A patient with severe pneumonia had a sputum culture revealing Gram-negative rods that are non-lactose fermenters. What is the most likely causative agent?

Correct Answer: A

Rationale: The correct answer is A: Pseudomonas aeruginosa. This is because Pseudomonas aeruginosa is a common Gram-negative rod that is a non-lactose fermenter and a common cause of severe pneumonia, especially in immunocompromised individuals. It is also known for its resistance to many antibiotics, making it difficult to treat. Summary of other choices: B: Escherichia coli is a lactose fermenter and is not commonly associated with severe pneumonia. C: Klebsiella pneumoniae is a lactose fermenter and is more commonly associated with pneumonia in alcoholics or debilitated patients. D: Enterobacter cloacae is a lactose fermenter and is not a common cause of severe pneumonia.

Correct Answer: A

Rationale: The correct answer is A: Capsule. A capsule is a mucous structure tightly bound to the bacterial cell wall with distinct outer boundaries. This structure helps bacteria evade the host immune system, resist desiccation, and adhere to surfaces. In contrast, spores are resistant structures formed by certain bacteria for survival, filaments are long chains of bacterial cells, and ribosomes are cellular organelles responsible for protein synthesis. Therefore, based on the characteristics described in the question, the most appropriate choice is A: Capsule.

Correct Answer: B

Rationale: The correct answer is B: Ascomycota. Penicillin is produced by the mold Penicillium, which belongs to the phylum Ascomycota. Ascomycota is known for its sac-like structures called asci that contain ascospores. Penicillium produces penicillin as a defense mechanism against bacteria. Basidiomycota (A) are known for producing mushrooms, Zygomycota (C) includes bread molds like Rhizopus, and Deuteromycota (D) is a classification for fungi with no known sexual reproductive stage.

Correct Answer: D

Rationale: The correct answer is D: Kinyoun stain. This stain is the most widely used differential stain in hematology labs because it is specifically designed for acid-fast bacteria like Mycobacterium tuberculosis. It differentiates these bacteria from others based on their cell wall composition. Carbolfuchsin stain (A) is used for acid-fast bacteria in microbiology. Wright's stain (B) is used for blood cell morphology. Ziehl-Neelsen stain (C) is also used for acid-fast bacteria but is less commonly used compared to Kinyoun stain in hematology labs.

Correct Answer: C

Rationale: The correct answer is C: IFA - Immunofluorescence assay. Toxoplasmosis and chronic gonorrhea can be detected using serological tests like IFA. IFA detects specific antibodies in the patient's serum by using fluorescently labeled antibodies. This method is highly sensitive and specific for detecting both acute and latent infections. Explanation of Incorrect Choices: A: RIHA - Reverse indirect hemagglutination assay - This test is not commonly used for detecting toxoplasmosis or chronic gonorrhea. B: RDHA - Reverse direct hemagglutination assay - This test is not typically used for these specific infections. D: Immunoblot analysis - While Immunoblot analysis is a useful confirmatory test for certain infections, it is not the primary method for detecting toxoplasmosis or chronic gonorrhea.

Correct Answer: A

Rationale: The correct answer is A: Treponema. The characteristics described match Treponema pallidum, the causative agent of syphilis. Treponema has long, spiral shape with 8-12 regular coils. Leptospira (B) is a spirochete but has fewer coils and causes leptospirosis. Borrelia (C) is another spirochete but typically has irregular coils and causes Lyme disease. Vibrios (D) are curved rods and not spirochetes.

Correct Answer: B

Rationale: The correct answer is B: Campylobacter jejuni. This bacteria is commonly associated with foodborne illnesses due to its presence in undercooked poultry and unpasteurized milk. Campylobacteriosis is a leading cause of bacterial gastroenteritis. Streptococcus pneumoniae (A) causes pneumonia, not foodborne illnesses. Mycobacterium tuberculosis (C) causes tuberculosis, not foodborne illnesses. Haemophilus influenzae (D) can cause respiratory infections but is not commonly associated with foodborne illnesses.

Correct Answer: C

Rationale: The correct answer is C because plasmids do not encode essential bacterial properties. They are non-essential, extra-chromosomal DNA molecules that can replicate independently within bacterial cells. Plasmids mainly contain genes for antibiotic resistance, genetic transfer, and other specific functions. Choice A is correct as many plasmids do carry antibiotic resistance genes. Choice B is also accurate as plasmids are indeed smaller, circular, and exist outside the bacterial chromosome. Choice D is true as plasmids can facilitate bacterial conjugation, allowing the transfer of genetic material between bacteria.

Correct Answer: D

Rationale: The correct answer is D because fires from flammable metals require specialized Class D fire extinguishers designed to extinguish these unique types of fires. Class A, B, and C fire extinguishers are not suitable for flammable metal fires as they are designed for different types of materials and fire classes. Class A extinguishers are for ordinary combustibles, Class B for flammable liquids, and Class C for electrical fires. Therefore, Class D fire extinguishers are specifically designed for flammable metal fires, making them the correct choice for this scenario.