Penicillin G is used primarily for which type of bacteria?

Penicillin G is used primarily for which type of bacteria?

• A. Gram-negative bacteria
• B. Gram-positive bacteria including MSSA
• C. Anaerobes
• D. Fungi

Answer: (B)

Penicillin G has a narrow spectrum that is strongest against Gram-positive bacteria. It works by inhibiting cell-wall synthesis, and Gram-positive organisms have thick peptidoglycan and no outer membrane, making them highly susceptible to this drug. In contrast, Gram-negative bacteria have an outer membrane that limits penicillin G’s access and many produce beta-lactamases that inactivate the drug, so its activity against them is poor. It doesn’t treat fungi. While Staphylococcus aureus strains often produce beta-lactamase (limiting penicillin G’s usefulness for MSSA infections), the classic description of Penicillin G’s primary target is Gram-positive bacteria, including common Gram-positive cocci such as MSSA in broad terms. That's why this choice best matches Penicillin G’s typical clinical spectrum.

Penicillin G has a narrow spectrum that is strongest against Gram-positive bacteria. It works by inhibiting cell-wall synthesis, and Gram-positive organisms have thick peptidoglycan and no outer membrane, making them highly susceptible to this drug. In contrast, Gram-negative bacteria have an outer membrane that limits penicillin G’s access and many produce beta-lactamases that inactivate the drug, so its activity against them is poor. It doesn’t treat fungi. While Staphylococcus aureus strains often produce beta-lactamase (limiting penicillin G’s usefulness for MSSA infections), the classic description of Penicillin G’s primary target is Gram-positive bacteria, including common Gram-positive cocci such as MSSA in broad terms. That's why this choice best matches Penicillin G’s typical clinical spectrum.