The most commonly acquired laboratory infections are caused by

Correct Answer: A

Rationale: The correct answer is A: bacteria. Bacteria are the most common cause of laboratory-acquired infections due to their ability to survive and multiply in various environments. They can easily contaminate lab equipment and surfaces, leading to infections if proper precautions are not taken. Viruses (choice B) are less common in laboratory-acquired infections as they require specific conditions to survive outside a host. Protozoans (choice C) are larger and less likely to be transmitted in a laboratory setting. Prions (choice D) are misfolded proteins and are not considered living organisms, making them an unlikely source of laboratory infections.

Correct Answer: B

Rationale: The correct answer is B: Clostridium botulinum. This bacterium belongs to the Clostridium genus, known for its ability to produce endospores. Endospores are dormant, resistant structures that help bacteria survive harsh conditions. Staphylococcus aureus (A), Escherichia coli (C), and Neisseria gonorrhoeae (D) do not produce endospores. Staphylococcus aureus is a gram-positive bacterium known for causing various infections, but it does not form endospores. Escherichia coli is a gram-negative bacterium commonly found in the intestines of humans and animals, but it does not produce endospores. Neisseria gonorrhoeae is a gram-negative bacterium that causes the sexually transmitted infection gonorrhea, but it also does not form endospores.

Correct Answer: C

Rationale: The correct answer is C: prions. Prions are misfolded proteins that can cause transmissible spongiform encephalopathies like Creutzfeldt-Jakob disease. Prions are not viruses like flavoviruses (A) or orthomyxoviruses (D). Virusoids (B) are small, circular, single-stranded RNA molecules that require a helper virus to replicate and are not associated with transmissible spongiform encephalopathies. Therefore, the correct answer is C as prions are the only choice that correctly links to the etiology of transmissible spongiform encephalopathies.

Correct Answer: A

Rationale: The correct answer is A: Robert Hooke. Hooke published Micrographia in 1665, showcasing detailed illustrations of insects, sponges, and plant cells under the microscope. Hooke's work was groundbreaking in advancing the field of microscopy. Van Leeuwenhoek is known for discovering microorganisms but did not publish Micrographia. Janssen and Needham were not associated with Micrographia. Therefore, A is the correct answer.

Correct Answer: B

Rationale: The correct answer is B: non-spore forming encapsulated gram-negative bacterium. Francisella tularensis is a non-spore forming bacterium, which rules out choices A and D. It is encapsulated, which eliminates choice C. The encapsulation of the bacterium helps it evade the host immune system, leading to its pathogenicity. This encapsulated bacterium is responsible for causing the zoonotic disease tularemia in humans.

Correct Answer: A

Rationale: The correct answer is A: Sabouraud. Sabouraud agar is specifically designed for the cultivation of fungi and yeasts, making it ideal for identifying Candida species causing candidosis. It contains antibiotics to inhibit bacterial growth, promoting the growth of fungi. Endo, Loewenstein-Jensen, and Roux are not suitable for fungal cultures and are used for different purposes like bacterial isolation or mycobacterial cultures. Sabouraud agar is the best choice for confirming candidosis due to its fungal-selective properties.

Correct Answer: A

Rationale: The correct answer is A: Pseudomonas aeruginosa. P. aeruginosa is a Gram-negative rod that is oxidase-positive and lactose non-fermenting. The positive oxidase test indicates the presence of cytochrome c oxidase, a characteristic of P. aerugin. E. coli is lactose fermenting. Salmonella and Shigella are also Gram-negative rods, but they are lactose fermenters, unlike the lactose non-fermenting P. aeruginosa.

Correct Answer: A

Rationale: The correct answer is A: BCG. BCG vaccine is commonly used for tuberculosis prevention because it provides immunity against Mycobacterium tuberculosis. Mantoux is a test, not a vaccine. DTaP vaccine is for diphtheria, tetanus, and pertussis, not tuberculosis. Anatoxin is a type of toxoid vaccine, not used for tuberculosis prevention. BCG vaccine has been shown to be effective in preventing severe forms of tuberculosis in infants, making it the appropriate choice in this scenario.

Correct Answer: A

Rationale: The correct answer is A: Corynebacterium diphtheriae. The presence of rod-shaped bacteria with dark blue polar granules suggests the presence of Corynebacterium diphtheriae, the causative agent of diphtheria. This bacterium is known for causing sore throat and fever, and the characteristic appearance on smear helps identify it. Streptococcus pyogenes (Choice B) typically appears as chains of cocci and is associated with strep throat. Haemophilus influenzae (Choice C) is a small, pleomorphic Gram-negative coccobacillus and is more commonly associated with respiratory infections. Klebsiella pneumoniae (Choice D) is a Gram-negative bacillus and is not typically associated with sore throat and fever in children.