During an outbreak of cholera, a fecal smear revealed Gram-negative, comma-shaped, motile bacteria. What staining method would best confirm the diagnosis?

Correct Answer: A

Rationale: The correct answer is A: Gram staining. This method is used to differentiate bacteria based on their cell wall composition. In cholera, the causative agent is Vibrio cholerae, which is Gram-negative. By performing Gram staining, the bacteria will appear pink/red under the microscope, confirming the presence of Gram-negative bacteria. Choice B: Neisser's staining is used for staining capsules of bacteria, not suitable for confirming cholera diagnosis. Choice C: Ziehl-Neelsen staining is used for acid-fast bacteria like Mycobacterium tuberculosis, not for confirming cholera diagnosis. Choice D: Burri-Gins staining is not a standard staining method in microbiology and is not relevant for confirming cholera diagnosis.

Correct Answer: A

Rationale: The correct answer is A: Helicobacter pylori. This bacterium is a major cause of gastric ulcers by disrupting the balance between aggressive (acid, pepsin) and defensive (mucus, bicarbonate, prostaglandins) factors in the stomach lining. H. pylori infection leads to inflammation, weakening the protective mucosal barrier, making the stomach more susceptible to damage. Choices B, C, and D are defensive factors that help protect the stomach lining and prevent ulcer formation, so they do not contribute to the development of gastric ulcers.

Correct Answer: B

Rationale: The correct answer is B: Motility. The bacterial flagellum is a whip-like appendage that helps bacteria move by rotating like a propeller. This motility allows bacteria to navigate their environment, find nutrients, and avoid harmful conditions. Choices A, C, and D are incorrect because the bacterial flagellum is not involved in protein synthesis, DNA replication, or spore formation. Protein synthesis occurs in ribosomes, DNA replication takes place in the nucleus or nucleoid, and spore formation is a specialized process involving the production of spores for survival in harsh conditions.

Correct Answer: D

Rationale: The correct answer is D: Tuberculosis. Tuberculosis is considered a reemerging disease due to the increase in drug-resistant strains, high global prevalence, and challenges in diagnosis and treatment. This is supported by global health organizations' reports on the resurgence of TB cases. A: AIDS is not considered a reemerging disease as there has been significant progress in HIV prevention and treatment. B: Ebola outbreaks are sporadic and localized, not considered reemerging on a global scale. C: West Nile virus outbreaks occur periodically, but it is not considered a reemerging disease compared to TB.

Correct Answer: B

Rationale: The main function of bacterial pili is to facilitate conjugation and adhesion. Pili are hair-like appendages on bacteria that help in cell-to-cell interactions. They play a crucial role in bacterial conjugation by allowing the transfer of genetic material between cells. Additionally, pili help bacteria adhere to surfaces or host cells, aiding in colonization and biofilm formation. Choices A and D are incorrect because protein synthesis and toxin secretion are not the primary functions of pili. Choice C is incorrect as bacterial motility is mainly mediated by flagella, not pili.