microbiology chapter 10 test bank

Correct Answer: A

Rationale: The correct answer is A: Listeria monocytogenes. This pathogen can cross the placenta and infect the fetus, leading to serious complications. Listeria can cause miscarriage, stillbirth, or severe neonatal infections. Staphylococcus aureus and Corynebacterium diphtheriae do not typically cross the placenta. Choice D is incorrect because Listeria monocytogenes can indeed be transmitted through the placenta, unlike the other pathogens listed.

Correct Answer: C

Rationale: The correct answer is C: Van Leeuwenhoek. Van Leeuwenhoek was a Dutch scientist known for his pioneering work in microscopy. He was the first to observe microbial life, including bacteria on teeth, using his handmade microscopes in the 17th century. Jenner (choice A) is known for developing the smallpox vaccine, not for microbial observations. Semmelweis (choice B) discovered the importance of handwashing in preventing infections. Pasteur (choice D) is famous for his work on pasteurization and germ theory, but not specifically for observing microbial life on teeth. Van Leeuwenhoek's meticulous observations and groundbreaking discoveries make him the correct choice in this context.

Correct Answer: A

Rationale: Step-by-step rationale for why the correct answer is A (Cholera): 1. Gram-negative curved mobile monotrichous bacilli: Vibrio cholerae, the causative agent of cholera, fits this description. 2. Do not produce spores or capsules: Vibrio cholerae does not produce spores or capsules. 3. Require alkaline reaction (pH 8.5-9.5): Vibrio cholerae thrives in alkaline environments. 4. Enteric infection: Cholera is a classic example of an enteric infection transmitted through contaminated food or water. Summary of why other choices are incorrect: B: Shigellosis is caused by Shigella species, which are gram-negative, but they are not curved bacilli and do not require an alkaline pH. C: Typhoid fever is caused by Salmonella Typhi, which are gram-negative but are not curved bacilli and do not require an alkaline pH.

Correct Answer: D

Rationale: The correct answer is D because bacterial vaginitis is often caused by an imbalance in the vaginal flora, which can be disrupted by frequent douching (eliminating beneficial bacteria), tight clothing (restricting airflow), and non-breathable underwear. Avoiding tight pants and using cotton underwear allow for better ventilation, promoting a healthy vaginal environment. Infrequent douching helps maintain the natural balance of bacteria in the vagina. Choices A and B are incorrect because they recommend practices that can disrupt the vaginal flora and increase the risk of bacterial vaginitis. Choice C is partially correct but lacks the emphasis on avoiding frequent douching, which is crucial in preventing bacterial vaginitis.

Correct Answer: B

Rationale: The correct answer is B: Diarrhea. Brucellosis typically presents with symptoms such as arthralgia, headache, and undulating fever, but diarrhea is not a common symptom associated with the disease. Brucellosis is primarily characterized by systemic symptoms like fever, joint pain, and headache due to the bacterial infection. Diarrhea is more commonly seen in gastrointestinal infections rather than brucellosis. Therefore, the absence of diarrhea as a symptom in brucellosis helps in differentiating it from other diseases with similar clinical presentations.