Ch. 35 Pathogenicity and Infection

In general, infectious diseases that are commonly fatal are newly evolved relationships btwn the parasitic organism and the host. Why is this so?

Causing death in the host does not usually benefit the fitness of the pathogen. Thus over time, the pathogen will evolve away from killing the host

Which of the following has no effect on the outcome of the host-parasite relationship? a. The number of parasites on or in the host b. The virulence of the parasite c. The defenses of the host d. All of these have an effect on the outcome of the host-parasite relationship

d. All of these have an effect on the outcome of the host-parasite relationship

The final outcome of most host-parasite relationships depends on: a. The number of organisms present in or on the host b. The virulence of the organism c. The host's defenses d. All of the choices

d. All of the choices

Which of the following is required of a pathogen to possess in order for it to be successful at causing infectious disease? a. Initially be transported to the host b. Be able to exit the host c. Ability to adhere to, colonize, or invade the host d. Ability to damage the host e. All of the choices

e. All of the choices

Transfer of pathogens from host to environment and then to another host are said to be transmitted ___.

Indirectly

Explain the observation that different pathogens infect different parts of the host.

Infectious agents are very specific, even to the level of the type of cell they can infect. Typically infectious agents bind to specific receptor molecules on the host cell surface. Each is adapted to its niche in the host

Many types of bacteria are only ___ when dispersing from more stable and heterogeneous communities known as biofilms.

Planktonic

The capacity of an organism to produce a toxin is called ___.

Toxigenicity

Endotoxins can be denatured by iodine to form ___ which are useful in vaccines.

Toxoids

Why does a parasitic organism not have to be a parasite?

the definition of pathogen is focused on the organism causing disease and damage to the host. The term parasite is focused instead on using energy and nutrients from the host. Some parasites cause little noticeable damage to the host.

A ___ infection is a disease caused by a parasitic organism that is normally found in animals other than humans

Zoonotic

The condition in the host that results from pathogenic parasitic organism growing and multiplying within or on the host is called: a. An infection b. An infectious disease c. Pathogenesis d. All of these

a. An infection

The toxic component of lipopolysaccharide is called: a. Lipid A b. Exotoxin c. Hemolysin d. Antigen polysaccharide

a. Lipid A

Which of the following is a facultative intracellular pathogen? a. Viruses b. Brucella abortus c. Rickettsia d. All of the choices

b. Brucella abortus

An inanimate object that may be contaminated with a pathogen is called a a. Vector b. Fomite c. Zoonoses d. None of the choices

b. Fomite

Listeria monocytogenes propels itself through mammalian host cells using a. A modified form of gliding motility b. Host cell actin and other cytoskeleton proteins c. Periplasmic flagella d. Fimbriae based twitching motility

b. Host cell actin and other cytoskeleton proteins

Endotoxins include which of the following? a. Diphtheria toxin b. Lipopolysaccharide c. Tetanus toxin d. Botulinum toxin

b. Lipopolysaccharide

Vector-borne transmission can be either external or internal. In external (mechanical) transmission, the pathogen is carried: a. On a fomite b. On the body surface of a vector c. Within the vector d. All of the choices

b. On the body surface of a vector

Which of the following is not a biological effect associated with endotoxin? a. Coagulation b. Paralysis c. Fever d. Fibrinolysis

b. Paralysis

If a symbiont either harms or lives at the expense of another organisms, the relationship is called a. Symbiosis b. Parasitism c. Commensalisms d. Pathogenicity

b. Parasitism

Any organism that can cause disease in the host after direct interaction is a: a. Focal pathogen b. Opportunistic pathogen c. Primary pathogen d. Secondary pathogen

c. Primary pathogen

Bacteria within biofilms exchange a. Plasmids b. Quorum-sensing molecules c. Nutrients

d. All of the choices

The characteristics of a pathogen that determine its virulence include which of the following? a. Pathogenicity b. Invasiveness c. Infectivity d. All of the choices

d. All of the choices

Which of the following is not a characteristic of lipid A? a. Heat stable b. Toxic in nanogram amounts c. Weakly immunogenic d. Neurotoxic

d. Neurotoxic

T/F: Colonization specifically refers to the multiplication of a pathogen on or within a host, and includes the resulting tissue invasion and damage.

false

T/F: Generally, exotoxins tend to be more heat stable than endotoxins.

false

Once a pathogen has infected the host, ___ is a measure of the pathogen's ability to spread to adjacent or other tissues.

invasiveness

An ___ pathogen can cause disease in a host with impaired resistance.

opportunistic

T/F: Fever response can be triggered by an endogenous pyrogen called interleukin-1.

true

T/F: Macrophages are phagocytic cells.

true

T/F: The only organisms to produce endotoxins are gram (-) bacteria.

true

T/F: While exotoxin production is most generally associated with gram (+) bacteria, some gram (-) bacteria also produce exotoxins.

true

A neutralizing antibody against a toxin is called a(n) ___.

Antitoxin

Because LPS is bound to the surface of bacteria, it is called a(n) ___.

Endotoxin

T/F: Inanimate materials involved in pathogen transmission are called reservoirs.

False

Intracellular bacterial infections present a particular difficulty for the host. Why is it harder to defend against these infection than against viral infections and extracellular bacterial infections?

Intracellular pathogens are mostly protected from humoral immunity. Most intracellular bacterial pathogens are also resistant to killing by phagocytes. Generally CD4+ T cells are responsible for mediating immunity against intracellular bacteria

Virulence may be measured experimentally at the host level by the ___ ___ ____, which measures the number of pathogens that kills 50% of an experimental group of hosts within a specific amount of time.

Lethal dose 50

Many bacteria are pathogenic because they carry large segments of DNA called ___ ___, which were acquired by horizontal gene transfer, and which carry genes responsible for virulence.

Pathogenicity islands

A ___ is an organism that transfers pathogens from one host to another.

Vector

The term ___ refers to the degree or intensity of pathogenicity.

Virulence

Matching: 1) latent 2) antitoxin 3) opportunistic 4) localized A. requires weakened immune system B. organisms present in tissue for long periods of time C. not general infection D. a neutralizing antibody

1-B, 2-D, 3-A, 4-C

Matching: 1) reservoir 2) fomite 3) opportunistic 4) nosocomial A. does not harm a healthy host B. develops during a hospital stay C. site where the pathogen normally resides D. inanimate object that may be involved in transmission

1-C, 2-D, 3-A, 4-B

Pathogenicity islands are typically associated with a. Genes encoding tRNA b. Genes encoding rRNA c. G+C content similar to the rest of the bacterial genome d. None of the choices

a. Genes encoding tRNA

Endotoxin is released when: a. Gram (-) pathogens lyse or divide b. Cells are starved for iron c. Cells are lysogenic for the beta phage d. All of the choices

a. Gram (-) pathogens lyse or divide

An organism other than a human that is infected with a parasitic organism that can also infect humans is called a(n) ___ host. a. Reservoir b. Endoparasite c. Transfer d. Intermediate

a. Reservoir