Correct Answer: B

Rationale: The correct answer is B: For HIV. Pneumocystis pneumonia in a young man with CD4+ cells less than 200/mm3 is highly suggestive of HIV infection. HIV weakens the immune system, leading to opportunistic infections like pneumocystis pneumonia. Testing for HIV is crucial for diagnosis and appropriate management. Explanation for other choices: A: Testing for ureaplasma urealyticum is not indicated in this case as the symptoms and CD4+ cell count point towards an HIV-related infection. C: Testing for Treponema pallidum (syphilis) is not relevant in the context of a young man with pneumocystis pneumonia and low CD4+ cell count. D: Testing for Neisseria gonorrhoea is not appropriate in this scenario as the symptoms and CD4+ cell count suggest an underlying HIV infection rather than a bacterial sexually transmitted infection.

Correct Answer: C

Rationale: The correct descending order of taxonomic categories is domain, kingdom, phylum, class, order, family, genus, species. This hierarchical classification system helps organize and categorize living organisms based on their shared characteristics and evolutionary relationships. Explanation: - Domain is the broadest category, representing the highest level of classification. - Kingdom further divides organisms into major groups based on similar characteristics. - Phylum, class, order, family, and genus successively narrow down the classification based on more specific shared characteristics. - Species is the most specific category, representing individual organisms capable of interbreeding. Summary of other choices: A: Incorrect as it has the incorrect order of phylum, kingdom, and division. B: Incorrect as it has the incorrect order of family and species. D: Incorrect as it has the incorrect order of domain, kingdom, and class.

Correct Answer: C

Rationale: The correct staining technique for staining sputum smears from a tuberculosis patient is Ziehl-Neelsen staining. This technique uses a carbol fuchsin stain that specifically stains acid-fast organisms like Mycobacterium tuberculosis. The steps involved include staining with carbol fuchsin, decolorizing with acid-alcohol, counterstaining with methylene blue, and then examining under a microscope. This staining method is crucial for detecting the acid-fast bacilli characteristic of tuberculosis. Explanation for incorrect choices: A: Gram staining is used to differentiate bacteria into Gram-positive and Gram-negative, not suitable for acid-fast organisms like Mycobacterium tuberculosis. B: Giemsa staining is used for detecting parasites and certain types of white blood cells, not specific for acid-fast bacteria. D: Burry staining is not a recognized staining technique in microbiology for staining acid-fast organisms.

Correct Answer: A

Rationale: The most probable diagnosis is A: Candidous cheilitis. Candidous cheilitis is a fungal infection caused by Candida species. In this case, the presence of mycelium on the plaques indicates a fungal infection. The symptoms of pain, burning, and grey plaques that can be easily removed leaving hyperemia are typical for Candidous cheilitis. Choice B (Exfoliative cheilitis) is characterized by scaling and peeling of the lips, not plaques with mycelium. Choice C (Leukoplakia) is a precancerous condition causing white plaques that cannot be easily removed. Choice D (Contactant allergic cheilitis) is an allergic reaction causing inflammation, not fungal plaques.

Correct Answer: D

Rationale: The correct answer is D, chemotherapy combined with surgical therapy. Actinomycosis is a bacterial infection that requires a combination of antibiotics to target the bacteria and surgery to remove abscesses or infected tissues. Antibiotics alone may not penetrate abscesses effectively. Waiting for self-clearance can lead to complications. Surgical treatment alone may not eradicate the infection entirely. Therefore, the most effective therapeutic plan is to combine chemotherapy to treat the infection systemically and surgery to remove localized infections.