In vitro activity of meropenem combined with vaborbactam against KPC-producing Enterobacteriaceae in China

Ceftazidime/Avibactam and Meropenem/Vaborbactam for the Management of Enterobacterales Infections: A Narrative Review, Clinical Considerations, and Expert Opinion

This comprehensive review examines the unique attributes, distinctions, and clinical implications of ceftazidime-avibactam (CAZ-AVI) and meropenem-vaborbactam (MEM-VAB) against difficult-to-treat Enterobacterales infections. Our manuscript explores these antibiotics' pharmacokinetic and pharmacodynamic properties, antimicrobial activities, in vitro susceptibility testing, and clinical data. Moreover, it includes a meticulous examination of comparative clinical and microbiological studies, assessed and presented to provide clarity in making informed treatment choices for clinicians. Finally, we propose an expert opinion from a microbiological and a clinical point of view about their use in appropriate clinical settings. This is the first review aiming to provide healthcare professionals with valuable insights for making informed treatment decisions when combating carbapenem-resistant pathogens.

What to Do with the New Antibiotics?

Multidrug-resistant Gram-negative bacteria-related infections have become a real public health problem and have exposed the risk of a therapeutic impasse. In recent years, many new antibiotics have been introduced to enrich the therapeutic armamentarium. Among these new molecules, some are mainly of interest for the treatment of the multidrug-resistant infections associated with Pseudomonas aeruginosa (ceftolozane/tazobactam and imipenem/relebactam); others are for carbapenem-resistant infections associated with Enterobacterales (ceftazidime/avibactam, meropenem/vaborbactam); and finally, there are others that are effective on the majority of multidrug-resistant Gram-negative bacilli (cefiderocol). Most international guidelines recommend these new antibiotics in the treatment of microbiologically documented infections. However, given the significant morbidity and mortality of these infections, particularly in the case of inadequate therapy, it is important to consider the place of these antibiotics in probabilistic treatment. Knowledge of the risk factors for multidrug-resistant Gram-negative bacilli (local ecology, prior colonization, failure of prior antibiotic therapy, and source of infection) seems necessary in order to optimize antibiotic prescriptions. In this review, we will assess these different antibiotics according to the epidemiological data.

Pharmacokinetic-Pharmacodynamic Target Attainment Analyses as Support for Meropenem-Vaborbactam Dosing Regimens and Susceptibility Breakpoints

Meropenem-vaborbactam is a fixed-dose beta-lactam/beta-lactamase inhibitor with potent in vitro and in vivo activity against Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacterales. Pharmacokinetic-pharmacodynamic (PK-PD) target attainment analyses were undertaken using population pharmacokinetic models, nonclinical PK-PD targets for efficacy, in vitro surveillance data, and simulation to provide support for 2 g meropenem-2 g vaborbactam every 8 h (q8h) administered as a 3-h intravenous (i.v.) infusion, and dosing regimens adjusted for patients with renal impairment. Simulated patients varying by renal function measure (estimated glomerular filtration rate [eGFR], mL/min/1.73 m² and absolute eGFR, mL/min) and resembling the clinical trial population (complicated urinary tract infection, including acute pyelonephritis) were generated. The PK-PD targets for meropenem, the percentage of time on day 1 that free-drug plasma concentrations were above the MIC (%T>MIC), and vaborbactam, the ratio of free-drug plasma area under the concentration-time curve (AUC) on day 1 to the MIC (AUC:MIC ratio), were calculated. Percent probabilities of achieving meropenem free-drug plasma %T>MIC and vaborbactam free-drug plasma AUC:MIC ratio targets were assessed. MIC distributions for Enterobacterales, KPC-producing Enterobacterales, and Pseudomonas aeruginosa were considered as part of an algorithm to assess PK-PD target attainment. For assessments of free-drug plasma PK-PD targets associated with a 1-log₁₀ CFU reduction from baseline, percent probabilities of PK-PD target attainment ranged from 81.3 to 100% at meropenem-vaborbactam MIC values of 4 or 8 μg/mL among simulated patients. The results of these PK-PD target attainment analyses provide support for a dosing regimen of 2 g meropenem-2 g vaborbactam q8h administered as a 3-h i.v. infusion, with dosing regimens adjusted for patients with renal impairment and a meropenem-vaborbactam susceptibility breakpoint of ≤8 μg/mL (tested with a fixed vaborbactam concentration of 8 μg/mL) for Enterobacterales and P. aeruginosa based on these dosing regimens.

Clinical Outcomes and Microbiological Characteristics of Sequence Type 11 Klebsiella pneumoniae Infection

Background

Sequence type 11 (ST11) Klebsiella pneumoniae (Kp) is highly prevalent in China and is a typical sequence type among KPC-producing isolates. This study aimed to evaluate the clinical outcomes and microbiological features of ST11 Kp infections.

Methods

A retrospective cohort study was conducted at Peking University Third Hospital from January 2017 to March 2021. Clinical data were collected from medical records. Antimicrobial susceptibility testing and string tests were performed. Whole-genome sequencing was used to analyze the capsular serotypes, detect virulence-associated genes, and perform multilocus sequence typing. The risk of all-cause mortality in ST11 Kp-infected patients was compared to that in non-ST11 Kp-infected patients.

Results

From 139 patients infected with Kp, 49 ST11 Kp (35.3%) strains were isolated. The Charlson comorbidity index in the ST11 group was higher than that in the non-ST11 group (3.94 ± 1.59 vs. 2.41 ± 1.54, P = 0.001). A greater number of ST11 Kp-infected patients required ICU admission (46.9 vs. 16.7%, P < 0.001) and mechanical ventilation (28.6 vs. 10.0%, P = 0.005). All ST11 isolates presented a multidrug-resistant (MDR) phenotype, and twenty-nine (59.2%) hypervirulent Kp (hvKp) were identified. Twenty-four ST11 strains presented with hypermucoviscosity. The presence of capsular types K47 and K64 was frequent in the ST11 Kp strains (P < 0.001). The key virulence-associated genes rmpA, rmpA2, iucA, iroB, and peg344 were present in 26.5, 42.9, 59.2, 0, and 26.5% of the isolates, respectively, in the ST11 group. Twenty-one ST11 isolates harbored the combination of iucA+rmpA2. The 30-day mortality rate and sequential organ failure assessment (SOFA) score were significantly higher in ST11 Kp-infected patients than in non-ST11 Kp-infected patients (P < 0.01). ST11 Kp infection appeared to be an independent risk factor for mortality in ST11 Kp-infected patients.

Conclusions

A high prevalence of the ST11 clone was found in the hospital, which accounted for elevated antimicrobial resistance and exhibited great molecularly inferred virulence. Patients with ST11 Kp infection had a tendency toward increased 30-day mortality and SOFA scores. ST11 Kp infection was an independent risk factor for mortality, suggesting that enhanced surveillance and management are essential.

Resistance to Ceftazidime/Avibactam, Meropenem/Vaborbactam and Imipenem/Relebactam in Gram-Negative MDR Bacilli: Molecular Mechanisms and Susceptibility Testing

Multidrug resistance (MDR) represents a serious global threat due to the rapid global spread and limited antimicrobial options for treatment of difficult-to-treat (DTR) infections sustained by MDR pathogens. Recently, novel β-lactams/β-lactamase inhibitor combinations (βL-βLICs) have been developed for the treatment of DTR infections due to MDR Gram-negative pathogens. Although novel βL-βLICs exhibited promising in vitro and in vivo activities against MDR pathogens, emerging resistances to these novel molecules have recently been reported. Resistance to novel βL-βLICs is due to several mechanisms including porin deficiencies, increasing carbapenemase expression and/or enzyme mutations. In this review, we summarized the main mechanisms related to the resistance to ceftazidime/avibactam, meropenem/vaborbactam and imipenem/relebactam in MDR Gram-negative micro-organisms. We focused on antimicrobial activities and resistance traits with particular regard to molecular mechanisms related to resistance to novel βL-βLICs. Lastly, we described and discussed the main detection methods for antimicrobial susceptibility testing of such molecules. With increasing reports of resistance to novel βL-βLICs, continuous attention should be maintained on the monitoring of the phenotypic traits of MDR pathogens, into the characterization of related mechanisms, and on the emergence of cross-resistance to these novel antimicrobials.

Infectious Diseases Society of America 2022 Guidance on the Treatment of Extended-Spectrum β-lactamase Producing Enterobacterales (ESBL-E), Carbapenem-Resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with Difficult-to-Treat Resistance (DTR-P. aeruginosa)

BACKGROUND

The Infectious Diseases Society of America (IDSA) is committed to providing up-to-date guidance on the treatment of antimicrobial-resistant infections. The initial guidance document on infections caused by extended-spectrum β-lactamase producing Enterobacterales (ESBL-E), carbapenem-resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with difficult-to-treat resistance (DTR-P. aeruginosa) was published on 17 September 2020. Over the past year, there have been a number of important publications furthering our understanding of the management of ESBL-E, CRE, and DTR-P. aeruginosa infections, prompting a rereview of the literature and this updated guidance document.

METHODS

A panel of 6 infectious diseases specialists with expertise in managing antimicrobial-resistant infections reviewed, updated, and expanded previously developed questions and recommendations about the treatment of ESBL-E, CRE, and DTR-P. aeruginosa infections. Because of differences in the epidemiology of resistance and availability of specific anti-infectives internationally, this document focuses on the treatment of infections in the United States.

RESULTS

Preferred and alternative treatment recommendations are provided with accompanying rationales, assuming the causative organism has been identified and antibiotic susceptibility results are known. Approaches to empiric treatment, duration of therapy, and other management considerations are also discussed briefly. Recommendations apply for both adult and pediatric populations.

CONCLUSIONS

The field of antimicrobial resistance is highly dynamic. Consultation with an infectious diseases specialist is recommended for the treatment of antimicrobial-resistant infections. This document is current as of 24 October 2021. The most current versions of IDSA documents, including dates of publication, are available at www.idsociety.org/practice-guideline/amr-guidance/.

In vitro Activity of Meropenem-Vaborbactam versus Other Antibiotics Against Carbapenem-Resistant Escherichia coli from Southeastern China

Purpose

This study aimed to evaluate the in vitro activity of meropenem-vaborbactam (MVB) against a collection of carbapenem-resistant Escherichia coli (CREC) isolates and to compare the activity with other antibiotics with regard to different separation sites, carbapenem-resistant mechanisms, and sequence types (STs).

Methods

A total of 58 CREC strains were used as the experimental strains from the First Affiliated Hospital of Wenzhou Medical University in southeastern China. The minimum inhibitory concentrations of MVB, ceftazidime-avibactam, and tigecycline against all the experimental strains were determined by the microdilution broth method.

Results

MVB exhibited higher antimicrobial activity (83% susceptibility) than that of other antibiotics, except for colistin and tigecycline. The susceptibility of CREC strains towards MVB varied with regard to carbapenem-resistant mechanisms and STs, especially in Klebsiella pneumoniae carbapenemase (KPC)-positive isolates and ST8 isolates.

Conclusion

MVB exhibited considerably high activity against KPC-producing and ST8 CREC isolates. It has the great potential to be an alternative for the treatment of infections caused by CREC after determining the type of carbapenemase, the susceptibility to MVB and/or STs.

Carbapenemase producing Klebsiella pneumoniae: implication on future therapeutic strategies

Introduction: The emergence of carbapenemase resistant Gram-negative is designated as an 'urgent' priority of public health. Carbapenemase producing Klebsiella pneumoniae (CPKP) is linked with significant mortality. Conventionally used antibiotics (polymyxins, tigecycline, aminoglycosides, etc.) are associated with poor efficacy and toxicity profiles are quite worrisome.Areas covered: This article reviews mechanism of resistance and evidence regarding novel treatments of infections caused by CPKP, focusing mainly on currently approved new therapies and implications on future therapeutic strategies. A review of novel β-lactam/β-lactamase inhibitors (BLI) recently approved and in clinical development as well as cefiderocol, eravacycline and apramycin are discussed.Expert opinion: Newly approved and forthcoming antimicrobial agents are promising to combat infections caused by CPKP. Ceftazidime-avibactam, meropenem-vaborbactam, and imipenem-cilastatin-relebactam are novel agents with favorable outcome and associated with improved mortality in KPC-producing K. pneumoniae infections. However, are inactive against metallo-β-lactamases (MBL). Novel BLI in later stage of development, i.e. aztreonam-avibactam, cefepime-zidebactam, cefepime-taniborbactam, and meropenem-nacubactam as well as cefiderocol are active in vitro against both KPC and MBL. Potential expectations of future therapeutic strategies are improved potency against CPKP, more tolerable safety profile, and capability of overcoming current resistance mechanism of multidrug-resistant K. pneumoniae.

Co-Occurrence of NDM-5 and RmtB in a Clinical Isolate of Escherichia coli Belonging to CC354 in Latin America

New Delhi metallo-β-lactamase (NDM)-producing isolates are usually resistant to most β-lactams and other antibiotics as a result of the coexistence of several resistance markers, and they cause a variety of infections associated to high mortality rates. Although NDM-1 is the most prevalent one, other variants are increasing their frequency worldwide. In this study we describe the first clinical isolate of NDM-5- and RmtB-producing Escherichia coli in Latin America. E. coli (Ec265) was recovered from a urine sample of a female outpatient. Phenotypical and genotypical characterization of resistance markers and conjugation assays were performed. Genetic analysis of Ec265 was achieved by whole genome sequencing. Ec265 belonging to ST9693 (CC354), displayed resistance to most β-lactams (including carbapenems), aminoglycosides (gentamicin and amikacin), and quinolones. Several resistance genes were found, including bla_NDM-5 and rmtB, located on a conjugative plasmid. bla_NDM-5 genetic context is similar to others found around the world. Co-transfer of multiple antimicrobial resistance genes represents a particular challenge for treatment in clinical settings, whereas the spread of pathogens resistant to last resort antibiotics should raise an alarm in the healthcare system worldwide.

New Carbapenemase Inhibitors: Clearing the Way for the β-Lactams

Carbapenem resistance is a major global health problem that seriously compromises the treatment of infections caused by nosocomial pathogens. Resistance to carbapenems mainly occurs via the production of carbapenemases, such as VIM, IMP, NDM, KPC and OXA, among others. Preclinical and clinical trials are currently underway to test a new generation of promising inhibitors, together with the recently approved avibactam, relebactam and vaborbactam. This review summarizes the main, most promising carbapenemase inhibitors synthesized to date, as well as their spectrum of activity and current stage of development. We particularly focus on β-lactam/β-lactamase inhibitor combinations that could potentially be used to treat infections caused by carbapenemase-producer pathogens of critical priority. The emergence of these new combinations represents a step forward in the fight against antimicrobial resistance, especially in regard to metallo-β-lactamases and carbapenem-hydrolysing class D β-lactamases, not currently inhibited by any clinically approved inhibitor.

Resistance to Novel β-Lactam-β-Lactamase Inhibitor Combinations: The "Price of Progress"

Significant advances were made in antibiotic development during the past 5 years. Novel agents were added to the arsenal that target critical priority pathogens, including multidrug-resistant Pseudomonas aeruginosa and carbapenem-resistant Enterobacterales. Of these, 4 novel β-lactam-β-lactamase inhibitor combinations (ceftolozane-tazobactam, ceftazidime-avibactam, meropenem-vaborbactam, and imipenem-cilastatin-relebactam) reached clinical approval in the United States. With these additions comes a significant responsibility to reduce the possibility of emergence of resistance. Reports in the rise of resistance toward ceftolozane-tazobactam and ceftazidime-avibactam are alarming. Clinicians and scientists must make every attempt to reverse or halt these setbacks.

Meropenem/vaborbactam: a next generation β-lactam β-lactamase inhibitor combination

INTRODUCTION

infections due to carbapenem-resistant Enterobacterales (CRE) constitute a worldwide threat and are associated with significant mortality, especially in fragile patients, and costs. Meropenem-vaborbactam (M/V) is a combination of a group 2 carbapenem with a novel cyclic boronic acid-based β-lactamase inhibitor which has shown good efficacy against KPC carbapenemase-producing Klebsiella pneumoniae, which are amongst the most prevalent types of CRE.

AREAS COVERED

This article reviews the microbiological and pharmacological profile and current clinical experience and safety of M/V in the treatment of infections caused by CRE.

EXPERT OPINION

M/V is a promising drug for the treatment of infections due to KPC-producing CRE (KPC-CRE). It exhibited an almost complete coverage of KPC-CRE isolates from large surveillance studies and a low propensity for resistance selection, retaining activity also against strains producing KPC mutants resistant to ceftazidime-avibactam. Both meropenem and vaborbactam have a favorable pharmacokinetic profile, with similar kinetic properties, a good intrapulmonary penetration, and are efficiently cleared during continuous venovenous hemofiltration (CVVH). According to available data, M/V monotherapy is associated with higher clinical cure rates and lower rates of adverse events, especially in terms of nephrotoxicity, if compared to 'older' combination therapies.

Phenylboronic Acids Probing Molecular Recognition against Class A and Class C β-lactamases

Worldwide dissemination of pathogens resistant to almost all available antibiotics represent a real problem preventing efficient treatment of infectious diseases. Among antimicrobial used in therapy, β-lactam antibiotics represent 40% thus playing a crucial role in the management of infections treatment. We report a small series of phenylboronic acids derivatives (BAs) active against class A carbapenemases KPC-2 and GES-5, and class C cephalosporinases AmpC. The inhibitory profile of our BAs against class A and C was investigated by means of molecular docking, enzyme kinetics and X-ray crystallography. We were interested in the mechanism of recognition among class A and class C to direct the design of broad serine β-Lactamases (SBLs) inhibitors. Molecular modeling calculations vs GES-5 and crystallographic studies vs AmpC reasoned, respectively, the ortho derivative 2 and the meta derivative 3 binding affinity. The ability of our BAs to protect β-lactams from BLs hydrolysis was determined in biological assays conducted against clinical strains: Fractional inhibitory concentration index (FICI) tests confirmed their ability to be synergic with β-lactams thus restoring susceptibility to meropenem. Considering the obtained results and the lack of cytotoxicity, our derivatives represent validated probe for the design of SBLs inhibitors.

X-ray Crystallography Deciphers the Activity of Broad-Spectrum Boronic Acid β-Lactamase Inhibitors

Recent decades have witnessed a dramatic increase of multidrug resistant (MDR) bacteria, compromising the efficacy of available antibiotics, and a continual decline in the discovery of novel antibacterials. We recently reported the first library of benzo[b]thiophen-2-ylboronic acid inhibitors sharing broad spectrum activity against β-lactamases (BLs). The ability of these compounds to inhibit structurally and mechanistically different types of β-lactamases has been here structurally investigated. An extensive X-ray crystallographic analysis of boronic acids (BAs) binding to proteins representative of serine BLs (SBLs) and metallo β-lactamases (MBLs) have been conducted to depict the role played by the boronic group in driving molecular recognition, especially in the interaction with MBLs. Our derivatives are the first case of noncyclic boronic acids active against MBLs and represent a productive route toward potent broad-spectrum inhibitors.

Ten Years with New Delhi Metallo-β-lactamase-1 (NDM-1): From Structural Insights to Inhibitor Design

The worldwide emergence of New Delhi metallo-β-lactamase-1 (NDM-1) as a carbapenemase able to hydrolyze nearly all available β-lactam antibiotics has characterized the past decade, endangering efficacious antibacterial treatments. No inhibitors for NDM-1 are available in therapy, nor are promising compounds in the pipeline for future NDM-1 inhibitors. We report the studies dedicated to the design and development of effective NDM-1 inhibitors. The discussion for each agent moves from the employed design strategy to the ability of the identified inhibitor to synergize β-lactam antibiotics. A structural analysis of NDM-1 mechanism of action based on selected X-ray complexes is also reported: the intrinsic flexibility of the binding site and the comparison between penicillin/cephalosporin and carbapenem mechanisms of hydrolysis are evaluated. Despite the valuable progress in terms of structural and mechanistic information, the design of a potent NDM-1 inhibitor to be introduced in therapy remains challenging. Certainly, only the deep knowledge of NDM-1 architecture and of the variable mechanism of action that NDM-1 employs against different classes of substrates could orient a successful drug discovery campaign.