Which statement about the epidemiology and specific prophylactic of Haemophilus influenzae is NOT CORRECT?

Correct Answer: B

Rationale: The correct answer is B because there is no effective killed vaccine that is protective against all capsular types of Haemophilus spp. The Haemophilus influenzae vaccine primarily targets specific capsular types, not all of them. Choice A is incorrect because non-encapsulated strains can indeed be isolated from healthy carriers. Choice C is incorrect as Haemophilus influenzae is primarily transmitted through respiratory droplets, not through the air. Choice D is not correct because Choice B is indeed incorrect, making it the right answer.

Correct Answer: A

Rationale: Step 1: A bacterial colony is a visible formation: Correct as colonies are visible to the naked eye. Step 2: Formed by clustering of cells: Correct as colonies are made up of numerous bacterial cells. Step 3: Belonging to different bacterial species: Correct as colonies can consist of one or multiple species. Summary: Choice A is correct as it accurately describes a bacterial colony. Choice B is incorrect as colonies can also form on solid nutrient mediums. Choice C is incorrect as choice A is correct. Choice D is incorrect as there is a correct option provided.

Correct Answer: C

Rationale: The correct answer is C because disinfectants are non-selective and can harm a wide range of microbial cells. Disinfectants work by disrupting cell membranes, proteins, and nucleic acids, affecting both harmful and beneficial microorganisms. Choices A and B are incorrect because disinfectants are designed to be potent and non-selective. Choice D is incorrect because the effects of disinfectants are often permanent and irreversible on microbial cells.

Correct Answer: A

Rationale: The correct answer is A: Clostridium perfringens. This is because Clostridium perfringens is a Gram-positive rod bacterium that forms terminal spores. It is commonly associated with deep tissue infections and can cause gas gangrene. Bacillus anthracis (B) causes anthrax and does not typically form spores at the terminal end. Clostridium tetani (C) causes tetanus and Bacillus cereus (D) is more commonly associated with food poisoning. In this case, the presence of terminal spores along with the clinical presentation of a deep tissue infection points towards Clostridium perfringens as the most likely causative agent.

Correct Answer: A

Rationale: The most likely causative agent in this case is Staphylococcus epidermidis. This conclusion can be drawn based on the characteristics provided: Gram-positive cocci in clusters, catalase-positive, and coagulase-negative. Staphylococcus epidermidis fits all these criteria. Explanation of other choices: - Staphylococcus aureus: Typically coagulase-positive, so it does not match the characteristics given. - Streptococcus pyogenes: Gram-positive cocci in chains, not clusters. Also, it is catalase-negative. - Enterococcus faecalis: Gram-positive cocci in pairs or chains, not clusters. Additionally, it is catalase-negative. Therefore, Staphylococcus epidermidis is the most likely causative agent based on the provided characteristics.

Correct Answer: B

Rationale: The correct answer is B: Availability of cell-mediated immunity to tuberculosis. A negative Mantoux test indicates the presence of an immune response to the TB bacteria, as the test measures the body's delayed hypersensitivity reaction to TB antigens. This means the child has been exposed to TB in the past or has been vaccinated, resulting in the development of cell-mediated immunity against TB. Incorrect choices: A: No cell-mediated immunity to tuberculosis - This is incorrect as a negative Mantoux test actually indicates the presence of cell-mediated immunity. C: No antibodies to the tuberculosis bacteria - Mantoux test measures cell-mediated immunity, not antibody response. D: No anti-toxic immunity to tuberculosis - Mantoux test does not assess anti-toxic immunity, it specifically measures cell-mediated immunity.

Correct Answer: D

Rationale: The correct answer is D because the flu vaccine primarily stimulates systemic immunity rather than local immunity. It is administered parenterally (C) as it is injected into the body. It is a subunit vaccine (B) as it contains only specific antigens of the virus. It is a recommended vaccine (A) due to its effectiveness in preventing influenza. In summary, D is the correct choice as the flu vaccine mainly targets systemic immunity, not local immunity, unlike the other characteristics listed.

Correct Answer: A

Rationale: The correct answer is A: Anthrax. The clinical presentation of painless necrotic ulcers with black eschar, along with the gram-positive spore-forming bacilli seen on Gram's staining, is classic for cutaneous anthrax. Anthrax is caused by Bacillus anthracis, which produces spores and can lead to skin lesions in individuals working with animals or animal products. Choice B, Chickenpox, typically presents with vesicular rash all over the body. Choice C, Syphilis, is caused by Treponema pallidum and does not present with the characteristic eschar seen in the patient. Choice D, Tularemia, caused by Francisella tularensis, presents with ulceroglandular lesions but lacks the black eschar characteristic of anthrax.

Correct Answer: A

Rationale: Rationale: 1. Gram-negative rods suggest Enterobacteriaceae family. 2. Lactose fermenters narrow down to E. coli. 3. Green colonies on MacConkey agar indicate acid production. 4. E. coli is a common cause of pneumonia. Therefore, the most likely causative agent is Escherichia coli. Other choices are incorrect as Klebsiella is non-lactose fermenter, Pseudomonas is oxidase-positive, and Proteus is non-lactose fermenter.