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Reclaiming the efficacy of ?-lactam-?-lactamase inhibitor combinations: avibactam restores the susceptibility of CMY-2-producing Escherichia coli to ceftazidime.

ABSTRACT: CMY-2 is a plasmid-encoded Ambler class C cephalosporinase that is widely disseminated in Enterobacteriaceae and is responsible for expanded-spectrum cephalosporin resistance. As a result of resistance to both ceftazidime and ?-lactamase inhibitors in strains carrying blaCMY, novel ?-lactam-?-lactamase inhibitor combinations are sought to combat this significant threat to ?-lactam therapy. Avibactam is a bridged diazabicyclo [3.2.1]octanone non-?-lactam ?-lactamase inhibitor in clinical development that reversibly inactivates serine ?-lactamases. To define the spectrum of activity of ceftazidime-avibactam, we tested the susceptibilities of Escherichia coli clinical isolates that carry bla(CMY-2) or bla(CMY-69) and investigated the inactivation kinetics of CMY-2. Our analysis showed that CMY-2-containing clinical isolates of E. coli were highly susceptible to ceftazidime-avibactam (MIC(90), ? 0.5 mg/liter); in comparison, ceftazidime had a MIC90 of >128 mg/liter. More importantly, avibactam was an extremely potent inhibitor of CMY-2 ?-lactamase, as demonstrated by a second-order onset of acylation rate constant (k2/K) of (4.9 ± 0.5) × 10(4) M(-1) s(-1) and the off-rate constant (k(off)) of (3.7 ± 0.4) × 10(-4) s(-1). Analysis of the reaction of avibactam with CMY-2 using mass spectrometry to capture reaction intermediates revealed that the CMY-2-avibactam acyl-enzyme complex was stable for as long as 24 h. Molecular modeling studies raise the hypothesis that a series of successive hydrogen-bonding interactions occur as avibactam proceeds through the reaction coordinate with CMY-2 (e.g., T316, G317, S318, T319, S343, N346, and R349). Our findings support the microbiological and biochemical efficacy of ceftazidime-avibactam against E. coli containing plasmid-borne CMY-2 and CMY-69.

SUBMITTER: Papp-Wallace KM

PROVIDER: S-EPMC4136032 | biostudies-literature | 2014 Aug

REPOSITORIES: biostudies-literature

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Reclaiming the efficacy of β-lactam-β-lactamase inhibitor combinations: avibactam restores the susceptibility of CMY-2-producing Escherichia coli to ceftazidime.

Papp-Wallace Krisztina M KM Winkler Marisa L ML Gatta Julian A JA Taracila Magdalena A MA Chilakala Sujatha S Xu Yan Y Johnson J Kristie JK Bonomo Robert A RA

Antimicrobial agents and chemotherapy 20140512 8

CMY-2 is a plasmid-encoded Ambler class C cephalosporinase that is widely disseminated in Enterobacteriaceae and is responsible for expanded-spectrum cephalosporin resistance. As a result of resistance to both ceftazidime and β-lactamase inhibitors in strains carrying blaCMY, novel β-lactam-β-lactamase inhibitor combinations are sought to combat this significant threat to β-lactam therapy. Avibactam is a bridged diazabicyclo [3.2.1]octanone non-β-lactam β-lactamase inhibitor in clinical developm ...[more]

PMID: 24820081

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Project description:Metallo-?-lactamase (MBL)-producing Enterobacteriaceae are of grave clinical concern, particularly as there are no metallo-?-lactamase inhibitors approved for clinical use. The discovery and development of MBL inhibitors to restore the efficacy of available ?-lactams are thus imperative. We investigated a zinc-chelating moiety, 1,4,7-triazacyclononane (TACN), for its inhibitory activity against clinical carbapenem-resistant Enterobacteriaceae MICs, minimum bactericidal concentrations (MBCs), the serum effect, fractional inhibitory concentration indexes, and time-kill kinetics were determined using broth microdilution techniques according to Clinical and Laboratory Standards Institute (CSLI) guidelines. Enzyme kinetic parameters and the cytotoxic effects of TACN were determined using spectrophotometric assays. The interactions of the enzyme-TACN complex were investigated by computational studies. Meropenem regained its activity against carbapenemase-producing Enterobacteriaceae, with the MIC decreasing from between 8 and 64?mg/liter to 0.03?mg/liter in the presence of TACN. The TACN-meropenem combination showed bactericidal effects with an MBC/MIC ratio of ?4, and synergistic activity was observed. Human serum effects on the MICs were insignificant, and TACN was found to be noncytotoxic at concentrations above the MIC values. Computational studies predicted that TACN inhibits MBLs by targeting their catalytic active-site pockets. This was supported by its inhibition constant (Ki ), which was 0.044??M, and its inactivation constant (K inact), which was 0.0406 min-1, demonstrating that TACN inhibits MBLs efficiently and holds promise as a potential inhibitor.IMPORTANCE Carbapenem-resistant Enterobacteriaceae (CRE)-mediated infections remain a significant public health concern and have been reported to be critical in the World Health Organization's priority pathogens list for the research and development of new antibiotics. CRE produce enzymes, such as metallo-?-lactamases (MBLs), which inactivate ?-lactam antibiotics. Combination therapies involving a ?-lactam antibiotic and a ?-lactamase inhibitor remain a major treatment option for infections caused by ?-lactamase-producing organisms. Currently, no MBL inhibitor-?-lactam combination therapy is clinically available for MBL-positive bacterial infections. Hence, developing efficient molecules capable of inhibiting these enzymes could be a promising way to overcome this phenomenon. TACN played a significant role in the inhibitory activity of the tested molecules against CREs by potentiating the activity of carbapenem. This study demonstrates that TACN inhibits MBLs efficiently and holds promises as a potential MBL inhibitor to help curb the global health threat posed by MBL-producing CREs.

Dataset Information

Reclaiming the efficacy of ?-lactam-?-lactamase inhibitor combinations: avibactam restores the susceptibility of CMY-2-producing Escherichia coli to ceftazidime.

Publications

Reclaiming the efficacy of β-lactam-β-lactamase inhibitor combinations: avibactam restores the susceptibility of CMY-2-producing Escherichia coli to ceftazidime.

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