In a bacteriology lab, bacteria cultured from fecal samples produced red colonies on Endo agar. What is the most likely microorganism?

Correct Answer: A

Rationale: The correct answer is A: Escherichia coli. E. coli typically produces red colonies on Endo agar due to its ability to ferment lactose. This results in the production of acid, causing the colonies to appear red. Salmonella and Shigella are non-lactose fermenters, so they would appear colorless or transparent on Endo agar. Proteus vulgaris is not commonly associated with red colonies on Endo agar. Therefore, based on the characteristic lactose fermentation pattern, E. coli is the most likely microorganism in this scenario.

Correct Answer: D

Rationale: Interferon is a cell-specific protein that is produced and released from infected cells in response to viral infections. It acts extracellularly to interfere with viral replication, not to inactivate the virus itself. Interferon is not coded for by cellular DNA, but by viral RNA during infection. Therefore, the correct answer, D, is that interferon is not virus-specific but is cell-specific. This is because interferon can be produced by various cell types in response to different types of viral infections, making it a broad-spectrum antiviral defense mechanism.

Correct Answer: A

Rationale: The correct answer is A: Air. In transmissive infections, the vector refers to the means by which the infectious agent is transmitted from one host to another. Air can carry pathogens such as viruses and bacteria, leading to respiratory infections like the flu or tuberculosis. Airborne transmission occurs when droplets containing the pathogens are inhaled. Objects (B), medical devices (C), and water (D) can also transmit infections, but they are not specifically related to transmissive infections. Objects and medical devices can harbor pathogens, while waterborne infections are transmitted through contaminated water sources. However, in the context of transmissive infections, the primary vector is the air due to its ability to carry infectious agents over distances.

Correct Answer: A

Rationale: The correct answer is A because lipophilization is the process of removing water from cells under deep vacuum in a frozen state. Dehydration of the cell at a low temperature helps to preserve the cellular structure and components. Choice B is incorrect as hydration does the opposite of what lipophilization aims to achieve. Choice C is incorrect as lipophilization does not involve enriching cells with proteins. Choice D is incorrect as lipophilization does not involve removing protein content from cells.

Correct Answer: D

Rationale: The correct answer is D because all three viruses, Vaccinia virus, Smallpox virus, and Cowpox virus, belong to the genus Orthopoxvirus. They share similar characteristics and genetic makeup. Vaccinia virus is used as a vaccine against smallpox, Smallpox virus causes smallpox disease, and Cowpox virus can infect both animals and humans. Choice A, B, and C are incorrect because each of these viruses is a member of the Orthopoxvirus genus.