Chapter 16

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.

2, 4, 3, 1

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

3

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

3

Please select the correct definition of balanced pathogenicity.

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.

The suffix -emia means in the:

blood

An example of genetic variation used in pathogen survival may be

changing the pilus type

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

commensalism

The infectious dose is:

defined as the number of microbes needed to cause infection.

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

ecosystem

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

endocytosis

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

endocytosis

True or false: A strong attachment of a microorganism to a host cell automatically leads to disease.

false

True or false: Infection always leads to disease.

false

True or false: Obligate intracellular parasites may be grown in special synthetic media.

false

True or false: The infectious dose of most pathogens is about equal.

false

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

fever of 39 C.

The composition of the normal microbiota may be affected by

hormonal changes use of antibiotics diet obesity level ALL ARE CORRECT.

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

incubation period

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

infection

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

infection

The number of organisms necessary to cause infection is termed the

infectious dose

Species of both Shigella and Streptococcus

invade host cells AND produce a toxin.

Adhesins are:

involved in the first step of the infectious process AND are often found at the tip of pili.

Adhesins are

involved in the first step of the infectious process AND often found at the tip of pili.

C5a peptidase

is a virulence factor.

The "hygiene hypothesis" proposes that:

lack of exposure to microbes can lead to development of allergies.

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

lack of receptors that are recognized by adherence factors.

The chemical nature of endotoxins is that of a

lipopolysaccharide

Bacteria may survive phagocytosis by:

preventing fusion of the lysosome with the phagosome AND lysing the phagosome.

The chemical nature of exotoxins is that of a

protein

Bacteria that resist killing by complement proteins are termed

serum resistant

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

shingles, genital herpes, AND cold sores.

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

symbiosis

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

symbiosis.

Opportunists or opportunistic pathogens

take advantage of special circumstances.

True or false: A human fetus has no resident microbial population.

true

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

true

True or false: The most successful parasites are the ones that live in harmony with their hosts.

true

Attributes of an organism that promote pathogenicity are called:

virulence factors

Newborn babies acquire microbiota

when passing through the birth canal through breastfeeding by contact with the mother's skin from the environment ALL are correct.

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

T. pallidum cannot be grown in pure culture

C5a peptidase is:

a virulence factor.

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

the parasite's immune response

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

the parasite's immune response.

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

attach to host cells.

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

capsule.

Virulent pathogens are

more likely to cause severe disease.

The spread of toxin via circulation is called ______.

toxemia

True or False? Infection always leads to disease.

False

CORRECT definitions regarding the progression of an infectious disease:

-Illness phase—period of time during which symptoms and signs of disease occur. -Incubation period—interval between the entrance of a pathogen into a susceptible host and the onset of illness caused by that pathogen. -Prodromal period—a period of early, vague symptoms indicating the onset of a disease. -Period of convalescence—period of recuperation and recovery from an illness.

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

-competition for nutrients. -the physical blocking of organs. -the direct digestion of host tissue. -the host's immune response.

Colonization of the body is inhibited by:

-the shedding of skin cells. -the movement of mucus by cilia. -peristalsis in the digestive tract. -the flushing action of the urinary tract. ALL OF THE CHOICES ARE CORRECT

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

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.

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?

Because pathogens are often more virulent strains of our own normal microbiota, so they will appear similiar to those cells to our immune system, and may be acted upon by our immune responses.

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?

Because the heat would denature the botulism exotoxin and inactivate it. The exotoxin is what leads to the disease symptoms, so this would make food safer.

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

Carrier phase—period in which a pathogen is harbored without noticeable ill effects, but may be transmitted to other hosts.

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

Dysbiosis- an imbalance in the microbiome that may be caused by taking antimicrobial medications.

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?

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.

True or False? A strong attachment of a microorganism to a host cell automatically leads to disease.

False

True or False? Only gram-positive bacteria produce exotoxins.

False

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

Koch

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

Koch's postulates

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

Koch's postulates.

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

Koch.

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

Lactobacillus species

Which of the following is/are true about endotoxins?

Lipid A is the toxic portion of the molecule.

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

Ribosomes

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

Some microbes produce IgA protease that cleaves IgA, the class of antibody found in mucus and other secretions.

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

Some viruses produce enzymes that, when activated, make holes in the phagocyte membrane, killing the cell.

Which of the following cause a foodborne intoxication?

Staphylococcus aureus, E. Coli 0157:H7, AND Clostridium botulinum

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?

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.

Which is true about superantigens?

They are a type of exotoxin AND they bind to MHC class II molecules on T cells.

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

They inhibit the innate immune system.

Which is/are TRUE of viruses?

They may prevent induction of host cell apoptosis.

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

Toxicity

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

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.

True or False? An infectious disease is an infection that impairs the normal state of health.

True

True or False? During incubation and convalescence a person may still spread infectious organisms.

True

True or False? The most successful parasites are the ones that live in harmony with their hosts.

True

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

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.

A more modern equivalent to Koch's postulates is termed:

molecular postulates.

A symbiotic relationship wherein both partners benefit is termed

mutualism

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

normal microbiota

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

number of infectious cells or virions encountered, the host's condition, AND the growth rate of the pathogen.

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

parasitism

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

pathogen

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

pathogen

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

transient microbiota

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

transient microbiota