CHAPTER 20: Serological and Molecular Detection of Bacterial Infections Flashcards
All of the following are protective mechanisms against bacteria except
a. production of antimicrobial defense peptides.
b. phagocytosis.
c. activation of complement.
d. release of lipid A from the bacterial cell.
d. release of lipid A from the bacterial cell.
All of the following are characteristics of streptococcal M proteins except
a. it is the chief virulence factor of Group A streptococci.
b. it provokes an immune response.
c. antibodies to one serotype protect against other serotypes.
d. it limits phagocytosis of the organism.
c. antibodies to one serotype protect against other serotypes.
An ASO titer and a streptozyme test are performed on a patient’s serum. The ASO titer is negative, the streptozyme test is positive, and both the positive and negative controls react appropriately. What can you conclude from these test results?
a. The ASO is falsely negative.
b. The patient has an antibody to a streptococcal exoenzyme other than streptolysin O.
c. The patient has not had a previous streptococcal infection.
d. The patient has scarlet fever.
b. The patient has an antibody to a streptococcal exoenzyme other than streptolysin O.
Which of the following applies to acute rheumatic fever?
a. Symptoms begin after S. pyogenes infection of the throat or the skin.
b. Antibodies to Group A streptococci are believed to cross-react with heart tissue.
c. Diagnosis is usually made by culture of the organism.
d. All patients suffer permanent disability.
b. Antibodies to Group A streptococci are believed to cross-react with heart tissue.
Which of the following indicates the presence of anti-DNase B activity in serum?
a. Reduction of methyl green from green to colorless
b. Clot formation when acetic acid is added
c. Inhibition of red blood cell hemolysis
d. Lack of change in the color indicator
a. Reduction of methyl green from green to colorless
Which of the following is considered to be a nonsuppurative complication of streptococcal infection?
a. Acute rheumatic fever
b. Scarlet fever
c. Impetigo
d. Pharyngitis
a. Acute rheumatic fever
All of the following are ways that bacteria can evade host defenses except
a. presence of a capsule.
b. stimulation of chemotaxis.
c. production of toxins.
d. lack of adhesion to phagocytic cells.
b. stimulation of chemotaxis.
Antibody testing for Rocky Mountain spotted fever may not be helpful for which reason?
a. It is not specific.
b. It is too complicated to perform.
c. It is difficult to obtain a blood specimen.
d. Antibody production takes at least a week before detection.
d. Antibody production takes at least a week before detection.
Which of the following enzymes is used to detect the presence of H pylori infections?
a. DNase
b. Hyaluronidase
c. Urease
d. Peptidase
c. Urease
Which of the following reasons make serological identification of a current infection with Helicobacter pylori difficult?
a. No antibodies appear in the blood.
b. Only IgM is produced.
c. Antibodies remain after initial treatment.
d. No ELISA tests have been developed.
c. Antibodies remain after initial treatment.
M pneumoniae infections are associated with the production of which antibodies?
a. Cold agglutinins
b. Antibodies to ATPase
c. Antibodies to DNase
d. Antibodies to Proteus bacteria
a. Cold agglutinins
Which of the following best describes the principle of the IFA test for detection of antibodies produced in Rocky Mountain spotted fever?
a. Patient serum is applied to a microtiter plate coated with a monoclonal antibody directed against the target antigen. A detection antibody labeled with biotin and directed against the target antigen is added. After addition of a substrate, a color reaction develops indicating presence of the antigen.
b. Specific antibodies in the serum sample attach to the antigens fixed to a microscope slide. In a second step, the attached antibodies are stained with fluorescein-labeled anti-human immunoglobulin and visualized with the fluorescence microscope.
c. The serum sample is treated chemically to link the target antibodies to a fluorophore. The labeled sample is applied to a microscope slide to which the antigen has been attached. Following a wash step, the slide is examined for fluorescence.
d.Patient serum is applied to a slide to which a specific antigen is bound. Following a wash step, a chromogenic dye is applied that binds to the Fc region of IgG and IgM antibodies. After a second wash step, the slide is examined for fluorescence.
b. Specific antibodies in the serum sample attach to the antigens fixed to a microscope slide. In a second step, the attached antibodies are stained with fluorescein-labeled anti-human immunoglobulin and visualized with the fluorescence microscope.
Which of the following is true regarding exotoxins and endotoxins?
a. Both endotoxin and exotoxins are highly immunogenic allowing for the development of protective antibodies and vaccines.
b. Endotoxin has targeted activity whereas exotoxins have systemic effects when released.
c. Endotoxin is released from the cell wall of dead bacteria, whereas exotoxin is released from live bacteria.
d. Both endotoxin and exotoxins bind to specific receptors on a bacterial cell leading to cell lysis.
c. Endotoxin is released from the cell wall of dead bacteria, whereas exotoxin is released from live bacteria.
Characteristics of a bacterial capsule include which of the following?
a. It cannot be used for vaccine development.
b. It is composed of peptidoglycan.
c. It is an important mechanism for protecting a bacterium against ingestion by PMNs.
d. It is what causes bacteria to stain as gram-negative.
c. It is an important mechanism for protecting a bacterium against ingestion by PMNs.
Which of the following statements regarding Helicobacter pylori is not true?
a. It is associated with an increased risk of gastric carcinoma.
b. It is the cause of most cases of acute food poisoning in the United States.
c. It is a major cause of peptic ulcers in the United States.
d. It is positive for urease.
b. It is the cause of most cases of acute food poisoning in the United States.
