Functional and structural analyses of amino acid sequence variation in PDC β-lactamase reveal different mechanistic pathways toward cefiderocol resistance in .

A wide variety of clinically observed amino acid alterations in the chromosomal β-lactamase AmpC (-derived cephalosporinase [PDC]) are associated with increased resistance to cefepime, ceftolozane/tazobactam, or ceftazidime/avibactam, but their impact on cefiderocol resistance is unclear. We took advantage of a previously engineered collection of wild-type (PAO1) and iron uptake-deficient (PAO Δ) isolates producing 19 distinct PDC variants with substitutions in key catalytic regions. While most variants had moderate effects on cefiderocol minimum inhibitory concentrations compared to PDC-1, the E219K (Ω-loop) and L293P (helix H10) variants significantly affected cefiderocol activity.

The novel polymyxin analogue SPR206 exhibits higher activity than colistin against both colistin-susceptible and colistin-resistant strains of .

Colistin resistance is increasing globally and complicates treatments of infections. The next-generation polymyxin SPR206 shows potent activity against multidrug-resistant Gram-negative pathogens with low toxicity. SPR206 exhibited higher activity against colistin-susceptible and colistin-resistant strains (MIC/MIC = 0.

Rapid prediction of carbapenemases in by imipenem/relebactam and MALDI-TOF MS.

is a major nosocomial pathogen commonly involved in multidrug-resistant (MDR) infections that are very difficult to treat. Imipenem/relebactam is a new carbapenem/β-lactamase inhibitor combination with robust activity against . However, resistance is increasingly reported, and rapid detection is, therefore, crucial so that appropriate treatments can be prescribed.

Advancements in the fight against globally distributed OXA-48 carbapenemase: evaluating the new generation of carbapenemase inhibitors.

Carbapenemase OXA-48 and its variants pose a serious threat to the development of effective treatments for bacterial infections. OXA-48-producing Enterobacterales are the most prevalent carbapenemase-producing bacteria in large parts of the world. Although these bacteria exhibit low-level carbapenem resistance , the infections they cause are challenging to treat with conventional therapies, owing to their spread and complex detection in clinical settings.

Activity and resistance mechanisms of the third generation tetracyclines tigecycline, eravacycline and omadacycline against nationwide Spanish collections of carbapenemase-producing Enterobacterales and Acinetobacter baumannii.

Introduction: The rise in multidrug-resistant bacteria challenges clinical microbiology. Tigecycline, eravacycline, and omadacycline show promise against carbapenem-resistant Enterobacterales and Acinetobacter baumannii. This study evaluates their activity and resistance mechanisms.

Mutant prevention concentrations, resistance evolution dynamics, and mechanisms of resistance to imipenem and imipenem/relebactam in carbapenem-susceptible isolates showing ceftazidime/avibactam resistance.

carbapenemase (KPC) variants selected during ceftazidime/avibactam treatment usually develop susceptibility to carbapenems and carbapenem/β-lactamase inhibitors, such as imipenem and imipenem/relebactam. We analyzed imipenem and imipenem/relebactam single-step mutant frequencies, resistance development trajectories and differentially selected resistance mechanisms using two representative isolates that had developed ceftazidime/avibactam resistance during therapy (ST512/KPC-31 and ST258/KPC-35). Mutant frequencies and mutant prevention concentrations were measured in Mueller-Hinton agar plates containing incremental concentrations of imipenem or imipenem/relebactam.

Impact of transferable β-lactamases and intrinsic AmpC amino acid substitutions on the activity of cefiderocol against wild-type and iron uptake-deficient mutants of Pseudomonas aeruginosa.

Objectives: We aimed to analyse the interplay between impaired iron uptake and β-lactamases on cefiderocol resistance in Pseudomonas aeruginosa.

Methods: Thirty-one transferable β-lactamases and 16 intrinsic P. aeruginosa AmpC (PDC) variants were cloned and expressed in wild-type (PAO1) and iron uptake-deficient (PAO ΔpiuC) P.

Impact of chromosomally encoded resistance mechanisms and transferable β-lactamases on the activity of cefiderocol and innovative β-lactam/β-lactamase inhibitor combinations against Pseudomonas aeruginosa.

Objectives: We aimed to compare the stability of the newly developed β-lactams (cefiderocol) and β-lactam/β-lactamase inhibitor combinations (ceftazidime/avibactam, ceftolozane/tazobactam, aztreonam/avibactam, cefepime/taniborbactam, cefepime/zidebactam, imipenem/relebactam, meropenem/vaborbactam, meropenem/nacubactam and meropenem/xeruborbactam) against the most clinically relevant mechanisms of mutational and transferable β-lactam resistance in Pseudomonas aeruginosa.

Methods: We screened a collection of 61 P. aeruginosa PAO1 derivatives.

Epidemiology, resistance genomics and susceptibility of species: results from the 2020 Spanish nationwide surveillance study.

BackgroundAs increasing antibiotic resistance in poses a global healthcare challenge, understanding its evolution is crucial for effective control strategies.AimWe aimed to evaluate the epidemiology, antimicrobial susceptibility and main resistance mechanisms of spp. in Spain in 2020, and to explore temporal trends of .

In vitro development of imipenem/relebactam resistance in KPC-producing Klebsiella pneumoniae involves multiple mutations including OmpK36 disruption and KPC modification.

Objectives: In order to inform and anticipate potential strategies aimed at combating KPC-producing Klebsiella pneumoniae infections, we analysed imipenem/relebactam and ceftazidime/avibactam single-step mutant frequencies, resistance development trajectories, differentially selected resistance mechanisms and their associated fitness cost using four representative high-risk K. pneumoniae clones.

Methods: Mutant frequencies and mutant preventive concentrations were determined using agar plates containing incremental concentrations of β-lactam/β-lactamase inhibitor.

Antimicrobial Activity of Cefiderocol against the Carbapenemase-Producing Enterobacter cloacae Complex and Characterization of Reduced Susceptibility Associated with Metallo-β-Lactamase VIM-1.

Emergence of cefiderocol resistance among carbapenemase-producing Enterobacterales, particularly those in the Enterobacter cloacae complex (ECC), is becoming of alarming concern; however, the mechanistic basis of this phenomenon remains poorly understood. We describe the acquisition of VIM-1-mediated reduced cefiderocol susceptibility (MICs 0.5 to 4 mg/L) in a collection of 54 carbapenemase-producing isolates belonging to the ECC.

Simultaneous and divergent evolution of resistance to cephalosporin/β-lactamase inhibitor combinations and imipenem/relebactam following ceftazidime/avibactam treatment of MDR Pseudomonas aeruginosa infections.

Objectives: To describe and characterize the emergence of resistance to ceftolozane/tazobactam, ceftazidime/avibactam and imipenem/relebactam in a patient receiving ceftazidime/avibactam treatment for an MDR Pseudomonas aeruginosa CNS infection.

Methods: One baseline (PA1) and two post-exposure (PA2 and PA3) isolates obtained before and during treatment of a nosocomial P. aeruginosa meningoventriculitis were evaluated.

Activity of aztreonam in combination with novel β-lactamase inhibitors against metallo-β-lactamase-producing Enterobacterales from Spain.

Metallo-β-lactamase (MBL)-producing Enterobacterales are of particular concern because they are widely disseminated and difficult to treat, being resistant to almost all β-lactam antibiotics. Aztreonam is not hydrolysed by MBLs but is labile to serine β-lactamases (SBLs), which are usually co-produced by MBL-producing Enterobacterales. This study investigated the activity of aztreonam in combination with novel β-lactamase inhibitors (BLIs) against a national multi-centre study collection of strains co-producing MBLs and SBLs.

Activity of cefiderocol, imipenem/relebactam, cefepime/taniborbactam and cefepime/zidebactam against ceftolozane/tazobactam- and ceftazidime/avibactam-resistant Pseudomonas aeruginosa.

Objectives: To evaluate the activity of cefiderocol, imipenem/relebactam, cefepime/taniborbactam and cefepime/zidebactam against a clinical and laboratory collection of ceftolozane/tazobactam- and ceftazidime/avibactam-resistant Pseudomonas aeruginosa β-lactamase mutants.

Methods: The activity of cefiderocol, imipenem/relebactam, cefepime/taniborbactam, cefepime/zidebactam and comparators was evaluated against a collection of 30 molecularly characterized ceftolozane/tazobactam- and/or ceftazidime/avibactam-resistant P. aeruginosa isolates from patients previously treated with cephalosporins.

Selection of AmpC β-Lactamase Variants and Metallo-β-Lactamases Leading to Ceftolozane/Tazobactam and Ceftazidime/Avibactam Resistance during Treatment of MDR/XDR Pseudomonas aeruginosa Infections.

Infections caused by ceftolozane-tazobactam and ceftazidime-avibactam-resistant P. aeruginosa infections are an emerging concern. We aimed to analyze the underlying ceftolozane-tazobactam and ceftazidime-avibactam resistance mechanisms in all multidrug-resistant or extensively drug-resistant (MDR/XDR) P.