Microbiology Chapter 15 Review

Which of the following are properties of exotoxins?

-Exotoxins target specific cellular structures or molecules. -Exotoxins are protein molecules. -Very small amounts of exotoxin can be lethal.

Disease research and epidemiology bring together many different facets to help us better understand disease pathology and spread. Which of the following statements are true?

-The interactions that occur between a microbe and host influence the evolution of both. -Bacterial exotoxins can be altered to create toxoids, which can be used to produce protective immunity in a host. -Some pathogens are able to cause disease within a host without penetrating the body.

The ability of Vibrio cholerae to cause disease depends on a number of factors. Which of the following are requirements for causing disease within a host?

-evasion of host defenses -gaining access to the host via a portal of entry -adherence to host tissues

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

A-B toxin

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

A-B toxins

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

All of the listed choices are possible cytopathic effects of viruses.

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

Although cholera can be treated with antibiotics, data suggest that antibiotic treatment alone is NOT the most effective therapy. Which of the following statements describes the most likely reason for supplementing antibiotic therapy?

Antibiotic therapy addresses only the growth of V. cholerae; it doesn't address the extreme dehydration suffered by a person infected with V. cholerae.

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.

Match each item related to the penetration or evasion of host defenses with its best description.

Capsules: This viscous outer covering found in certain microorganisms helps pathogens evade the host 19s defenses by impairing phagocytosis. Cell wall components: These structures contain substances that contribute to a pathogen 19s virulence; for example, M protein mediates microbial attachment to epithelial cells. Enzymes: These proteins contribute to a pathogen 19s virulence by, for example, forming and breaking down fibrin clots, breaking down connective proteins, and countering certain types of antibodies. Antigenic variation: This process allows pathogens to alter their surface antigens to avoid attack by antibodies produced by the immune system. Invasins: These microbial surface proteins rearrange the host cell 19s actin filaments, allowing pathogens to enter and move in and between cells.

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

Cholera

All of the following bacteria release endotoxin EXCEPT

Clostridium botulinum

Which of the following statements is FALSE?

Coagulase destroys blood clots

Mucous membrane

Conjunctiva, Genitourinary Tract, Respiratory Tract, Gastrointestinal Tract

Which of the following statements about lysogenic conversion is true?

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

In A-B exotoxins, the A component binds to the host cell receptor so that the B component can enter the cell.

False

In general, the LD50 for exotoxins is much greater than the LD50 for endotoxins.

False

Most symptoms of endotoxins can be treated with administration of anti-endotoxin antibodies.

False

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

Fever

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

Flagella

Place the following statements in the order that best reflects the chronology of events during V. cholerae infection.

From left to right: - V.cholerae is ingested via contaminated water - V. cholerae survives passage through the stomach and enters the intestine - V. cholerae attaches via pili - V. cholerae produces cholera toxin - The host intestinal cells are destroyed resulting in a profuse, watery diarrhea - V. cholerae exits the host via the feces

Drag the following statements onto the figure to label the events in the correct order of events leading to the activity of cholera toxin.

From top to bottom: -Cholera toxin A subunit -Cholera toxin B subunit -B subunit mediates binding to host cell via interaction with specific cell receptor -A-B toxin enters host cell via endocyotosis -A and B subunits seperate -B subunit leaves the cell -A subunit alters host cell function

Skin

Hair follicles, Sweat Gland Ducts

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.

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 statements about M protein is FALSE?

It is readily digested by phagocytes

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.

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

Part complete Where is the site of Shigella attachment in the host?

M cells

What are leukocidins?

Molecules that are capable of destroying phagocytes

Which of the following statements about adherence is true?

Most bacterial adhesins are glycoproteins or lipoproteins.

Meningitis and gonorrhea are caused by

Neisseria species.

Each of the following scenarios describes factors that influence infection at the portal of entry. For each scenario, determine whether the pathogen's ability to cause infection relates to the number of invading microbes or adherence to the host tissue.

Number of invading microbes: -for cutaneous anthrax, the infectious dose is 10 to 50 endospores, wheas for inhalation antrax and gastrointestinal antrax, the infectious doses are 10,000 to 20,000 and 250,000 to 1,000,000 endospores, respectively -For Vibrio cholerae, the infectious dose is 10^8 cells, but if stomach acid is neutralized with bicarbonate, this number decreases significantly Adherence to the host tissue: -Enteropathogenic strains of E. coli have fimbriae that bind to specific regions of the small intestine Neisseria gonorrhoeae uses fimbriae to attach to cells in the genitourinary tract, eyes, and pharynx -Staphylococcus aureus binds and infects skin by a mechanism that resembles viral attachment -Treponema pallidum uses its tapered end as a hook to attach to host cells during a syphilis infection

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

All of the following organisms produce exotoxins EXCEPT

Salmonella typhi

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.

Match each item related to damage to host cells with its description.

Siderophores: These proteins bind up iron obtained from the host cell 19s iron-transport proteins and transport this iron to bacteria through interactions with cell surface receptors. Direct Damage: This occurs as a result of nutrient depletion, accumulation of waste products, pathogen entry and exit, and ruptured host cells. Toxins: These poisonous substances cause most of the damage to host cells; they can be transported by the blood or lymph and may produce far-reaching effects. Lysogenic conversion: This results in a change in microbe characteristics due to the presence of prophage genes that confer new properties. Cytopathic effects: These describe the visible effects of viral infections that results in host cell damage.

Portal`s of both Entry and Exit in the body

Skin, Mucous membrane, parenteral route

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.

Parenteral route

Surgery, Deep wounds, Injections

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.

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

Which of the following statements about exotoxins is generally FALSE?

They are resistant to heat.

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.

Some studies have indicated that the ID50 for Vibrio cholerae can be as high as 108 organisms. Which of the following most likely explains the requirement for this relatively high ID50?

To establish infection, V. cholerae must survive the host immune response and the acidic environment of the stomach.

Biofilms provide pathogens with an adhesion mechanism and aid in resistance to antimicrobial agents

True

Cytopathic effects, such as inclusion bodies and syncytium formation, are the visible signs of viral infections.

True

Ergot and aflatoxin are toxins sometimes found in grains contaminated with fungi.

True

Infections with some viruses may induce chromosomal changes that alter the growth properties of host cells.

True

Many pathogens use the same portal for entry and exit from the body.

True

Part complete The Limulus amoebocyte assay is used to detect minute amounts of endotoxin in drugs and medical devices.

True

The M protein enhances the virulence of Streptococcus by preventing phagocytosis

True

Which of the following microorganisms actually grows inside the macrophage?

Tuberculosis bacterium

Which of the following toxins and descriptions do NOT match?

Vibrio enterotoxin: a superantigen that destroys epithelial cells

When would endotoxins be released from a bacterial cell?

When the cell dies

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

a decrease in blood pressure

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

adhesins and ligands

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

antigenic variation

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

boiling food prior to consumption

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

cell walls

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.

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

engulf the bacteria

Most pathogens that gain access through the skin

enter through hair follicles and sweat ducts.

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

fibrinolysin

Lysogenic bacteriophages contribute to bacterial virulence because bacteriophages

give new gene sequences to the host bacteria.

Antibiotics can lead to septic shock if used to treat

gram-negative bacterial infections.

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

inducing TNF

Siderophores are bacterial proteins that compete with the host's

iron-transport proteins

All of the following are methods of avoiding host antibodies EXCEPT

membrane-disrupting toxins.

The most frequently used portal of entry for pathogens is the

mucous membranes of the respiratory tract

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

mucous membranes only

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.

Which of the following cytopathic effects is cytocidal?

release of enzymes from lysosomes

Endotoxins in sterile injectable drugs could cause

septic shock symptoms.

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

staphylococcal enterotoxin.

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.

Injectable drugs are tested for endotoxins by

the Limulus amoebocyte lysate test.

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

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.

Part complete 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 is NOT a cytopathic effect of viruses?

toxin production

All of the following contribute to a pathogen's invasiveness EXCEPT

toxins

Nonpathogenic Vibrio cholerae can acquire the cholera toxin gene by

transduction.

Cytopathic effects are changes in host cells due to

viral infections

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

virulence factors.