penicillin

(noun)

Any of a group of broad-spectrum antibiotics obtained from Penicillium molds or synthesized; they have a beta-lactam structure; most are active against gram-positive bacteria and used in the treatment of various infections and diseases.

Related Terms

Examples of penicillin in the following topics:

  • Beta-Lactam Antibiotics: Penicillins and Cephalosporins

    • The β-lactam ring is part of the core structure of several antibiotic families, the principal ones being the penicillins, cephalosporins, carbapenems, and monobactams, which are, therefore, also called β-lactam antibiotics.
    • Penicillin (sometimes abbreviated PCN or pen) is a group of antibiotics derived from Penicillium fungi.
    • They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V.
    • Penicillins are still widely used today, though many types of bacteria are now resistant.
    • All penicillins are β-lactam antibiotics and are used in the treatment of bacterial infections caused by susceptible, usually Gram-positive, organisms.

  • Damage to the Cell Wall

    • An example of an antibiotic that interferes with bacterial cell wall synthesis is Penicillin.
    • Penicillin acts by binding to transpeptidases and inhibiting the cross-linking of peptidoglycan subunits.
    • Penicillin acts by binding to penicillin binding proteins and inhibiting the cross-linking of peptidoglycan subunits.

  • Inhibiting Cell Wall Synthesis

    • This includes penicillin derivatives (penams), cephalosporins (cephems), monobactams, and carbapenems. β-Lactam antibiotics are bacteriocidal and act by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls .
    • The final step in the synthesis of the peptidoglycan is facilitated by penicillin-binding proteins (PBPs).
    • PBPs vary in their affinity for binding penicillin or other β-lactam antibiotics.
    • Diagram depicting the failure of bacterial cell division in the presence of a cell wall synthesis inhibitor (e.g. penicillin, vancomycin).1- Penicillin (or other cell wall synthesis inhibitor) is added to the growth medium with a dividing bacterium.2- The cell begins to grow, but is unable to synthesize new cell wall to accommodate the expanding cell.3- As cellular growth continues, cytoplasm covered by plasma membrane begins to squeeze out through the gap(s) in the cell wall.4- Cell wall integrity is further violated.

  • Origins of Antimicrobial Drugs

    • Before penicillin became a viable medical treatment in the early 1940s, no true cure for gonorrhea, strep throat, or pneumonia existed.
    • The discovery of antimicrobials like penicillin by Alexander Fleming and tetracycline paved the way for better health for millions around the world.
    • Before penicillin became a viable medical treatment in the early 1940s, no true cure for gonorrhea, strep throat, or pneumonia existed.
    • In 1928 Alexander Fleming observed antibiosis against bacteria by a fungus of the genus Penicillium and postulated the effect was mediated by an antibacterial compound, penicillin, and that its antibacterial properties could be exploited for chemotherapy.

  • Antibiotic Classifications

    • Examples include the Beta-lactam antibiotics (penicillin derivatives (penams) ), cephalosporins (cephems), monobactams, and carbapenems) and vancomycin.
    • Penicillin and most other β-lactam antibiotics act by inhibiting penicillin-binding proteins, which normally catalyze cross-linking of bacterial cell walls.

  • Allergic Responses to Drugs

    • The most reported drug allergy is to Beta-lactam antibiotics, of which penicillin is the most well-known type, affecting 1-5% of people who take penicillin.
    • Additionally the allergic reaction may not even be due to the penicillin, as dyes and other chemicals added to antimicrobial drugs may in fact cause the allergic response instead.
    • Taken together, recent studies show that perhaps only 1/5 people who suspect they have an allergy to penicillin do indeed have such an allergy.

  • Relative Resistance of Microbes

    • In addition, they are naturally resistant to a number of antibiotics that disrupt cell-wall biosynthesis, such as penicillin.
    • Examples include Pseudomonas spp. which are naturally resistant to penicillin and the majority of related beta-lactam antibiotics.
    • It was one of the earlier bacteria in which penicillin resistance was found—in 1947, just four years after the drug started being mass-produced.

  • Four-Membered Rings

    • Finally, the β-lactam cleavage of penicillin G (reaction 6) testifies to the enhanced acylating reactivity of this fused ring system.
    • Such electron pair delocalization is diminished in the penicillins, leaving the nitrogen with a pyramidal configuration and the carbonyl function more reactive toward nucleophiles.

  • Related Carbonyl Derivatives

    • Penicillin G has two amide functions, one of which is a β-lactam.

  • Syphilis

    • Syphilis can be effectively treated with antibiotics, specifically the preferred intramuscular penicillin G (given intravenously for neurosyphilis), or else ceftriaxone, and in those who have a severe penicillin allergy, oral doxycycline or azithromycin.
    • Rates decreased dramatically after the widespread availability of penicillin in the 1940s.
    • Treatment for neurosyphilis is the same as any other stage of syphilis, requiring only a short course of penicillin.