Question 1

Which of the following statements concerning influenza is incorrect?

Accepted Answer

Antigenic drift refers to a gradual change in the virus strain, not an abrupt change.

Question 2

What is the name of the tiny roundworm whose female normally lays her eggs during the nighttime hours in the anal area of the human host, causing itching of this area?

Accepted Answer

The description matches the life cycle and symptoms of Enterobius vermicularis, also known as the human pinworm.

Question 3

Wet mounts can be done to detect the presence of "clue cells," vaginal epithelial cells covered with what organism?

Accepted Answer

The presence of clue cells on a wet mount is indicative of bacterial vaginosis, which is caused by Gardnerella vaginalis. Therefore, choice A is the best answer. Trichomonas vaginalis is a protozoan parasite that can also cause vaginitis but is not associated with clue cells. Neisseria gonorrhoeae and Chlamydia trachomatis are bacteria that can cause sexually transmitted infections, but they do not produce clue cells.

Question 4

Which of the following Strep organisms causes strep throat and demonstrates beta hemolysis?

Accepted Answer

Streptococcus pyogenes is the organism that causes strep throat and demonstrates beta hemolysis. Streptococcus pneumoniae is also a cause of respiratory infections, but it demonstrates alpha hemolysis. Streptococcus viridans and Streptococcus agalactiae are not typically associated with strep throat.

Question 5

In the Gram stain procedure, what is the most critical differentiating step?

Accepted Answer

The decolorizer step is the most critical differentiating step in the Gram stain procedure. It determines whether the bacterial cells will retain the crystal violet stain (Gram-positive) or lose it and take on the safranin stain (Gram-negative). If the decolorizer is left on too long, it can cause false results by washing away the crystal violet from both Gram-positive and Gram-negative cells.

Question 6

Which of the following describes a coccus bacterium?

Accepted Answer

A coccus bacterium is a round organism that can be found as singles, pairs, clusters, or chains.

Question 7

A sensitivity test is done to:

Accepted Answer

A sensitivity test is done to determine which antibiotics would be most effective for treating patients' bacterial infections. The test measures the effectiveness of various antibiotics against the bacteria isolated from the patient's infection. This information helps the healthcare provider to choose the most appropriate antibiotic for treatment.

Question 8

Which of the following steps are incorrect when collecting a throat culture?

Accepted Answer

The correct procedure for collecting a throat culture involves swabbing the back of the throat, tonsils, and any inflamed or lesioned areas, avoiding contact with other parts of the mouth like the teeth and tongue to prevent contamination.

Question 9

Which of the following statements is incorrect concerning the Acceava Strep test?

Accepted Answer

For the Acceava Strep A test, a valid positive result is indicated by the presence of both a blue test line and a pink control line, not just a blue test line alone. The absence of the pink control line indicates an invalid test, regardless of the presence of the blue line.

Question 10

No growth around the "A" disk can be used to identify Streptococcus pyogenes.What substance is in the "A" disk?

Accepted Answer

The substance in the "A" disk is bacitracin. No growth around the bacitracin disk can be used to identify Streptococcus pyogenes, as this bacterial species is sensitive to bacitracin. Vancomycin, penicillin, and tetracycline are not typically used for identifying Streptococcus pyogenes.

Question 11

Complications such as scarlet fever, rheumatic fever, and glomerulonephritis are found in which of the following organisms?

Accepted Answer

Scarlet fever, rheumatic fever, and glomerulonephritis are all complications commonly associated with infections caused by Streptococcus pyogenes.

Question 12

Which of the following organisms has a characteristic jerky movement? (Hint: It was seen in the microscopic urinalysis video.)

Accepted Answer

Trichomonas vaginalis has a characteristic jerky movement due to the presence of multiple flagella.

Question 13

Which of the following is incorrect regarding microorganisms?

Accepted Answer

Parasites can include not only one-celled protozoa but also multicellular organisms such as worms and arthropods.

Question 14

Which of the following statements about Neisseria gonorrhoeae is incorrect?

Accepted Answer

Neisseria gonorrhoeae is a gram-negative diplococcus, not a gram-positive bacillus. The other statements are all correct.

Question 15

In a properly performed Gram stain procedure, what color are the gram-negative organisms immediately after the decolorizing stage?

Accepted Answer

Gram-negative organisms should be colorless after the decolorizing stage, as the crystal violet has been washed out of their thin peptidoglycan layer, leaving them unable to retain the counterstain safranin. Gram-positive organisms, on the other hand, retain the crystal violet and appear purple after the decolorizing stage.

Question 16

Which of the following is the correct way to write the name of an organism?

Accepted Answer

In scientific writing, it is convention to use lowercase letters for species or subspecies names, while using uppercase for genus names. Therefore, "Escherichia coli" is the correct way to write the name of the organism.

Question 17

Which of the following organisms are referred to as acid-fast bacilli? (Note: They are stained with an acid-fast stain rather than the Gram stain.)

Accepted Answer

Acid-fast bacilli are bacteria that are resistant to decolorization by acids after being stained with a dye such as Ziehl-Neelsen stain. The most well-known acid-fast bacillus is Mycobacterium tuberculosis, the causative agent of tuberculosis. Therefore, the best choice is A, as Escherichia coli, Streptococcus pneumoniae, and Neisseria gonorrhoeae are not acid-fast bacilli.

Question 18

Which of the following statements is incorrect concerning influenza testing?

Accepted Answer

The influenza test strips usually test for influenza A and B only, not for type C.

Question 19

When collecting microbiologic specimens, medical professionals must strive to prevent the spread of infection to others or to themselves.Which of the following precautions is incorrect?

Accepted Answer

Disinfecting specimen containers before collection is not a standard precaution. Specimen containers are typically sterile or clean when obtained from the manufacturer and do not require disinfection by the collector before use. The focus should be on preventing contamination during and after specimen collection.

Question 20

Which of the following represents incomplete hemolysis, producing a green halo around the colony?

Accepted Answer

Alpha hemolysis is incomplete and produces a green halo around the colony due to the partial breakdown of red blood cells. Beta hemolysis results in complete lysis of red blood cells, while gamma hemolysis displays no hemolysis. Delta hemolysis is not a recognized type of hemolysis.

Quiz 8: Microbiology