Imipenem/Cilastatin/Relebactam Alone and in Combination against Pseudomonas aeruginosa in the In Vitro Pharmacodynamic Model

Differential frequency of persister cells in clinically derived isolates of Pseudomonas aeruginosa after exposure to cefiderocol and ceftolozane/tazobactam

BACKGROUND

Bacterial persistence is a phenomenon whereby a subpopulation of bacteria survive high concentrations of an active antibiotic in the absence of phenotypic alterations. Persisters are associated with chronic and recurrent infections for pathogens including Pseudomonas aeruginosa. Understanding persister profiles of newer antibiotics such as cefiderocol and ceftolozane/tazobactam against P. aeruginosa is warranted as these agents generally target difficult-to-treat infections.

METHODS

Persister formation was assessed using in vitro assays against nine clinical P. aeruginosa isolates exposed to cefiderocol or ceftolozane/tazobactam. Quantitative persister assays were performed using a stationary phase of bacteria challenged with 10-fold MIC drug concentrations. Persisters were quantitated as the percent persisters at 24 h and the log ratio (LR) difference in AUC for cfu for each antibiotic alone compared with growth control. The tolerance disc test (TDtest) was used to qualitatively detect persisters.

RESULTS

Percent persisters at 24 h was lower with cefiderocol compared with ceftolozane/tazobactam for six of the nine tested isolates. Eight of the nine isolates had higher reduction in LR for cefiderocol groups, suggesting an overall higher and more rapid bacterial reduction in cefiderocol groups. For cefiderocol, five of the nine tested isolates lacked regrowth after replacement with glucose disc, suggesting no persistence via the TDtest. For ceftolozane/tazobactam, three isolates lacked persister formation.

CONCLUSIONS

Cefiderocol resulted in less bacterial persistence relative to ceftolozane/tazobactam against nine clinical P. aeruginosa isolates. Cefiderocol's siderophore mechanism may be advantageous over ceftolozane/tazobactam through enhanced anti-persister effects. Clinical correlation of these findings is warranted as persisters can lead to antibiotic resistance and treatment failure.

Antimicrobial activity of Geranyl acetate against cell wall synthesis proteins of P. aeruginosa and S. aureus using molecular docking and simulation

Incidences of Methicillin-Resistant Staphylococcus aureus and Multi-Drug Resistant Pseudomonas aeruginosa causing skin and soft tissue infections are becoming more prevalent due to repeated mutations and changes in the environment. Coriandrum sativum, a well-known Indian herbal medicinal plant, is shown to have antioxidant, antibacterial, and anti-inflammatory activity. This comparative study focuses on the molecular docking (PyRx v0.9.8) of ligand binding domains of WbpE Aminotransferase involved in O-antigen assembly in Pseudomonas aeruginosa (3NU7) and Beta-Lactamase found in Staphylococcus aureus (1BLC) with selected phytocompounds of Coriandrum sativum along with a known binder and a clinical reference drug. This was followed by molecular dynamics simulation studies (GROMACS v2019.4) for the docked complexes (with Geranyl acetate) with the best binding affinities (-23.4304 kJ/mol with Beta-Lactamase and -28.4512 kJ/mol with WbpE Aminotransferase) and maximum hydrogen bonds. Molecular dynamics simulation studies for both the proteins demonstrated that the complex with Geranyl acetate showed stability comparable to the complex with reference drug observed via Root Mean Square Deviation (RMSD), Root Mean Square Fluctuation (RMSF) and H-bond analyses. Changes in the secondary structural elements indicated that Geranyl acetate could possibly cause improper functioning of WbpE Aminotransferase leading to disrupted cell wall formation. Further, MM/PBSA analyses showed significant binding affinity of Geranyl acetate with WbpE Aminotransferase and Beta-Lactamase. This study aims to provide rationale for further studies of Coriandrum sativum as an antimicrobial, and to contextualise the results in the current scenario of growing antimicrobial resistance. HIGHLIGHTSPhytoconstituents present in Coriandrum sativum show significant binding affinity to the proteins in Pseudomonas aeruginosa and Staphylococcus aureus.Geranyl acetate exhibited the highest binding affinity with WbpE Aminotransferase involved in O-antigen assembly in Pseudomonas aeruginosa (PDB ID:3NU7) and Beta-Lactamase found in Staphylococcus aureus (PDB ID: 1BLC)Molecular dynamics simulation analyses show that the phytoconstituent, Geranyl acetate has an effect similar to the clinical reference drug, thus exhibiting potential antibacterial activity.Communicated by Ramaswamy H. Sarma.

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.

Chenodeoxycholic Acid-Amikacin Combination Enhances Eradication of Staphylococcus aureus

The rise of antibiotic resistance and dearth of novel antibiotics have posed a serious health crisis worldwide. In this study, we screened a combination of antibiotics and nonantibiotics providing a viable strategy to solve this issue by broadening the antimicrobial spectrum. We found that chenodeoxycholic acid (CDCA), a cholic acid derivative of the traditional Chinese medicine (TCM) Tanreqing (TRQ), synergizes with amikacin against Staphylococcus aureus in vitro, and this synergistic killing was effective against diverse methicillin-resistant S. aureus (MRSA) variants, including small-colony variants (SCVs), biofilm strains, and persisters. The CDCA-amikacin combination protects a mouse model from S. aureus infections. Mechanistically, CDCA increases the uptake of aminoglycosides in a proton motive force-dependent manner by dissipating the chemical potential and potentiates reactive oxygen species (ROS) generation by inhibiting superoxide dismutase activity. This work highlights the potential use of TCM components in treating S. aureus-associated infections and extend the use of aminoglycosides in eradicating Gram-positive pathogens. IMPORTANCE Multidrug resistance (MDR) is spreading globally with increasing speed. The search for new antibiotics is one of the key strategies in the fight against MDR. Antibiotic resistance breakers that may or may not have direct antibacterial action and can either be coadministered or conjugated with other antibiotics are being studied. To better expand the antibacterial spectrum of certain antibiotics, we identified one component from a traditional Chinese medicine, Tanreqing (TRQ), that increased the activity of aminoglycosides. We found that this so-called agent, chenodeoxycholic acid (CDCA), sensitizes Staphylococcus aureus to aminoglycoside killing and protects a mouse model from S. aureus infections. CDCA increases the uptake of aminoglycosides in a proton motive force-dependent manner by dissipating the chemical potential and potentiates ROS generation by inhibiting superoxide dismutase activity in S. aureus. Our work highlights the potential use of TCM or its effective components, such as CDCA, in treating antibiotic resistance-associated infections.

Treatment of severe multi-drug resistant Pseudomonas aeruginosa infections

Pseudomonas aeruginosa is the microorganism most frequently involved in the main ICU-acquired infections, with special importance in ventilator associated pneumonia. Its importance lies, in addition to its high incidence in critically ill patients, in the severity of the infections it causes and in the difficulty of its antimicrobial treatment, directly related to the high percentage of resistance to antibiotics classically considered first-line. New active antibiotics have recently been developed against Pseudomonas aeruginosa, even against multi-drug resistant strains. This review analyzes both the differential characteristics of Pseudomonas aeruginosa infections and the new therapeutic options, focusing on multi-drug resistant Pseudomonas aeruginosa.

Treatment of carbapenem-resistant Pseudomonas aeruginosa infections: a case for cefiderocol

INTRODUCTION

Carbapenem-resistant (CR) Pseudomonas aeruginosa infections constitute a serious clinical threat globally. Patients are often critically ill and/or immunocompromised. Antibiotic options are limited and are currently centered on beta-lactam-beta-lactamase inhibitor (BL-BLI) combinations and the siderophore cephalosporin cefiderocol.

AREAS COVERED

This article reviews the mechanisms of P. aeruginosa resistance and their potential impact on the activity of current treatment options, along with evidence for the clinical efficacy of BL-BLI combinations in P. aeruginosa infections, some of which specifically target infections due to CR organisms. The preclinical and clinical evidence supporting cefiderocol as a treatment option for P. aeruginosa involving infections is also reviewed.

EXPERT OPINION

Cefiderocol is active against most known P. aeruginosa mechanisms mediating carbapenem resistance. It is stable against different serine- and metallo-beta-lactamases, and, due to its iron channel-dependent uptake mechanism, is not impacted by porin channel loss. Furthermore, the periplasmic level of cefiderocol is not affected by upregulated efflux pumps. The potential for on-treatment resistance development currently appears to be low, although more clinical data are required. Information from surveillance programs, real-world compassionate use, and clinical studies demonstrate that cefiderocol is an important treatment option for CR P. aeruginosa infections.

New Perspectives on Antimicrobial Agents: Imipenem-Relebactam

Imipenem (IMI)/cilastatin/relebactam (REL) (I/R) is a novel β-lactam/β-lactamase inhibitor combination with expanded microbiologic activity against carbapenem-resistant non-Morganellaceae Enterobacterales (CR-NME) and difficult-to-treat (DTR) Pseudomonas aeruginosa. Relebactam, a bicyclic diazabicyclooctane, has no direct antimicrobial activity but provides reliable inhibition of many Ambler class A and class C enzymes. It is currently approved for the treatment of adult patients with hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia (HABP/VABP) and those with complicated urinary tract infections (cUTIs) and complicated intra-abdominal infections (cIAIs) when limited or no alternative treatments are available. Given the number of recently approved β-lactams with expanded activity against highly resistant Gram-negative pathogens, this review summarizes the published literature on I/R, with a focus on its similar and distinguishing characteristics relative to those of other recently approved agents. Overall, available data support its use for the treatment of patients with HABP/VABP, cUTI, and cIAI due to CR-NME and DTR P. aeruginosa. Data indicate that I/R retains some activity against CR-NME and DTR P. aeruginosa isolates that are resistant to the newer β-lactams and vice versa, suggesting that susceptibility testing be performed for all the newer agents to determine optimal treatment options for patients with CR-NME and DTR P. aeruginosa infections. Further comparative PK/PD and clinical studies are warranted to determine the optimal role of I/R, alone and in combination, for the treatment of patients with highly resistant Gram-negative infections. Until further data are available, I/R is a potential treatment for patients with CR-NME and DTR P. aeruginosa infections when the benefits outweigh the risks.

Imipenem/Cilastatin/Relebactam: A Review in Gram-Negative Bacterial Infections

Imipenem/cilastatin/relebactam (Recarbrio™) is an intravenously administered combination of the carbapenem imipenem, the renal dehydropeptidase-I inhibitor cilastatin, and the novel β-lactamase inhibitor relebactam. Relebactam is a potent inhibitor of class A and class C β-lactamases, conferring imipenem activity against many imipenem-nonsusceptible strains. Imipenem/cilastatin/relebactam is approved in the USA and EU for the treatment of hospital-acquired bacterial pneumonia (HABP) and ventilator-associated bacterial pneumonia (VABP) in adults and other gram-negative infections, including complicated urinary tract infections (cUTIs) [including pyelonephritis] and complicated intra-abdominal infections (cIAIs), in adults with limited or no alternative treatment options. In pivotal phase II and III trials, imipenem/cilastatin/relebactam was noninferior to piperacillin/tazobactam in patients with HABP/VABP and to imipenem/cilastatin in patients with cUTIs and cIAIs. It was also effective in imipenem-nonsusceptible infections. Imipenem/cilastatin/relebactam was generally well tolerated, with a safety profile consistent with that of imipenem/cilastatin. Available evidence indicates that imipenem/cilastatin/relebactam is an effective and generally well tolerated option for gram-negative infections in adults, including critically ill and/or high-risk patients, and a potential therapy for infections caused by carbapenem-resistant pathogens.