exotoxin
E) either type 1, type 2, or type 3 exotoxins

Question 7

The degree or extent of disease that a pathogen causes is

A) virulence.
B) toxicity.
C) a host factor.
D) attenuation.
E) pathogenicity.

Question 8

Septic shock is typically associated with

A) exotoxins or endotoxin.
B) either Gram- negative or Gram- positive infections.
C) Gram- negative infections.
D) superantigens.
E) exotoxins.

Question 9

Properties that contribute to virulence

A) are determined by both the microbe and the host, and are fixed and unchanging.
B) are determined solely by the host.
C) are fixed and unchanging.
D) are determined solely by the microbe.
E) are determined by both the microbe and the host, and may evolve over time.

Question 10

What is an example of a virulence factor that is related to immune system evasion?

A) iron- binding protein
B) LPS in Gram- negative cell wall
C) fimbriae
D) flagella
E) capsule

Question 11

Which factor is responsible for many emerging pathogens in humans?

A) expanded host or tissue range of the pathogen
B) increased use of antibiotics in the past half- century
C) longer life spans resulting in a larger elderly population
D) improved sanitation and hygiene practices
E) availability of vaccines

Question 12

Exotoxins are

A) secreted.
B) the targets of some childhood vaccines.
C) only made by Gram- positive bacteria.
D) secreted and only made by Gram- positive bacteria.
E) secreted and the targets of some childhood vaccines.

Question 13

The preference of a pathogen for a specific host is

A) opportunism.
B) tropism.
C) virulence.
D) dysbiosis.
E) pathogenicity.

Question 14

Which is not an example of virulence as an evolving property?

A) Cold viruses which generate more coughs and sneezes while allowing the host to remain mobile will have an evolutionary advantage over those that cause their host to be bedridden.
B) As hosts evolve more effective defenses against a given pathogen, the pathogen in turn will evolve virulence factors to combat those defenses.
C) Historically, smallpox appeared to shift from a highly virulent pathogen which killed its victims quickly to one that did not kill immediately but more easily spread from person to person.
D) The 1918 influenza pandemic primarily killed young adults rather than elderly persons which is more typical of influenza both before and after that time.
E) Each of these is an example of virulence as an evolving property.

Question 15

An attenuated pathogen

A) is part of the normal human microbiome.
B) has lost virulence factors needed to cause disease in an immune competent host.
C) has recently acquired virulence factors allowing it to jump species.
D) has become antibiotic- resistant.
E) produces toxins.

Question 16

Toxemia is a condition

A) where a toxin is acting on tissues locally.
B) where a toxin acts as a superantigen.
C) where a toxin has entered the bloodstream resulting in systemic effects.
D) that may describe both localized and systemic effects.
E) where a vaccine is used to protect against a toxin.

Question 17

Which factors may result in a normal microbiota species causing disease?

A) dysbiosis due to antibiotic therapy or invasion of other tissues by the microbiota species
B) immune system attack on the host's own tissues
C) dysbiosis due to antibiotic therapy
D) dysbiosis due to antibiotic therapy or immune system attack on the host's own tissue
E) invasion of other tissues by the microbiota species

Question 18

Which type of bacterial toxin is matched incorrectly with its description?

A) type 3 exotoxin: bind to a membrane receptor then enter the cell
B) toxemia: a toxin produced during a viral infection
C) endotoxin: enters the bloodstream during infection with Gram- negative bacteria
D) type 1 exotoxin: bind to the targeted host cell at a membrane receptor but do not enter the cell
E) type 2 exotoxin: disrupt and damage the host cell membrane leading to cell lysis

Question 19

Which portal of exit will a bloodborne pathogen likely use?

A) respiratory mucosa
B) ocular
C) parenteral
D) GI mucosa
E) skin

Question 20

Which portal of entry is mismatched to its description?

A) parenteral: pathogen is passed from mother to child through the placenta
B) ocular: via the conjunctiva
C) otic: pathogen enters via the ear
D) urogenital: often associated with sexually- transmitted pathogens
E) gastrointestinal: often involves fecal- to- oral transmission

Question 21

How are symptoms of an infection associated with the mode of transmission of the pathogen?

A) Lack of symptoms indicates that the infection is not transmissible to others.
B) The worse the patient feels, the more likely the disease is transmissible to others.
C) There is no relationship between symptoms and mode of transmission.
D) Bodily fluids produced during an illness are often rich in infectious organisms.
E) Bodily fluids are rarely a source of disease transmission during an infection.

Question 22

A pathogen which uses a specific portal of entry will only be able to establish an infection in the system associated with that portal.

Question 23

Which type of invasin allows a pathogen to break down a blood clot that the body has generated to trap their spread?

A) flagella
B) kinase
C) neuraminidase
D) collagenase
E) coagulase

Question 24

The role of healthcare workers in the management of disease outbreaks

A) should be addressed through periodic training and re- training.
B) is limited to properly using personal protective equipment.
C) is only important in BSL- 3 or higher facilities.
D) can be approached casually.
E) is not critical in U.S. healthcare facilities.

Question 25

Which statement is true about standard precautions?

A) They are used in student labs that only handle BSL- 1 pathogens
B) They are in force only for bloodborne pathogens.
C) They apply to all healthcare providers working with all patients.
D) They require full face shields, gloves, and barrier gowns for all patient contact situations.
E) They are used only when the patient is known to be infected with a BSL- 2 or higher pathogen.

Question 26

Which of the following microbes are classified as BSL- 2?

A) Both Staphylococcus aureus and Staphylococcus epidermidis
B) Staphylococcus epidermidis
C) E. coli K- 12
D) Bacillus subtilis
E) Staphylococcus aureus

Question 27

A microbe with a low ID50 does not necessarily cause severe disease.

Question 28

Which method of hiding from the host immune system is incorrectly matched with its description?

A) antigen mimicry: the pathogen's antigens are similar in structure to host molecules
B) living intracellularly: a pathogen resides on the surface of a host cell where it is hidden by host cell surface molecules
C) antigen variation: the pathogen frequently switches its antigens
D) antigen masking: the pathogen covers itself in host factors to avoid detection of its own antigens
E) latency: a pathogen exists quietly inside the host cell

Question 29

A microbe is either pathogenic or it is not. A microbe is either virulent or it is not. Both pathogenicity and virulence are all- or- nothing terms.

Question 30

Adhesins

A) include molecules that are typically found deep inside the pathogenic cell.
B) make poor targets for vaccine development.
C) include molecules that bind to host factors such as fibronectin, sialic acid, and heparin / heparin sulfate.
D) allow pathogens to stick to host tissues only in a nonspecific manner.
E) are limited to only a few known types.

Question 31

Which of the following can be a potential disease reservoir for a pathogen which infects humans?

A) only humans or inanimate objects that an infected human directly handles
B) Humans, non- human animals, inanimate objects, or environmental niches can all serve as reservoirs for a pathogen which infects humans.
C) environmental niches such as soil or water
D) only humans
E) only humans or non- human animals

Question 32

A pathogen will always use the same portal for both entry and exit.

Question 33

A potential antimicrobial drug is tested and found to strip away the capsules made by certain pathogenic bacteria. How would this drug affect the bacteria's ability to cause disease?

A) The bacteria would be unable to acquire needed nutrients from the body.
B) The bacteria would only be able to colonize surface tissues and not penetrate more deeply.
C) The bacteria would be unable to survive inside the phagocyte.
D) The phagocytes would be better able to ingest the bacteria.
E) The bacteria would not be able to kill phagocytes.

Question 34

Which mode of transmission is not addressed by transmission precautions?

A) airborne and droplet
B) airborne
C) direct contact
D) droplet
E) vector

Question 35

Which biosafety level is incorrectly matched with its description?

A) BSL- 3: serious, lethal pathogens though some diseases may be treatable
B) BSL- 1: non- pathogens or those that rarely cause disease in healthy people
C) BSL- 2+: known animal pathogens which do not infect humans
D) BSL- 4: dangerous, lethal pathogens with no cures or treatments
E) BSL- 2: known pathogens but the disease is treatable or preventable

Question 36

Which of the following is not a way that pathogens can avoid destruction by the phagocytes of the host immune system?

A) release toxins which kill the phagocyte
B) make a capsule which is toxic to the phagocyte
C) adapt to living inside the phagocyte
D) block fusion of the phagosome with the lysosome inside the phagocyte
E) neutralize the hydrolytic enzymes produced by the phagocyte

Question 37

Droplet and airborne precautions

A) both involve diseases of the respiratory system and/or diseases transmitted through a respiratory route.
B) both involve transmission through fine aerosols which require close contact for transmission.
C) both require isolation in a specially- ventilated room (AIIR).
D) both require the use of a procedural mask.
E) both require use of an N95 respirator.

Question 38

Pathogens can obtain iron from the body using

A) transferrin.
B) lipases.
C) proteases.
D) siderophores or transferrin.
E) siderophores.

Question 39

Criteria for assigning pathogens to a biosafety level include all the following except

A) mode of transmission.
B) level of infectivity.
C) ability to culture the pathogen using standard laboratory media and equipment.
D) availability of disease prevention and/or treatment.
E) extent of disease and mortality rates.

Question 40

More than half of new infectious diseases in humans emerged due to expanded host tropism by the infectious organism.

Question 41

While a reservoir can be a source of infection, not all sources of infection are reservoirs.

Question 42

Members of the genus Vibrio, which includes the species which cause cholera are found in marine environments. However, most cases of cholera occur when people drink water that has been contaminated with feces from other humans with cholera. If an effective vaccine against cholera were developed so that humans would become immune to the disease, both the reservoir and the source of the cholera bacteria would be eliminated.

Question 43

A newly emerged infectious disease whose pathogen cause has not yet been identified is lethal in more than 90% of cases. Epidemiological evidence suggests that this pathogen is transmitted only through direct contact with the blood of ill or recently deceased patients. Patient blood and tissue samples would best be handled at BSL- 2 until more information can be learned about the pathogen.

Question 44

If you had the ability to genetically engineer a pathogenic bacterium, what features would you include? Choose a portal of entry and a portal of exit for your pathogen. Then choose three virulence factors from at least two the following areas: toxins, adhesins, invasins, acquisition of nutrients, and avoidance of the immune system, and describe how each factor will help your bacterium survive in the host. Your virulence factors should make sense for the portals of entry and exit that you chose.

Question 45

You are a consultant with an architectural firm designing a BSL- 3 hospital facility for patient care and diagnostic laboratory services. The facility will specialize in airborne pathogens such as Mycobacterium tuberculosis. Describe the characteristics of pathogens handled in a BSL- 3 facility and describe at least five features that must go into the facility design.

Question 46

Contrast pathogenicity and virulence, and describe why virulence can be considered an evolving property.