mastering microbiology test bank

Correct Answer: B

Rationale: The correct answer is B: Outer membrane with lipopolysaccharides. Gram-negative bacteria have an outer membrane containing lipopolysaccharides (LPS), which are important in pathogenesis and immune response. This feature is unique to Gram-negative bacteria, distinguishing them from Gram-positive bacteria (choice A). Teichoic acids (choice C) are found in the cell walls of Gram-positive bacteria, not Gram-negative. The statement in choice D, absence of a cell wall, is incorrect as all bacteria have a cell wall, although the composition may vary between Gram-negative and Gram-positive bacteria.

Correct Answer: A

Rationale: Rationale: 1. Bacillary dysentery primarily affects the intestinal tract, not the bloodstream. 2. Bacteremia is rare in bacillary dysentery, as the infection is localized. 3. Isolating bacteria from the blood is not a typical diagnostic feature. 4. Therefore, the correct answer is A. Summary: Bacteria causing bacillary dysentery are not typically isolated from the patient's blood due to the localized nature of the infection. Choices B and C are incorrect as they suggest specific timeframes, which are not relevant to bacteremia in this context. Choice D is incorrect as bacteremia is not associated with bacillary dysentery.

Correct Answer: A

Rationale: Step 1: Streptococcus pyogenes is commonly known as Group A Streptococcus, which is the primary bacteria responsible for causing strep throat. Step 2: Staphylococcus aureus is not typically associated with strep throat but can cause skin infections and other illnesses. Step 3: Neisseria gonorrhoeae is the bacteria responsible for gonorrhea, a sexually transmitted infection, not strep throat. Step 4: Clostridium tetani causes tetanus, a bacterial infection that affects the nervous system and is not related to strep throat.

Correct Answer: C

Rationale: The correct answer is C: Anti-measles IgM. During acute measles infection, the body produces IgM antibodies specific to the measles virus. This indicates a recent or current infection. A: Anti-mumps IgM and B: Anti-rubella IgM are specific to mumps and rubella viruses, respectively, not measles. D: Anti-CMV IgM is specific to cytomegalovirus, not measles. In summary, choice C is correct because Anti-measles IgM is the specific antibody indicating acute measles infection, while the other choices are antibodies related to different viruses.

Correct Answer: B

Rationale: The correct answer is B: resisting phagocytosis. Bacterial capsules are composed of polysaccharides that help bacteria evade phagocytosis by immune cells. This physical barrier prevents immune cells from engulfing and destroying the bacteria. Facilitating motility (A), synthesizing DNA (C), and producing energy (D) are not primary functions of bacterial capsules. Motility is usually facilitated by flagella, DNA synthesis occurs in the bacterial chromosome, and energy production is typically carried out by metabolic processes within the bacterial cell.