Dataset Information

In Vitro Activity of Meropenem-Vaborbactam against Clinical Isolates of KPC-Positive Enterobacteriaceae.

ABSTRACT: Vaborbactam (formerly RPX7009) is a novel inhibitor of serine ?-lactamases, including Ambler class A carbapenemases, such as KPCs. The current study evaluated the in vitro activity of the combination agent meropenem-vaborbactam against a global collection of 991 isolates of KPC-positive Enterobacteriaceae collected in 2014 and 2015 using the Clinical and Laboratory Standards Institute (CLSI) standard broth microdilution method. The MIC90 of meropenem (when tested with a fixed concentration of 8 ?g/ml of vaborbactam) for isolates of KPC-positive Enterobacteriaceae was 1 ?g/ml, and MIC values ranged from ?0.03 to >32 ?g/ml; 99.0% (981/991) of isolates had meropenem-vaborbactam MICs of ?4 ?g/ml, the U.S. FDA-approved MIC breakpoint for susceptibility to meropenem-vaborbactam (Vabomere). Vaborbactam lowered the meropenem MIC50 from 32 to 0.06 ?g/ml and the MIC90 from >32 to 1 ?g/ml. There were no differences in the activity of meropenem-vaborbactam when the isolates were stratified by KPC variant type. We conclude that meropenem-vaborbactam demonstrates potent in vitro activity against a worldwide collection of clinical isolates of KPC-positive Enterobacteriaceae collected in 2014 and 2015.

SUBMITTER: Hackel MA

PROVIDER: S-EPMC5740317 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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In Vitro Activity of Meropenem-Vaborbactam against Clinical Isolates of KPC-Positive Enterobacteriaceae.

Hackel Meredith A MA Lomovskaya Olga O Dudley Michael N MN Karlowsky James A JA Sahm Daniel F DF

Antimicrobial agents and chemotherapy 20171221 1

Vaborbactam (formerly RPX7009) is a novel inhibitor of serine β-lactamases, including Ambler class A carbapenemases, such as KPCs. The current study evaluated the in vitro activity of the combination agent meropenem-vaborbactam against a global collection of 991 isolates of KPC-positive Enterobacteriaceae collected in 2014 and 2015 using the Clinical and Laboratory Standards Institute (CLSI) standard broth microdilution method. The MIC90 of meropenem (when tested with a ...[more]

PMID: 29084745

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Project description:The activities of meropenem-vaborbactam and comparators against 152 (1.1%) carbapenem-resistant Enterobacterales (CRE) isolates identified among 13,929 Enterobacterales isolates collected from U.S. hospitals during 2016 to 2018 were evaluated. CRE rates were higher in the Middle Atlantic census division (3.5%) than in the other divisions (range, 0.0% for the West North Central division to 1.4% for the West South Central division). Among the CRE isolates, 134 carried carbapenemase genes, and these included 72 isolates carrying blaKPC-3, 51 isolates carrying blaKPC-2, 4 isolates carrying blaNDM-1, 3 isolates carrying blaSME-4, 2 isolates carrying blaVIM-1, 1 isolate carrying blaOXA-232, and 1 isolate carrying blaKPC-4 Meropenem-vaborbactam was active against 95.4% of the CRE isolates and 94.8% of the carbapenem-producing Enterobacterales (CPE) isolates when applying the CLSI breakpoints. All isolates producing serine carbapenemases were inhibited by meropenem-vaborbactam at ≤8 mg/liter. One Citrobacter freundii isolate carrying blaKPC-3 had a meropenem-vaborbactam MIC of 8 mg/liter and was resistant according to CLSI breakpoints (the isolate was susceptible when the EUCAST criterion of an MIC of ≤8 mg/liter for susceptible was applied), had disrupted OmpC and OmpF sequences, and overexpressed AcrAB-TolC. All carbapenemase-negative CRE isolates (n = 18) were inhibited by meropenem-vaborbactam at ≤4 mg/liter, and the MIC values of this combination ranged from 0.25 to 4 mg/liter. Among 7 isolates carrying metallo-β-lactamases and/or oxacillinases with carbapenemase activity, meropenem-vaborbactam susceptibility was 14.3% and 57.1% when applying CLSI and EUCAST breakpoints, respectively. CRE isolates were resistant to many comparator agents, and the most active agents were tigecycline, colistin, and amikacin (to which 63.2% to 96.7% of the isolates were susceptible). Understanding the epidemiology of CRE isolates in U.S. hospitals and the resistance mechanisms among these isolates is important to form guidelines for the treatment of infections caused by these organisms, which have high mortality rates.

Project description:Carbapenem-resistant Enterobacteriaceae (CRE) are resistant to most antibiotics, making CRE infections extremely difficult to treat with available agents. Klebsiella pneumoniae carbapenemases (KPC-2 and KPC-3) are predominant carbapenemases in CRE in the United States. Nacubactam is a bridged diazabicyclooctane (DBO) β-lactamase inhibitor that inactivates class A and C β-lactamases and exhibits intrinsic antibiotic and β-lactam "enhancer" activity against Enterobacteriaceae In this study, we examined a collection of meropenem-resistant K. pneumoniae isolates carrying blaKPC-2 or blaKPC-3; meropenem-nacubactam restored susceptibility. Upon testing isogenic Escherichia coli strains producing KPC-2 variants with single-residue substitutions at important Ambler class A positions (K73, S130, R164, E166, N170, D179, K234, E276, etc.), the K234R variant increased the meropenem-nacubactam MIC compared to that for the strain producing KPC-2, without increasing the meropenem MIC. Correspondingly, nacubactam inhibited KPC-2 (apparent Ki [Ki app] = 31 ± 3 μM) more efficiently than the K234R variant (Ki app = 270 ± 27 μM) and displayed a faster acylation rate (k2/K), which was 5,815 ± 582 M-1 s-1 for KPC-2 versus 247 ± 25 M-1 s-1 for the K234R variant. Unlike avibactam, timed mass spectrometry revealed an intact sulfate on nacubactam and a novel peak (+337 Da) with the K234R variant. Molecular modeling of the K234R variant showed significant catalytic residue (i.e., S70, K73, and S130) rearrangements that likely interfere with nacubactam binding and acylation. Nacubactam's aminoethoxy tail formed unproductive interactions with the K234R variant's active site. Molecular modeling and docking observations were consistent with the results of biochemical analyses. Overall, the meropenem-nacubactam combination is effective against carbapenem-resistant K. pneumoniae Moreover, our data suggest that β-lactamase inhibition by nacubactam proceeds through an alternative mechanism compared to that for avibactam.

Project description:To evaluate the resistance mechanisms among Pseudomonas aeruginosa clinical isolates exhibiting meropenem (MEM) MIC values higher than meropenem-vaborbactam (MEV). P. aeruginosa clinical isolates collected in US hospitals from 2014 to 2019 were susceptibility tested. Whole-genome and transcriptome sequencing were performed. Results were analyzed for strain typing, acquired β-lactamases, and mutations in chromosomal genes; gene expression was measured for known β-lactam resistance contributors. Results were compared to a control group of 10 P. aeruginosa isolates displaying MIC values at 8 mg/L for meropenem ± vaborbactam (MEM = MEV). Out of 88 isolates displaying MEM > MEV, 33 (37.5%) isolates had reproducibly lower MIC values for meropenem-vaborbactam compared to meropenem when retested. The expression of mexX, mexY, mexZ, and ampC was significantly greater among a higher percentage of the MEM > MEV isolates. Furthermore, the association of mexXY and ampC overexpression was detected in 17/33 MEM > MEV isolates and only 1/10 MEM = MEV isolate. In addition, the Pseudomonas-derived cephalosporinase amino acid substitution R79Q was detected among 33.3% of the isolates displaying MEM > MEV, and none of the isolates displayed MEM = MEV. Other resistance mechanisms were not observed or were equally observed in both groups. In rare cases, vaborbactam plays a role in lowering the meropenem MIC values in P. aeruginosa clinical isolates likely due to the inhibition of the AmpC gene that was overexpressed in the presence of upregulation of MexXY with or without alterations in the AmpC gene. IMPORTANCE Pseudomonas aeruginosa isolates are intrinsically resistant to multiple antimicrobial agents and meropenem is an important therapeutic option to treat infections caused by this organism. Meropenem-vaborbactam activity is similar to that of meropenem alone against P. aeruginosa isolates. Isolates belonging to this species that display lower meropenem-vaborbactam compared to meropenem are rare. We initiated this study to understand the resistance mechanisms that could lead to lower meropenem-vaborbactam MIC values when compared to meropenem alone. We documented that isolates displaying lower meropenem-vaborbactam exhibited overexpression of MexXY and AmpC. In addition, isolates displaying the R79Q PDC (AmpC) mutation were more likely to display lower meropenem-vaborbactam when compared to isolates displaying the same MIC values for these agents.

Dataset Information

In Vitro Activity of Meropenem-Vaborbactam against Clinical Isolates of KPC-Positive Enterobacteriaceae.

Publications

<i>In Vitro</i> Activity of Meropenem-Vaborbactam against Clinical Isolates of KPC-Positive Enterobacteriaceae.

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