In vitro activity of ceftazidime/avibactam, cefiderocol, meropenem/vaborbactam and imipenem/relebactam against clinical strains of the Stenotrophomonas maltophilia complex.

BACKGROUND: Infections caused by Stenotrophomonas maltophilia and related species are increasing worldwide. Unfortunately, treatment options are limited, whereas the antimicrobial resistance is increasing. METHODS: We included clinical isolates identified as S. maltophilia by VITEK 2 Compact. Ceftazidime/avibactam, meropenem/vaborbactam, imipenem/relebactam, cefiderocol, quinolones, and tetracycline family members were evaluated by broth microdilution method and compared with first-line treatment drugs. Minimum inhibitory concentrations (MICs) were reported for all antibiotics. We sequenced the Whole Genome of cefiderocol resistant strains (CRSs) and annotated their genes associated with cefiderocol resistance (GACR). Presumptive phylogenetic identification employing the 16S marker was performed. RESULTS: One hundred and one clinical strains were evaluated, sulfamethoxazole and trimethoprim, levofloxacin and minocycline showed susceptibilities of 99.01%, 95.04% and 100% respectively. Ceftazidime was the antibiotic with the highest percentage of resistance in all samples (77.22%). Five strains were resistant to cefiderocol exhibiting MIC values ≥ 2 µg/mL (4.95%). The ß-lactamase inhibitors meropenem/vaborbactam and imipenem/relebactam, failed to inhibit S. maltophilia, preserving both MIC50 and MIC90 ≥64 µg/mL. Ceftazidime/avibactam restored the activity of ceftazidime decreasing the MIC range. Tigecycline had the lowest MIC range, MIC50 and MIC90. Phylogeny based on 16S rRNA allowed to identify to cefiderocol resistant strains as putative species clustered into Stenotrophomonas maltophilia complex (Smc). In these strains, we detected GARCs such as Mutiple Drug Resistance (MDR) efflux pumps, L1-type ß-lactamases, iron transporters and type-1 fimbriae. CONCLUSION: Antimicrobial resistance to first-line treatment is low. The in vitro activity of new ß-lactamase inhibitors against S. maltophilia is poor, but avibactam may be a potential option. Cefiderocol could be considered as a potential new option for multidrug resistant infections. Tetracyclines had the best in vitro activity of all antibiotics evaluated.

In vitro activity of meropenem-vaborbactam plus aztreonam against metallo-ß-lactamase-producing Klebsiella pneumoniae.

We evaluated the in vitro activity of meropenem-vaborbactam plus aztreonam (MEV-ATM) against 140 metallo-ß-lactamase (MBL)-producing Klebsiella pneumoniae isolates. Among them, 25 isolates (17.9%) displayed minimum inhibitory concentrations (MIC) ≥ 8 µg/mL, while 112 (80.0%) had MIC ≤ 2 µg/mL. Genomic analysis and subsequent gene cloning experiments revealed OmpK36 134-135GD-insertion and increased carbapenemase gene (blaNDM-1 and blaOXA-48-like) copy numbers are the main factors responsible for MEV-ATM non-susceptibility. Notably, MEV-ATM is actively against aztreonam-avibactam-resistant mutants due to CMY-16 mutations.

High ceftazidime-avibactam resistance among carbapenem-resistant Enterobacter species: Data from the Antimicrobial Testing Leadership and Surveillance (ATLAS) programme, 2014-2021.

OBJECTIVES: Trends in the susceptibility to ceftazidime-avibactam (CZA) and tigecycline (TGC) among Enterobacter species from different geographic areas are unknown.This study aimed to analyse the trends in CZA and TGC susceptibility changes across different continents from 2014 to 2021 utilizing Antimicrobial Testing Leadership and Surveillance (ATLAS) data. METHODS: A total of 23 669 isolates of Enterobacter species were collected over an 8-y period. RESULTS: The overall non-susceptibility rate of Enterobacter isolates to both CZA and TGC was 3.2%. India (16.5%), Guatemala (15.4%), and the Philippines (13.1%) exhibited the highest resistance to CZA. The increase in CZA resistance rates was particularly evident in Asia, with an increase from 4.0% to 8.3%, and in Latin America, from 1.5% to 5%. The non-susceptibility rate for TGC mildly increased in Africa/Middle East but decreased in other continents during the study period. The overall rate of carbapenem resistance increased from 2.9% in 2014-2017 to 4.3% in 2018-2021. Among carbapenem-resistant Enterobacter isolates, the CZA resistance rate was highest in Asia (87.4%), followed by Europe (69.2%) and Africa/Middle East (60.8%). Among the 380 Enterobacter isolates resistant to CZA and carbapenem, the most common genotype of carbapenemase genes was blaNDM (59.2%), followed by blaVIM (24.2%), blaOXA (4.2%), blaIMP (1.1%), and blaKPC (1.1%). The susceptibility of carbapenem-resistant Enterobacter to TGC remained high, with an overall susceptibility rate of 90%. CONCLUSIONS: The heterogeneous distribution of CZA resistance rates among different geographical regions highlights the divergent therapeutic options for drug-resistant Enterobacter species.

Global trends in nonsusceptibility rates of Escherichia coli isolates to meropenem and ceftazidime/avibactam: Data from the Antimicrobial Testing Leadership and Surveillance (ATLAS) programme, 2014-21.

OBJECTIVE: To understand the global changes in the nonsusceptibility rates of Escherichia coli to meropenem and ceftazidime-avibactam (CZA), we conducted a study using the Antimicrobial Testing Leadership and Surveillance database. METHODS: A total of 49 394 E. coli isolates were collected during the 8-year study period. RESULT: The countries with the highest nonsusceptible rates for meropenem were India (16.6%), followed by Pakistan (6.7%), Ukraine (5.4%), Qatar (5.3%), and Guatemala (3.2%). For CZA, the nonsusceptible rate was highest in India (15.6%), followed by Qatar (4.0%), Guatemala (3.9%), China (2.6%), and Thailand (2.5%). During the study period, the nonsusceptible rates of meropenem and CZA in E. coli increased in Asia, Latin America, and Africa/Middle East. Isolates from the medical ICU (odds ratio [OR], 4.62) and surgical ICU (OR, 3.98) were associated with a higher risk of CZA nonsusceptible rates. Compared to intestinal specimens, respiratory and genitourinary specimens had the highest OR (2.32 and 2.17) associated with CZA resistance. Further analysis of carbapenemase distribution showed an increase in the percentage of blaNDM-positive isolates and a decrease in blaKPC-positive isolates worldwide, especially in Latin America. Additionally, we observed a gradual decline in the prevalence of blaOXA-positive E. coli without concomitant carriage of metallo-ß-lactamase genes in the worldwide surveillance. CONCLUSIONS: Further surveillance is necessary to determine whether blaNDM -positive E. coli (i.e., CZA-resistant isolates) is increasing and leading to more superbugs spreading worldwide.

Activity of aztreonam-avibactam against Enterobacterales resistant to recently approved beta-lactamase inhibitor combinations collected in Europe, Latin America, and the Asia-Pacific Region (2020-2022).

BACKGROUND: Aztreonam-avibactam is under clinical development for treatment of infections caused by carbapenem-resistant Enterobacterales (CRE), especially those resistant to recently approved ß-lactamase inhibitor combinations (BLICs). OBJECTIVES: To evaluate a large collection of CRE isolates, including those non-susceptible to ceftazidime-avibactam, meropenem-vaborbactam, and/or imipenem-relebactam. METHODS: Overall, 24 580 Enterobacterales isolates were consecutively collected (1/patient) in 2020-2022 from 64 medical centres located in Western Europe (W-EU), Eastern Europe (E-EU), Latin America (LATAM), and the Asia-Pacific region (APAC). Of those, 1016 (4.1%) were CRE. Isolates were susceptibility tested by broth microdilution. CRE isolates were screened for carbapenemase genes by whole genome sequencing. RESULTS: Aztreonam-avibactam inhibited 99.6% of CREs at ≤8 mg/L. Ceftazidime-avibactam, meropenem-vaborbactam, and imipenem-relebactam were active against 64.6%, 57.4%, and 50.7% of CRE isolates, respectively; most of the non-susceptible isolates carried metallo-beta-lactamases. Aztreonam-avibactam was active against ≥98.9% of isolates non-susceptible to these BLICs. The activity of these BLICs varied by region, with highest susceptibility rates observed in W-EU (76.9% for ceftazidime-avibactam, 72.5% for meropenem-vaborbactam, 63.8% for imipenem-relebactam) and the lowest susceptibility rates identified in the APAC region (39.9% for ceftazidime-avibactam, 37.8% for meropenem-vaborbactam, and 27.5% for imipenem-relebactam). The most common carbapenemase types overall were KPC (44.6% of CREs), NDM (29.9%), and OXA-48-like (16.0%). KPC predominated in LATAM (64.1% of CREs in the region) and W-EU (61.1%). MBL occurrence was highest in APAC (59.5% of CREs in the region), followed by LATAM (34.0%), E-EU (28.9%), and W-EU (23.6%). CONCLUSIONS: Aztreonam-avibactam demonstrated potent activity against CRE isolates resistant to ceftazidime-avibactam, meropenem-vaborbactam, and/or imipenem-relebactam independent of the carbapenemase produced.

Effect of modification of penicillin-binding protein 3 on susceptibility to ceftazidime-avibactam, imipenem-relebactam, meropenem-vaborbactam, aztreonam-avibactam, cefepime-taniborbactam, and cefiderocol of Escherichia coli strains producing broad-spectrum ß-lactamases.

The impact of penicillin-binding protein 3 (PBP3) modifications that may be identified in Escherichia coli was evaluated with respect to susceptibility to ß-lactam/ß-lactamase inhibitor combinations including ceftazidime-avibactam, imipenem-relebactam, meropenem-vaborbactam, aztreonam-avibactam, cefepime-taniborbactam, and to cefiderocol. A large series of E. coli recombinant strains producing broad-spectrum ß-lactamases was evaluated. While imipenem-relebactam showed a similar activity regardless of the PBP3 background, susceptibility to other molecules tested was affected at various levels. This was particularly the case for ceftazidime-avibactam, aztreonam-avibactam, and cefepime-taniborbactam.

The pharmacokinetics/pharmacodynamics of ceftazidime/avibactam for central nervous system infections caused by carbapenem-resistant Gram-negatives: a prospective study.

OBJECTIVES: To describe the pharmacokinetics/pharmacodynamics (PK/PD) of ceftazidime/avibactam in critically ill patients with CNS infections. METHODS: A prospective study of critically ill patients with CNS infections who were treated with ceftazidime/avibactam and the steady-state concentration (Css) of ceftazidime/avibactam in serum and/or CSF was conducted between August 2020 and May 2023. The relationship between PK/PD goal achievement, microbial eradication and the clinical efficacy of ceftazidime/avibactam was evaluated. RESULTS: Seven patients were finally included. The ceftazidime/avibactam target attainment in plasma was optimal for three, quasi-optimal for one and suboptimal for three. In three patients with CSF drug concentrations measured, ceftazidime/avibactam target attainment in CSF was 100% (3/3), which was optimal. The AUCCSF/serum values were 0.59, 0.44 and 0.35 for ceftazidime and 0.57, 0.53 and 0.51 for avibactam. Of the seven patients, 100% (7/7) were treated effectively, 71.4% (5/7) achieved microbiological eradication, 85.7% (6/7) survived and 14.3% (1/7) did not survive. CONCLUSIONS: The limited clinical data suggest that ceftazidime/avibactam is effective in the treatment of CNS infections caused by MDR Gram-negative bacilli (MDR-GNB), can achieve the ideal drug concentration of CSF, and has good blood-brain barrier penetration.

The mechanism of ceftazidime and cefiderocol hydrolysis by D179Y variants of KPC carbapenemases is similar and involves the formation of a long-lived covalent intermediate.

Klebsiella pneumoniae carbapenemase (KPC) variants have been described that confer resistance to both ceftazidime-avibactam and cefiderocol. Of these, KPC-33 and KPC-31 are D179Y-containing variants derived from KPC-2 and KPC-3, respectively. To better understand this atypical phenotype, the catalytic mechanism of ceftazidime and cefiderocol hydrolysis by KPC-33 and KPC-31 as well as the ancestral KPC-2 and KPC-3 enzymes was studied. Steady-state kinetics showed that the D179Y substitution in either KPC-2 or KPC-3 is associated with a large decrease in both kcat and KM such that kcat/KM values were largely unchanged for both ceftazidime and cefiderocol substrates. A decrease in both kcat and KM is consistent with a decreased and rate-limiting deacylation step. We explored this hypothesis by performing pre-steady-state kinetics and showed that the acylation step is rate-limiting for KPC-2 and KPC-3 for both ceftazidime and cefiderocol hydrolysis. In contrast, we observed a burst of acyl-enzyme formation followed by a slow steady-state rate for the D179Y variants of KPC-2 and KPC-3 with either ceftazidime or cefiderocol, indicating that deacylation of the covalent intermediate is the rate-limiting step for catalysis. Finally, we show that the low KM value for ceftazidime or cefiderocol hydrolysis of the D179Y variants is not an indication of tight binding affinity for the substrates but rather is a reflection of the deacylation reaction becoming rate-limiting. Thus, the hydrolysis mechanism of ceftazidime and cefiderocol by the D179Y variants is very similar and involves the formation of a long-lived covalent intermediate that is associated with resistance to the drugs.

Meropenem-ANT3310, a unique ß-lactam-ß-lactamase inhibitor combination with expanded antibacterial spectrum against Gram-negative pathogens including carbapenem-resistant Acinetobacter baumannii.

ANT3310 is a novel broad-spectrum diazabicyclooctane serine ß-lactamase inhibitor being developed in combination with meropenem (MEM) for the treatment of serious infections in hospitalized patients where carbapenem-resistant Gram-negative pathogens are expected. In this study, we evaluated the in vitro antibacterial activity of MEM in the presence of ANT3310 at 8 µg/mL against global clinical isolates that included Acinetobacter baumannii (n = 905), carbapenem-resistant Enterobacterales (CRE), carrying either oxacillinase (OXA) (n = 252) or Klebsiella pneumoniae carbapenemase (KPC) (n = 180) carbapenemases, and Pseudomonas aeruginosa (n = 502). MEM was poorly active against A. baumannii, as were MEM-vaborbactam, ceftazidime-avibactam, aztreonam-avibactam, cefepime-taniborbactam, cefepime-zidebactam, and imipenem-relebactam (MIC90 values of ≥32 µg/mL). On the other hand, MEM-ANT3310 displayed an MIC90 value of 4 µg/mL, similar to that observed with sulbactam-durlobactam, a drug developed to specifically treat A. baumannii infections. ANT3310 (8 µg/mL) additionally restored the activity of MEM against OXA- and KPC-producing CREs decreasing MEM MIC90 values from >32 µg/mL to 0.25 and 0.5 µg/mL, respectively. The combination of 8 µg/mL of both MEM and ANT3310 prevented growth of 97.5% of A. baumannii and 100% of OXA- and KPC-positive CREs, with ~90% of P. aeruginosa isolates also displaying MEM MICs ≤8 µg/mL. Furthermore, MEM-ANT3310 was efficacious in both thigh and lung murine infection models with OXA-23 A. baumannii. This study demonstrates the potent in vitro activity of the MEM-ANT3310 combination against both carbapenem-resistant A. baumannii and Enterobacterales clinical isolates, a key differentiator to other ß-lactam/ß-lactamase combinations.

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-ß-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,' 'ß-lactam-ß-lactamase inhibitor,' 'KPC,' 'NDM,' 'metallo-ß-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 ß-lactam-ß-lactamase inhibitor combinations, though treatment options for infections with metallo-ß-lactamase producing Enterobacterales remain few and have limitations. Development of antibiotics with activity against metallo-ß-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.

Concomitant Resistance to Cefiderocol and Ceftazidime/Avibactam in Two Carbapenemase-Producing Klebsiella pneumoniae Isolates from Two Lung Transplant Patients.

In this study, we present two cases of Klebsiella pneumoniae, one KPC-33- and one NDM-1-producing, showing resistance to cefiderocol and ceftazidime/avibactam, collected in the intensive care unit of a hospital in Northern Italy from two patients who had recently undergone lung transplantation. Whole-genome sequencing was performed to investigate the molecular features of these strains.

Emergence of cefiderocol resistance during ceftazidime/avibactam treatment caused by a large genomic deletion, including ampD and piuCD genes, in Pseudomonas aeruginosa.

We report the emergence of cefiderocol resistance during the treatment of a ST312 Pseudomonas aeruginosa respiratory infection with ceftazidime/avibactam. whole genome sequencing (WGS) revealed that resistance was caused by a large genomic deletion, including PiuDC (iron transport system) and AmpD (ampC negative regulator), driven by the integration of phage DNA. Thus, our findings alert that this type of deletion could be an efficient (two mechanisms in one step) specific cefiderocol resistance mechanism that might occur nonspecifically upon treatment with ß-lactams that select for AmpC overexpression.

Therapeutic drug monitoring of ceftazidime/avibactam: why one leg is not enough to run.

BACKGROUND: Therapeutic drug monitoring (TDM) is becoming an increasingly recommended approach for assessing optimal pharmacokinetic/pharmacodynamic (PK/PD) target attainment of ceftazidime/avibactam. Some authors hypothesized that the PK/PD target attainment of ceftazidime/avibactam could be assessed by means of the TDM of solely ceftazidime, since avibactam concentrations might be extrapolated based on the fixed 4:1 ceftazidime-to-avibactam ratio present in the vial. The reliability of this hypothesis could be called into question if a wide interindividual variability in the ceftazidime-to-avibactam ratio would exist among patients. This study aimed to assess the distribution of the individual ceftazidime-to-avibactam ratios in relation to renal function in a cohort of adult patients who were treated with continuous infusion ceftazidime/avibactam and underwent TDM of both ceftazidime and avibactam. METHODS: Individual ceftazidime-to-avibactam ratio was calculated at each TDM assessment. Receiving operating characteristics (ROC) curve analysis was performed for testing the potential impact of renal function on ceftazidime-to-avibactam ratio variability. RESULTS: A total of 188 TDM assessments were collected from 107 patients. The ceftazidime-to-avibactam ratios ranged from 1.29:1 to 13.46:1. Seventy-seven out of 188 ceftazidime-to-avibactam ratios (41.0%) were >5:1, and 36 (19.1%) were >6:1. Patients without renal dysfunction had significantly higher proportions of ceftazidime-to-avibactam ratio >5:1 (59.3% versus 23.8%; P < 0.001) and >6:1 (32.1% versus 6.3%; P < 0.001) compared with those with mild-to-severe renal dysfunction. CONCLUSIONS: The findings may strengthen the contention that for properly assessing the PK/PD target attainment of ceftazidime/avibactam, both ceftazidime and avibactam concentrations should be measured, given the unpredictability of the ceftazidime-to-avibactam ratio occurring among patients.

Moving towards a standardized definition of antimicrobial resistance: a comparison of the antimicrobial susceptibility profile of difficult-to-treat resistance (DTR) versus multidrug-resistant (MDR) Pseudomonas aeruginosa clinical isolates (CANWARD, 2016-2021).

Pseudomonas aeruginosa clinical isolates demonstrating difficult-to-treat resistance (DTR) and multidrug-resistant (MDR) phenotypes were evaluated by broth microdilution. Susceptibility was lower for all antimicrobials versus DTR relative to MDR isolates. Ceftazidime-avibactam, ceftolozane-tazobactam, and imipenem-relebactam susceptibility was 35.9%, 64.5%, and 47.0% for DTR isolates and 60.5%, 80.6%, and 71.5% for MDR isolates.

Functional features of KPC-109, a novel 270-loop KPC-3 mutant mediating resistance to avibactam-based ß-lactamase inhibitor combinations and cefiderocol.

OBJECTIVES: To investigate a ceftazidime/avibactam (CZA)-resistant Klebsiella pneumoniae (NE368), isolated from a patient exposed to CZA, expressing a novel K. pneumoniae carbapenemase (KPC)-3 variant (KPC-109). METHODS: Antimicrobial susceptibility testing was performed by reference broth microdilution. Whole-genome sequencing (WGS) analysis of NE368 was performed combining a short- and long-reads approach (Illumina and Oxford Nanopore Technologies). Functional characterization of KPC-109 was performed to investigate the impact of KPC-109 production on the ß-lactam resistance phenotype of various Escherichia coli and Klebsiella pneumoniae strains, including derivatives of K. pneumoniae with OmpK35 and OmpK36 porin alterations. Horizontal transfer of the KPC-109-encoding plasmid was investigated by conjugation and transformation experiments. RESULTS: K. pneumoniae NE368 was isolated from a patient after repeated CZA exposure, and showed resistance to CZA, fluoroquinolones, piperacillin/tazobactam, expanded-spectrum cephalosporins, amikacin, carbapenems and cefiderocol. WGS revealed the presence of a large chimeric plasmid of original structure (pKPN-NE368), encoding a novel 270-loop mutated KPC-3 variant (KPC-109; ins_270_KYNKDD). KPC-109 production mediated resistance/decreased susceptibility to avibactam-based combinations (with ceftazidime, cefepime and aztreonam) and cefiderocol, with a trade-off on carbapenem resistance. However, in the presence of porin alterations commonly encountered in high-risk clonal lineages of K. pneumoniae, KPC-109 was also able to confer clinical-level resistance to carbapenems. Resistance of NE368 to cefiderocol was likely contributed by KPC-109 production acting in concert with a mutated EnvZ sensor kinase. The KPC-109-encoding plasmid did not appear to be conjugative. CONCLUSIONS: These findings expand current knowledge about the diversity of emerging KPC enzyme variants with 270-loop alterations that can be encountered in the clinical setting.

A descriptive pharmacokinetic/pharmacodynamic analysis of ceftazidime-avibactam in a case series of critically ill patients with augmented renal clearance.

To describe the pharmacokinetics/pharmacodynamics (PK/PD) of a 2 h infusion of ceftazidime-avibactam (CAZ-AVI) in critically ill patients with augmented renal clearance (ARC). A retrospective review of all critically ill patients with ARC who were treated with CAZ-AVI between August 2020 and May 2023 was conducted. Patients whose 12-h creatinine clearance prior to CAZ-AVI treatment and steady-state concentration (Css) of CAZ-AVI were both monitored were enrolled. The free fraction (fCss) of CAZ-AVI was calculated from Css. The joint PK/PD targets of CAZ-AVI were considered optimal when a Css/minimum inhibitory concentration (MIC) ratio for CAZ ≥4 (equivalent to 100% fT > 4 MIC) and a Css/CT ratio of AVI >1 (equivalent to 100% fT > CT 4.0 mg/L) were reached simultaneously, quasioptimal when only one of the two targets was reached, and suboptimal when neither target was reached. The relationship between PK/PD goal achievement, microbial eradication and the clinical efficacy of CAZ-AVI was evaluated. Four patients were included. Only one patient achieved optimal joint PK/PD targets, while the other three reached suboptimal targets. The patient with optimal PK/PD targets achieved microbiological eradication, while the other three patients did not, but all four patients achieved good clinical efficacy. Standard dosages may not enable most critically ill patients with ARC to reach the optimal joint PK/PD targets of CAZ-AVI. Optimal drug dose adjustment of CAZ-AVI in ARC patients requires dynamic drug concentration monitoring.

In vitro activity of aztreonam-avibactam and comparators against Metallo-ß-Lactamase-producing Enterobacterales from ATLAS Global Surveillance Program, 2016-2020.

OBJECTIVES: Metallo-ß-lactamase (MBL)-producing Enterobacterales are a major challenge worldwide due to limited treatment options. Aztreonam-avibactam (ATM-AVI), which is under clinical development, has shown activity against MBL-positive isolates. This study evaluated the prevalence of MBL producers and the nature of enzymes among a global collection of clinical isolates of Enterobacterales from the Antimicrobial Testing Leadership and Surveillance program (ATLAS) surveillance program (2016-2020), and the antimicrobial activity of ATM-AVI and comparators against this collection. METHODS: Non-duplicate clinical isolates of Enterobacterales (N = 106 686) collected across 63 countries were analysed. Antimicrobial susceptibility was performed using broth microdilution. Minimum inhibitory concentrations (MICs) were interpreted using Clinical and Laboratory Standards Institute and European Committee on Antimicrobial Susceptibility Testing breakpoints. Provisional pharmacokinetic/pharmacodynamic breakpoint of ≤8 mg/L was considered for ATM-AVI. ß-lactamase genes were characterized by polymerase chain reaction and sequencing. The Cochran Armitage Trend test was used to determine significant trends in percentage of isolates over time. RESULTS: Overall, MBL-positive isolates were 1.6% of total Enterobacterales isolates globally, with a significant increasing trend observed over time, globally and across regions (P < 0.05). New Delhi MBL (NDM) was the most common MBL (83.3%). ATM-AVI demonstrated potent activity against MBL-positive isolates (MIC ≤8 mg/L: 99.4% isolates inhibited; MIC90, 1 mg/L). Consistent activity was also noted across different regions. Potent activity was demonstrated against different NDM variants and MBL-positive isolates co-carrying other carbapenemases (98.1% and 99.7% isolates inhibited at ≤8 mg/L, respectively). About 0.6% MBL-positive isolates (10/1707) had MICs >8 mg/L for ATM-AVI. CONCLUSION: ATM-AVI demonstrated potent activity against MBL-positive isolates, including NDM variants and MBL-positive isolates co-carrying other carbapenemases, and may represent a good option for treating infections caused by MBL-positive Enterobacterales.

Aromatic Diboronic Acids as Effective KPC/AmpC Inhibitors.

Over 30 compounds, including para-, meta-, and ortho-phenylenediboronic acids, ortho-substituted phenylboronic acids, benzenetriboronic acids, di- and triboronated thiophenes, and pyridine derivatives were investigated as potential ß-lactamase inhibitors. The highest activity against KPC-type carbapenemases was found for ortho-phenylenediboronic acid 3a, which at the concentration of 8/4 mg/L reduced carbapenems' MICs up to 16/8-fold, respectively. Checkerboard assays revealed strong synergy between carbapenems and 3a with the fractional inhibitory concentrations indices of 0.1-0.32. The nitrocefin hydrolysis test and the whole cell assay with E. coli DH5α transformant carrying blaKPC-3 proved KPC enzyme being its molecular target. para-Phenylenediboronic acids efficiently potentiated carbapenems against KPC-producers and ceftazidime against AmpC-producers, whereas meta-phenylenediboronic acids enhanced only ceftazidime activity against the latter ones. Finally, the statistical analysis confirmed that ortho-phenylenediboronic acids act synergistically with carbapenems significantly stronger than other groups. Since the obtained phenylenediboronic compounds are not toxic to MRC-5 human fibroblasts at the tested concentrations, they can be considered promising scaffolds for the future development of novel KPC/AmpC inhibitors. The complexation of KPC-2 with the most representative isomeric phenylenediboronic acids 1a, 2a, and 3a was modeled by quantum mechanics/molecular mechanics calculations. Compound 3a reached the most effective configuration enabling covalent binding to the catalytic Ser70 residue.