Effects of KPC Variant and Porin Genotype on the In Vitro Activity of Meropenem-Vaborbactam against Carbapenem-Resistant Enterobacteriaceae

Ceftazidime-avibactam resistance in KPC-producing Klebsiella pneumoniae accompanied hypermucoviscosity acquisition

BACKGROUND

Antimicrobial resistance and bacterial hypermucoviscosity, associated with escalating production of capsules, constitute major challenges for the clinical management of Klebsiella pneumoniae (K. pneumoniae) infections. This study investigates the association and underlying mechanism between ceftazidime-avibactam (CAZ-AVI) resistance and bacterial hypermucoviscosity in Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-Kp).

RESULTS

The proportion of CAZ-AVI-sensitive clinical isolates exhibiting the hypermucoviscous phenotype was significantly lower than that of the resistant strains (5.6% vs. 46.7%, P < 0.001). To further verify the correlation and molecular mechanism between CAZ-AVI resistance and hypermucoviscosity, 10 CAZ-AVI-resistant isolates were generated through in vitro resistance selection from CAZ-AVI-sensitive KPC-Kp. The results showed the same association as it showed in the clinical isolates, with four out of ten induced CAZ-AVI-resistant isolates transitioning from negative to positive in the string tests. Comparative genomic analysis identified diverse mutations in the wzc gene, crucial for capsule polysaccharide (CPS) synthesis, in all four CAZ-AVI-resistant hypermucoviscous KPC-Kp strains compared to the parent strains. However, these mutations were absent in the other six KPC-Kp strains that did not exhibit induced hypermucoviscosity. Cloning of the wzc gene variants and their expression in wild-type strains confirmed that mutations in the wzc gene can induce bacterial hypermucoviscosity and heightened virulence, however, they do not confer resistance to CAZ-AVI.

CONCLUSIONS

These results indicated that resistance to CAZ-AVI in KPC-Kp isolates may be accompanied by the acquisition of hypermucoviscosity, with mutations in the wzc gene often involving in this process.

Systematic Review and Meta-Analysis of Clinical Efficacy and Safety of Meropenem-Vaborbactam versus Best-Available Therapy in Patients with Carbapenem-Resistant Enterobacteriaceae Infections

Antimicrobial resistance is increasingly concerning, causing millions of deaths and a high cost burden. Given that carbapenemase-producing Enterobacterales are particularly concerning due to their ability to develop structural modifications and produce antibiotic-degrading enzymes, leading to high resistance levels, we sought to summarize the available data on the efficacy and safety regarding the combination of meropenem-vaborbactam (MV) versus the best available therapy (BAT). Articles related to our objective were searched in the PubMed and Scopus databases inception to July 2024. To assess the quality of the studies, we used the Cochrane risk-of-bias tool, RoB2. The outcomes were pooled as a risk ratio (RR) and a 95% confidence interval (95%CI). A total of four published studies were involved: one retrospective cohort study and three phase 3 trials, including 432 patients treated with MV and 426 patients treated with BAT (mono/combination therapy with polymyxins, carbapenems, aminoglycosides, colistin, and tigecycline; or ceftazidime-avibactam; or piperacillin-tazobactam). No significant difference in the clinical response rate was observed between MV and the comparators at the TOC (RR = 1.29, 95%CI [0.92, 1.80], p = 0.14) and EOT (RR = 1.66, 95%CI [0.58, 4.76], p = 0.34) visits. MV was associated with a similar microbiological response as the comparators at TOC (RR = 1.63, 95%CI [0.85, 3.11], p = 0.14) and EOT assessment (RR = 1.16, 95%CI [0.88, 1.54], p = 0.14). In the pooled analysis of the four studies, 28-day all-cause mortality was lower for MV than the control groups (RR = 0.47, 95%CI [0.24, 0.92], p = 0.03). MV was associated with a similar risk of adverse events (AEs) as comparators (RR = 0.79, 95%CI [0.53, 1.17], p = 0.23). Additionally, MV was associated with fewer renal-related AEs than the comparators (RR = 0.32, 95%CI [0.15, 0.66], p = 0.002). MV was associated with a similar risk of treatment discontinuation due to AEs (RR = 0.76, 95%CI [0.38, 1.49], p = 0.42) or drug-related AEs (RR = 0.56, 95%CI [0.28, 1.10], p = 0.09) as the comparators. In conclusion, MV presents a promising therapeutic option for treating CRE infections, demonstrating similar clinical and microbiological responses as other comparators, with potential advantages in mortality outcomes and renal-related AEs.

Development of an effective meropenem/KPC-2 inhibitor combination to combat infections caused by carbapenem-resistant Klebsiella pneumoniae

The global public health threat of antibiotic resistance continues to escalate, and necessitates the implementation of urgent measures to expand the arsenal of antimicrobial drugs. This study identified a benzoxaborane compound, namely 5-chloro-1,3-dihydro-1-hydroxy-2,1-benzoxaborole (AN2178), which can inhibit the catalytic activity of the Klebsiella pneumoniae carbapenemase (KPC-2) enzyme effectively. The efficacy of AN2718 as an inhibitor for the KPC-2 enzyme was verified through various assays, including enzyme activity assays and isothermal titration calorimetry. Results of multiple biochemical assays, minimum inhibitory concentration assays and time-killing assays also showed that binding of AN2718 to KPC-2 enabled restoration of the bactericidal effect of meropenem. The survival rate of mice infected with carbapenem-resistant, high-virulence strains increased significantly upon treatment with AN2718. Most importantly, the meropenem and AN2718 combination was effective on KPC-2 mutations such as KPC-33, which evolved clinically and exhibited resistance to ceftazidime-avibactam after clinical use for a couple of years. Comprehensive safety tests both in vitro and in vivo, such as cytotoxicity, haemolytic activity and cytochrome P450 inhibition assays, demonstrated that AN2718 was safe for clinical use. These promising data indicate that AN2718 has high potential for approval for the treatment of drug resistant-bacterial infections, including those caused by ceftazidime-avibactam-resistant strains. AN2718 can be regarded as a valuable addition to the current antimicrobial armamentarium, and a promising tool to combat antimicrobial resistance.

Antimicrobial and Diagnostic Stewardship of the Novel β-Lactam/β-Lactamase Inhibitors for Infections Due to Carbapenem-Resistant Enterobacterales Species and Pseudomonas aeruginosa

Carbapenem-resistant Gram-negative bacterial infections are a major public health threat due to the limited therapeutic options available. The introduction of the new β-lactam/β-lactamase inhibitors (BL/BLIs) has, however, altered the treatment options for such pathogens. Thus, four new BL/BLI combinations-namely, ceftazidime/avibactam, meropenem/vaborbactam, imipenem/relebactam, and ceftolozane/tazobactam-have been approved for infections attributed to carbapenem-resistant Enterobacterales species and Pseudomonas aeruginosa. Nevertheless, although these antimicrobials are increasingly being used in place of other drugs such as polymyxins, their optimal clinical use is still challenging. Furthermore, there is evidence that resistance to these agents might be increasing, so urgent measures should be taken to ensure their continued effectiveness. Therefore, clinical laboratories play an important role in the judicious use of these new antimicrobial combinations by detecting and characterizing carbapenem resistance, resolving the presence and type of carbapenemase production, and accurately determining the minimum inhibitor concentrations (MICs) for BL/BLIs. These three targets must be met to ensure optimal BL/BLIs use and prevent unnecessary exposure that could lead to the development of resistance. At the same time, laboratories must ensure that results are interpreted in a timely manner to avoid delays in appropriate treatment that might be detrimental to patient safety. Thus, we herein present an overview of the indications and current applications of the new antimicrobial combinations and explore the diagnostic limitations regarding both carbapenem resistance detection and the interpretation of MIC results. Moreover, we suggest the use of alternative narrower-spectrum antibiotics based on susceptibility testing and present data regarding the effect of synergies between BL/BLIs and other antimicrobials. Finally, in order to address the absence of a standardized approach to using the novel BL/BLIs, we propose a diagnostic and therapeutic algorithm, which can be modified based on local epidemiological criteria. This framework could also be expanded to incorporate other new antimicrobials, such as cefiderocol, or currently unavailable BL/BLIs such as aztreonam/avibactam and cefepime/taniborbactam.

New Antibiotics Against Multidrug-Resistant Gram-Negative Bacteria in Liver Transplantation: Clinical Perspectives, Toxicity, and PK/PD Properties

Antimicrobial resistance is a growing global health problem, and it is especially relevant among liver transplant recipients where infections, particularly when caused by microorganisms with a difficult-to-treat profile, are a significant cause of morbidity and mortality. We provide here a complete dissection of the antibiotics active against multidrug-resistant Gram-negative bacteria approved over the last years, focusing on their activity spectrum, toxicity profile and PK/PD properties, including therapeutic drug monitoring, in the setting of liver transplantation. Specifically, the following drugs are presented: ceftolozane/tazobactam, ceftazidime/avibactam, meropenem/vaborbactam, imipenem/relebactam, cefiderocol, and eravacycline. Overall, studies on the safety and optimal employment of these drugs in liver transplant recipients are limited and especially needed. Nevertheless, these pharmaceuticals have undeniably enhanced therapeutic options for infected liver transplant recipients.

In Vitro Activity of "Old" and "New" Antimicrobials against the Klebsiella pneumoniae Complex

The Klebsiella pneumoniae complex is a commonly isolated bacteria in human infections. These opportunistic pathogens pose a serious threat to public health due to their potential transmission to the human population. Resistance to carbapenems is a significant antimicrobial resistance mechanism, leading to limited therapeutic options. Therefore, the aim of this study was to evaluate the in vitro activity of fosfomycin, colistin, ceftazidime-avibactam, and meropenem-vaborbactam against multidrug-resistant K. pneumoniae complex strains. This study involved 160 strains of Gram-negative rods, comprising 138 K. pneumoniae and 22 K. variicola. The minimal inhibitory concentration of fosfomycin was estimated using the agar dilution method, and for colistin, the microdilution method was employed. Susceptibility to ceftazidime-avibactam and meropenem-vaborbactam was determined using the gradient strip method. All analyzed K. pneumoniae complex isolates produced extended-spectrum β-lactamases, and 60.0% exhibited carbapenemases. The majority of the analyzed strains were susceptible to fosfomycin and colistin (62.5%). Among pandrug-resistant K. pneumoniae complex isolates, the highest susceptibility was observed with colistin (43.9%). Fosfomycin demonstrated good activity against ESβLs- and VIM-positive isolates from this complex. Colistin also exhibited satisfactory in vitro activity against VIM- and KPC-positive isolates from the K. pneumoniae complex. Ceftazidime-avibactam displayed good activity against K. pneumoniae complex strains producing ESβLs, KPC, and OXA enzymes. Additionally, meropenem-vaborbactam showed satisfactory in vitro activity against ESβLs- and KPC-positive isolates from this complex.

Approaches to Testing Novel β-Lactam and β-Lactam Combination Agents in the Clinical Laboratory

The rapid emergence of multi-drug resistant Gram-negative pathogens has driven the introduction of novel β-lactam combination agents (BLCs) to the antibiotic market: ceftolozane-tazobactam, ceftazidime-avibactam, meropenem-vaborbactam, imipenem-relebactam, cefiderocol, and sulbactam-durlobactam. These agents are equipped with innovative mechanisms that confer broad Gram-negative activity, notably against certain challenging carbapenemases. While their introduction offers a beacon of hope, clinical microbiology laboratories must navigate the complexities of susceptibility testing for these agents due to their diverse activity profiles against specific β-lactamases and the possibility of acquired resistance mechanisms in some bacterial isolates. This review explores the complexities of these novel antimicrobial agents detailing the intricacies of their application, providing guidance on the nuances of susceptibility testing, interpretation, and result reporting in clinical microbiology laboratories.

Mutations in ompK36 differentially impact in vitro synergy of meropenem/vaborbactam and ceftazidime/avibactam in combination with other antibiotics against KPC-producing Klebsiella pneumoniae

Objectives

Ceftazidime/avibactam and meropenem/vaborbactam are preferred agents for Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-Kp) infections and are often used in combination with other agents. We aimed to characterize the synergy of combinations against KPC-Kp with varying ompK36 genotypes.

Methods

KPC-Kp that harboured ompK36 WT, IS5 or glycine-aspartic acid duplication (GD) genotypes were selected. MICs were determined in triplicate. Synergy was assessed by time-kill assays for ceftazidime/avibactam and meropenem/vaborbactam in combination with colistin, gentamicin, tigecycline, meropenem or fosfomycin against 1 × 108 cfu/mL KPC-Kp.

Results

KPC-Kp harboured ompK36 WT (n = 5), IS5 (n = 5) or GD (n = 5); 11 were KPC-2 and 4 were KPC-3. All were susceptible to ceftazidime/avibactam and meropenem/vaborbactam. In time-kill analysis, ceftazidime/avibactam and meropenem/vaborbactam 1 × MIC exhibited mean 24 h log-kills of -2.01 and -0.84, respectively. Ceftazidime/avibactam was synergistic in combination with colistin independent of ompK36 genotype. Ceftazidime/avibactam combinations impacted by porin mutations (compared to WT) were meropenem (-5.18 versus -6.62 mean log-kill, P < 0.001) and fosfomycin (-3.98 versus -6.58, P = 0.058). Mean log-kills with meropenem/vaborbactam were greatest in combination with gentamicin (-5.36). In the presence of porin mutations, meropenem/vaborbactam killing activity was potentiated by the addition of colistin (-6.65 versus -0.70, P = 0.03) and fosfomycin (-3.12 versus 1.54, P = 0.003).

Conclusions

Our results shed new light on the synergy of ceftazidime/avibactam and meropenem/vaborbactam combinations against KPC-Kp with or without porin mutations. Killing activity of ceftazidime/avibactam with other cell wall active agents was decreased against isolates with porin mutations. On the other hand, some meropenem/vaborbactam combinations demonstrated enhanced killing in the presence of porin mutations.

Dynamic evolution of ceftazidime-avibactam resistance due to interchanges between blaKPC-2 and blaKPC-145 during treatment of Klebsiella pneumoniae infection

Background

The emergence of ceftazidime-avibactam (CZA) resistance among carbapenem-resistant Klebsiella pneumoniae (CRKP) is of major concern due to limited therapeutic options.

Methods

In this study, 10 CRKP strains were isolated from different samples of a patient with CRKP infection receiving CZA treatment. Whole-genome sequencing (WGS) and conjugation experiments were performed to determine the transferability of the carbapenem resistance gene.

Results

This infection began with a KPC-2-producing K. pneumoniae (CZA MIC = 2 μg/mL, imipenem MIC ≥ 16 μg/mL). After 20 days of CZA treatment, the strains switched to the amino acid substitution of T263A caused by a novel KPC-producing gene, blaKPC-145, which restored carbapenem susceptibility but showed CZA resistance (CZA MIC ≥ 256 μg/mL, imipenem MIC = 1 μg/mL). The blaKPC-145 gene was located on a 148,185-bp untransformable IncFII-type plasmid. The subsequent use of carbapenem against KPC-145-producing K. pneumoniae infection led to a reversion of KPC-2 production (CZA MIC = 2 μg/mL, imipenem MIC ≥ 16 μg/mL). WGS analysis showed that all isolates belonged to ST11-KL47, and the number of SNPs was 14. This implied that these blaKPC-positive K. pneumoniae isolates might originate from a single clone and have been colonized for a long time during the 120-day treatment period.

Conclusion

This is the first report of CZA resistance caused by blaKPC-145, which emerged during the treatment with CZA against blaKPC-2-positive K. pneumoniae-associated infection in China. These findings indicated that routine testing for antibiotic susceptibility and carbapenemase genotype is essential during CZA treatment.

Rationale and evidence for the use of new beta-lactam/beta-lactamase inhibitor combinations and cefiderocol in critically ill patients

BACKGROUND

Healthcare-associated infections involving Gram-negative bacteria (GNB) with difficult-to-treat resistance (DTR) phenotype are associated with impaired patient-centered outcomes and poses daily therapeutic challenges in most of intensive care units worldwide. Over the recent years, four innovative β-lactam/β-lactamase inhibitor (BL/BLI) combinations (ceftolozane-tazobactam, ceftazidime-avibactam, imipenem-relebactam and meropenem-vaborbactam) and a new siderophore cephalosporin (cefiderocol) have been approved for the treatment of certain DTR-GNB infections. The literature addressing their microbiological spectrum, pharmacokinetics, clinical efficacy and safety was exhaustively audited by our group to support the recent guidelines of the French Intensive Care Society on their utilization in critically ill patients. This narrative review summarizes the available evidence and unanswered questions on these issues.

METHODS

A systematic search for English-language publications in PUBMED and the Cochrane Library database from inception to November 15, 2022.

RESULTS

These drugs have demonstrated relevant clinical success rates and a reduced renal risk in most of severe infections for whom polymyxin- and/or aminoglycoside-based regimen were historically used as last-resort strategies-namely, ceftazidime-avibactam for infections due to Klebsiella pneumoniae carbapenemase (KPC)- or OXA-48-like-producing Enterobacterales, meropenem-vaborbactam for KPC-producing Enterobacterales, ceftazidime-avibactam/aztreonam combination or cefiderocol for metallo-β-lactamase (MBL)-producing Enterobacterales, and ceftolozane-tazobactam, ceftazidime-avibactam and imipenem-relebactam for non-MBL-producing DTR Pseudomonas aeruginosa. However, limited clinical evidence exists in critically ill patients. Extended-infusion scheme (except for imipenem-relebactam) may be indicated for DTR-GNB with high minimal inhibitory concentrations and/or in case of augmented renal clearance. The potential benefit of combining these agents with other antimicrobials remains under-investigated, notably for the most severe presentations. Other important knowledge gaps include pharmacokinetic information in particular situations (e.g., pneumonia, other deep-seated infections, and renal replacement therapy), the hazard of treatment-emergent resistance and possible preventive measures, the safety of high-dose regimen, the potential usefulness of rapid molecular diagnostic tools to rationalize their empirical utilization, and optimal treatment durations. Comparative clinical, ecological, and medico-economic data are needed for infections in whom two or more of these agents exhibit in vitro activity against the causative pathogen.

CONCLUSIONS

New BL/BLI combinations and cefiderocol represent long-awaited options for improving the management of DTR-GNB infections. Several research axes must be explored to better define the positioning and appropriate administration scheme of these drugs in critically ill patients.

Use of Newer and Repurposed Antibiotics against Gram-Negative Bacteria in Neonates

Antimicrobial resistance has become a significant public health problem globally with multidrug resistant Gram negative (MDR-GN) bacteria being the main representatives. The emergence of these pathogens in neonatal settings threatens the well-being of the vulnerable neonatal population given the dearth of safe and effective therapeutic options. Evidence from studies mainly in adults is now available for several novel antimicrobial compounds, such as new β-lactam/β-lactamase inhibitors (e.g., ceftazidime-avibactam, meropenem-vaborbactam, imipenem/cilastatin-relebactam), although old antibiotics such as colistin, tigecycline, and fosfomycin are also encompassed in the fight against MDR-GN infections that remain challenging. Data in the neonatal population are scarce, with few clinical trials enrolling neonates for the evaluation of the efficacy, safety, and dosing of new antibiotics, while the majority of old antibiotics are used off-label. In this article we review data about some novel and old antibiotics that are active against MDR-GN bacteria causing sepsis and are of interest to be used in the neonatal population.

The Effectiveness of Imipenem-Relebactam against Ceftazidime-Avibactam Resistant Variants of the KPC-2 β-Lactamase

BACKGROUND

Ceftazidime-avibactam was approved by the FDA to treat infections caused by Enterobacterales carrying bla_KPC-2. However, variants of KPC-2 with amino acid substitutions at position 179 have emerged and confer resistance to ceftazidime-avibactam.

METHODS

The activity of imipenem-relebactam was assessed against a panel of 19 KPC-2 D179 variants. KPC-2 and the D179N and D179Y variants were purified for biochemical analyses. Molecular models were constructed with imipenem to assess differences in kinetic profiles.

RESULTS

All strains were susceptible to imipenem-relebactam, but resistant to ceftazidime (19/19) and ceftazidime-avibactam (18/19). KPC-2 and the D179N variant hydrolyzed imipenem, but the D179N variant's rate was much slower. The D179Y variant was unable to turnover imipenem. All three β-lactamases hydrolyzed ceftazidime at varying rates. The acylation rate of relebactam for the D179N variant was ~2.5× lower than KPC-2. Poor catalytic turnover by the D179Y variant precluded the determination of inhibitory kinetic parameters. Acyl-complexes with imipenem and ceftazidime were less prevalent with the D179N variant compared to the D179Y variant, supporting the kinetic observations that the D179Y variant was not as active as the D179N variant. Relebactam was slower to form an acyl-complex with the D179Y variant compared to avibactam. The D179Y model with imipenem revealed that the catalytic water molecule was shifted, and the carbonyl of imipenem was not within the oxyanion hole. Conversely in the D179N model, imipenem was oriented favorably for deacylation.

CONCLUSIONS

Imipenem-relebactam overcame the resistance of the D179 variants, suggesting that this combination will be active against clinical isolates harboring these derivatives of KPC-2.

Novel Antimicrobial Agents for Gram-Negative Pathogens

Gram-negative bacterial resistance to antimicrobials has had an exponential increase at a global level during the last decades and represent an everyday challenge, especially for the hospital practice of our era. Concerted efforts from the researchers and the industry have recently provided several novel promising antimicrobials, resilient to various bacterial resistance mechanisms. There are new antimicrobials that became commercially available during the last five years, namely, cefiderocol, imipenem-cilastatin-relebactam, eravacycline, omadacycline, and plazomicin. Furthermore, other agents are in advanced development, having reached phase 3 clinical trials, namely, aztreonam-avibactam, cefepime-enmetazobactam, cefepime-taniborbactam, cefepime-zidebactam, sulopenem, tebipenem, and benapenem. In this present review, we critically discuss the characteristics of the above-mentioned antimicrobials, their pharmacokinetic/pharmacodynamic properties and the current clinical data.

In vitro susceptibility of carbapenem resistant Enterobacterales to meropenem-vaborbactam and ceftazidime-avibactam at a single academic medical centre

BACKGROUND

Carbapenem-resistant Enterobacterales (CRE) are considered an urgent threat. Ceftazidime-avibactam and meropenem-vaborbactam contain β-lactamase inhibitors active against CRE isolates including those that produce Klebsiella pneumoniae carbapenemases (KPC).

METHODS

Retrospective chart review of CRE isolates from 1 January 2016 to 1 November 2018. Collected data includes a descriptive overview of measured MIC values, resistance mechanism via a polymerase chain reaction test (Xpert Carba-R, Cepheid, Sunnyvale CA), as well as clinical outcomes.

RESULTS

Of 106 isolates reviewed, 86 isolates met the inclusion criteria from 85 individual subjects. The breakpoint:MIC ratio for ceftazidime-avibactam overall was 4, while for meropenem-vaborbactam this ratio was 32 (p < 0.0001). For KPC isolates, ceftazidime-avibactam MIC₅₀/MIC₉₀ in 2016, 2017, and 2018 were 2/4 mg/L (n = 32), 2/4 mg/L (n = 17), and 2/8 mg/L (n = 30), respectively. The meropenem-vaborbactam MIC₅₀/MIC₉₀, for KPC isolates in 2016, 2017, and 2018 were 0.06/0.125 mg/L (n = 32), 0.06/0.1 mg/L (n = 17), and 0.06/0.5 mg/L (n = 30), respectively. Microbiologic cure was 75% (n = 16) in ceftazidime-avibactam subjects and 58.3% (n = 12) in subjects treated with alternative agents (p = 0.43). The 14- and 30-day mortality was numerically higher in subjects treated with alternate agents when compared ceftazidime-avibactam 2/9 (22.2%) vs 3/17 (17.6%) (p = 1.00) and 4/9 (44.4%) vs 4/17 (28.6%) (p = 0.38), respectively. For ceftazidime-avibactam, 30-day mortality in 2016, 2017, and 2018 was 0/5 (0%), 0/2 (0%), and 4/10 (40%).

CONCLUSION

Selective pressure from the use of ceftazidime-avibactam at our institution may be decreasing its utility as a first-line agent for CRE infections. Meropenem-vaborbactam maintained low MIC values and may be a promising treatment option for CRE.

Ceftazidime-Avibactam (C/A) Resistant, Meropenem Sensitive KPC-Producing Klebsiella pneumoniae in ICU Setting: We Are What We Are Treated with?

The continuous spread of carbapenem-resistant Klebsiella pneumoniae (CP-Kp) strains presents a severe challenge to the healthcare system due to limited therapeutic options and high mortality. Since its availability, ceftazidime/avibactam (C/A) has become a first-line option against KPC-Kp, but C/A-resistant strains have been reported increasingly, especially with pneumonia or prior suboptimal blood exposure to C/A treatment. A retrospective, observational study was conducted with all patients admitted to the Intensive Care Unit (ICU) dedicated to COVID-19 patients at the City of Health & Sciences in Turin, between 1 May 2021 and 31 January 2022, with the primary endpoint to study strains with resistance to C/A, and secondly to describe the characteristics of this population, with or without previous exposure to C/A. Seventeen patients with colonization or invasive infection due to Klebsiella pneumoniae, C/A resistance, and susceptibility to meropenem (MIC = 2 µg/L) were included; the bla_KPC genotype was detected in all isolates revealing D179Y mutation in the bla_KPC-2 (bla_KPC-33) gene. Cluster analysis showed that 16 out of the 17 C/A-resistant KPC-Kp isolates belonged to a single clone. Thirteen strains (76.5%) were isolated in a 60-day period. Only some patients had a previous infection with non-mutant KPC at other sites (5; 29.4%). Eight patients (47.1%) underwent previous large-spectrum antibiotic treatment, and four patients (23.5%) had prior treatment with C/A. The secondary spread of the D179Y mutation in the bla_KPC-2 during the COVID-19 pandemic needs to be addressed constantly by an interdisciplinary interaction between microbiologists, infection control personnel, clinicians, and infectious diseases consultants to properly diagnose and treat patients.

In vitro-obtained meropenem-vaborbactam resistance mechanisms among clinical Klebsiella pneumoniae carbapenemase-producing K. pneumoniae isolates

OBJECTIVES

A novel ß-lactam-β-lactamase inhibitor (BLBI), meropenem (MEM), combined with the boronate-based inhibitor vaborbactam (VAB), has recently been introduced for the treatment of infections caused by Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacterales. The purpose of this study was to select for MEM-VAB resistance using a collection of eight KPC-producing K. pneumoniae clinical isolates, including three that produce KPC variants conferring ceftazidime-avibactam (CAZ-AVI) resistance, and subsequently decipher the corresponding resistance mechanisms.

METHODS

Mutants were selected in a stepwise process on agar plates containing different MEM-VAB concentrations. Susceptibility testing was performed by broth microdilution, and complementation assays were performed with wildtype ompK36. Whole genome sequencing was performed on mutants, and KPC copy number was assessed by quantitative polymerase chain reaction .

RESULTS

Mutants were obtained from 6/8 tested isolates and reduced susceptibility to all tested β-lactams, and BLBIs, including CAZ-AVI, imipenem-relebactam, and aztreonam-AVI, were observed. No mutations were identified in the bla_KPC. However, mutations in ompK36 were observed in four mutant lineages, and complementation with a wild-type ompK36 resulted in a reduction of minimal inhibitory concentrations to both MEM-VAB and other ß-lactams/BLBIs. bla_KPC gene copy numbers were significantly increased in four mutant lineages. Whole genome sequencing identified genomic rearrangements in two lineages comprising mutations in the plasmid replicon encoding gene and duplication of the Tn4401 transposon bearing the bla_KPC gene into a ColE-like, high copy number plasmid.

CONCLUSIONS

In contrast to what is observed with KPC-producing mutants exhibiting resistance to CAZ-AVI, mainly corresponding to mutated KPC enzymes, here the MEM-VAB-resistant mutants showed permeability defects combined with increased KPC production, resulting from genomic rearrangement.

Clinical effectiveness of tigecycline in combination therapy against nosocomial pneumonia caused by CR-GNB in intensive care units: a retrospective multi-centre observational study

BACKGROUND

Tigecycline has in vitro bacteriostatic activity against a broad spectrum of bacteria, including carbapenem-resistant Gram-negative bacteria (CR-GNB). However, the role of tigecycline in treatment of nosocomial pneumonia caused by CR-GNB remains controversial and clinical evidences are limited. We aimed to investigate the clinical benefits of tigecycline as part of the combination treatment of nosocomial CR-GNB pneumonia in intensive care unit (ICU).

METHODS

This multi-centre cohort study retrospectively enrolled ICU-admitted patients with nosocomial pneumonia caused by CR-GNB. Patients were categorized based on whether add-on tigecycline was used in combination with at least one anti-CR-GNB antibiotic. Clinical outcomes and all-cause mortality between patients with and without tigecycline were compared in the original and propensity score (PS)-matched cohorts. A subgroup analysis was also performed to explore the differences of clinical efficacies of add-on tigecycline treatment when combined with various anti-CR-GNB agents.

RESULTS

We analysed 395 patients with CR-GNB nosocomial pneumonia, of whom 148 received tigecycline and 247 did not. More than 80% of the enrolled patients were infected by CR-Acinetobacter baumannii (CRAB). A trend of lower all-cause mortality on day 28 was noted in tigecycline group in the original cohort (27.7% vs. 36.0%, p = 0.088). In PS-matched cohort (102 patient pairs), patients with tigecycline had significantly lower clinical failure (46.1% vs. 62.7%, p = 0.017) and mortality rates (28.4% vs. 52.9%, p < 0.001) on day 28. In multivariate analysis, tigecycline treatment was a protective factor against clinical failure (PS-matched cohort: aOR 0.52, 95% CI 0.28-0.95) and all-cause mortality (original cohort: aHR 0.69, 95% CI 0.47-0.99; PS-matched cohort: aHR 0.47, 95% CI 0.30-0.74) at 28 days. Kaplan-Meier survival analysis in subgroups of patients suggested significant clinical benefits of tigecycline when added to a colistin-included (log rank p value 0.005) and carbapenem-included (log rank p value 0.007) combination regimen.

CONCLUSIONS

In this retrospective observational study that included ICU-admitted patients with nosocomial pneumonia caused by tigecycline-susceptible CR-GNB, mostly CRAB, tigecycline as part of a combination treatment regimen was associated with lower clinical failure and all-cause mortality rates.

New antimicrobial treatment options for severe Gram-negative infections

PURPOSE OF REVIEW

This review will provide rationale for the development of new antibiotics to treat severe or multidrug-resistant (MDR) Gram-negative infections. It will also provide an overview of recently approved and pipeline antibiotics for severe/MDR Gram-negative infections.

RECENT FINDINGS

MDR Gram-negative infections are recognized as critical threats by global and national organizations and carry a significant morbidity and mortality risk. Increasing antibiotic resistance amongst Gram-negative bacteria, including carbapenem-resistant Acinetobacter baumannii , extended-spectrum β-lactamase-producing Enterobacterales, carbapenem-resistant Enterobacterales and Pseudomonas aeruginosa , with difficult-to-treat-resistance has made both empiric and definitive treatment of these infections increasingly problematic. In recent years, several antibiotics have been approved for treatment of MDR Gram-negative infections and ongoing clinical trials are poised to provide additional options to clinicians' armamentarium. These agents include various β-lactam/β-lactamase inhibitor combinations, eravacycline, plazomicin and cefiderocol.

SUMMARY

Severe/MDR Gram-negative infections continue to be important infections due to their impact on patient outcomes, especially in critically ill and immunocompromised hosts. The availability of new antibiotics offers an opportunity to improve empiric and definitive treatment of these infections.

Epidemiology, Drug Resistance, and Risk Factors for Mortality Among Hematopoietic Stem Cell Transplantation Recipients with Hospital-Acquired Klebsiella pneumoniae Infections: A Single-Center Retrospective Study from China

Objective

Infection is the most common complication and cause of death after hematopoietic stem cell transplantation (HSCT). Our study aims to investigate the clinical characteristics and risk factors for death of Klebsiella pneumoniae infections in HSCT recipients, so as to provide evidence for guiding antibiotic use and improving prognosis in the future.

Methods

The epidemiology, clinical manifestations and drug resistance rate with K. pneumoniae infections among HSCT recipients between January 1, 2012 and September 30, 2021 were retrospectively reviewed. Logistic regression model and Cox regression model were respectively used to determine the risk factors for carbapenem-resistant Klebsiella pneumoniae (CRKP) acquisition and death.

Results

Fifty-nine HSCT recipients suffered from K. pneumoniae infections, with a mortality rate of 42.4%. The most common site was lung, followed by blood stream. The resistance rate of K. pneumoniae to various clinically common antibiotics was high, especially CRKP, which was only sensitive to amikacin and tigecycline. Independent risk factor for CPKP acquisition was a previous infection within 3 months before transplantation (OR=10.981, 95% CI 1.474-81.809, P=0.019). Independent risk factors for mortality included interval from diagnosis to transplantation > 180 days (HR=3.963, 95% CI 1.25-12.561, P=0.019), engraftment period > 20 days (HR=8.015, 95% CI 2.355-27.279, P=0.001), non-use of anti-CMV immunoglobulin/rituximab after transplantation (HR=10.720, 95% CI 2.390-48.089, P=0.002), and PCT > 5 μg/L (HR=5.906, 95% CI 1.623-21.500, P=0.007).

Conclusion

K. pneumoniae infection has become a serious threat for HSCT recipients, which reminds us to pay enough attention and actively seek new strategies.

Fluoroquinolones Hybrid Molecules as Promising Antibacterial Agents in the Fight against Antibacterial Resistance

The emergence of bacterial resistance has motivated researchers to discover new antibacterial agents. Nowadays, fluoroquinolones keep their status as one of the essential classes of antibacterial agents. The new generations of fluoroquinolones are valuable therapeutic tools with a spectrum of activity, including Gram-positive, Gram-negative, and atypical bacteria. This review article surveys the design of fluoroquinolone hybrids with other antibacterial agents or active compounds and underlines the new hybrids' antibacterial properties. Antibiotic fluoroquinolone hybrids have several advantages over combined antibiotic therapy. Thus, some challenges related to joining two different molecules are under study. Structurally, the obtained hybrids may contain a cleavable or non-cleavable linker, an essential element for their pharmacokinetic properties and mechanism of action. The design of hybrids seems to provide promising antibacterial agents helpful in the fight against more virulent and resistant strains. These hybrid structures have proven superior antibacterial activity and less susceptibility to bacterial resistance than the component molecules. In addition, fluoroquinolone hybrids have demonstrated other biological effects such as anti-HIV, antifungal, antiplasmodic/antimalarial, and antitumor activity. Many fluoroquinolone hybrids are in various phases of clinical trials, raising hopes that new antibacterial agents will be approved shortly.

The Ins and Outs of Susceptibility Testing for New β-Lactam/β-Lactamase Inhibitor Combinations for Gram-Negative Organisms

Ceftazidime-avibactam, meropenem-vaborbactam, and imipenem-relebactam are among the newest β-lactam/β-lactamase inhibitors (BL/BLIs) introduced to the North American antibiotic market. All have broad Gram-negative activity, including against certain carbapenemases. Despite this, susceptibility testing is warranted due to variable activity against certain β-lactamases (e.g., oxacillinases) and the presence of acquired resistance mechanisms in some isolates. Here, we discuss what we know about these new antimicrobial agents and how to navigate implementation of susceptibility testing and reporting of these agents in clinical laboratories.

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/.

Microbiological, Clinical, and PK/PD Features of the New Anti-Gram-Negative Antibiotics: β-Lactam/β-Lactamase Inhibitors in Combination and Cefiderocol—An All-Inclusive Guide for Clinicians

Bacterial resistance mechanisms are continuously and rapidly evolving. This is particularly true for Gram-negative bacteria. Over the last decade, the strategy to develop new β-lactam/β-lactamase inhibitors (BLs/BLIs) combinations has paid off and results from phase 3 and real-world studies are becoming available for several compounds. Cefiderocol warrants a separate discussion for its peculiar mechanism of action. Considering the complexity of summarizing and integrating the emerging literature data of clinical outcomes, microbiological mechanisms, and pharmacokinetic/pharmacodynamic properties of the new BL/BLI and cefiderocol, we aimed to provide an overview of data on the following compounds: aztreonam/avibactam, cefepime/enmetazobactam, cefepime/taniborbactam, cefepime/zidebactam, cefiderocol, ceftaroline/avibactam, ceftolozane/tazobactam, ceftazidime/avibactam, imipenem/relebactam, meropenem/nacubactam and meropenem/vaborbactam. Each compound is described in a dedicated section by experts in infectious diseases, microbiology, and pharmacology, with tables providing at-a-glance information.

Risk factors for and clinical outcomes of ceftazidime-avibactam-resistant carbapenem-resistant Klebsiella pneumoniae nosocomial infections: a single-center retrospective study

PURPOSE

The emergence of ceftazidime-avibactam (CZA) resistance in carbapenem-resistant Klebsiella pneumoniae (CRKP) has been increasingly reported in recent years. We aimed to identify the risk factors of CZA-resistant CRKP infection and assess clinical outcomes of the patients.

METHODS

The study retrospectively analyzed the clinical and microbiological data of patients with CRKP infection to identify risk factors, clinical features, and outcomes using multivariate logistic regression analysis.

RESULTS

A total of 103 patients with CRKP infection were enrolled in this study. Multivariate analysis showed previous renal replacement therapy (OR 3.966, 95% CI 1.301-12.090, P = 0.015) was an independent risk factor for CZA-resistant CRKP infection. The 28-day mortality was higher in patients infected with CZA-resistant CRKP (27.9%) than those with CZA-susceptible CRKP (7.1%) (P = 0.009). CZA-resistant CRKP infection (OR 20.308, 95% CI 1.461-282.293, P = 0.025), and mechanical ventilation (OR 14.950, 95% CI 1.034-216.212, P = 0.047) were independent predictors for 28-day mortality in patients with CRKP infection. Lower level of platelet count (OR 0.987, 95% CI 0.975-0.999, P = 0.032) on the day of CRKP infection onset was related to 28-day mortality. Kaplan-Meier curves showed that the CZA-resistant CRKP group had a shorter survival time than the CZA-susceptible CRKP group.

CONCLUSION

The prevalence and mortality of CZA-resistant CRKP are still increasing. Strengthening the hospital infection control of renal replacement therapy and mechanical ventilation may help to prevent CZA-resistant CRKP.

Meropenem-vaborbactam: a critical positioning for the management of infections by Carbapenem-resistant Enterobacteriaceae

INTRODUCTION

The review aims to review the positioning of meropenem-vaborbactam in clinical practice, taking into consideration the characteristics of other available drugs, namely ceftazidime-avibactam, plazomicin and colistin.

AREAS COVERED

The search terms "meropenem-vaborbactam" or RX7009 for the years 2006 until 2021 were used.

EXPERT OPINION

Coupling of meropenem with the cyclic boronate derivative varobactam enhances considerably the in vitro intrinsic activity of meropenem against isolates producing KPC (Klebsiella pneumoniae-producing carbapenemase). The drug has linear elimination and the ratio of the area under the curve of the free drug to the minimum inhibitory concentration is the main pharmacodynamics variable determining bacterial clearance. Meropenem-vaborbactam is currently approved for the management of complicated urinary tract infections including acute pyelonephritis, complicated intraabdominal infections and hospital-acquired pneumonia including ventilator-associated pneumonia.

The Ultra-Broad-Spectrum Beta-lactamase Inhibitor QPX7728 Restores the Potency of Multiple Oral Beta-lactam Antibiotics against Beta-lactamase Producing Strains of Resistant Enterobacterales

QPX7728 is a cyclic boronate ultrabroad-spectrum beta-lactamase inhibitor, with potent activity against both serine beta-lactamases and metallo-beta-lactamases. QPX7728 can be delivered systemically by the intravenous (i.v.) or oral route of administration. Oral beta-lactam antibiotics alone or in combination with QPX7728 were evaluated for (i) sensitivity to hydrolysis by various common beta-lactamases and inhibition of hydrolysis by QPX7728, (ii) the impact of non-beta-lactamase-mediated resistance mechanisms on potency of beta-lactams, and (iii) in vitro activity against a panel of clinical strains producing diverse beta-lactamases. The carbapenem tebipenem had stability for many serine beta-lactamases from all molecular classes, followed by the cephalosporin ceftibuten. Addition of QPX7728 to tebipenem, ceftibuten, and amdinocillin completely reversed beta-lactamase-mediated resistance in cloned beta-lactamases from serine enzyme and metalloenzyme classes; the degree of potentiation of other beta-lactams varied according to the beta-lactamase produced. Tebipenem, ceftibuten, and cefixime had the lowest MICs against laboratory strains with various combinations of beta-lactamases and the intrinsic drug resistance mechanisms of porin and efflux mutations. There was a high degree of correlation between potency of various combinations against cloned beta-lactamases and efflux/porin mutants and the activity against clinical isolates, showing the importance of inhibition of beta-lactamase along with minimal impact of general intrinsic resistance mechanisms affecting the beta-lactam. Tebipenem and ceftibuten appeared to be the best beta-lactam antibiotics when combined with QPX7728 for activity against Enterobacterales that produce serine beta-lactamases or metallo-beta-lactamases.

The role of new carbapenem combinations in the treatment of multidrug-resistant Gram-negative infections

Multi-drug resistant (MDR) Gram-negative bacteria represent a growing threat, with an increasing prevalence of carbapenem-resistant Enterobacterales (CRE) infections, for which treatment options are limited. New treatment combinations composed of a β-lactam antibiotic plus a potent β-lactamase inhibitor (BLI) with anti-carbapenemase activity have been developed, including two carbapenem/BLI combinations that are commercially available-meropenem/vaborbactam (Vabomere® in the US, Vaborem® in Europe; Melinta Therapeutics) and imipenem/cilastatin/relebactam (Recarbrio®; Merck Sharp & Dohme), plus one other (meropenem/nacubactam) in early clinical development. This review provides a summary of the preclinical evidence supporting the use of carbapenem/BLI combinations and presents the clinical evidence across a range of MDR Gram-negative infections, with a focus on the use of meropenem/vaborbactam. All three BLIs have shown in vivo activity against Klebsiella pneumoniae carbapenemase and other class A carbapenemases. In 2019, meropenem/vaborbactam was listed in the WHO's list of essential medicines, because of its activity against priority 1 antibiotic-resistant pathogens. Meropenem/vaborbactam has considerable in vitro and in vivo activity against CRE, and in vitro evidence showing a low potential for resistance at clinically relevant doses. In randomized trials, meropenem/vaborbactam was non-inferior to piperacillin/tazobactam in patients with complicated urinary tract infection and more effective than the best-available treatment in patients with serious CRE infections. Meropenem/vaborbactam is well tolerated and, based on clinical experience, demonstrated lower toxicity compared with the combination regimens that have previously been the standard of care. In conclusion, carbapenem/BLI combinations represent an important therapeutic strategy in patients with MDR Gram-negative infections.

Multicenter clinical evaluation of VITEK® 2 meropenem-vaborbactam for susceptibility testing of Enterobacterales and Pseudomonas aeruginosa

The carbapenem/beta-lactamase inhibitor (meropenem-vaborbactam; MEV) used to treat complicated urinary tract infections and pyelonephritis in adults was approved in 2017 by the U.S. Food and Drug Administration (FDA). We evaluated VITEK 2 MEV (bioMérieux, Durham, NC) compared to the reference broth microdilution (BMD) method. Of 449 Enterobacterales isolates analyzed per FDA/CLSI breakpoints, overall performance was 98.2% Essential Agreement (EA), 98.7% Category Agreement (CA), and 0% Very Major Errors (VME) or Major Errors (ME). For FDA intended for use 438 Enterobacterales isolates, performance was 98.2% EA, 98.6% CA, and 0% VME or ME. Evaluable EA was 81.0% but with only 42 on-scale evaluable results. Individual species demonstrated EA and CA rates ≥ 90% without any VME or ME. When evaluated using European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, overall VITEK 2 MEV performance for Enterobacterales and Pseudomonas aeruginosa demonstrated 97.3% EA, 99.2% CA, 2.3% VME, and 0.6% ME (after error resolution: 97.3% EA, 99.4% CA, 2.2% VME, and 0.4% ME) compared to the reference BMD method. Performance for P. aeruginosa included 92.2% EA, 97.4% CA, 0% VME, and 3.0% ME (after error resolution: 92.2% EA, 98.7% CA, 0% VME, and 1.5% ME). Performance for Enterobacterales included 98.2% EA, 99.6% CA, 3.0% VME, and 0.2% ME. Evaluable EA was 80.6% but due to only 67 evaluable results. These findings support VITEK 2 MEV as an accurate automated system for MEV susceptibility testing of Enterobacterales and P. aeruginosa and could be an alternate solution to the manual labor intensive reference BMD method.

Mutations in porin LamB contribute to ceftazidime-avibactam resistance in KPC-producing Klebsiella pneumoniae

Ceftazidime-avibactam (CAZ-AVI) shows promising activity against carbapenem-resistant Klebsiella pneumoniae (CRKP), however, CAZ-AVI resistance have emerged recently. Mutations in KPCs, porins OmpK35 and/or OmpK36, and PBPs are known to contribute to the resistance to CAZ-AVI in CRKP. To identify novel CAZ-AVI resistance mechanism, we generated 10 CAZ-AVI-resistant strains from 14 CAZ-AVI susceptible KPC-producing K. pneumoniae (KPC-Kp) strains through in vitro multipassage resistance selection using low concentrations of CAZ-AVI. Comparative genomic analysis for the original and derived mutants identified CAZ-AVI resistance-associated mutations in KPCs, PBP3 (encoded by ftsI), and LamB, an outer membrane maltoporin. CAZ-AVI susceptible KPC-Kp strains became resistant when complemented with mutated bla_KPC genes. Complementation experiments also showed that a plasmid borne copy of wild-type lamB or ftsI gene reduced the MIC value of CAZ-AVI in the induced resistant strains. In addition, bla_KPC expression level increased in four of the six CAZ-AVI-resistant strains without KPC mutations, indicating a probable association between increased bla_KPC expression and increased resistance in these strains. In conclusion, we here identified a novel mechanism of CAZ-AVI resistance associated with mutations in porin LamB in KPC-Kp.

Activity of meropenem/vaborbactam and comparators against Gram-negative isolates from Eastern and Western European patients hospitalized with pneumonia including ventilator-associated pneumonia (2014-19)

Objectives

Meropenem/vaborbactam has been approved in Europe for the treatment of hospital-acquired bacterial pneumonia, ventilator-associated pneumonia (VAP) and bacteraemia among other indications. Vaborbactam is an inhibitor of class A and C β-lactamases, including Klebsiella pneumoniae carbapenemase (KPC) enzymes, but not class B or D carbapenemases. We analysed the activity of meropenem/vaborbactam and comparators against 6846 Enterobacterales and 3567 Pseudomonas aeruginosa isolates from patients hospitalized with pneumonia (PHP), including VAP.

Methods

Isolates from PHP were consecutively collected during 2014–19 from 42 European hospitals located in 21 countries and susceptibility tested using the broth microdilution method. Carbapenem-resistant Enterobacterales (CRE) isolates were molecularly characterized to identify their carbapenem-resistance mechanisms. EUCAST (2020) interpretive criteria were used.

Results

The most common Gram-negative pathogens isolated from PHP were P. aeruginosa (n = 3567), K. pneumoniae (n = 1877) and Escherichia coli (n = 1646). Overall, 98.0% of Enterobacterales and 82.1% of P. aeruginosa were susceptible to meropenem/vaborbactam, with 99.8% of Enterobacterales and 89.7% of P. aeruginosa in Western Europe (WE) and 92.7% of Enterobacterales and 69.1% of P. aeruginosa in Eastern Europe (EE). CRE were more common in EE (15.1%) than WE (2.1%). KPC was the most common carbapenemase in WE, while OXA-48-like was the most common carbapenemase in EE. Meropenem/vaborbactam susceptibility was 63.0% for all CRE (92.2% in WE and 51.5% in EE). Meropenem/vaborbactam inhibited 99.1% of KPC-producing isolates and 40.5% of OXA-48-like-producing isolates.

Conclusions

These in vitro data demonstrate that meropenem/vaborbactam has potent activity against isolates from PHP, including isolates producing KPC, and may be a useful treatment option for PHP, including VAP.

Ceftazidime-avibactam: are we safe from class A carbapenemase producers' infections?

Recently, new combinations of β-lactams and β-lactamase inhibitors became available, including ceftazidime-avibactam, and increased the ability to treat infections caused by carbapenem-resistant Enterobacterales (CRE). Despite the reduced time of clinical use, isolates expressing resistance to ceftazidime-avibactam have been reported, even during treatment or in patients with no previous contact with this drug. Here, we detailed review data on global ceftazidime-avibactam susceptibility, the mechanisms involved in resistance, and the molecular epidemiology of resistant isolates. Ceftazidime-avibactam susceptibility remains high (≥ 98.4%) among Enterobacterales worldwide, being lower among extended-spectrum β-lactamase (ESBL) producers and CRE. Alterations in class A β-lactamases are the major mechanism involved in ceftazidime-avibactam resistance, and mutations are mainly, but not exclusively, located in the Ω loop of these enzymes. Modifications in Klebsiella pneumoniae carbapenemase (KPC) 3 and KPC-2 have been observed by many authors, generating variants with different mutations, insertions, and/or deletions. Among these, the most commonly described is Asp179Tyr, both in KPC-3 (KPC-31 variant) and in KPC-2 (KPC-33 variant). Changes in membrane permeability and overexpression of efflux systems may also be associated with ceftazidime-avibactam resistance. Although several clones have been reported, ST258 with Asp179Tyr deserves special attention. Surveillance studies and rationale use are essential to retaining the activity of this and other antimicrobials against class A CRE.

QPX7728, An Ultra-Broad-Spectrum B-Lactamase Inhibitor for Intravenous and Oral Therapy: Overview of Biochemical and Microbiological Characteristics

QPX7728 is a novel β-lactamase inhibitor (BLI) that belongs to a class of cyclic boronates. The first member of this class, vaborbactam, is a BLI in the recently approved Vabomere (meropenem-vaborbactam). In this paper we provide the overview of the biochemical, structural and microbiological studies that were recently conducted with QPX7728. We show that QPX7728 is an ultra-broad-spectrum β-lactamase inhibitor with the broadest spectrum of inhibition reported to date in a single BLI molecule; in addition to potent inhibition of clinically important serine β-lactamases, including Class A and D carbapenemases from Enterobacterales and notably, diverse Class D carbapenemases from Acinetobacter, it also inhibits many metallo β-lactamases. Importantly, it is minimally affected by general intrinsic resistance mechanisms such as efflux and porin mutations that impede entry of drugs into gram-negative bacteria. QPX7728 combinations with several intravenous (IV) β-lactam antibiotics shows broad coverage of Enterobacterales, Acinetobacter baumannii and Pseudomonas aeruginosa, including strains that are resistant to other IV β-lactam-BLI combinations, e.g., ceftazidime-avibactam, ceftolozane-tazobactam, meropenem-vaborbactam and imipenem-relebactam that were recently approved for clinical use. Based on studies with P. aeruginosa, different partner β-lactams in combination with QPX7728 may be optimal for the coverage of susceptible organisms. This provides microbiological justification for a stand-alone BLI product for co-administration with different β-lactams. QPX7728 can also be delivered orally; thus, its ultra-broad β-lactamase inhibition spectrum and other features could be also applied to oral QPX7728-based combination products. Clinical development of QPX7728 has been initiated.

Role of new antibiotics for KPC-producing Klebsiella pneumoniae

Klebsiella pneumoniae has accumulated a wide range of resistance determinants and has evolved into a difficult-to-treat pathogen that poses an increasing healthcare threat. KPC is an important marker for extensively drug-resistant (XDR) organisms with limited treatment options. In response to the medical need for new treatment options, several new antibiotics have been developed and registered recently. The β-lactamase inhibitor (BLI) combinations ceftazidime/avibactam, meropenem/vaborbactam and imipenem/relebactam, the cephalosporin-siderophore conjugate cefiderocol, the aminoglycoside derivative plazomicin and the tetracycline derivative eravacycline, focus on carbapenem-resistant Enterobacterales. These modified agents from old antibiotic classes illustrate the challenges of this requirement to address class-specific resistance mechanisms while critical gaps and some cross-resistance within a class, or to unrelated antibiotic classes, remain. The diverse molecular mechanisms and increasing diversification of carbapenem resistance among Klebsiella isolates requires improved rapid molecular diagnostic capabilities and stringent stewardship programmes to preserve the efficacy of new antibiotics for as long as possible.

Treatment for carbapenem-resistant Enterobacterales infections: recent advances and future directions

Carbapenem-resistant Enterobacterales (CRE) are a growing threat to human health worldwide. CRE often carry multiple resistance genes that limit treatment options and require longer durations of therapy, are more costly to treat, and necessitate therapies with increased toxicities when compared with carbapenem-susceptible strains. Here, we provide an overview of the mechanisms of resistance in CRE, the epidemiology of CRE infections worldwide, and available treatment options for CRE. We review recentlyapproved agents for the treatment of CRE, including ceftazidime-avibactam, meropenem-vaborbactam, imipenem-relebactam, cefiderocol, and novel aminoglycosides and tetracyclines. We also discuss recent advances in phage therapy and antibiotics that are currently in development targeted to CRE. The potential for the development of resistance to these therapies remains high, and enhanced antimicrobial stewardship is imperative both to reduce the spread of CRE worldwide and to ensure continued access to efficacious treatment options.

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.

Multidrug-resistant Klebsiella pneumoniae: mechanisms of resistance including updated data for novel β-lactam-β-lactamase inhibitor combinations

Introduction: Multi-drug-resistant Klebsiella pneumoniae is currently one of the most pressing emerging issues in bacterial resistance. Treatment of K.pneumoniae infections is often problematic due to the lack of available therapeutic options, with a relevant impact in terms of morbidity, mortality and healthcare-associated costs. Soon after the launch of Ceftazidime-Avibactam, one of the approved new β-lactam/β-lactamase inhibitor combinations, reports of ceftazidime-avibactam-resistant strains developing resistance during treatment were published. Being a hospital-associated pathogen, K.pneumoniae is continuously exposed to multiple antibiotics resulting in constant selective pressure, which in turn leads to additional mutations that are positively selected.Areas covered: Herein the authors present the K.pneumoniae mechanisms of resistance to different antimicrobials, including updated data for ceftazidime-avibactam.Expert opinion: K.pneumoniae is a nosocomial pathogen commonly implicated in hospital outbreaks with a propensity for antimicrobial resistance toward mainstay β-lactam antibiotics and multiple other antibiotic classes. Following the development of drug resistance and understanding the mechanisms involved, we can improve the efficacy of current antimicrobials, by applying careful stewardship and rational use to preserve their potential utility. The knowledge on antibiotic resistance mechanisms should be used to inform the design of novel therapeutic agents that might not be subject to, or can circumvent, mechanisms of resistance.

Early Experience With Meropenem-Vaborbactam for Treatment of Carbapenem-resistant Enterobacteriaceae Infections

Twenty patients with carbapenem-resistant Enterobacteriaceae infections were treated with meropenem-vaborbactam. Thirty-day clinical success and survival rates were 65% (13/20) and 90% (18/20), respectively. Thirty-five percent of patients had microbiologic failures within 90 days. One patient developed a recurrent infection due to meropenem-vaborbactam-nonsusceptible, ompK36 porin mutant Klebsiella pneumoniae.

Present and Future Perspectives on Therapeutic Options for Carbapenemase-Producing Enterobacterales Infections

Carbapenem-resistant Enterobacterales (CRE) are included in the list of the most threatening antibiotic resistance microorganisms, being responsible for often insurmountable therapeutic issues, especially in hospitalized patients and immunocompromised individuals and patients in intensive care units. The enzymatic resistance to carbapenems is encoded by different β-lactamases belonging to A, B or D Ambler class. Besides compromising the activity of last-resort antibiotics, CRE have spread from the clinical to the environmental sectors, in all geographic regions. The purpose of this review is to present present and future perspectives on CRE-associated infections treatment.

Nosocomial Pneumonia in the Era of Multidrug-Resistance: Updates in Diagnosis and Management

Nosocomial pneumonia (NP), including hospital-acquired pneumonia in non-intubated patients and ventilator-associated pneumonia, is one of the most frequent hospital-acquired infections, especially in the intensive care unit. NP has a significant impact on morbidity, mortality and health care costs, especially when the implicated pathogens are multidrug-resistant ones. This narrative review aims to critically review what is new in the field of NP, specifically, diagnosis and antibiotic treatment. Regarding novel imaging modalities, the current role of lung ultrasound and low radiation computed tomography are discussed, while regarding etiological diagnosis, recent developments in rapid microbiological confirmation, such as syndromic rapid multiplex Polymerase Chain Reaction panels are presented and compared with conventional cultures. Additionally, the volatile compounds/electronic nose, a promising diagnostic tool for the future is briefly presented. With respect to NP management, antibiotics approved for the indication of NP during the last decade are discussed, namely, ceftobiprole medocaril, telavancin, ceftolozane/tazobactam, ceftazidime/avibactam, and meropenem/vaborbactam.

New β-Lactam-β-Lactamase Inhibitor Combinations

The limited armamentarium against drug-resistant Gram-negative bacilli has led to the development of several novel β-lactam-β-lactamase inhibitor combinations (BLBLIs). In this review, we summarize their spectrum of in vitro activities, mechanisms of resistance, and pharmacokinetic-pharmacodynamic (PK-PD) characteristics. A summary of available clinical data is provided per drug. Four approved BLBLIs are discussed in detail. All are options for treating multidrug-resistant (MDR) Enterobacterales and Pseudomonas aeruginosa Ceftazidime-avibactam is a potential drug for treating Enterobacterales producing extended-spectrum β-lactamase (ESBL), Klebsiella pneumoniae carbapenemase (KPC), AmpC, and some class D β-lactamases (OXA-48) in addition to carbapenem-resistant Pseudomonas aeruginosa Ceftolozane-tazobactam is a treatment option mainly for carbapenem-resistant P. aeruginosa (non-carbapenemase producing), with some activity against ESBL-producing Enterobacterales Meropenem-vaborbactam has emerged as treatment option for Enterobacterales producing ESBL, KPC, or AmpC, with similar activity as meropenem against P. aeruginosa Imipenem-relebactam has documented activity against Enterobacterales producing ESBL, KPC, and AmpC, with the combination having some additional activity against P. aeruginosa relative to imipenem. None of these drugs present in vitro activity against Enterobacterales or P. aeruginosa producing metallo-β-lactamase (MBL) or against carbapenemase-producing Acinetobacter baumannii Clinical data regarding the use of these drugs to treat MDR bacteria are limited and rely mostly on nonrandomized studies. An overview on eight BLBLIs in development is also provided. These drugs provide various levels of in vitro coverage of carbapenem-resistant Enterobacterales, with several drugs presenting in vitro activity against MBLs (cefepime-zidebactam, aztreonam-avibactam, meropenem-nacubactam, and cefepime-taniborbactam). Among these drugs, some also present in vitro activity against carbapenem-resistant P. aeruginosa (cefepime-zidebactam and cefepime-taniborbactam) and A. baumannii (cefepime-zidebactam and sulbactam-durlobactam).

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.

Microbiology of Meropenem-Vaborbactam: A Novel Carbapenem Beta-Lactamase Inhibitor Combination for Carbapenem-Resistant Enterobacterales Infections

Vaborbactam is a novel boron-based beta-lactamase inhibitor developed to be effective against Klebsiella pneumoniae carbapenemase (KPC)-producing bacteria. This enzyme is a key driver in the global spread of β-lactam resistance among carbapenem-resistant Enterobacterales. Alone, vaborbactam has no antibacterial activity; however, the combination of meropenem-vaborbactam has enhanced activity against gram-negative organisms, particularly Enterobacterales with class A and C carbapenemases. Multiple in vitro studies evaluating isolates from various geographic regions, and over different time periods, have demonstrated the high potency of meropenem-vaborbactam against organisms containing KPC2 and KPC3. However, meropenem-vaborbactam does not have activity against OXA-48 or metallo-beta lactamases. This review covers the in vitro studies of meropenem-vaborbactam performed to date, which evaluated both large cohorts of clinical isolates and engineered isolates, to determine efficacy in various settings, including the presence of porin mutations and efflux pump upregulation.

Meropenem-vaborbactam is a new combination antibiotic that was designed specifically for efficacy against bacteria that produce the Klebsiella pneumoniae carbapenemase (KPC) enzyme, which enables resistance to beta-lactam antibiotics. The global spread and increase of difficult-to-treat infections caused by carbapenem-resistant Enterobacterales (CRE) is in part because they produce KPC enzymes. The authors review the in vitro studies of meropenem-vaborbactam activity, which have included isolates from different geographic regions, time periods, and settings, showing that it has high potency against organisms containing KPC enzymes-KPC2 and KPC3. Meropenem-vaborbactam was tested against globally sourced isolates that carried different resistance mechanisms, including carbapenem resistance, multidrug resistant (MDR), and resistance to colistin and/or tigecycline; it inhibited activity of 99.1% Enterobacterales isolates tested at ≤ 1 µg/ml, and at ≤ 8 µg/ml it inhibited 96.5% of MDR isolates and 82% of XDR isolates. Against OXA-48 or metallo-beta lactamase enzymes, meropenem-vaborbactam has limited or no activity, so in the Asia-Pacific region where MLBs are prevalent it was least effective, but and was most effective against US strains where KPC is prevalent. In multiple studies, meropenem-vaborbactam showed strong in vitro activity against E. coli, Enterobacter spp., and K. pneumoniae. Compared to available antibiotics, against both clinical and engineered isolates, as well as engineered E. coli strains with KPC, SHV, and TEM enzymes, meropenem-vaborbactam demonstrated lower MIC values. Overall, in vitro studies of meropenem-vaborbactam have shown enhanced activity against CRE and KPC producers compared to other antibiotics, which is needed in the current CRE environment where KPC is dominant.

Is it time to move away from polymyxins?: evidence and alternatives

Increasing burden of carbapenem resistance and resultant difficult-to-treat infections are of particular concern due to the lack of effective and safe treatment options. More recently, several new agents with activity against certain multidrug-resistant (MDR) and extensive drug-resistant (XDR) Gram-negative pathogens have been approved for clinical use. These include ceftazidime-avibactam, meropenem-vaborbactam, imipenem-cilastatin-relebactam, plazomicin, and cefiderocol. For the management of MBL infections, clinically used triple combination comprising ceftazidime-avibactam and aztreonam is hindered due to non-availability of antimicrobial susceptibility testing methods and lack of information on potential drug-drug interaction leading to PK changes impacting its safety and efficacy. Moreover, in several countries including Indian subcontinent and developing countries, these new agents are yet to be made available. Under these circumstances, polymyxins are the only last resort for the treatment of carbapenem-resistant infections. With the recent evidence of suboptimal PK/PD particularly in lung environment, limited efficacy and increased nephrotoxicity associated with polymyxin use, the Clinical and Laboratory Standards Institute (CLSI) has revised both colistin and polymyxin B breakpoints. Thus, polymyxins 'intermediate' breakpoint for Enterobacterales, P. aeruginosa, and Acinetobacter spp. are now set at ≤ 2 mg/L, implying limited clinical efficacy even for isolates with the MIC value 2 mg/L. This change has questioned the dependency on polymyxins in treating XDR infections. In this context, recently approved cefiderocol and phase 3 stage combination drug cefepime-zidebactam assume greater significance due to their potential to act as polymyxin-supplanting therapies.

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.

Treatment options for K. pneumoniae, P. aeruginosa and A. baumannii co-resistant to carbapenems, aminoglycosides, polymyxins and tigecycline: an approach based on the mechanisms of resistance to carbapenems

The management of carbapenem-resistant infections is often based on polymyxins, tigecycline, aminoglycosides and their combinations. However, in a recent systematic review, we found that Gram-negative bacteria (GNB) co-resistant to carbapanems, aminoglycosides, polymyxins and tigecycline (CAPT-resistant) are increasingly being reported worldwide. Clinical data to guide the treatment of CAPT-resistant GNB are scarce and based exclusively on few case reports and small case series, but seem to indicate that appropriate (in vitro active) antimicrobial regimens, including newer antibiotics and synergistic combinations, may be associated with lower mortality. In this review, we consolidate the available literature to inform clinicians dealing with CAPT-resistant GNB about treatment options by considering the mechanisms of resistance to carbapenems. In combination with rapid diagnostic methods that allow fast detection of carbapenemase production, the approach proposed in this review may guide a timely and targeted treatment of patients with infections by CAPT-resistant GNB. Specifically, we focus on the three most problematic species, namely Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii. Several treatment options are currently available for CAPT-resistant K. pneumonia. Newer β-lactam-β-lactamase combinations, including the combination of ceftazidime/avibactam with aztreonam against metallo-β-lactamase-producing isolates, appear to be more effective compared to combinations of older agents. Options for P. aeruginosa (especially metallo-β-lactamase-producing strains) and A. baumannii remain limited. Synergistic combination of older agents (e.g., polymyxin- or fosfomycin-based synergistic combinations) may represent a last resort option, but their use against CAPT-resistant GNB requires further study.

α-Triazolylboronic Acids: A Promising Scaffold for Effective Inhibitors of KPCs

Boronic acids are known reversible covalent inhibitors of serine β-lactamases. The selectivity and high potency of specific boronates bearing an amide side chain that mimics the β-lactam's amide side chain have been advanced in several studies. Herein, we describe a new class of boronic acids in which the amide group is replaced by a bioisostere triazole. The boronic acids were obtained in a two-step synthesis that relies on the solid and versatile copper-catalyzed azide-alkyne cycloaddition (CuAAC) followed by boronate deprotection. All of the compounds show very good inhibition of the Klebsiella pneumoniae carbapenemase KPC-2, with Ki values ranging from 1 nM to 1 μM, and most of them are able to restore cefepime activity against K. pneumoniae harboring blaKPC-2 . In particular, compound 1 e, bearing a sulfonamide substituted by a thiophene ring, proved to be an excellent KPC-2 inhibitor (Ki =30 nM); it restored cefepime susceptibility in KPC-Kpn cells (MIC=0.5 μg/mL) with values similar to that of vaborbactam (Ki =20 nM, MIC in KPC-Kpn 0.5 μg/mL). Our findings suggest that α-triazolylboronates might represent an effective scaffold for the treatment of KPC-mediated infections.

Impact of Intrinsic Resistance Mechanisms on Potency of QPX7728, a New Ultrabroad-Spectrum Beta-Lactamase Inhibitor of Serine and Metallo-Beta-Lactamases in Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter baumannii

QPX7728 is an ultrabroad-spectrum boronic acid beta-lactamase inhibitor that demonstrates inhibition of key serine and metallo-beta-lactamases at a nanomolar concentration range in biochemical assays with purified enzymes. The broad-spectrum inhibitory activity of QPX7728 observed in biochemical experiments translates into enhancement of the potency of many beta-lactams against strains of target pathogens producing beta-lactamases. The impacts of bacterial efflux and permeability on inhibitory potency were determined using isogenic panels of KPC-3-producing isogenic strains of Klebsiella pneumoniae and Pseudomonas aeruginosa and OXA-23-producing strains of Acinetobacter baumannii with various combinations of efflux and porin mutations.

QPX7728 is an ultrabroad-spectrum boronic acid beta-lactamase inhibitor that demonstrates inhibition of key serine and metallo-beta-lactamases at a nanomolar concentration range in biochemical assays with purified enzymes. The broad-spectrum inhibitory activity of QPX7728 observed in biochemical experiments translates into enhancement of the potency of many beta-lactams against strains of target pathogens producing beta-lactamases. The impacts of bacterial efflux and permeability on inhibitory potency were determined using isogenic panels of KPC-3-producing isogenic strains of Klebsiella pneumoniae and Pseudomonas aeruginosa and OXA-23-producing strains of Acinetobacter baumannii with various combinations of efflux and porin mutations. QPX7728 was minimally affected by multidrug resistance efflux pumps either in Enterobacteriaceae or in nonfermenters, such as P. aeruginosa or A. baumannii. Against P. aeruginosa, the potency of QPX7728 was further enhanced when the outer membrane was permeabilized. The potency of QPX7728 against P. aeruginosa was not affected by inactivation of the carbapenem porin OprD. While changes in OmpK36 (but not OmpK35) reduced the potency of QPX7728 (8- to 16-fold), QPX7728 (4 μg/ml) nevertheless completely reversed the KPC-mediated meropenem resistance in strains with porin mutations, consistent with the lesser effect of these mutations on the potency of QPX7728 compared to that of other agents. The ultrabroad-spectrum beta-lactamase inhibition profile, combined with enhancement of the activity of multiple beta-lactam antibiotics with various sensitivities to the intrinsic resistance mechanisms of efflux and permeability, indicates that QPX7728 is a useful inhibitor for use with multiple beta-lactam antibiotics.

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.