chapter 15 Flashcards
The most frequently used portal of entry for pathogens is the
mucous membranes of the respiratory tract. mucous membranes of the gastrointestinal tract.
skin.
parenteral route.
All of these portals are used equally.
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 host’s antibodies is called antigenic variation. lysogenic conversion. virulence. cytopathic effect. cytocidal effect.
antigenic variation.
Most pathogens that gain access through the skin
can penetrate intact skin.
just infect the skin itself.
enter through hair follicles and sweat ducts.
must adhere first while their invasive factors allow them to penetrate.
must be injected.
enter through hair follicles and sweat ducts.
The ID50 is
a measure of pathogenicity.
the dose that will cause an infection in 50 percent of the test population.
the dose that will kill some of the test population.
the dose that will cause an infection in some of the test population.
the dose that will kill 50 percent of the test population.
the dose that will cause an infection in 50 percent of the test population.
All of the following contribute to a pathogen’s invasiveness EXCEPT toxins. capsules. cell wall components. hyaluronidase. coagulases.
toxins
Which of the following statements is FALSE?
Leukocidins destroy neutrophils.
Hemolysins lyse red blood cells.
Hyaluronidase breaks down substances between cells.
Kinase destroys fibrin clots.
Coagulase destroys blood clots.
Coagulase destroys blood clots
Which of the following statements about exotoxins is generally FALSE?
They are more potent than endotoxins.
They are composed of proteins.
They are resistant to heat.
They have specific methods of action.
They are produced by gram-positive bacteria.
They are resistant to heat
Endotoxins are associated with gram-positive bacteria. molecules that bind nerve cells. part of the gram-negative cell wall. excreted from the cell. A-B toxins.
part of the gram-negative cell wall
Which of the following is NOT a membrane-disrupting toxin? A-B toxin hemolysin leukocidin streptolysin O streptolysin S
A-B toxin
Cytopathic effects are changes in host cells due to viral infections. protozoan infections. fungal infections. bacterial infections. helminthic infections.
viral infections.
Siderophores are bacterial proteins that compete with the host's antibodies. red blood cells. iron-transport proteins. white blood cells. receptors.
iron-transport proteins.
The fimbriae of Neisseria gonorrhea and enteropathogenic E. coli are examples of adhesins. ligands. receptors. adhesins and ligands. adhesins, ligands, and receptors.
adhesins and ligands.
All of the following are examples of entry via the parenteral route EXCEPT injection. bite. surgery. hair follicle. skin cut.
hair follicle.
Botulism is caused by ingestion of a proteinaceous exotoxin; therefore, it can easily be prevented by boiling food prior to consumption. administering antibiotics to patients. not eating canned food. preventing fecal contamination of food. filtering food.
boiling food prior to consumption
All of the following organisms produce exotoxins EXCEPT Salmonella typhi. Clostridium botulinum. Corynebacterium diphtheriae. Clostridium tetani. Staphylococcus aureus
Salmonella typhi.
All of the following are used by bacteria to attach to host cells EXCEPT M protein. ligands. fimbriae. capsules. A-B toxins.
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.
products released from damaged tissues.
tissue damage due to growth of the parasite on the tissues and waste products excreted by the parasite.
tissue damage due to growth of the parasite on the tissues, waste products excreted by the parasite, and products released from damaged tissues.
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 contributes to the virulence of a pathogen?
numbers of microorganisms that gain access to a host
evasion of host defenses
toxin production
numbers of microorganisms that gain access to a host and evasion of host defenses
numbers of microorganisms that gain access to a host, evasion of host defenses, and toxin production
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.
produce toxins.
carry plasmids.
kill the bacteria, causing release of endotoxins.
kill human cells.
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 botulinum toxin. aflatoxin. staphylococcal enterotoxin. erythrogenic toxin. cholera toxin.
staphylococcal enterotoxin.
Which of the following statements about M protein is FALSE? It is found on Streptococcus pyogenes. It is found on fimbriae. It is heat- and acid-resistant. It is readily digested by phagocytes. It is a protein.
It is readily digested by phagocytes.
Symptoms of intense inflammation and shock occur in some gram-positive bacterial infections due to A-B toxins. lipid A. membrane-disrupting toxins. superantigens. erythrogenic toxin.
superantigens.
Which of the following is an example of direct damage due to bacterial infection?
the uncontrolled muscle contractions in Clostridium tetani infection
the invasion and lysis of intestinal cells by E. coli
the hemolysis of red blood cells in a staphylococcal infection
the fever, nausea, and low blood pressure in a Salmonella infection
the excessive secretion of fluids in a Vibrio cholera 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? skin only parenteral only mucous membranes only skin and parenteral skin, parenteral, and mucous membranes
mucous membranes only
All of the following bacteria release endotoxin EXCEPT Clostridium botulinum. Salmonella typhi. Neisseria meningitidis. Proteus vulgaris. Haemophilus influenzae.
Clostridium botulinum
Gram-negative septic shock results from the following events. What is the second step?
Body temperature is reset in the hypothalamus.
Fever occurs.
IL-1 is released.
LPS is released from gram-negative bacteria.
Phagocytes ingest gram-negative bacteria.
LPS is released from gram-negative bacteria.
Antibiotics can lead to septic shock if used to treat viral infections. gram-negative bacterial infections. gram-positive bacterial infections. protozoan infections. helminth infestations.
gram-negative bacterial infections.
In general, the LD50 for exotoxins is much greater than the LD50 for endotoxins
False
Biofilms provide pathogens with an adhesion mechanism and aid in resistance to antimicrobial agents.
True
The M protein enhances the virulence of Streptococcus by preventing phagocytosis
True
In A-B exotoxins, the A component binds to the host cell receptor so that the B component can enter the cell.
False
Many pathogens use the same portal for entry and exit from the body
True
