Activity of meropenem/vaborbactam and comparators against non-carbapenemase-producing carbapenem-resistant Enterobacterales isolates from Europe

Rates of resistance and heteroresistance to newer β-lactam/β-lactamase inhibitors for carbapenem-resistant Enterobacterales

Background

Heteroresistance (HR), the presence of antibiotic-resistant subpopulations within a primary isogenic population, may be a potentially overlooked contributor to newer β-lactam/β-lactamase inhibitor (BL/BLI) treatment failure in carbapenem-resistant Enterobacterales (CRE) infections.

Objectives

To determine rates of susceptibility and HR to BL/BLIs ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam in clinical CRE isolates.

Methods

The first CRE isolate per patient per year from two >500 bed academic hospitals from 1 January 2016 to 31 December 2021, were included. Reference broth microdilution (BMD) was used to determine antibiotic susceptibility, and population analysis profiling (PAP) to determine HR. Carbapenemase production (CP) was determined using the Carba NP assay.

Results

Among 327 CRE isolates, 46% were Enterobacter cloacae, 38% Klebsiella pneumoniae and 16% Escherichia coli. By BMD, 87% to 98% of CRE were susceptible to the three antibiotics tested. From 2016 to 2021, there were incremental decreases in the rates of susceptibility to each of the three BL/BLIs. HR was detected in each species-antibiotic combination, with the highest rates of HR (26%) found in K. pneumoniae isolates with imipenem/relebactam. HR or resistance to at least one BL/BLI by PAP was found in 24% of CRE isolates and 65% of these had detectable CP.

Conclusion

Twenty-four percent of CRE isolates tested were either resistant or heteroresistant (HR) to newer BL/BLIs, with an overall decrease of ∼10% susceptibility over 6 years. While newer BL/BLIs remain active against most CRE, these findings support the need for ongoing antibiotic stewardship and a better understanding of the clinical implications of HR in CRE.

Reviewing novel treatment options for carbapenem-resistant Enterobacterales

INTRODUCTION

Carbapenem resistant Enterobacterales (CRE) are a major threat to global health and hospital-onset CRE infections have risen during the COVID-19 pandemic. Novel antimicrobials are now available for the treatment of CRE infections. There remains an urgent need for new antimicrobials for CRE, especially for those producing metallo-β-lactamases.

AREAS COVERED

This article discusses previously published research supporting currently available novel antimicrobials for the treatment of CRE infections. Newer compounds currently being evaluated in clinical trials are covered. A literature search was conducted in PubMed over all available dates for relevant published papers and conference abstracts with the search terms, 'CRE,' 'carbapenem-resistant Enterobacterales,' 'β-lactam-β-lactamase inhibitor,' 'KPC,' 'NDM,' 'metallo-β-lactamase,' 'ceftazidime-avibactam,' 'meropenem-vaborbactam,' 'imipenem-cilastatin-relebactam,' 'cefiderocol,' 'eravacycline,' 'plazomicin,' 'taniborbactam,' 'zidebactam,' and 'nacubactam.'

EXPERT OPINION

Novel antimicrobials for CRE infections have been developed, most notably the β-lactam-β-lactamase inhibitor combinations, though treatment options for infections with metallo-β-lactamase producing Enterobacterales remain few and have limitations. Development of antibiotics with activity against metallo-β-lactamase producing Enterobacterales is eagerly awaited, and there are promising new compounds in clinical trials. Finally, more clinical research is needed to optimize and individualize treatment approaches, which will help guide antimicrobial stewardship initiatives aimed at reducing the spread of CRE and development of further resistance.

Meropenem-Vaborbactam Activity against U.S. Multidrug-Resistant Enterobacterales Strains, Including Carbapenem-Resistant Isolates

Carbapenems are a common first-line therapy for serious Gram-negative infections, but carbapenem-resistant Enterobacterales (CRE) isolates have become an urgent health concern. Klebsiella pneumoniae serine carbapenemases (KPCs) now have been disseminated worldwide and are endemic in many hospitals globally. Isolates producing metallo-β-lactamases (MBLs) or class D OXA-48 carbapenemases are also increasingly common in Europe, although they are less common in the United States. Meropenem-vaborbactam is a combination of the carbapenem meropenem and vaborbactam, which is a β-lactamase inhibitor with activity against serine carbapenemases, including KPC-producing isolates. We examined the susceptibility of U.S. multidrug-resistant (MDR) isolates to meropenem-vaborbactam. A total of 1,697 MDR Enterobacterales isolates were collected in 31 U.S. medical centers in 2016 to 2020. Susceptibility testing was performed using the Clinical and Laboratory Standards Institute (CLSI) broth microdilution method. Whole-genome sequencing was performed for all CRE strains (MIC values of >2 mg/L for imipenem or meropenem). The rate of susceptibility of all MDR Enterobacterales strains to meropenem-vaborbactam was 99.1%, and 86.2% of the isolates were susceptible to meropenem. There were 222 CRE isolates (13.1%). KPC was the most common carbapenemase (81.1%). Thirteen CRE isolates produced NDM (n = 7), VIM (n = 3), and/or OXA-48-like (n = 4) carbapenemases; 29 CRE isolates (13.1%) had no detected carbapenemase. The rate of susceptibility of all CRE strains to meropenem-vaborbactam was 93.2%, and the rate of susceptibility of the KPC-producing isolates to meropenem-vaborbactam was 98.9%. The primary carbapenemase in the United States continues to be KPC, while MBL and OXA-48-like carbapenemases remain uncommon. Overall, the rate of susceptibility of these U.S. MDR organisms to meropenem-vaborbactam was 99.1%, indicating that meropenem-vaborbactam is a valuable treatment option for Gram-negative infections caused by U.S. MDR organisms. IMPORTANCE Carbapenems are a common first-line therapy for serious Gram-negative infections, but CRE isolates have become an urgent health concern. Meropenem-vaborbactam is a combination of the carbapenem meropenem and vaborbactam, which is a β-lactamase inhibitor with activity against serine carbapenemases, including KPC-producing isolates. We examined the susceptibility of U.S. MDR Gram-negative isolates to meropenem-vaborbactam. A total of 1,697 U.S. MDR Enterobacterales isolates collected in 2016 to 2020 were tested. Susceptibility testing was performed using the CLSI broth microdilution method. Whole-genome sequencing was performed for all CRE strains (MIC values of >2 mg/L for imipenem or meropenem). The rate of susceptibility of all MDR Enterobacterales strains to meropenem-vaborbactam was 99.1%, and 86.2% of the isolates were susceptible to meropenem. A total of 13.1% of the isolates were CRE strains, and KPC was the most common carbapenemase. Overall, the rate of susceptibility of these U.S. MDR organisms to meropenem-vaborbactam indicates that meropenem-vaborbactam is a valuable treatment option for Gram-negative infections caused by U.S. MDR Gram-negative pathogens.