Definition of penicillin in US English:



  • 1An antibiotic or group of antibiotics produced naturally by certain blue molds, and now usually prepared synthetically.

    • ‘The antibiotics used were mainly cephalosporins, penicillins, fluoroquinolones, aminoglycosides, tetracyclines and antituberculosis drugs.’
    • ‘Antibiotic categories to consider include penicillins, cephalosporins, and macrolides.’
    • ‘All the usual range of antibiotics, penicillins and cephalosporins are pretty much useless against these things.’
    • ‘Major classes of antibiotics include tetracyclines, aminoglycosides, penicillins, cephalosporins, fluoroquinolones, streptogramins, sulfonamides, and erythromycins.’
    • ‘Exanthematous eruptions most commonly occur in association with the administration of penicillins or cephalosporins.’
    • ‘Overuse of antibiotics has been shown to drive the evolution of mutant strains of bacteria immune to a broad spectrum of drugs, including penicillins, cephalosporins, and quinolones.’
    • ‘In general, cephalosporins and penicillins are not very effective in treating acne.’
    • ‘While the incidence of true cross-reactivity between penicillins and cephalosporins is low, the possible reactions include anaphylaxis, which can be fatal.’
    • ‘Most antibiotics such as penicillins, cyclosporines, and aminoglycosides can be used safely during pregnancy, but tetracyclines should be avoided.’
    • ‘Oral antibiotics are usually used in the treatment and include first-generation cephalosporins, penicillinase-resistant penicillins, macrolides, and fluoroquinolones.’
    • ‘For the patient who is allergic to penicillins, the use of trimethoprim/sulfamethoxazole is indicated.’
    • ‘The aminopenicillins were the first penicillins discovered to be active against gram-negative rods such as E. coli and H. influenzae.’
    • ‘Enterococci are inherently resistant to cephalosporins, semi-synthetic penicillins, and clindamycin.’
    • ‘Many were originally sensitive to antibiotics such as penicillins, but overuse of these drugs has resulted in many multi-resistant bacteria.’
    • ‘Studies from the late 1960s and the 1970s revealed that streptococcal eradication was equal with intramuscularly and orally administered penicillins.’
    • ‘The lactams are a family of antimicrobial agents consisting of four major groups: penicillins, cephalosporins, monobactams, and carbapenems.’
    • ‘The surprising finding was that people who had reacted to sulphonamides were more likely to react to penicillins than to sulphonamide non-antibiotics.’
    • ‘It is well established that far less expensive antibiotics, including the penicillins and tetracyclines, are highly effective against Anthrax.’
    • ‘Within these two therapeutic drug classes, penicillins were identified 22 times, cephalosporins 21 times, and opioids 20 times.’
    • ‘Unlike Streptococcus pneumoniae, group A beta-hemolytic streptococci have not developed resistance to penicillins.’
  • 2A blue mold of a type that produces penicillin.

    Genus Penicillium, subdivision Deuteromycotina


From the modern Latin genus name Penicillium (see penicillium) + -in.