Penicillin G

Penicillin G, or benzylpenicillin, is a natural β-lactam antibiotic that blocks bacterial cell-wall synthesis. It is used against susceptible bacteria, especially Gram-positive species.

Penicillin-binding proteins: Bacterial enzymes that build and remodel peptidoglycan in the cell wall. Penicillin G binds these enzymes and disrupts the cross-linking that strengthens the bacterial wall.
Streptococcal infections: Illnesses caused by bacteria in the genus Streptococcus. Many streptococci remain susceptible, making Penicillin G useful for selected infections.
Penicillin V: An orally active natural penicillin used for susceptible bacterial infections. Unlike Penicillin G, it is more stable in stomach acid and commonly given by mouth.
Antibiotic: A substance that kills bacteria or inhibits their growth. Penicillin G is an antibiotic whose effect depends on bacterial susceptibility.
Peptidoglycan: A mesh-like polymer of sugars and amino acids that gives bacterial cell walls strength. Penicillin G prevents the final cross-linking steps in this wall material.
Syphilis: A sexually transmitted infection caused by the spirochete Treponema pallidum. Penicillin G is the preferred treatment for most stages of syphilis.
Oxacillin: A penicillinase-resistant penicillin used mainly against susceptible staphylococci. Its resistance to many staphylococcal penicillinases contrasts with Penicillin G's vulnerability.
Gram-positive bacteria: Bacteria whose cell walls retain crystal violet dye during Gram staining. Their exposed, thick peptidoglycan layer often makes them accessible to Penicillin G.
β-lactam: A four-membered cyclic amide ring found in several major antibiotic families. This ring is the reactive structural feature that lets Penicillin G inhibit its targets.
Neurosyphilis: Syphilis involving the central nervous system, which can occur at any stage of infection. High-dose intravenous Penicillin G is a standard treatment because adequate drug levels are needed in the nervous system.

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