microbiology basic and clinical principles test bank

Correct Answer: D

Rationale: The correct answer is D: Propionibacterium acnes. This bacterium is not a fungus, but a common skin bacteria. Fungal vaginitis is typically caused by Candida albicans or other fungal species, not by bacteria like Escherichia coli, Streptococcus agalactiae, or Klebsiella oxytoca. Propionibacterium acnes is not associated with vaginal infections, making it the correct answer in this context.

Correct Answer: A

Rationale: The correct answer is A: bacteria. Bacteria are the most common cause of laboratory-acquired infections due to their ability to survive and multiply in various environments. They can easily contaminate lab equipment and surfaces, leading to infections if proper precautions are not taken. Viruses (choice B) are less common in laboratory-acquired infections as they require specific conditions to survive outside a host. Protozoans (choice C) are larger and less likely to be transmitted in a laboratory setting. Prions (choice D) are misfolded proteins and are not considered living organisms, making them an unlikely source of laboratory infections.

Correct Answer: A

Rationale: The correct answer is A: Mycolic acid. Ziehl-Neelsen method is used to stain acid-fast bacteria, such as Mycobacterium species. Mycolic acid in the cell wall of these bacteria resists decolorization, leading to red-colored bacilli on a blue background. Capsule, flagella, and endospores do not play a role in this staining property. Capsules are usually stained using special techniques, flagella are not typically visible with this stain, and endospores are stained using the Schaeffer-Fulton method.

Correct Answer: A

Rationale: The correct answer is A: Trichomonas vaginalis. Trichomonas vaginalis is a protozoan parasite that causes trichomoniasis, a sexually transmitted infection characterized by inflammation of urogenital tracts. The description of big unicellular pyriform organisms with a sharp spike on the back end of their bodies, big nucleus, and undulating membrane matches the morphology of Trichomonas vaginalis. Trichomonas hominis and Trichomonas buccalis are different species that do not cause urogenital infections. Trypanosoma gambiense is a protozoan parasite causing African trypanosomiasis and does not match the described morphology or symptoms.

Correct Answer: C

Rationale: Correct Answer: C: Halophiles Rationale: 1. Halophiles are bacteria adapted to high salt environments. 2. They have specific mechanisms to tolerate high salt concentrations. 3. Acidophiles thrive in acidic conditions. 4. Thermophiles prefer high temperature environments. 5. Mesophiles grow best at moderate temperatures.