Gram-positive organisms are bacteria that are able to retain crystal violet stain due to relatively high amount of peptidoglycan in the cell wall. Because penicillin inhibits the formation of peptidoglycan cross-linking in the bacterial cell wall, penicillin is bactericidal for many gram-positive organisms.
Spirochetes are bacteria with a long, helical coiled structure. Penicillin remains the drug of choice for many spirochete infections including syphilis.
Penicillin-binding protein (PBP), also known as the enzyme transpeptidase, is a component of many bacterial cell walls and is important for cell wall synthesis. Beta-lactam antibiotics in general bind to this protein which leads to abnormal cell wall structure and cell death.
Transpeptidase, also known as PBP, is a critical enzyme in bacteria that cross-links peptidoglycan to form the cell wall. Penicillin blocks this enzyme and therefore inhibits bacterial cell wall synthesis.
This is the third mechanism of penicillin which activates autolytic enzymes in the bacteria to cause cell death.
Unlike bacteriostatic agents, which simply stop bacteria from reproducing, bactericidal agents actually cause bacterial cell death.
Penicillin hypersensitivity reactions are characterized by an overreaction of the body's immune response to a penicillin antibiotic. Common symptoms include rashes, hives, itchy eyes, and swollen tongue or face. Some individuals can have an anaphylactic reaction.
Penicillin in high doses can induce an immune mediated hemolysis of red blood cells. This occurs via the hapten mechanism in which antibodies are targeted against the combination of penicillin attached to red blood cells. This leads to complement activation and removal of red blood cells by the spleen.
Beta-lactamase is an enzyme that is produced by some bacteria to cleave beta-lactam antibiotics rendering them ineffective. Antibiotics that are beta-lactamase sensitive are susceptible to cleavage by beta-lactamases and are therefore likely to be ineffective against beta-lactamase producing bacteria.
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