ATI RN
microbiology test bank Questions
Question 1 of 5
During an outbreak of cholera, a fecal smear revealed Gram-negative, comma-shaped, motile bacteria. What staining method would best confirm the diagnosis?
Correct Answer: A
Rationale: The correct answer is A: Gram staining. This method is used to differentiate bacteria based on their cell wall composition. In cholera, the causative agent is Vibrio cholerae, which is Gram-negative. By performing Gram staining, the bacteria will appear pink/red under the microscope, confirming the presence of Gram-negative bacteria.
Choice B: Neisser's staining is used for staining capsules of bacteria, not suitable for confirming cholera diagnosis.
Choice C: Ziehl-Neelsen staining is used for acid-fast bacteria like Mycobacterium tuberculosis, not for confirming cholera diagnosis.
Choice D: Burri-Gins staining is not a standard staining method in microbiology and is not relevant for confirming cholera diagnosis.
Question 2 of 5
A 5-year-old kindergartener has diphtheria. To find the carriers of the disease among the kindergarten staff, samples of pharyngeal mucus were obtained from the employers. One of the employers had gram-positive bacilli in her sample. They were situated at an angle to each other and colored unevenly, when stained according to Loeffler. What method can confirm that this carrier is dangerous to other people?
Correct Answer: A
Rationale: The correct answer is A:
Toxin production test.
Rationale:
1. Diphtheria is caused by a toxin produced by Corynebacterium diphtheriae.
2.
To confirm if the carrier is dangerous, we need to test if they are producing the toxin.
3. The toxin production test directly assesses if the bacteria are producing the harmful toxin.
4. Positive results indicate the carrier is dangerous and can transmit the disease to others.
Summary of other choices:
B: Mouse neutralization test - Used to detect diphtheria antitoxin levels in blood, not to confirm if the carrier is dangerous.
C: Immunofluorescence test - Used to detect specific antigens or antibodies, not directly related to confirming the carrier's danger.
D: Complement fixation test - Measures immune response, not specific to toxin production confirmation.
Question 3 of 5
Which bacteria produce toxins that cause damage to host tissues?
Correct Answer: D
Rationale: The correct answer is D because all three bacteria listed produce toxins that cause damage to host tissues. Clostridium tetani produces tetanospasmin toxin causing tetanus, Vibrio cholerae produces cholera toxin leading to severe diarrhea, and Staphylococcus aureus releases toxins causing tissue damage in various infections.
Therefore, all of the above choices are correct in terms of producing toxins that harm host tissues.
Question 4 of 5
Passage of antibodies from one person to another is called
Correct Answer: A
Rationale: Passive immunity is the transfer of pre-formed antibodies from one individual to another, providing immediate protection. This process does not involve the recipient's immune response, hence it is called passive. Active immunity, on the other hand, involves the individual's immune system producing its own antibodies after exposure to an antigen. Innate immunity refers to the body's natural defense mechanisms present from birth, not involving antibodies.
Therefore, the correct answer is A: passive immunity.
Question 5 of 5
After long-term antibiotic treatment a patient has developed whitish spots on the oral mucosa. Gram- positive oval budding cells were detected in the smear preparations. What causative agents were detected?
Correct Answer: A
Rationale: The correct answer is A: Candida fungi. Candida fungi are known to cause oral thrush, characterized by whitish spots on the oral mucosa. The presence of gram-positive oval budding cells in the smear preparations is indicative of Candida species. Staphylococci (choice
B) are gram-positive cocci, not oval budding cells. Sarcinae (choice
C) are gram-positive bacteria that form cuboidal packets, not oval budding cells. Actinomycetes (choice
D) are filamentous gram-positive bacteria, not oval budding cells like Candida fungi.