microbiology an introduction 12th edition test bank

Correct Answer: D

Rationale: The correct answer is D because hospital-acquired infections can be caused by a variety of microorganisms, including opportunistic pathogens and obligate pathogens such as bacteria or viruses. Opportunistic microorganisms take advantage of weakened immune systems in hospital patients, while obligate pathogens are capable of causing infections in healthy individuals. Therefore, all the choices are correct in this context as they represent potential etiological causes of hospital-acquired infections.

Correct Answer: D

Rationale: The correct answer is D: Hyaluronidase synthesis. Hyaluronidase is an enzyme produced by some pathogens to break down hyaluronic acid in the extracellular matrix, aiding their spread. This action does not directly counteract the immune system's mechanisms. Antigenic heterogeneity and mimicry can evade immune recognition. IgA proteases degrade IgA antibodies, impairing mucosal immunity. Therefore, D is the only choice not directly involved in counteracting the immune system.

Correct Answer: A

Rationale: The correct answer is A: Gin's stain method. Gin's stain method is specifically used to detect capsules of bacteria. This method involves staining the bacteria with crystal violet and copper sulfate, which highlights the capsules as a clear halo around the stained bacterial cells. Ziehl-Neelsen's stain is used for acid-fast bacteria like Mycobacterium tuberculosis, Neisser's stain is for detecting Neisseria species, and Gram's stain is for differentiating bacteria based on their cell wall composition (Gram-positive vs. Gram-negative). Therefore, choices B, C, and D are incorrect for this scenario.

Correct Answer: D

Rationale: The correct answer is D: chemoheterotrophs. Chemoheterotrophs use organic compounds as both their carbon source and energy source. They obtain energy by breaking down organic molecules through cellular respiration. Photoautotrophs (A) use light energy to produce organic compounds, chemoautotrophs (B) use inorganic compounds for energy, and photoheterotrophs (C) use light energy but require organic compounds as a carbon source. Therefore, chemoheterotrophs best describe bacteria that obtain both carbon and energy from organic compounds.

Correct Answer: A

Rationale: Step 1: Large, oval protozoa with a single nucleus and four flagella indicate Giardia lamblia. Step 2: Giardia lamblia is a flagellated protozoan causing diarrhea. Step 3: It has a distinct appearance under microscopy. Step 4: Entamoeba histolytica causes dysentery with no flagella. Step 5: Balantidium coli is a ciliated protozoan with a larger size. Step 6: Trichomonas vaginalis lacks a cyst stage and causes genitourinary infections.