BIOL 400 Ch. 35

Vehicle transmission

the vehicle, often a fomite, spreads the pathogen to multiple hosts.

Select the best example of indirect contact transmission.

HIV infection via IV drug use with a contaminated shared needle

Large segments of bacterial chromosomal and plasmid DNA encoding virulence factors are known as pathogenicity "islands" because ______.

they appear to have been inserted intact into existing DNA

True or false: A disease syndrome is one defining symptom of a particular disease.

False

Select the definition of infectious dose 50 (ID50).

The number of microbes required to induce disease in 50% of the inoculated hosts.

Select the best definition of lethal dose 50 (LD50).

The number of microbes required to kill 50% of inoculated host organisms.

Among the most lethal substances known, heat-labile proteins secreted mainly by Gram positive bacteria are called ______.

exotoxins

Vehicles

inanimate materials that indirectly transmit pathogens

The time period between when a pathogen enters a host and the development of symptoms is called the _____ period and it will vary from disease to disease.

incubation

Prodromal stage

The prodromal stage occurs with an onset of signs and symptoms that are not yet specific enough to make a clear diagnosis. However, the patient often is contagious.

Hepatitis B virus (HBV) produces large amounts of proteins that are not associated with the complete, infectious virus. How do these these proteins benefit the virus?

They act as decoys for the host immune response.

What do these infectious diseases have in common: Lyme disease, malaria, plague, Rocky Mountain Spotted fever, and West Nile virus?

They are all transmitted by arthropod vectors.

Infection

invasion of the body by a pathogenic organism

When a microorganism is restricted to infecting only a particular cell or tissue type, this is known as a(n) _____

tropism

Because their expression is associated with the production of disease in their host, bacterial toxins, superantigens, and attachment factors are all be considered to be _____ factors.

virulence

The degree of harm (pathogenicity) inflicted on the host is best defined as a pathogen's _____

virulence

Which of the following is a general class of molecules that enables a microorganism to cause host cell or tissue damage?

virulence factors

Illness period

when the disease is most severe and displays characteristic signs and symptoms. The host immune response is typically triggered at this stage.

An infectious disease that is transmitted from an animal to a human is termed a(n) ______.

zoonosis

Host

An organism on which a parasite lives.

Arrange the four stages of a (nonfatal) infectious disease according to the order in which they occur, with the earliest stage that follows the initial infection at the top.

(1) incubation period; (2) prodromal stage; (3) Illness period; (4) convalescence

Zoonoses

Diseases transmitted from animals to humans

A high LD50 value means ______.

a relatively large number of microorganisms is required to kill an infected organism

Disease syndrome

a set of signs and symptoms that are characteristic of the disease.

Infectivity

ability of a biological agent to enter and grow in the host

Pathogenicity

ability of a pathogen to cause disease

The image illustrates different microbial molecules that are specifically involved in ______.

adherence

Antitoxins are ______.

antibodies that inactivate toxins

Antibodies that recognize and inactivate bacterial exotoxins are generally called _____.

antitoxins

Select the best definition of pathogen.

any organism that causes disease

In an AB exotoxin molecule, the B portion ______.

binds to the target receptor on a host cell

Select three signs (as opposed to symptoms) of an infectious disease.

blood in the stool rash fever

Bacteria such as Streptococcus pneumoniae and Haemophilus influenzae resist phagocytosis by producing an outer mucoid structure called a(n) _____.

capsule

The term that most specifically describes the establishment of a site of microbial replication on or within a host is ______.

colonization

Microbial pathogens that only grow and replicate outside of a host cell are typically called _____ pathogens.

extracellular

The best term to describe an inanimate vehicle (e.g. surgical instrument, bedding, or drinking vessel) that can spread a pathogen to multiple hosts is a ______.

fomite

The spread of a pathogen via some type of contact between two individuals is generally called _____ transmission, whereas _____ transmission occurs when an unborn child acquires a pathogen from an infected mother.

horizontal or direct; vertical

Select the strategy each pathogen uses to evade the immune responses of the host.

influenza virus = changes surface proteins by genetic recombination N. gonorrhoeae = phase variation of pili proteins; also produces proteases S. pyrogenes = produces a capsule that resembles host tissue components; also produces protein G staphylococcus = produces protein A to interfere with immune system recognition

Microbial pathogens that are able to grow and replicate within a host cell are typically called _____ pathogens.

intracellular

Select all correct descriptions of bacterial exotoxins.

often encoded on plasmids or prophages among the most toxic substances known heat-labile (inactivated at 60-80 degrees C)

Select all correct descriptions of lipid A (endotoxin).

only weakly immunogenic component of the outer membrane of Gram-negative bacteria heat stable

An organism that infects a host when it gets out of its typical niche (normal location in the body) is a(n) ______.

opportunistic pathogen

Facultative intracellular pathogens

organisms that can reside within the cells of the host or in the environment but can also be grown in pure culture without host-cell support.

Select the best term for a large segment (10-200 kilobases) of bacterial chromosomal and plasmid DNA that encodes virulence factors.

pathogenicity island

The ability of an organism (usually a microbe) to cause disease is its _____

pathogenicity or virulence

Viral glycoproteins utilized for attachment are particularly effective when there is a complementary _____ on the host cell for them to bind to.

receptor

A low ID50 value means ______.

relatively small numbers of microorganisms are required to establish an infection

droplet nuclei

residue of evaporated droplets emitted by an infected host. 1 to 5 um in diameter.

What type of shock can result from exposure to relatively large amounts of the lipid A component of Gram-negative bacteria, and the subsequent release of large amounts of cytokines like IL-1 and tumor necrosis factor?

septic shock

In the context of infectious diseases, objective changes in the body that can be directly observed or measured (such as fever) are called _____

signs

Symptoms

subjective changes, such as pain and loss of appetite, that are experienced by the patient.

Which type of bacterial exotoxin stimulates a large proportion of the host T cell population to produce excessive amounts of cytokines?

superantigen

The human immunodeficiency virus (HIV) is an example of a pathogen that has evolved to ______ the host's immune response.

suppress

A(n) _____ is an organism that facilitates the spread of disease from one host to another. Examples include mosquitoes, ticks, and fleas.

vector

Direct living transmitters of a pathogen, such as arthropods, are called _____

vectors

Inanimate materials (e.g. food, water, biological materials) that indirectly transmit pathogens to new hosts are called _____

vehicles or fomites

Tropism

(1) the movement of living organisms toward or away from a focus of heat, light, or other stimulus. (2) the selective infection of certain organisms or host tissue by a virus due to the presence of the specific receptor to which the virus binds.

See the graph showing the four stages of a typical infectious disease, and match the letter of each labeled area with its correct name.

(A) Incubation period (B) Prodromal stage (C) Illness period (D) Convalescence

In an AB exotoxin molecule, the A portion ______.

produces the negative effect of the toxin inside the cell

Opportunistic pathogens

A microorganism that is usually free living or a part of the host's normal microbiota but may become pathogenic under certain circumstances, such as when the immune system is compromised.

Pathogen

An organism that causes disease

Match the pathogen(s) with the mechanism used to suppress the host immune response.

Human immunodeficiency virus (HIV) = Infect cells of the immune system and diminish their function Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae = Produce slippery mucoid capsule that prevents host immune cells from effectively capturing them Neisseria gonorrhoaea = Produce modified lipooligosaccharides on their surface to interfere with host mechanisms that would otherwise lyse them

Extracellular pathogens

If the pathogens remain in tissues and fluids but never enter host cells during the course of disease.

An opportunistic pathogen is one that is particularly like to cause disease in what type of host?

Immunocompromised

Obligate intracellular pathogens

Incapable of growth and multiplication outside of a host. By definition, all viruses are obligate intracellular pathogens in that they require a host cell for replication, often to the detriment of that cell.

When a pathogen is growing and multiplying within or on a host (which may or may not result in overt symptoms) this is known as a(n) ______.

Infection

When the presence of a pathogen or its products results in the impairment or loss of function of a host system, this is a(n) ______.

Infectious disease

Infectious disease

Is any change from a stage of health in which part or all of the host is incapable of carrying on its normal functions due to the presence of a pathogen or its products (e.g., toxins)

Select the best description of vector-borne transmission.

Lyme disease contracted through a bite from a tick

Intracellular pathogens

Microbes that grow and multiply within host cells; further divided into two groups below.

Match each pathogen with the strategy used to evade the immune responses of the host.

N. gonorrhoeae = Produces proteases that digest host proteins such as lgA H. influenzae = Produces a capsule that prevents deposition of host complement S. pyogenes = Expresses M protein on their surface to prevent detection

Infectious dose 50 (ID50)

Refers to the number of organisms that infect 50% of an experimental group of hosts within a specified time period. The lower the infections does (i.e., the fewer organisms needed for infection), the higher the risk of infection.

What does it mean to say a microbe has a specific tropism?

The microbe infects only specific cell or tissue types as dictated by the correct receptor being present on them.

An organism's ______ is the degree of harm (pathogenicity) inflicted on its host.

Virulence

In _____ transmission, a pathogen is often sneezed or coughed into the air and suspended in dust, droplet nuclei, or larger respiratory droplets.

airborne

Suppose a student infected with influenza virus is sitting three feet across from you in class, coughing frequently. You do not touch the student or share any items with her. A few days later, you come down with influenza. What was the most likely route of transmission?

airborne

When a microorganism establishes a site on or within a host allowing replication, _____ has occurred.

colonization

Fomite

common inanimate materials that transmit pathogens to humans.

Virulence

degree of pathogenicity (harm) inflicted on its host

______ contact transmission typically results from an actual physical interaction with the infectious source (e.g. person to person contact). ______ contact transmission depends upon something acting to "transfer" the infectious agent between hosts.

direct; indirect

Superantigens cause disease by ______.

dramatically stimulating a large portion of circulating host T cells, causing them to overexpress and release cytokines

Lipopolysaccharide (LPS) is also called _____ because it is bound to the outer membrane of Gram-negative bacteria, and it is harmful to humans.

endotoxin

Signs

objective changes in the body, such as a fever or rash, that can be directly observed.

Vertical transmission

pathogens are passed from parent to offspring in an egg or sperm, across the placenta, in breast milk, or in the birth canal

A body surface where infectious agents may gain access to host tissue is called a _____ of entry.

portal

In relation to infectious diseases, the skin, respiratory system, gastrointestinal tract, urogenital system, and conjunctiva of the eye are all examples of ______.

portals of entry through which infectious agents may gain access to host tissues

One mechanism used by some bacteria to evade specific immune responses (e.g. antibodies) is to ______.

produce capsules that resemble host tissue components, acting as a disguise of sorts

A disease _____ is a set of signs and symptoms that are characteristic of the disease.

syndrome

Invasiveness

the ability of the organism to spread to adjacent or other tissues

Lethal dose 50 (LD50)

the dose or number of pathogens that kills 50% of an experimental group of hosts within a specified period. Highly virulent pathogens kill at lower dose when compared to less virulent organisms.

septicemia

the infectious disease process caused by bacterial or fungal toxins in the blood

Reservoir

the natural environmental location in with the pathogen normally resides.

The best definition of the incubation period of an infectious disease is when ______.

the pathogen has entered the host and is multiplying, but hasn't reached high enough levels to cause clinical manifestations

bacteremia

the presence of viable bacteria in the bloodstream

Convalescene

the recovery stage.

portal of entry

the skin, resp. system, gastrointestinal system, urogenital system, or the conjunctiva of the eye.

Incubation period

the time between pathogen entry and development of signs and symptoms. The pathogen is reproducing but has not reached a sufficient level to cause clinical manifestations.

Which term describes the ability of a microorganism to produce substances that alter host cell metabolism in a negative way?

toxigenicity

Which term refers to a substance that alters the normal metabolism of host cells with negative effects on the host organism?

toxin

Which is an example of vertical transmission of a pathogen?

transmission of a German measles virus across the placenta to a developing fetus