The most important reason for highly restricted use of penicillin G injections in present-day therapeutics is its

Correct Answer: B

Rationale: The correct answer is B) Potential to cause hypersensitivity reaction. Penicillin G injections are highly restricted in present-day therapeutics primarily due to their high potential to cause hypersensitivity reactions, including severe allergic reactions such as anaphylaxis. These reactions can range from mild rashes to life-threatening conditions, making the use of penicillin G injections risky and potentially harmful to patients. Option A) Narrow spectrum of activity is incorrect because penicillin G has a broad spectrum of activity against many gram-positive bacteria, although it is less effective against gram-negative bacteria. Option C) Short duration of action is incorrect because penicillin G actually has a relatively long half-life compared to other penicillins, allowing for less frequent dosing in some cases. Option D) Neurotoxicity is incorrect as penicillin G is not known for causing neurotoxicity as a primary reason for its restricted use. In an educational context, understanding the limitations and potential risks associated with penicillin G injections is crucial for healthcare professionals to make informed decisions regarding its use in patient care. It is essential to consider factors such as drug allergies and potential adverse reactions when selecting appropriate treatment options for patients, highlighting the importance of individualized medicine and patient safety.

Correct Answer: A

Rationale: In this scenario, the correct answer is A) Methicillin resistant Staph. aureus. Amoxicillin + Clavulanic acid is a combination antibiotic that includes amoxicillin, a penicillin-type antibiotic, and clavulanic acid, a beta-lactamase inhibitor. Methicillin-resistant Staphylococcus aureus (MRSA) is resistant to many antibiotics including methicillin, penicillin, and amoxicillin. Amoxicillin alone is not effective against MRSA because MRSA produces penicillinase, an enzyme that breaks down penicillins. However, the addition of clavulanic acid in amoxicillin + clavulanic acid combination helps to inhibit the action of beta-lactamase enzymes, thereby making the antibiotic effective against penicillinase-producing organisms like Staphylococcus aureus and Neisseria gonorrhoeae. Regarding the incorrect options: - B) Penicillinase producing Staph. aureus: This option is incorrect because amoxicillin + clavulanic acid is active against penicillinase-producing Staphylococcus aureus. - C) Penicillinase producing N. gonorrhoeae: This option is incorrect because the combination is effective against penicillinase-producing N. gonorrhoeae. - D) β-lactamase producing E. coli: This option is incorrect because amoxicillin + clavulanic acid is effective against β-lactamase-producing E. coli due to the action of clavulanic acid. Understanding the spectrum of activity of antibiotics is crucial in clinical practice to ensure appropriate selection of antibiotics for specific infections based on the susceptibility patterns of the organisms involved. It is essential for healthcare professionals to be aware of the mechanisms of resistance and the rationale behind combination therapies like amoxicillin + clavulanic acid to optimize patient care and combat the rise of antibiotic resistance.

Correct Answer: B

Rationale: The correct answer is B) They bind to 30S ribosomes and inhibit bacterial protein synthesis. Tetracycline antibiotics act by binding to the 30S subunit of bacterial ribosomes, preventing the attachment of aminoacyl-tRNA molecules to the mRNA-ribosome complex. This inhibition halts the elongation of the polypeptide chain during protein synthesis, ultimately leading to bacterial cell death. Option A) They chelate Ca²⁺ ions and alter permeability of the bacterial cell membrane is incorrect because tetracyclines do not exert their antimicrobial action through this mechanism. Option C) They bind to 50S ribosomes and interfere with translocation of the growing peptide chain in the bacteria is incorrect as tetracyclines specifically target the 30S ribosomal subunit. Option D) They interfere with DNA-mediated RNA synthesis in bacteria is also incorrect as tetracyclines primarily target protein synthesis, not DNA replication or transcription. In an educational context, understanding the specific mechanism of action of tetracycline antibiotics is crucial for healthcare professionals to effectively prescribe these drugs and for students to grasp the fundamental principles of antimicrobial therapy. This knowledge helps in selecting the appropriate antibiotics for treating bacterial infections and avoiding resistance development.

Correct Answer: A

Rationale: In this question about doxycycline and superinfection diarrhea, the correct answer is A) It is completely absorbed in the small intestines so that drug concentration in the colonic contents is low. This is because doxycycline's property of being well-absorbed in the small intestines means that there is minimal residual drug present in the colon where the normal gut flora reside, reducing the risk of disrupting the balance and causing superinfection diarrhea. Option B) It is inactivated by the gut microflora is incorrect because doxycycline is not primarily inactivated by gut microflora, but rather its absorption pattern helps in reducing its concentration in the colon. Option C) It is not active against the microbes of the normal gut flora is incorrect as doxycycline, being a broad-spectrum antibiotic, can affect normal gut flora. Option D) It is a potent tetracycline and inhibits the superinfection-causing microbes as well is incorrect because while it may inhibit some microbes, its lower concentration in the colon is the primary reason for the reduced incidence of superinfection diarrhea. Educationally, this question highlights the importance of understanding the pharmacokinetics of antibiotics in relation to their side effects, particularly in the context of gut flora disruption and superinfection. It also underscores the significance of choosing antibiotics wisely to minimize adverse effects.

Correct Answer: B

Rationale: In the context of drugs for the immune system, understanding mechanisms of antibiotic resistance is crucial for healthcare professionals. The correct answer to the question is B) Acquisition of a plasmid encoded for chloramphenicol acetyl transferase. This is because the production of chloramphenicol acetyl transferase enzyme inactivates chloramphenicol by acetylation, rendering it ineffective against the bacteria. This mechanism is a common way for bacteria to develop resistance to chloramphenicol. Option A) Decreased permeability into the bacterial cell is a mechanism seen in resistance to some antibiotics but not specifically chloramphenicol. Option C) Lowered affinity of the bacterial ribosome for chloramphenicol is not a common mechanism of resistance. Option D) Switching over from ribosomal to mitochondrial protein synthesis is unrelated to the acquisition of chloramphenicol resistance. In an educational context, understanding antibiotic resistance mechanisms is essential for effective patient care and for combatting the rise of multidrug-resistant bacteria. Healthcare professionals need to grasp these concepts to make informed decisions regarding antibiotic therapy and to prevent the spread of resistant strains.