Part 3/CH 15/HW #15

Adherence

(attachment) is accomplished by means of surface molecules called adhesions or ligands located on the pathogen. Adhesions bind specifically to complementary surface receptors on host tissue.

Which of the following is NOT a membrane-disrupting toxin?

A-B toxin ARE: leukocidin streptolysin S hemolysin streptolysin O

Which of the following would be an example of an infection initiated via the parenteral route?

An individual contracts hepatitis B from an accidental stick with a contaminated needle.

Which domain of the A-B toxin binds to cell surface receptors on the host cell?

B domain

How can capsules enable bacteria to evade the immune system?

Capsules block the complement biding sites on the surface of the pathogen.

Antibiotics can kill gram-negative bacteria, but symptoms of fever and low blood pressure can persist. Why?

Endotoxins are a part of the outer membrane of the gram-negative bacterial cell wall. The endotoxin is the Lipid A portion of the lipopolysaccharide (LPS) in the outer membrane. Endotoxins are only released from the bacterial cell when the cell dies (or cell division). When bacterial endotoxins are released, they stimulate macrophages to produce cytokines called interleuken 1 which is a protein messenger. It travels to the hypothalamus causing production of prostagladins. Prostagladins cause fever. The release of endotoxins into the bloodstream is potentially deadly because it can lower blood pressure and cause the patient to go into shock.

Which of the following would be the first sign of an infection that resulted in the release of endotoxin?

Fever endotoxin stimulate prostoglandins that stimulate fever

Which of the following features of Salmonella prevent it from being phagocytosed?

Flagella

Which of the following enzymes breaks down the "glue" that holds cells together?

Hyaluronidase

Where do Salmonella pathogens grow and replicate in the infected host?

Inside phagocytes

How does the protozoan Trypanosoma evade detection by the immune system?

It can change the surface antigens frequently, preventing the immune system from tracking it.

Why is a release of endotoxin into the bloodstream potentially deadly?

It can lower blood pressure and cause the patient to go into shock.

Bacillus anthracis can cause infection via three different portals of entry. The ID50 of cutaneous anthrax is 10 to 50 endospores, while inhalation anthrax requires 10,000 to 20,000 endospores, and gastrointestinal anthrax requires 250,000 to 1,000,000 endospores. Which statement best describes a conclusion that can be drawn based on this information?

It is significantly easier to be infected with cutaneous anthrax as compared to other forms of anthrax. The ID50 through the skin is only 10 to 50 endospores, making it easier to acquire cutaneous anthrax as compared to other forms of anthrax.

Gram-negative septic shock results from the following events. What is the second step?

LPS is released from gram-negative bacteria.

Reviewing the overall microbial mechanisms of pathogenicity (Figure 15.9), predict the ability of the pathogen to cause infection in each of the following scenarios. Factors such as the portal of entry, infectious dose, and adherence to host tissue each impact a pathogen's ability to initiate an infection.

Likely to cause infection: - A pathogen that causes gastrointestinal infections is accidentally ingested in contaminated food - A population of microbes less than the infectious dose is introduced in a compromised human host - A healthy individual inhales droplets from a person infected with a respiratory virus - A pathogen in quantities more than double its infectious dose is introduced at the appropriate portal of entry Not likely to cause infection: - A population of microbes greater than the infectious dose is introduced in a healthy individual, but these microbes are unable to adhere to hose tissues - A pathogen that causes urinary tract infections is accidentally ingested in contaminated water -A pathogen with multiple virulence, factors is introduced in a healthy host, but in quantities far below its infectious dose

Endotoxins are also known as

Lipid A (on gram-negative cell wall) of LPS of outer membrane

Where is the site of Shigella attachment in the host?

M cells

Which of the following virulence factors could directly prevent phagocytosis and/or phagocytic degradation?

M proteins waxy lipids capsules

What are leukocidins?

Molecules that are capable of destroying phagocytes

According to your Concept Map, which of the following organisms exhibits antigenic variation?

N. gonorrheae

Meningitis and gonorrhea are caused by

Neisseria species.

Which statement regarding endotoxins is true?

One consequence of endotoxins is the activation of blood-clotting proteins.

What is the etiologic agent of typhoid?

Salmonella

In mice, the LD50 for staphylococcal enterotoxin is 1350 ng/kg, and the LD50 for Shiga toxin is 250 ng/kg. Which of the following statements is true?

Shiga toxin is more lethal than staphylococcal enterotoxin.

Which of the following virulence factors would be found in Staphylococcus aureus?

Staphylokinase

How are superantigens different from other types of exotoxins?

Superantigens cause an overstimulation of the host immune system.

How does a capsule help certain bacteria evade detection by the immune system?

The capsule is composed of polysaccharides that are similar to those found in the host; thus, the immune system does not recognize it as foreign.

infectious dose (ID50)

The number of invading microbes needed to cause infection in 50% of a sample population This number is determined based on pathogen and portal of entry

siderophores

These bind up iron obtained from the host cell's iron-transport proteins and transport this iron to bacteria through interactions with cell surface receptor.

toxins

These cause most of the damage to host cells; these poisonous substances can be transported by the blood or lymph and may produce far-reaching effects.

cytopathic effects

These describe the visible effects of viral infections that results in host cell damage.

invasins

These microbial surface proteins rearrange the host cell's actin filaments, allowing pathogens to enter and move in and between cells.

enzymes

These proteins contribute to a pathogen's virulence, for example, by forming and breaking down fibrin clots, breaking down connective proteins, and countering certain types of antibodies.

How are immune cells able to detect foreign pathogens?

They are able to detect structures on the surfaces of foreign cells that are not found in the host.

What do hyaluronidase and kinase have in common?

They are both enzymes involved in evading host defense.

How do fibrinolysins enhance a pathogen's virulence?

They break down fibrin proteins that are involved in clot formation, allowing the cells to penetrate deep into damaged skin.

How do Shigella cells move between host cells?

They can polymerize actin molecules from the epithelial cells into tail-like structures that propel them from one cell to another.

How do superantigens enable pathogens to hide from the immune system if they actually stimulate the immune system?

They cause the immune system to produce an exaggerated response, distracting it from the actual pathogen.

direct damage

This occurs due to nutrient depletion, accumulation of waste products, pathogen entry and exit, and ruptured host cells.

antigenic variation

This process allows pathogens to alter their surface antigens to avoid attack by antibodies produced by the immune system

lysogenic conversion

This results in a change in microbe characteristics due to the presence of prophage genes that confer new properties.

cell wall components

This structure contains substances that contribute to a pathogen's virulence, for example, M protein mediates microbial attachment to epithelial cells.

capsules

This viscous outer-covering found in certain microorganisms helps pathogens evade the host's defenses by impairing phagocytosis

Which of the following microorganisms actually grows inside the macrophage?

Tuberculosis bacterium

When would endotoxins be released from a bacterial cell?

When the cell dies

Exotoxin

a protein toxin released from living, mostly gram-positive bacterial cells

The fimbriae of Neisseria gonorrhea and enteropathogenic E. coli are examples of

adhesins and ligands.

superantigen

antigen that activates many different T cells, thereby eliciting a large immune response

The ability of some microbes, such as Trypanosoma or Giardia to alter their surface molecules and evade destruction by the hosts antibodies is called

antigenic variation.

neurotoxin

attack nerve cells

enterotoxin

attack the lining of the GI tract

A-B toxin.

bacterial exotoxins consisting of two polypeptides

Which disease would be potentially propagated in an environment without functional plumbing and in which drinking water is contaminated with sewage?

cholera

Superantigens produce intense immune responses by stimulating lymphocytes to produce

cytokines

An exotoxin that has the ability to kill or damage host cells is referred to as a(n)

cytotoxin

the table shows the ID50 for Staphylococcus aureus in wounds with and without the administration of ampicillin before surgery. Based on the data, the administration of ampicillin before surgery

decreases the risk of staphylococcal infection.

Patients developed inflammation a few hours following eye surgery. Instruments and solutions were sterile, and the Limulus assay was positive. The patients inflammation was due to

endotoxin

5 types of exotoxins

enterotoxin. cytotoxin. A-B toxin. superantigen. neurotoxin

Which type of bacterial enzyme helps spread Streptococcus pyogenes by digesting blood clots?

fibrinolysin

skin:

hair follicles, sweat gland ducts, penetration, and infection of a skin layer; and,

Siderophores are bacterial proteins that compete with the host's

iron-transport proteins.

Both portal of entry and port of exit

mucous membrane skin parenteral route

The most frequently used portal of entry for pathogens is the

mucous membranes of the respiratory tract.

A patient who has been hospitalized with uncontrolled muscle spasms has probably been infected with bacteria that secrete a(n)

neurotoxin

Which of the following contributes to the virulence of a pathogen?

numbers of microorganisms that gain access to a host, evasion of host defenses, and toxin production

Endotoxins are

part of the gram-negative cell wall.

Cholera toxin polypeptide A binds to surface gangliosides on target cells. If the gangliosides were removed,

polypeptide B would not be able to enter the cells.

parenteral route:

punctures, injections, wounds, surgery, splits due to swelling or drying of the skin or mucous membrane.

mucous membranes:

respiratory tract, gastrointestinal tract, genitourinary (genital and urinary) tract, and conjunctiva (the mucous membrane that covers the front of the eye and lines the inside of the eyelids)

Endotoxins in sterile injectable drugs could cause

septic shock symptoms.

Bacteria that cause periodontal disease have adhesins for receptors on streptococci that colonize on teeth. This indicates that

streptococcal colonization is necessary for periodontal disease.

A person who attended a picnic early in the day develops a very high fever and is unresponsive by the evening. This person most likely has been exposed to a(n)

superantigen

Symptoms of intense inflammation and shock occur in some gram-positive bacterial infections due to

superantigens

Measles viruses are capable of inactivating host defenses by

suppressing the immune system.

pathogenicity

the ability of a microorganism to cause disease by overcoming the defenses of a host the ability of an organism to cause disease (ie, harm the host)

portal of entry

the avenue by which a pathogen gains access to the body

virulence

the degree of pathogenicity

The ID50 is

the dose that will cause an infection in 50 percent of the test population.

Which of the following is an example of direct damage due to bacterial infection?

the invasion and lysis of intestinal cells by E. coli

etiology

the study of causes or origins of a disease

In which of the following cases would the Limulus amebocyte lysate (LAL) assay be used?

to ensure that a sterilized medical device is free of endotoxin

Certain traits that allow pathogens to create infection and cause disease are termed

virulence factors.