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Beta-Lactam Antibiotics: Mechanism of Action and Classification

β-lactam antibiotics contain a four-membered lactam ring (three C and 1 N) and a variable chemical residue.

Mechanism of Action

β-lactam antibiotics inhibit the peptidoglycan synthesis of the bacterial wall: they bind to so-called penicillin-binding proteins (peptidoglycan synthetases) and thereby inhibit the polymerization of the peptidoglycan and covalent cross-linking of the bacterial wall. The bacteria-specific mechanism of action leads to a good tolerance.

Classification of Urologically Significant β-Lactam Antibiotics:

Penicillins:

• β-Lactamase-sensitive penicillins: Penicillin G und V
• β-lactamase-resistant and extended-spectrum penicillins: Amoxicillin, Ampicillin, Pivmecillinam, Piperacillin, Flucloxacillin

Cephalosporins:

Cephalosporins are β-lactam antibiotics, which are grouped into four generations according to their antibiotic spectrum of activity. The first generation has mainly gram-positive activity. The second and third generations have more gram-negative activity with decreased activity against gram-positive bacteria. The fourth generation of cephalosporins has a broad spectrum of activity. The following list provides an overview of the generations of cephalosporins with significant substances for urologists:

• First generation: cefazolin
• Second generation: cefaclor, cefuroxime
• Third generation: cefotaxime, ceftriaxone, ceftazidime for parenteral application. Cefpodoxime and ceftibuten for oral formulations.
• Fourth generation: cefepime, ceftolozan (combined with tazobactam)

Carbapenems:

Carbapenems are reserve antibiotics with a broad spectrum of activity.

• Imipenem, meropenem, ertapenem, doripenem

Monobactams:

Monobactams are effective in the gram-negative range and are an option in patients with an allergy to β lactams.

• Aztreonam

β-Lactamase Inhibitors:

β-lactamase inhibitors are combined with β-lactam antibiotics to extend the spectrum of activity.

• Clavulanic acid (combined with amoxicillin)
• Sulbactam (combined with ampicillin)
• Tazobactam (combined with piperacillin)
• Avibactam (combined with ceftazidime or aztreonam)

References

H. R. Brodt, A. Hörauf, M. Kresken, W. Solbach, and T. Welte, Infektionstherapie: Antibiotika, Virostatika, Antimykotika, Antiparasitäre Wirkstoffe. Thieme, 2023.

  Deutsche Version: Beta-Lactam Antibiotika

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