Microbiology An Introduction Tortora Test Bank

Correct Answer: B

Rationale: The correct answer is B: Mefloquine. Mefloquine is a histoschizontocidal antimalarial drug commonly prescribed for prevention of malaria in travelers. It is effective against the liver stage of the malaria parasite, which is crucial for preventing the development of the disease. Chingamin (A) is not a commonly used antimalarial drug. Biseptol (C) is a combination antibiotic and is not effective against malaria parasites. Quinine (D) is primarily used for treating malaria, not preventing it, and it is not specifically histoschizontocidal.

Correct Answer: A

Rationale: Rationale: 1. Gram-negative rods suggest Enterobacteriaceae family. 2. Lactose fermenters narrow down to E. coli. 3. Green colonies on MacConkey agar indicate acid production. 4. E. coli is a common cause of pneumonia. Therefore, the most likely causative agent is Escherichia coli. Other choices are incorrect as Klebsiella is non-lactose fermenter, Pseudomonas is oxidase-positive, and Proteus is non-lactose fermenter.

Correct Answer: C

Rationale: The correct answer is C: Staphylococcus aureus. This bacterium is commonly associated with hospital-acquired infections due to its ability to cause a wide range of infections and its resistance to multiple antibiotics. Staphylococcus aureus can cause skin infections, pneumonia, bloodstream infections, and surgical site infections, making it a significant threat in healthcare settings. Escherichia coli (choice A) is more commonly associated with foodborne illnesses. Clostridium difficile (choice B) is known for causing antibiotic-associated diarrhea. Bacillus anthracis (choice D) is primarily associated with anthrax infections, which are not typically acquired in hospital settings.

Correct Answer: B

Rationale: The correct answer is B. Vaginitis is often caused by an imbalance in vaginal flora. Antibiotics can disrupt the natural balance, leading to overgrowth of harmful bacteria or yeast. Pregnancy alters hormone levels, making the vagina more susceptible to infection. Menopause decreases estrogen levels, thinning the vaginal walls and reducing beneficial bacteria. A: Urinary blockage does not directly relate to vaginitis. Drug use and stress may weaken the immune system but are not direct causes of vaginitis. C: Puberty, HPV exposure, and smoking/tobacco use do not directly increase the chances of vaginitis. HPV is a viral infection, not a direct cause of vaginitis. D: While menopause can increase the risk of vaginitis due to hormonal changes, stress and steroid use are not primary factors in developing vaginitis.

Correct Answer: C

Rationale: The correct answer is C because F pili are proteins on the F+ donor cell that are attached to specific receptors on the recipient cell's cell wall. This is essential for the transfer of genetic material during conjugation. Choice A is incorrect because F pili are not made up of nucleotides, but rather proteins. Choice B is incorrect because F pili are not transferred to the recipient cell itself, but they facilitate the transfer of genetic material. Choice D is incorrect because F pili are not part of the recipient cell, but rather part of the donor cell for attachment to the recipient cell.