Beta-lactam antibiotics: penicillins, cephalosporins and carbapenems
How beta-lactams inhibit penicillin-binding proteins, the spectrum logic of each penicillin, cephalosporin and carbapenem group and their gaps (MRSA, enterococci, Listeria, atypicals), beta-lactamase inhibitors including avibactam, pharmacokinetics, class and drug-specific adverse effects (neurotoxicity, flucloxacillin cholestasis, carbapenem-valproate interaction), and penicillin allergy cross-reactivity and de-labelling with PEN-FAST.
Tier 1Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Beta-lactams bind penicillin-binding proteins (PBPs), block cell wall cross-linking and are bactericidal against growing bacteria. Killing is time-dependent: see antimicrobial PK/PD.
- Spectrum widens from benzylpenicillin to piperacillin-tazobactam and carbapenems, but every group has gaps: no activity against bacteria without a cell wall (Mycoplasma) or living inside cells (Legionella, Chlamydia), and none (bar ceftaroline) against MRSA.
- Resistance comes from beta-lactamases, altered PBPs and reduced porin entry, covered in mechanisms of antimicrobial resistance.
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Sources
- Therapeutic Guidelines: AntibioticAU/NZTherapeutic Guidelines Limited, current online edition, checked November 2026
- Australian Medicines HandbookAU/NZAustralian Medicines Handbook Pty Ltd, 2026
- ASCIA Guidelines: Adult Penicillin Allergy Management 2026 UpdateAU/NZAustralasian Society of Clinical Immunology and Allergy, 2026
- Development and validation of a penicillin allergy clinical decision rule (PEN-FAST). JAMA Intern Med 2020;180:745-52AU/NZTrubiano et al., 2020
- Efficacy of a clinical decision rule to enable direct oral challenge in patients with low-risk penicillin allergy (PALACE). JAMA Intern Med 2023;183:944-52Copaescu et al., 2023
- Goodman & Gilman's The Pharmacological Basis of Therapeutics (14th ed.)McGraw Hill (Brunton and Knollmann, 2023), 2023
- FETROJA (cefiderocol) prescribing information (chemical structure, section 11)US National Library of Medicine DailyMed, 2026
- Last updated
- 14 November 2026
What changed
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