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β-Lactams and Related Compounds as Antibacterials and β-Lactamase Inhibitors
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2020
Ulrike Holzgrabe, Jens Schmitz
Inhibitors of the β-lactamases are capable of restoring the activity of the β-lactam antibiotics in resistant strains. Thus, such inhibitors were developed in the 1980s and administered in combination with some antibiotics. For a long time, only three β-lactamase inhibitors (BLIs) were available for clinical use. These are clavulanic acid, a penem being a natural compound from Streptomyces clavuligerus, which is administered mostly together with amoxicillin and ticarcillin, sulbactam with ampicillin and cefoperazone, and tazobactam with piperacillin (see Fig. 8.6). Tazobactam and sulbactam belong to the group of penamsulfones. All of them are applied for the treatment of severe, often life-threatening infections in hospitals (Anderson et al., 2012). Of note, these BLIs do not have any anti-infective activity!
Critical evaluation of rate coefficients for hydroxyl radical reactions with antibiotics: A review
Published in Critical Reviews in Environmental Science and Technology, 2018
László Wojnárovits, Tünde Tóth, Erzsébet Takács
β-lactam antibiotics are bactericide agents acting by inhibiting the synthesis of peptidoglycan layer of bacterial cell walls (Pochini et al., 2008). They contain a lactam ring fused to a 5-member (thiazolidine) ring (penicillins belong to this group named penam), or 6-member (e.g., dihydrothiazine) ring (cephalosporins together with cephamycins constitute a subgroup of β-lactam antibiotics called cephems) (Fig. 1). The β-lactam ring is a reactive acylating agent, which binds covalently to the serine residue of the enzyme, generating a practically dead acyl-enzyme complex. It follows that in the absence of the 4-member lactam ring (i.e. opening of the ring), they lose the antibacterial activity (Walsh, 2003). The molecules have ionizable carboxyl and/or amino groups, therefore, depending on the pH they exist in different ionization states in solution. In the practically important pH 5 – 7 range amoxicillin, ampicillin and cephalexin exist in zwitterionic form with protonated amino and deprotonated carboxyl group (Andreozzi et al., 2005). Most of the other molecules in Table 3, penicillin G and V, piperacillin, cloxacillin, cafalotin and cefotaxime are mainly in -1 ionization state with ionized carboxyl moiety (Rickman and Mezyk, 2010).