In vitro evaluation of BRL 42715, a novel beta-lactamase inhibitor

Abstract

The penem BRL 42715, C6-(N1-methyl-1,2,3-triazolylmethylene)penem, is a potent inhibitor of a broad range of bacterial P-lactamases, including the plasmid-mediated TEM, SHV, OXA, and staphylococcal enzymes, as well as the chromosomally mediated enzymes of Bacteroides, Enterobacter, Citrobacter, Serratia, Morganella, Escherichia, Klebsiella, and Proteus species. The concentration of BRL 42715 needed to reduce the initial rate of hydrolysis of most P-lactamase enzymes by 50% was <0.01 ,ug/ml, which was 10-to 100-fold lower than for other l-lactamase inhibitors. These potent inhibitory activities were reflected in the low concentrations of BRL 42715 needed to potentiate the antibacterial activity of ,-lactamase-susceptible Il-lactams. Concentrations of 0.25 ,ug/ml or less considerably enhanced the activity of amoxicillin against many jI-lactamase-producing strains. The MIC50 (MIC for 50% of strains tested) of amoxicillin for 412 ,3-lactamase-producing members of the family Enterobacteriaceae fell from >128 to 2 ,ug/ml in the presence of 1 jig of BRL 42715 per ml, whereas 5 jig of clavulanic acid per ml brought the MIC5. down to 8 jig/ml. Among these 412 strains were 73 Citrobacter and Enterobacter strains, and 1 ,ig of BRL 42715 per ml reduced the M1C50 of amoxicillin from >128 to 2 ,ug/mI for the 48 cefotaxime-susceptible strains and from >128 to 8 ,ig/ml for the 25 cefotaxime-resistant strains.The ,B-lactamase enzymes form a large and diverse group (3,19) and are recognized as a major cause of bacterial resistance to P-lactam antibiotics (14). This resistance can often be overcome either by using P-lactam antibiotics that are stable to hydrolysis by P-lactamases or by combining labile 3-lactams with enzyme inhibitors which may not themselves be useful antibacterial agents but which have the ability to inactivate P-lactamases. The first ,-lactamase inhibitor to have clinical application was clavulanic acid (8, 16), and formulations of amoxicillin plus clavulanic acid and of ticarcillin plus clavulanic acid are available which protect the antibiotics amoxicillin and ticarcillin from hydrolysis by many P-lactamase-producing organisms. More recently described P-lactamase inhibitors include sulbactam (5) and tazobactam (YTR 830; 1). Clavulanic acid is highly active against a broad range of P-lactamases, including the Ic enzymes produced by Proteus vulgaris and Bacteroides fragilis, but is only weakly active against other class I enzymes. Sulbactam is generally less potent than clavulanic acid (9), although it does have some activity against most class I enzymes, while tazobactam is similar in potency to clavulanic acid and also has moderate activity against the class I enzymes.Studies done in our laboratories on the structural modification of the penem nucleus culminated in the synthesis of compounds containing an alkylidene moiety at the C6 position of the penem ring system (I.

Three Decades of β-Lactamase Inhibitors

“…1, compound 16), is an effective inhibitor of class A, C, and D ␤-lactamases (119, 250). IC 50 s of BRL 42715 were 10-to 100-fold lower than those of clavulanate, tazobactam, and sulbactam for class A TEM-1 and SHV-1, class C P99, class D OXA-1, and the S. aureus ␤-lactamase NCTC 11561 (87). However, BRL 42715 was a substrate for class B metallo-␤-lactamases from Aeromonas hydrophila and S. maltophilia and for BcII (250).…”

“…However, BRL 42715 was a substrate for class B metallo-␤-lactamases from Aeromonas hydrophila and S. maltophilia and for BcII (250). In susceptibility testing, BRL 42715 concentrations of 0.25 g/ml or lower were able to restore amoxicillin MICs to Ͻ16 g/ml for TEM-1-and OXA-1-producing organisms (87). Further, amoxicillin-BRL 42715 combinations were more effective than amoxicillin-clavulanate for E. coli, K. pneumoniae, H. influenzae, S. aureus, and N. gonorrhoeae strains producing plasmid-mediated ␤-lactamases (mostly TEM and SHV expressors) and for K. oxytoca, Proteus vulgaris, and P. mirabilis strains producing chromosomal ␤-lactamases.…”

Emergence of clinical isolates of Escherichia coli producing TEM-1 derivatives or an OXA-1 beta-lactamase conferring resistance to beta-lactamase inhibitors

“…Eight strains produced a 3-lactamase which comigrated with OXA-1 and showed resistance to the combination of amoxicillin with different ,B-lactamase inhibitors, except BRL42715, as previously described (8). It was previously shown that the OXA-1 enzyme was not as well inhibited as TEM-1 by different 1-lactamase inhibitors (8,13,15). For clavulanate, as shown again in this study, this could be explained by a lesser affinity of OXA-1 than that of TEM-1 (6).…”

Novel Carbapenem-Hydrolyzing Oxacillinase OXA-62 from Pandoraea pnomenusa

“…The following antibiotics were obtained from the respective manufacturers: amoxicillin, Gruenenthal GmbH, Stolberg, Germany; ceftazidime, cefuroxime, clavulanate, and BRL 42715, GlaxoSmithKline GmbH & Co. KG, Munich, Germany; cefotaxime, Hoechst AG, Frankfurt/Main, Germany; cefepime and aztreonam, Bristol-Myers Squibb, Munich, Germany; cefoxitin and imipenem, Merck Sharp & Dohme, Munich, Germany; faropenem, Bayer AG, Wuppertal, Germany; meropenem, AstraZeneca GmbH, Plankstadt, Germany; nalidixic acid, reserpine, rifampin, and sodium azide, Sigma-Aldrich Chemie GmbH, Steinheim, Germany; piperacillin and tazobactam, Wyeth Pharma GmbH, Münster, Germany; chloramphenicol, Boehringer, Mannheim, Germany. The ␤-lactamase inhibitors clavulanate, tazobactam, and BRL 42715 (7,16) were used at a fixed concentration of 4 g/ml, and the efflux pump inhibitor reserpine was used at a fixed concentration of 20 g/ml. MICs were determined by an agar dilution technique on MuellerHinton agar inoculated with 10 4 CFU/spot with a multipoint inoculator following Clinical and Laboratory Standards Institute (formerly National Institute for Clinical and Laboratory Standards) guidelines (18).…”