Correct Answer: A

Rationale: The correct answer is A (Golden staphylococcus and hemolytic streptococcus) because these microorganisms are commonly found in the air of contaminated environments like drug-store premises. Golden staphylococcus and hemolytic streptococcus are pathogenic bacteria associated with infections in humans, indicating poor sanitation. The other choices are incorrect because: B: Diphtheria and tuberculosis bacilli are not commonly found in the air in drug-store premises. C: Colon and blue pus bacilli are not typical microorganisms associated with air contamination. D: Epidermal staphylococcus and sarcina are not likely to be present in high amounts in the air of drug-store premises.

Correct Answer: B

Rationale: The correct answer is B: Agglutination reaction. This is the most suitable serological reaction for the quick determination of the antigen of the epizootic agent causing mass rodent deaths. In agglutination reaction, antibodies cause the clumping of antigens, allowing for easy visual detection of the presence of the specific antigen. This is efficient for rapid diagnosis in cases of suspected infectious diseases like plague. A: Precipitation reaction is more suitable for identifying soluble antigens, not for quick determination of a specific antigen in this scenario. C: Reaction of passive hemagglutination is used for measuring the presence of antibodies, not antigens. D: Bordet-Gengou test is a specific test for the identification of Bordetella pertussis bacterium, not suitable for this scenario.

Correct Answer: A

Rationale: Step 1: Trichomonal gingivostomatitis is caused by the parasite Trichomonas tenax. Step 2: Metronidazole is the drug of choice for treating infections caused by anaerobic organisms like Trichomonas. Step 3: Metronidazole effectively targets and eliminates Trichomonas parasites in the oral cavity. Step 4: Therefore, the correct drug choice for treating trichomonal gingivostomatitis is Metronidazole. Summary: - Ampicillin (B) is an antibiotic effective against Gram-positive bacteria, not parasites. - Gentamicin sulfate (C) is an antibiotic used for bacterial infections, not parasitic infections. - Nystatin (D) is an antifungal medication used for treating fungal infections, not parasitic infections like trichomonal gingivostomatitis.

Correct Answer: A

Rationale: The correct answer is A: 1. Water testing facilities typically handle low-risk microorganisms, hence requiring Biosafety Level 1. BSL 1 is suitable for working with well-characterized agents not known to consistently cause disease in healthy adults. BSL 2 is for moderate-risk agents, BSL 3 for high-risk agents, and BSL 4 for dangerous pathogens. Therefore, choices B, C, and D are incorrect for water testing facilities due to the low risk involved in handling the microorganisms found in water samples.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is the most likely causative agent for pneumonia in this case due to the presence of Gram-positive cocci in pairs with a capsule, which is a typical characteristic of S. pneumoniae. This pathogen is a common cause of community-acquired pneumonia and is known for its encapsulated morphology. Staphylococcus aureus (B) is a Gram-positive cocci but does not typically present in pairs with a capsule in pneumonia cases. Klebsiella pneumoniae (C) is a Gram-negative bacterium and does not match the description provided. Pseudomonas aeruginosa (D) is a Gram-negative bacterium that is not typically associated with Gram-positive cocci in pneumonia samples.