A child with a persistent sore throat and fever had a smear from the throat revealing rod-shaped bacteria with dark blue polar granules. What is the likely causative agent?

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.

Correct Answer: C

Rationale: The correct answer is C: cytoplasmic membrane. The cytoplasmic membrane is the fluidlike portion of a cell that separates the cell's contents from the external environment. It regulates the passage of substances in and out of the cell, maintains cell shape, and provides protection. Rationale: 1. Cytosol (choice A) is the liquid component of the cytoplasm where organelles are suspended, not the fluidlike portion of the cell. 2. Nucleoplasm (choice B) refers to the liquid component of the nucleus, not the entire cell. 3. Inclusion (choice D) refers to non-living substances within the cell that are not considered the fluidlike portion. Summary: The cytoplasmic membrane is the correct answer as it encompasses the entire cell and is responsible for maintaining cell integrity and regulating transport. Choices A, B, and D are incorrect as they do not represent the fluidlike portion of the cell.

Correct Answer: D

Rationale: The correct answer is D: Monoclonal antibodies to anthrax causative agent. Monoclonal antibodies are highly specific for detecting anthrax spores, providing quick and accurate results. They bind only to the anthrax causative agent, allowing for precise identification. Choice A (Anti-anthrax fluorescent serum) is incorrect because it is not as specific and sensitive as monoclonal antibodies. Choice B (Standard anthrax antigen) is incorrect as it is used to stimulate antibody production in the body, not for direct detection of spores. Choice C (Anti-anthrax immunoglobulin) is incorrect as it is a general term for antibodies and may not be specific to anthrax spores. In summary, monoclonal antibodies are the most suitable option for quick and accurate detection of anthrax spores due to their high specificity and sensitivity.

Correct Answer: B

Rationale: Rationale: The correct answer is B because virulence factors of bacteria are characteristics that enable them to cause disease. Colonization allows bacteria to establish and multiply in the host. Invasion refers to the ability to penetrate host tissues. Toxins are substances produced by bacteria that harm the host. Adhesion is crucial for bacteria to attach to host cells. A: Size and mutation are not typical virulence factors. Resistance is not directly related to causing disease. C: While toxins and evasion of body defenses are correct, motility and size are not universally considered virulence factors. D: Chemotaxis and fermentation are not primary virulence factors, unlike colonization and toxins.

Correct Answer: B

Rationale: The correct answer is B: Neisseria meningitidis. This is because Neisseria meningitidis is a Gram-negative diplococci that is oxidase-positive and fermentative. Neisseria gonorrhoeae (choice A) is also a Gram-negative diplococci but is not fermentative. Haemophilus influenzae (choice C) is not a diplococci and Moraxella catarrhalis (choice D) is oxidase-negative. Thus, Neisseria meningitidis fits all the criteria provided in the question, making it the most likely causative agent for the sepsis in this patient.

Correct Answer: B

Rationale: The capsule of Bacillus anthracis is made of polypeptide. This is because the capsule is composed of a protein-based material that surrounds the bacterium, providing protection and aiding in its virulence. Polysaccharides, lipids, and the absence of capsules are not characteristic of Bacillus anthracis' capsule structure, making choices A, C, and D incorrect, respectively.

Correct Answer: D

Rationale: The correct answer is D, "All of these." Monotrichous bacteria have a single flagellum at one end, amphitrichous have flagella at both ends, and peritrichous have flagella distributed all over the surface. The answer D is correct because it includes all these possibilities based on flagella location. Monotrichous is incorrect as it only refers to a single flagellum, amphitrichous is incorrect as it only refers to flagella at both ends, and peritrichous is incorrect as it only refers to flagella all over the surface. Therefore, the correct answer encompasses all these options.

Correct Answer: D

Rationale: The correct answer is D: All are correct. Culture of samples from the respiratory tract can identify specific pathogens, Immunofluorescence can detect viral antigens, and PCR can amplify and detect specific DNA/RNA sequences. Using all methods together provides a comprehensive approach for diagnosing respiratory tract infections. Culture alone may miss fastidious organisms, Immunofluorescence has limitations in sensitivity, and PCR requires specific primers. Therefore, combining these methods increases the likelihood of accurate diagnosis by covering a range of pathogens and improving sensitivity and specificity.

Correct Answer: C

Rationale: The correct answer is C: the hydrolysis of the four-membered ring present in penicillin. Beta-lactamase enzyme catalyzes the hydrolysis of the four-membered beta-lactam ring present in penicillin, rendering the antibiotic ineffective against bacterial cell walls. This enzyme breaks the bond in the beta-lactam ring, thus inactivating the antibiotic. Incorrect choices: A: the final cross-linking reaction to form the bacterial cell wall - This is incorrect as beta-lactamase does not participate in the formation of bacterial cell walls. B: the biosynthesis of the penicillin structure from the amino acid valine and cysteine - This is incorrect as beta-lactamase is not involved in the biosynthesis of penicillin. D: the hydrolysis of the acyl side chain from penicillin structures - This is incorrect as beta-lactamase specifically targets the beta-lactam ring, not the