—Microbiology Chapter 15—

What do hyaluronidase and kinase have in common?

They are both enzymes involved in evading host defense.

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

N. gonorrheae

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

all of the above

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.

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.

Which of the following microorganisms actually grows inside the macrophage?

Tuberculosis bacterium

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.

What are leukocidins?

Molecules that are capable of destroying phagocytes

Measles viruses are capable of inactivating host defenses by

suppressing the immune system.

Meningitis and gonorrhea are caused by

Neisseria species.

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.

How can capsules enable bacteria to evade the immune system?

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

Endotoxins are also known as

Lipid A.

When would endotoxins be released from a bacterial cell?

When the cell dies

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

Fever

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

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

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

cytotoxin.

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

B domain

How are superantigens different from other types of exotoxins?

Superantigens cause an overstimulation of the host immune system.

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.

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

neurotoxin.

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 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 statement regarding endotoxins is true?

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

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

fibrinolysin

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

Which of the following statements about adherence is true?

Most bacterial adhesins are glycoproteins or lipoproteins.

Which of the following toxins and does NOT match the description?

Vibrio enterotoxin: a superantigen that destroys epithelial cells

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

cholera

Which of the following statements about lysogenic conversion is true?

Exotoxin production by bacteria is frequently the result of a lysogenic infection.

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

Flagella

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

Inside phagocytes

Where is the site of Shigella attachment in the host?

M cells

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.

What is the etiologic agent of typhoid?

Salmonella

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

virulence factors.

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

Hyaluronidase

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

Staphylokinase

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.

Which of the following is NOT a cytopathic effect (CPE) of viruses?

All of the above are possible CPE.

The most frequently used portal of entry for pathogens is the

mucous membranes of the respiratory tract.

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.

Most pathogens that gain access through the skin

enter through hair follicles and sweat ducts.

All of the following contribute to a pathogens invasiveness EXCEPT

toxins

The ID50 is

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

Which of the following statements is FALSE?

Coagulase destroys blood clots.

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

A-B toxin

Which of the following statements about exotoxins is generally FALSE?

They are resistant to heat.

Endotoxins are

part of the gram-negative cell wall.

Cytopathic effects are changes in host cells due to

viral infections.

Which of the following does NOT contribute to the symptoms of a fungal disease?

cell walls

All of the following are methods of avoiding host antibodies EXCEPT

membrane-disrupting toxins.

Siderophores are bacterial proteins that compete with the host’s

iron-transport proteins.

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

adhesins and ligands.

All of the following are examples of entry via the parenteral route EXCEPT

hair follicle.

Superantigens produce intense immune responses by stimulating lymphocytes to produce

cytokines

Botulism is caused by ingestion of a proteinaceous exotoxin; therefore, it can easily be prevented by

boiling food prior to consumption.

All of the following organisms produce exotoxins EXCEPT

Salmonella typhi.

Which of the following cytopathic effects is cytocidal?

release of enzymes from lysosomes

All of the following are used by bacteria to attach to host cells EXCEPT

A-B toxins.

Symptoms of protozoan and helminthic diseases are due to

tissue damage due to growth of the parasite on the tissues, waste products excreted by the parasite, and products released from damaged tissues.

Which of the following statements about staphylococcal enterotoxin is FALSE?

It is produced by Staphylococcus aureus growing in the host’s intestines.

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

Lysogenic bacteriophages contribute to bacterial virulence because bacteriophages

give new gene sequences to the host bacteria.

Twenty-five people developed symptoms of nausea, vomiting, and diarrhea three to six hours after attending a church picnic where they ate a ham and green bean casserole with cream sauce. The most likely cause of this case of food intoxication is

erythrogenic toxin.

Which of the following statements about M protein is FALSE?

It is readily digested by phagocytes.

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

superantigens.

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

the invasion and lysis of intestinal cells by E. coli

Polio is transmitted by ingestion of water contaminated with feces containing polio virus. What portal of entry does polio virus use?

mucous membranes only

All of the following bacteria release endotoxin EXCEPT

Clostridium botulinum.

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.

Bacteria such as E. coli and Salmonella produce invasins that bind host cells, thus causing the cells to

engulf the bacteria.

Which of the following mechanisms is used by gram-negative bacteria to cross the blood-brain barrier?

inducing TNF

Injectable drugs are tested for endotoxins by

the Limulus amoebocyte lysate test.

Endotoxins in sterile injectable drugs could cause

septic shock symptoms.

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

LPS is released from gram-negative bacteria.

Antibiotics can lead to septic shock if used to treat

gram-negative bacterial infections.

Which of the following is NOT a cytopathic effect of viruses?

toxin production

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.

Nonpathogenic Vibrio cholerae can acquire the cholera toxin gene by

transduction.

In response to the presence of endotoxin, phagocytes secrete tumor necrosis factor. This causes

a decrease in blood pressure.

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.