Decarboxylation of the Catalytic Lysine Residue by the C5α-Methyl-Substituted Carbapenem NA-1-157 Leads to Potent Inhibition of the OXA-58 Carbapenemase.

Antibiotic resistance in bacteria is a major global health concern. The wide spread of carbapenemases, bacterial enzymes that degrade the last-resort carbapenem antibiotics, is responsible for multidrug resistance in bacterial pathogens and has further significantly exacerbated this problem. is one of the leading nosocomial pathogens due to the acquisition and wide dissemination of carbapenem-hydrolyzing class D β-lactamases, which have dramatically diminished available therapeutic options.

Restricted Rotational Flexibility of the C5α-Methyl-Substituted Carbapenem NA-1-157 Leads to Potent Inhibition of the GES-5 Carbapenemase.

Carbapenem antibiotics are used as a last-resort treatment for infections caused by multidrug-resistant bacteria. The wide spread of carbapenemases in Gram-negative bacteria has severely compromised the utility of these drugs and represents a serious public health threat. To combat carbapenemase-mediated resistance, new antimicrobials and inhibitors of these enzymes are urgently needed.

The C5α-Methyl-Substituted Carbapenem NA-1-157 Exhibits Potent Activity against spp. Isolates Producing OXA-48-Type Carbapenemases.

The wide spread of carbapenem-hydrolyzing β-lactamases in Gram-negative bacteria has diminished the utility of the last-resort carbapenem antibiotics, significantly narrowing the available therapeutic options. In the family, which includes many important clinical pathogens such as and , production of class D β-lactamases from the OXA-48-type family constitutes the major mechanism of resistance to carbapenems. To address the public health threat posed by these enzymes, novel, effective therapeutics are urgently needed.

C6 Hydroxymethyl-Substituted Carbapenem MA-1-206 Inhibits the Major Carbapenemase OXA-23 by Impeding Deacylation.

Acinetobacter baumannii has become a major nosocomial pathogen, as it is often multidrug-resistant, which results in infections characterized by high mortality rates. The bacterium achieves high levels of resistance to β-lactam antibiotics by producing β-lactamases, enzymes which destroy these valuable agents. Historically, the carbapenem family of β-lactam antibiotics have been the drugs of choice for treating A.

Atypically Modified Carbapenem Antibiotics Display Improved Antimycobacterial Activity in the Absence of β-Lactamase Inhibitors.

Commercial carbapenem antibiotics are being used to treat multidrug resistant (MDR) and extensively drug resistant (XDR) tuberculosis. Like other β-lactams, carbapenems are irreversible inhibitors of serine d,d-transpeptidases involved in peptidoglycan biosynthesis. In addition to d,d-transpeptidases, mycobacteria also utilize nonhomologous cysteine l,d-transpeptidases (Ldts) to cross-link the stem peptides of peptidoglycan, and carbapenems form long-lived acyl-enzymes with Ldts.

Activity of Imipenem, Meropenem, Cefepime, and Sulbactam in Combination with the β-Lactamase Inhibitor LN-1-255 against spp.

Treatment of infections caused by spp., particularly , is a major clinical problem due to its high rates of antibiotic resistance. New strategies must be developed; therefore, restoration of β-lactam efficacy through the use of β-lactamase inhibitors is paramount.

Therapeutic Efficacy of LN-1-255 in Combination with Imipenem in Severe Infection Caused by Carbapenem-Resistant Acinetobacter baumannii.

The carbapenem-hydrolyzing class D β-lactamases (CHDLs) are the main mechanism of carbapenem resistance in CHDLs are not effectively inactivated by clinically available β-lactam-type inhibitors. We have previously described the efficacy of the inhibitor LN-1-255 in combination with carbapenems. The aim of this study was to compare the efficacy of LN-1-255 with that of imipenem in murine pneumonia using strains carrying their most extended carbapenemases, OXA-23 and OXA-24/40.

Virtual Screening and Experimental Testing of B1 Metallo-β-lactamase Inhibitors.

The global rise of metallo-β-lactamases (MBLs) is problematic due to their ability to inactivate most β-lactam antibiotics. MBL inhibitors that could be coadministered with and restore the efficacy of β-lactams are highly sought after. In this study, we employ virtual screening of candidate MBL inhibitors without thiols or carboxylates to avoid off-target effects using the Avalanche software package, followed by experimental validation of the selected compounds.

Activity of the β-Lactamase Inhibitor LN-1-255 against Carbapenem-Hydrolyzing Class D β-Lactamases from Acinetobacter baumannii.

The number of infections caused by Gram-negative pathogens carrying carbapenemases is increasing, and the group of carbapenem-hydrolyzing class D β-lactamases (CHDLs) is especially problematic. Several clinically important CHDLs have been identified in , including OXA-23, OXA-24/40, OXA-58, OXA-143, OXA-235, and the chromosomally encoded OXA-51. The selection and dissemination of carbapenem-resistant strains constitutes a serious global threat.

Functionalizing the γ-Position of α-Diazo-β-ketoesters.

Although α-diazo-β-ketoesters are synthetically versatile intermediates, methodology for introducing this functionality into complex molecules is still limited, most frequently involving a carboxylic acid precursor, which is then activated and transformed into a β-ketoester, with the diazo group being subsequently added with a diazo transfer reagent. While introducing this highly functional moiety in a convergent one step process would be ideal, such an objective is limited by the relatively few studies which address functionalization of the α-diazo-β-ketoester at the γ-position. In the present investigation, we evaluate strategies, both new and established, for functionalizing α-diazo-β-ketoesters, particularly with regard to generating compounds prospectively useful in the synthesis of C1-substituted carbapenems.

LN-1-255, a penicillanic acid sulfone able to inhibit the class D carbapenemase OXA-48.

Objectives: Carbapenemases are the most important mechanism responsible for carbapenem resistance in Enterobacteriaceae. Among carbapenemases, OXA-48 presents unique challenges as it is resistant to β-lactam inhibitors. Here, we test the capacity of the compound LN-1-255, a 6-alkylidene-2'-substituted penicillanic acid sulfone, to inhibit the activity of the carbapenemase OXA-48.

Meropenem and chromacef intermediates observed in IMP-25 metallo-β-lactamase-catalyzed hydrolysis.

Metallo-β-lactamases inactivate most β-lactam antibacterials, and much attention has been paid to their catalytic mechanism. One issue of controversy has been whether β-lactam hydrolysis generally proceeds through an anionic intermediate bound to the active-site Zn(II) ions or not. The formation of an intermediate has not been shown conclusively in imipenemase (IMP) enzymes to date.

Detecting a quasi-stable imine species on the reaction pathway of SHV-1 β-lactamase and 6β-(hydroxymethyl)penicillanic acid sulfone.

For the class A β-lactamase SHV-1, the kinetic and mechanistic properties of the clinically used inhibitor sulbactam are compared with the sulbactam analog substituted in its 6β position by a CH2OH group (6β-(hydroxymethyl)penicillanic acid). The 6β substitution improves both in vitro and microbiological inhibitory properties of sulbactam. Base hydrolysis of both compounds was studied by Raman and NMR spectroscopies and showed that lactam ring opening is followed by fragmentation of the dioxothiazolidine ring leading to formation of the iminium ion within 3 min.

Penam sulfones and β-lactamase inhibition: SA2-13 and the importance of the C2 side chain length and composition.

β-Lactamases are the major reason β-lactam resistance is seen in Gram-negative bacteria. To combat this resistance mechanism, β-lactamase inhibitors are currently being developed. Presently, there are only three that are in clinical use (clavulanate, sulbactam and tazobactam).

β-Lactamase inhibition by 7-alkylidenecephalosporin sulfones: allylic transposition and formation of an unprecedented stabilized acyl-enzyme.

The inhibition of the class A SHV-1 β-lactamase by 7-(tert-butoxycarbonyl)methylidenecephalosporin sulfone was examined kinetically, spectroscopically, and crystallographically. An 1.14 Å X-ray crystal structure shows that the stable acyl-enzyme, which incorporates an eight-membered ring, is a covalent derivative of Ser70 linked to the 7-carboxy group of 2-H-5,8-dihydro-1,1-dioxo-1,5-thiazocine-4,7-dicarboxylic acid.

β-Lactamase inhibitors: a review of the patent literature (2010 - 2013).

Introduction: New β-lactamases with ever-broadening substrate specificity are rapidly disseminating globally, thereby threatening the efficacy of our best β-lactam antibiotics. A potential solution to this problem is the development of wide-spectrum β-lactamase inhibitors, to be coadministered with existing and new β-lactams.

Areas Covered: This review covers the patent literature in the β-lactamase inhibitor area roughly from 2010 to 2013, with prior background being provided in the cases of key inhibitors and antibiotic/inhibitor combinations.

Early insights into the interactions of different β-lactam antibiotics and β-lactamase inhibitors against soluble forms of Acinetobacter baumannii PBP1a and Acinetobacter sp. PBP3.

Acinetobacter baumannii is an increasingly problematic pathogen in United States hospitals. Antibiotics that can treat A. baumannii are becoming more limited.

Carboxylation and decarboxylation of active site Lys 84 controls the activity of OXA-24 β-lactamase of Acinetobacter baumannii: Raman crystallographic and solution evidence.

The class D β-lactamases are characterized by the presence of a carboxylated lysine in the active site that participates in catalysis. Found in Acinetobacter baumannii, OXA-24 is a class D carbapenem hydrolyzing enzyme that exhibits resistance to most available β-lactamase inhibitors. In this study, the reaction between a 6-alkylidiene penam sulfone inhibitor, SA-1-204, in single crystals of OXA-24 is followed by Raman microscopy.

The importance of the trans-enamine intermediate as a β-lactamase inhibition strategy probed in inhibitor-resistant SHV β-lactamase variants.

The ability of bacteria to express inhibitor-resistant (IR) β-lactamases is stimulating the development of novel inhibitors of these enzymes. The 2'β-glutaroxypenicillinate sulfone, SA2-13, was previously designed to enhance the stabilization of the deacylation-refractory, trans-enamine inhibitory intermediate. To test whether this mode of inhibition can overcome different IR mutations, we determined the binding mode of SA2-13 through X-ray crystallography, obtaining co-crystals of the inhibitor-protein complex by soaking crystals of the IR sulfhydryl variable (SHV) β-lactamase variants S130G and M69V with the inhibitor.

Crystal structures of KPC-2 β-lactamase in complex with 3-nitrophenyl boronic acid and the penam sulfone PSR-3-226.

Class A carbapenemases are a major threat to the potency of carbapenem antibiotics. A widespread carbapenemase, KPC-2, is not easily inhibited by β-lactamase inhibitors (i.e.

Inactivation of a class A and a class C β-lactamase by 6β-(hydroxymethyl)penicillanic acid sulfone.

β-Lactamase inhibitors (clavulanic acid, sulbactam, and tazobactam) contribute significantly to the longevity of the β-lactam antibiotics used to treat serious infections. In the quest to design more potent compounds and to understand the mechanism of action of known inhibitors, 6β-(hydroxymethyl)penicillanic acid sulfone (6β-HM-sulfone) was tested against isolates expressing the class A TEM-1 β-lactamase and a clinically important variant of the AmpC cephalosporinase of Pseudomonas aeruginosa, PDC-3. The addition of the 6β-HM-sulfone inhibitor to ampicillin was highly effective.

Ligand-dependent disorder of the Omega loop observed in extended-spectrum SHV-type beta-lactamase.

Among Gram-negative bacteria, resistance to β-lactams is mediated primarily by β-lactamases (EC 3.2.6.

Modifications of the C6-substituent of penicillin sulfones with the goal of improving inhibitor recognition and efficacy.

In order to evaluate the importance of a hydrogen-bond donating substituent in the design of β-lactamase inhibitors, a series of C6-substituted penicillin sulfones, lacking a C2' substituent, and having an sp(3) hybridized C6, was prepared and evaluated against a representative classes A and C β-lactamases. It was found that a C6 hydrogen-bond donor is necessary for good inhibitory activity, but that this feature alone is not sufficient in this series of C6β-substituted penicillin sulfones. Other factors which may impact the potency of the inhibitor include the steric bulk of the C6 substituent (e.