A dimorphic fungus growing as a mold prefers what temperature?

Correct Answer: C

Rationale: The correct answer is C (25°C) because dimorphic fungi typically grow as molds at lower temperatures. At 25°C, the fungus is likely in its mold phase, which is the preferred temperature range for mold growth. Choices A, B, and D are incorrect because 15°C and 20°C are too low for optimal mold growth, and 37°C is too high as it typically favors the yeast phase of dimorphic fungi. Therefore, the preferred temperature for mold growth of a dimorphic fungus is 25°C.

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.

Correct Answer: B

Rationale: The correct answer is B: Escherichia coli. E. coli is a common bacterium found in the gastrointestinal tract and is a leading cause of UTIs. It has specific virulence factors that enable it to adhere to and infect the urinary tract. Salmonella enterica causes food poisoning, Vibrio cholerae causes cholera, and Streptococcus pyogenes causes strep throat and skin infections, not UTIs. Therefore, B is the correct answer as it is the only bacterium known for causing UTIs.

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: D

Rationale: The correct answer is D: Agglutination test type Gruber. This is because the Gruber agglutination test is not typically used for the serological identification of Yersinia pestis. The other options (A, B, C) are commonly used methods for serological identification of Y. pestis: A) Precipitation reaction involves the formation of a visible precipitate when Y. pestis antigen reacts with specific antibodies. B) Indirect hemagglutination test detects antibodies against Y. pestis by measuring the agglutination of red blood cells. C) Immunofluorescence test uses fluorescently labeled antibodies to detect specific antigens of Y. pestis. In summary, the Gruber agglutination test is not a standard method for serological identification of Yersinia pestis, unlike the other options provided.

Correct Answer: C

Rationale: Rationale: 1. Both Clostridium botulinum and Bacillus anthracis are known to form spores. 2. Spore formation is a mechanism for survival in harsh conditions. 3. Both bacteria are capable of causing severe diseases in humans. Summary: - Choice A and B are incorrect because each bacteria listed is capable of spore formation. - Choice D is incorrect as both bacteria mentioned can form spores to survive extreme conditions.

Correct Answer: A

Rationale: The correct answer is A: Isoniazid. Isoniazid is a first-line drug for treating active pulmonary tuberculosis due to its high efficacy and low toxicity. It works by inhibiting the synthesis of mycolic acids in the bacterial cell wall. Sulfalen, Cyclocerine, and Ethionamide are not first-line drugs for tuberculosis. Sulfalen is used for urinary tract infections, Cyclocerine for drug-resistant tuberculosis, and Ethionamide as a second-line drug for multidrug-resistant tuberculosis. Therefore, Isoniazid is the most appropriate initial choice for treating active focal pulmonary tuberculosis.

Correct Answer: B

Rationale: Fimbriae in bacteria are hair-like appendages that help in adhesion to surfaces. This is essential for colonization and infection. Fimbriae do not provide motility (flagella do), facilitate protein synthesis (ribosomes do), or help in endospore formation (specialized structures do). Adhesion is the primary function of fimbriae, allowing bacteria to stick to host cells or abiotic surfaces.

Correct Answer: D

Rationale: The correct answer is D, the rabies virus. Rabies virus has the widest infectious spectrum among the given choices because it can infect a wide range of mammals, including humans. This is due to its ability to infect nerve cells and spread throughout the central nervous system. The other choices have more limited infectious spectra. Anthrax bacillus primarily infects herbivores and humans, mumps virus infects mainly humans, and the causative agent of gonorrhea primarily infects humans through sexual contact. Therefore, the rabies virus is the correct answer as it has the broadest range of potential hosts.