Affinity of the new cephalosporin CXA-101 to penicillin-binding proteins of Pseudomonas aeruginosa

Resistance to ceftazidime-avibactam and other new β-lactams in Pseudomonas aeruginosa clinical isolates: a multi-center surveillance study

New β-lactam-β-lactamase inhibitor combinations represent last-resort antibiotics to treat infections caused by multidrug-resistant Pseudomonas aeruginosa. Carbapenemase gene acquisition can limit their spectrum of activity, and reports of resistance toward these new molecules are increasing. In this multi-center study, we evaluated the prevalence of resistance to ceftazidime-avibactam (CZA) and comparators among P. aeruginosa clinical isolates from bloodstream infections, hospital-acquired or ventilator-associated pneumonia, and urinary tract infections, circulating in Southern Italy. We also investigated the clonality and content of relevant β-lactam resistance mechanisms of CZA-resistant (CZAR) isolates. A total of 120 P. aeruginosa isolates were collected. CZA was among the most active β-lactams, retaining susceptibility in the 81.7% of cases, preceded by cefiderocol (95.8%) and followed by ceftolozane-tazobactam (79.2%), meropenem-vaborbactam (76.1%), imipenem-relebactam (75%), and aztreonam (69.6%). Among non-β-lactams, colistin and amikacin were active against 100% and 85.8% of isolates respectively. In CZAR strains subjected to whole-genome sequencing (n = 18), resistance was mainly due to the expression of metallo-β-lactamases (66.6% VIM-type and 5.5% FIM-1), followed by PER-1 (16.6%) and GES-1 (5.5%) extended-spectrum β-lactamases, mostly carried by international high-risk clones (ST111 and ST235). Of note, two strains producing the PER-1 enzyme were resistant to all β-lactams, including cefiderocol. In conclusion, the CZA resistance rate among P. aeruginosa clinical isolates in Southern Italy remained low. CZAR isolates were mostly metallo-β-lactamases producers and belonging to ST111 and ST253 epidemic clones. It is important to implement robust surveillance systems to monitor emergence of new resistance mechanisms and to limit the spread of P. aeruginosa high-risk clones.

IMPORTANCE

Multidrug-resistant Pseudomonas aeruginosa infections are a growing threat due to the limited therapeutic options available. Ceftazidime-avibactam (CZA) is among the last-resort antibiotics for the treatment of difficult-to-treat P. aeruginosa infections, although resistance due to the acquisition of transferable β-lactamase genes is increasing. With this work, we report that CZA represents a highly active antipseudomonal β-lactam compound (after cefiderocol), and that metallo-β-lactamases (VIM-type) and extended-spectrum β-lactamases (GES and PER-type) production is the major factor underlying CZA resistance in isolates from Southern Italian hospitals. In addition, we reported that such resistance mechanisms were mainly carried by the international high-risk clones ST111 and ST235.

Current and emerging strategies to curb antibiotic-resistant urinary tract infections

Rising rates of antibiotic resistance in uropathogenic bacteria compromise patient outcomes and prolong hospital stays. Consequently, new strategies are needed to prevent and control the spread of antibiotic resistance in uropathogenic bacteria. Over the past two decades, sizeable clinical efforts and research advances have changed urinary tract infection (UTI) treatment and prevention strategies to conserve antibiotic use. The emergence of antimicrobial stewardship, policies from national societies, and the development of new antimicrobials have shaped modern UTI practices. Future UTI management practices could be driven by the evolution of antimicrobial stewardship, improved and readily available diagnostics, and an improved understanding of how the microbiome affects UTI. Forthcoming UTI treatment and prevention strategies could employ novel bactericidal compounds, combinations of new and classic antimicrobials that enhance bacterial killing, medications that prevent bacterial attachment to uroepithelial cells, repurposing drugs, and vaccines to curtail the rising rates of antibiotic resistance in uropathogenic bacteria and improve outcomes in people with UTI.

Novel Beta Lactam Antibiotics for the Treatment of Multidrug-Resistant Gram-Negative Infections in Children: A Narrative Review

Infections due to carbapenem-resistant Enterobacterales (CRE) are increasingly prevalent in children and are associated with poor clinical outcomes, especially in critically ill patients. Novel beta lactam antibiotics, including ceftolozane-tazobactam, ceftazidime-avibactam, meropenem-vaborbactam, imipenem-cilastatin-relebactam, and cefiderocol, have been released in recent years to face the emerging challenge of multidrug-resistant (MDR) Gram-negative bacteria. Nonetheless, several novel agents lack pediatric indications approved by the Food and Drug Administration (FDA) and the European Medicine Agency (EMA), leading to uncertain pediatric-specific treatment strategies and uncertain dosing regimens in the pediatric population. In this narrative review we have summarized the available clinical and pharmacological data, current limitations and future prospects of novel beta lactam antibiotics in the pediatric population.

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.

Comparison of In Vitro Activity of Ceftazidime-Avibactam and Imipenem-Relebactam against Clinical Isolates of Pseudomonas aeruginosa

The role of novel β-lactam/β-lactamase inhibitor combinations in ceftazidime-nonsusceptible (CAZ-NS) and imipenem-nonsusceptible (IPM-NS) Pseudomonas aeruginosa has not been fully elucidated. This study evaluated the in vitro activity of novel β-lactam/β-lactamase inhibitor combinations against Pseudomonas aeruginosa clinical isolates, determined how avibactam restored ceftazidime activity, and compared the activity of ceftazidime-avibactam (CZA) and imipenem-relebactam (IMR) against KPC-producing P. aeruginosa. Similar high susceptibility rates for CZA, IMR, and ceftolozane-tazobactam (88.9% to 89.8%) were found for 596 P. aeruginosa clinical isolates from 11 hospitals in China, and a higher susceptibility rate to ceftazidime than imipenem was observed (73.5% versus 63.1%). For CAZ-NS and IPM-NS isolates, susceptibility rates for CZA, ceftolozane-tazobactam, and IMR were 61.5% (75/122), 54.9% (67/122), and 51.6% (63/122), respectively. For CAZ-NS, IPM-NS but CZA-susceptible isolates, 34.7% (26/75) harbored acquired β-lactamases with KPC-2 predominant (n = 19), and 45.3% (34/75) presented overexpression of chromosomal β-lactamase ampC. Among 22 isolates carrying KPC-2 carbapenemase alone, susceptibility rates to CZA and IMR were 86.4% (19/22) and 9.1% (2/22), respectively. Notably, 95% (19/20) of IMR-nonsusceptible isolates had an inactivating mutation of oprD gene. In conclusion, CZA, ceftolozane-tazobactam, and IMR exhibit high activity against P. aeruginosa, and CZA is more active than IMR against CAZ-NS and IPM-NS isolates as well as KPC-producing P. aeruginosa. Avibactam overcomes ceftazidime resistance engendered by KPC-2 enzyme and overexpressed AmpC. IMPORTANCE The emergence of antimicrobial resistance poses a particular challenge globally, and the concept of P. aeruginosa with "difficult-to-treat" resistance (DTR-P. aeruginosa) was proposed. Here, P. aeruginosa clinical isolates were highly susceptible to three β-lactamase inhibitor combinations, CZA, IMR, and ceftolozane-tazobactam. The combination of KPC-2 enzyme and nonfunctional porin OprD contributed to IMR resistance in P. aeruginosa, and CZA was more active than IMR in fighting against KPC-2-producing P. aeruginosa. CZA also showed good activity against CAZ-NS and IPM-NS P. aeruginosa, primarily by inhibiting KPC-2 enzyme and overproduced AmpC, supporting the clinical use of CZA in the treatment of infections caused by DTR-P. aeruginosa.

Ceftolozane/Tazobactam Probability of Target Attainment in Patients With Hospital-Acquired or Ventilator-Associated Bacterial Pneumonia

Probability of target attainment (PTA) analyses were conducted to support the recommended ceftolozane/tazobactam dosing regimens, adjusted for renal function, in patients with hospital-acquired/ventilator-associated bacterial pneumonia (HABP/VABP). Previously published population pharmacokinetic models describing the disposition of ceftolozane and tazobactam in plasma and epithelial lining fluid (ELF) in patients with HABP/VABP were used to simulate ceftolozane and tazobactam concentration-time profiles in plasma and ELF over the course of 14 days. The simulations were conducted for patients with normal renal function and for patients receiving adjusted doses for mild, moderate, and severe renal impairment. PTA was calculated using established pharmacokinetic/pharmacodynamic targets for ceftolozane and tazobactam. Across renal function groups, plasma PTA was 100% for ceftolozane and >99% for tazobactam; ELF PTA was >99% for ceftolozane and >87% for tazobactam. These results provided support for the currently recommended ceftolozane/tazobactam dosing regimens for HABP/VABP, which were efficacious and well tolerated in the Ceftolozane-Tazobactam Versus Meropenem for Treatment of Nosocomial Pneumonia (ASPECT-NP) trial.

Review of novel β-lactams and β-lactam/β-lactamase inhibitor combinations with implications for pediatric use

Antimicrobial resistance continues to surmount increasing concern globally, and treatment of difficult-to-treat (DTR) Pseudomonas aeruginosa, carbapenem-resistant (CR) Acinetobacter baumannii (CRAB), and CR Enterobacterales (CRE) remains a challenge for clinicians. Although previously rare, the incidence of multidrug-resistant (MDR) and CR infections in pediatric patients has increased drastically in the last decade and is associated with increased morbidity and mortality. To combat this issue, 14 novel antibiotics, including three β-lactam/novel β-lactamase inhibitor combinations (βL-βLIs) and two novel β-lactams (βLs), have received approval from the United States Food and Drug Administration since 2010. Improving clinician understanding of the utility of these novel therapies is imperative to improve judicious decision-making and prevent societal regression to a pre-penicillin era. In this review, we summarize the pharmacokinetic/pharmacodynamic (PK/PD) properties, clinical efficacy and safety data, dosing considerations, and subsequent role in therapy for ceftazidime-avibactam (CAZ-AVI), meropenem-vaborbactam (MER-VAB), imipenem-cilastatin-relebactam (IMI-REL), ceftolozane-tazobactam (TOL-TAZ), and cefiderocol in pediatric patients.

The efficacy and safety of ceftolozane-tazobactam in the treatment of GNB infections: a systematic review and meta-analysis of clinical studies

BACKGROUND

Ceftolozane-tazobactam is a novel cephalosporin/β-lactamase inhibitor combination with activity against Gram-negative bacteria (GNB). We aimed to comprehensively evaluate the clinical efficacy and safety of ceftolozane-tazobactam in treating GNB infections in adult patients.

RESEARCH DESIGN AND METHODS

PubMed, Embase, and Cochrane databases were retrieved until August 2022. Randomized trials and non-randomized controlled studies evaluating ceftolozane-tazobactam and its comparators in adult patients with GNB infections were included.

RESULTS

A total of 13 studies were included. Overall, patients receiving ceftolozane-tazobactam had significant advantages in clinical cure (odds ratio [OR], 1.62; 95% CI, 1.05-2.51) and microbiological eradication (OR, 1.43; 95% CI, 1.19-1.71), especially in Pseudomonas aeruginosa-infected patients. Ceftolozane-tazobactam had a significant advantage in clinical success or microbial eradication compared with polymyxin/aminoglycosides (PL/AG) or levofloxacin. There were no significant differences in adverse events (AEs), Clostridium difficile infection (CDI), and mortality between ceftolozane-tazobactam and comparators. Notably, ceftolozane-tazobactam showed a significantly lower risk of acute kidney injury compared with PL/AG.

CONCLUSIONS

Ceftolozane-tazobactam showed excellent clinical and microbiological efficacy in treating GNB, especially P. aeruginosa-induced infections. The overall safety profile of ceftolozane-tazobactam was comparable to other antimicrobials, with no increased risk of CDI and obvious advantage over antibacterial agents with high nephrotoxicity.

Probability of Target Attainment Analyses to Inform Ceftolozane/Tazobactam Dosing Regimens for Patients With Hospital-Acquired or Ventilator-Associated Bacterial Pneumonia and End-Stage Renal Disease Receiving Intermittent Hemodialysis

ASPECT-NP, a phase 3 trial of ceftolozane/tazobactam in hospital-acquired/ventilator-associated bacterial pneumonia (HABP/VABP), excluded patients with end-stage renal disease (ESRD). A modeling/simulation approach was undertaken to inform optimal dosing in this population, using previously developed ceftolozane and tazobactam population pharmacokinetic models informed by data from 16 clinical studies. Stochastic simulations were performed using NONMEM to support dose justification. Probability of target attainment (PTA) simulations in plasma and epithelial lining fluid were conducted using a 14-day treatment, with hemodialysis every other weekday for a high-dose (4X), middle-dose (3X), or low-dose (2X) regimen, where X was the recommended dose in patients with complicated intra-abdominal infection/complicated urinary tract infection and ESRD (500 mg/250 mg ceftolozane/tazobactam loading dose and 100 mg/50 mg ceftolozane/tazobactam maintenance dose administered by 1-hour infusion every 8 hours). PTA was determined using established pharmacokinetic/pharmacodynamic targets: ceftolozane, 30% of the interdose interval (8 hours) in which free ceftolozane concentration exceeded the minimum inhibitory concentration value of 4 µg/mL; tazobactam, 20% of the interdose interval in which free tazobactam concentration exceeded 1 µg/mL. Plasma PTA was >90% for both agents for all 3 regimens. Plasma ceftolozane exposures at the high-dose regimen exceeded those from phase 3 study experience. Epithelial lining fluid PTA was >90% for high- and middle-dose regimens but was <80% for tazobactam on dialysis days at the low-dose regimen. For patients with HABP/VABP and ESRD requiring intermittent hemodialysis, the middle-dose regimen of 1.5 g/0.75 g ceftolozane/tazobactam loading + 300 mg/150 mg maintenance every 8 hours by 1-hour infusion is recommended.

The Role of Colistin in the Era of New β-Lactam/β-Lactamase Inhibitor Combinations

With the current crisis related to the emergence of carbapenem-resistant Gram-negative bacteria (CR-GNB), classical treatment approaches with so-called “old-fashion antibiotics” are generally unsatisfactory. Newly approved β-lactam/β-lactamase inhibitors (BLBLIs) should be considered as the first-line treatment options for carbapenem-resistant Enterobacterales (CRE) and carbapenem-resistant Pseudomonas aeruginosa (CRPA) infections. However, colistin can be prescribed for uncomplicated lower urinary tract infections caused by CR-GNB by relying on its pharmacokinetic and pharmacodynamic properties. Similarly, colistin can still be regarded as an alternative therapy for infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) until new and effective agents are approved. Using colistin in combination regimens (i.e., including at least two in vitro active agents) can be considered in CRAB infections, and CRE infections with high risk of mortality. In conclusion, new BLBLIs have largely replaced colistin for the treatment of CR-GNB infections. Nevertheless, colistin may be needed for the treatment of CRAB infections and in the setting where the new BLBLIs are currently unavailable. In addition, with the advent of rapid diagnostic methods and novel antimicrobials, the application of personalized medicine has gained significant importance in the treatment of CRE infections.

New antibiotics for the treatment of nonfermenting Gram-negative bacteria

PURPOSE OF REVIEW

To discuss the current literature on novel agents for the treatment of carbapenem-resistant nonfermenting Gram-negative bacteria (NF-GNB) infections.

RECENT FINDINGS

Some novel agents have recently become available that are expected to replace classical polymyxins as the first-line options for the treatment of carbapenem-resistant NF-GNB infections.

SUMMARY

In this narrative review, we provide a brief overview of the differential activity of various recently approved agents against NF-GNB most encountered in the daily clinical practice, as well as the results from phase-3 randomized clinical trials and large postapproval observational studies, with special focus on NF-GNB. Since resistance to novel agents has already been reported, the use of novel agents needs to be optimized, based on their differential activity (not only in terms of targeted bacteria, but also of resistance determinants), the local microbiological epidemiology, and the most updated pharmacokinetic/pharmacodynamic data. Large real-life experiences remain of crucial importance for further refining the optimal treatment of NF-GNB infections in the daily clinical practice.

Advances in novel antibiotics to treat multidrug-resistant gram-negative bacterial infections

Antimicrobial resistance is a growing threat to public health and an increasingly common problem for acute care physicians to confront. Several novel antibiotics have been approved in the past decade to combat these infections; however, physicians may be unfamiliar with how to appropriately utilize them. The purpose of this review is to evaluate novel antibiotics active against resistant gram-negative bacteria and highlight clinical information regarding their use in the acute care setting. This review focuses on novel antibiotics useful in the treatment of infections caused by resistant gram-negative organisms that may be seen in the acute care setting. These novel antibiotics include ceftolozane/tazobactam, ceftazidime/avibactam, meropenem/vaborbactam, imipenem/cilistatin/relebactam, cefiderocol, plazomicin, eravacycline, and omadacycline. Acute care physicians should be familiar with these novel antibiotics so they can utilize them appropriately.

Molecular Basis of AmpC β-Lactamase Induction by Avibactam in Pseudomonas aeruginosa: PBP Occupancy, Live Cell Binding Dynamics and Impact on Resistant Clinical Isolates Harboring PDC-X Variants

Avibactam belongs to the new class of diazabicyclooctane β-lactamase inhibitors. Its inhibitory spectrum includes class A, C and D enzymes, including P. aeruginosa AmpC. Nonetheless, recent reports have revealed strain-dependent avibactam AmpC induction. In the present work, we wanted to assess the mechanistic basis underlying AmpC induction and determine if derepressed PDC-X mutated enzymes from ceftazidime/avibactam-resistant clinical isolates were further inducible. We determined avibactam concentrations that half-maximally inhibited (IC₅₀) bocillin FL binding. Inducer β-lactams were also studied as comparators. Live cells’ time-course penicillin-binding proteins (PBPs) occupancy of avibactam was studied. To assess the ampC induction capacity of avibactam and comparators, qRT-PCR was performed in wild-type PAO1, PBP4, triple PBP4, 5/6 and 7 knockout derivatives and two ceftazidime/avibactam-susceptible/resistant XDR clinical isolates belonging to the epidemic high-risk clone ST175. PBP4 inhibition was observed for avibactam and β-lactam comparators. Induction capacity was consistently correlated with PBP4 binding affinity. Outer membrane permeability-limited PBP4 binding was observed in the live cells’ assay. As expected, imipenem and cefoxitin showed strong induction in PAO1, especially for carbapenem; avibactam induction was conversely weaker. Overall, the inducer effect was less remarkable in ampC-derepressed mutants and nonetheless absent upon avibactam exposure in the clinical isolates harboring mutated AmpC variants and their parental strains.

Bacterial membrane vesicles from Acinetobacter baumannii induced by ceftazidime are more virulent than those induced by imipenem

Patients with Acinetobacter baumannii bacteremia treated with antipseudomonal cephalosporins showed higher 14-day mortality than patients treated with antipseudomonal carbapenems. We hypothesized that the bacterial membrane vesicles (BMVs) induced by antipseudomonal cephalosporins are more virulent than BMVs induced by antipseudomonal carbapenems.

To simulate the clinical condition with inadequate antimicrobial treatment, carbapenem-resistant A. baumannii was treated with ceftazidime (an antipseudomonal cephalosporin) or imipenem (an antipseudomonal carbapenem) at 1/2 the minimum inhibitory concentration. BMVs and BMV-carried lipopolysaccharide were measured by nanoparticle tracking analysis and western blotting, respectively. Cytokine expression in RAW264.7 macrophages or mice serum induced by the BMVs was determined by ELISA, fluorescent bead-based immunoassay or western blotting. The virulence of the BMVs was assessed in mice. Liquid chromatography tandem-mass spectrometry was used to determine the protein contents of the BMVs.

We found that ceftazidime induced a higher number of BMVs (CAZ-BMV), which carried more LPS, and induced higher expression levels of iNOS, IL-1β, and IL-6 in macrophages, higher expression of many cytokines in mice, more neutrophil infiltration in lung interstitium, and higher mortality in mice than imipenem-induced BMVs (IMP-BMV). When adjusted to same amount of LPS, CAZ-BMV still led to higher mortality than IMP-BMV. Proteomic analysis revealed different protein contents in CAZ-BMV and IMP-BMV. In conclusion, A. baumannii BMVs induced by ceftazidime are more virulent than BMVs induced by imipenem.

Evaluating Cefiderocol in the Treatment of Multidrug-Resistant Gram-Negative Bacilli: A Review of the Emerging Data

Infections due to multidrug-resistant Gram-negative bacteria (MDR-GNB), especially when carbapenem resistant, have been very difficult to manage in the last fifteen years, owing to the paucity of dependable therapeutic options. Cefiderocol is a siderophore cephalosporin recently approved by the Food and Drug Administration (FDA) and European Medicines Agency (EMA) that may have the potential to fill some of the remaining gaps in the treatment of MDR-GNB infections. Among others, cefiderocol demonstrated in vitro activity against carbapenem-resistant Acinetobacter baumannii and metallo-β-lactamases producers. Clinical data from both registrative studies and post-marketing experiences are essential to confirm whether these promises from in vitro studies could readily translate into clinical practice, as well as to delineate the precise place in therapy for cefiderocol for the treatment of MDR-GNB in the near future. Because of its unique potential, it is essential to provide both randomized controlled trials (RCT) and real-life data to improve the ability of clinicians to exploit its benefit in both empirical and targeted treatment of MDR-GNB infections. In this narrative review, we discuss the emerging data from pivotal RCT and initial real-life experiences on the use of cefiderocol for the treatment of MDR-GNB infections.

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).

Emerging Strategies to Combat β-Lactamase Producing ESKAPE Pathogens

Since the discovery of penicillin by Alexander Fleming in 1929 as a therapeutic agent against staphylococci, β-lactam antibiotics (BLAs) remained the most successful antibiotic classes against the majority of bacterial strains, reaching a percentage of 65% of all medical prescriptions. Unfortunately, the emergence and diversification of β-lactamases pose indefinite health issues, limiting the clinical effectiveness of all current BLAs. One solution is to develop β-lactamase inhibitors (BLIs) capable of restoring the activity of β-lactam drugs. In this review, we will briefly present the older and new BLAs classes, their mechanisms of action, and an update of the BLIs capable of restoring the activity of β-lactam drugs against ESKAPE (Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) pathogens. Subsequently, we will discuss several promising alternative approaches such as bacteriophages, antimicrobial peptides, nanoparticles, CRISPR (clustered regularly interspaced short palindromic repeats) cas technology, or vaccination developed to limit antimicrobial resistance in this endless fight against Gram-negative pathogens.

Healthcare Resource Utilization of Ceftolozane/Tazobactam Versus Meropenem for Ventilated Nosocomial Pneumonia from the Randomized, Controlled, Double-Blind ASPECT-NP Trial

Introduction

Hospital-acquired and ventilator-associated bacterial pneumonia (HABP and VABP) are associated with significant healthcare resource utilization (HCRU). This a priori, exploratory, secondary analysis from the ASPECT-NP clinical trial evaluated resource utilization among patients with ventilated HABP (vHABP)/VABP treated with ceftolozane/tazobactam or meropenem.

Methods

This analysis used data from the randomized, double-blind, noninferiority phase 3 ASPECT-NP trial of patients with vHABP/VABP randomized to receive ceftolozane/tazobactam 3 g (ceftolozane 2 g/tazobactam 1 g) or meropenem 1 g for 8–14 days. Day 28 outcomes included hospital length of stay (LOS), intensive care unit (ICU) LOS, and time to mechanical ventilation extubation in the microbiological intention-to-treat (mITT) population and in an HCRU population. The HCRU population, a subset of patients from the mITT population that were alive at day 28, was used to remove resource use bias influenced by mortality rates.

Results

Ceftolozane/tazobactam-treated versus meropenem-treated patients, respectively, had fewer deaths (20.1% vs. 25.5%), fewer hospital discharges (30.7% vs. 32.4%), and higher ICU discharges (60.0% vs. 58.3%) and extubations (51.9% vs. 48.2%) by day 28. In the HCRU population, adjusted LOS differences (95% confidence intervals) for ceftolozane/tazobactam compared with meropenem were 0.1 (− 1.4 to 1.6) hospitalization days, − 1.4 (− 2.9 to 0.2) ICU days, and − 0.9 (− 2.4 to 0.7) mechanical ventilation days. Patterns were similar among the VABP and Pseudomonas aeruginosa subgroups.

Conclusion

Similar 28-day resource utilization outcomes were observed between ceftolozane/tazobactam and meropenem in the mITT population of patients from ASPECT-NP with vHABP/VABP due to gram-negative pathogens. ASPECT-NP was not powered to detect differences in resource utilization outcomes between treatment groups; however, numerical differences in ICU LOS and duration of mechanical ventilation were noted. Further study is needed to assess resource utilization in the real-world practice setting, especially among patients excluded from ASPECT-NP, including those with resistant P. aeruginosa infections.

Trial Registrations

ClinicalTrials.gov: NCT02070757, registered February 25, 2014; EudraCT: 2012-002862-11.

Electronic supplementary material

The online version of this article (10.1007/s40121-020-00343-0) contains supplementary material, which is available to authorized users.

Efficacy and mechanism of actions of natural antimicrobial drugs

Microbial infections have significantly increased over the last decades, and the mortality rates remain unacceptably high. The emergence of new resistance patterns and the spread of new viruses challenge the eradication of infectious diseases. The declining efficacy of antimicrobial drugs has become a global public health problem. Natural products derived from natural sources, such as plants, animals, and microorganisms, have significant efficacy for the treatment of infectious diseases accompanied by less adverse effects, synergy, and ability to overcome drug resistance. As the Chinese female scientist Youyou Tu received the Nobel Prize for the antimalarial drug artemisinin, antimicrobial drugs developed from Traditional Chinese Medicine are expected to receive increasing attention again. This review summarizes the antimicrobial agents derived from natural products approved for nearly 20 years and describes their efficacy and mode of action. The aim of this unit is to review the current status of antimicrobial drugs from natural products in order to increase the value of natural products as a source of novel drug candidates for infectious diseases.

Modifiable Risk Factors for the Emergence of Ceftolozane-Tazobactam Resistance

BACKGROUND

Ceftolozane-tazobactam (TOL-TAZ) affords broad coverage against Pseudomonas aeruginosa. Regrettably, TOL-TAZ resistance has been reported. We sought to identify modifiable risk factors that may reduce the emergence of TOL-TAZ resistance.

METHODS

Twenty-eight patients infected with carbapenem-resistant P. aeruginosa isolates susceptible to TOL-TAZ and treated with ≥72 hours of TOL-TAZ between January 2018 and December 2019 in Baltimore, Maryland were included. The 28 patients had P. aeruginosa isolates available both before and after TOL-TAZ exposure. Cases were defined as patients with at least a four-fold increase in P. aeruginosa TOL-TAZ MICs after exposure to TOL-TAZ. Independent risk factors for the emergence of TOL-TAZ resistance comparing cases and controls were investigated using logistic regression. Whole genome sequencing of paired isolates was used to identify mechanisms of resistance that emerged during TOL-TAZ exposure.

RESULTS

Fourteen patients (50%) had P. aeruginosa isolates which developed high-level TOL-TAZ resistance (i.e., cases). Cases were more likely to have inadequate source control (29% vs. 0%, p=0.04) and were less likely to receive TOL-TAZ as an extended 3-hour infusion (0% vs. 29%; p=0.04). Eighty-six percent of index isolates susceptible to ceftazidime-avibactam (CAZ-AVI) had subsequent P. aeruginosa isolates with high-level resistance to CAZ-AVI, after TOL-TAZ exposure. Common mutations identified in TOL-TAZ resistant isolates involved AmpC, a known binding site for both ceftolozane and ceftazidime, and DNA polymerase.

CONCLUSION

Due to our small sample size, our results remain exploratory but forewarn of the potential emergence of TOL-TAZ resistance during therapy and suggest extending TOL-TAZ infusions may be protective. Larger studies are needed to investigate this association.

Ceftolozane and tazobactam for the treatment of hospital acquired pneumonia

INTRODUCTION

Patients admitted to hospitals are at risk of developing nosocomial infections. These types of infections typically occur in immune-compromised patients. Furthermore, nosocomial infections are frequently caused by resistant organisms, including nonfermenting gram-negative bacilli such as Pseudomonas aeruginosa.

AREAS COVERED

P. aeruginosa is a hazardous pathogen. It can resist numerous antibiotics, due to several resistance mechanisms. It is associated with serious illnesses, particularly hospital-acquired infections including ventilator-associated pneumonia. In the past, only a limited number of anti-pseudomonal drugs were available. However, several therapeutic advancements have been made, in recent years, to target P. aeruginosa, including the development of the new cephalosporin: ceftolozane-tazobactam.

EXPERT OPINION

Ceftolozane-tazobactam is a combination of a novel semi-synthetic fifth-generation cephalosporin with a well-established beta-lactamase inhibitor. From a structural perspective, ceftolozane-tazobactam has attested increased stability to AmpC β-lactamases. Additionally, ceftolozane-tazobactam is less affected by changes in efflux pumps and porin permeability due to an enhanced affinity to certain penicillin-binding proteins (PBPs). This enables the molecule to overcome the most common anti-drug resistant mechanisms of bacteria. According to previous clinical trials conducted, ceftolozane-tazobactam must be considered when treating patients with confirmed or suspected P. aeruginosa respiratory tract infections, either nosocomial pneumonia or ventilator-associated pneumonia.

New cephalosporins for the treatment of pneumonia in internal medicine wards

The burden of hospital admission for pneumonia in internal medicine wards may not be underestimated; otherwise, cases of pneumonia are a frequent indication for antimicrobial prescriptions. Community- and hospital-acquired pneumonia are characterized by high healthcare costs, morbidity and non-negligible rates of fatality. The overcoming prevalence of resistant gram-negative and positive bacteria (e.g., methicillin-resistant Staphylococcus aureus, penicillin and ceftriaxone-resistant Streptococcus pneumoniae, extended-spectrum β-lactamases and carbapenemases producing Enterobacteriaceae) has made the most of the first-line agents ineffective for treating lower respiratory tract infections. A broad-spectrum of activity, favourable pulmonary penetration, harmlessness and avoiding in some cases a combination therapy, characterise new cephalosporins such as ceftolozane/tazobactam, ceftobiprole, ceftazidime/avibactam and ceftaroline. We aimed to summarise the role and place in therapy of new cephalosporins in community- and hospital-acquired pneumonia within the setting of internal medicine wards. The "universal pneumonia antibiotic strategy" is no longer acceptable for treating lung infections. Antimicrobial therapy should be individualized considering local antimicrobial resistance and epidemiology, the stage of the illness and potential host factors predisposing to a high risk for specific pathogens.

Drugs for Gram-Negative Bugs From 2010-2019: A Decade in Review

A literature review spanning January 1, 2010, to December 31, 2019, was conducted using the PubMed and ISI Web of Science databases to determine the breadth of publication activity in the area of gram-negative bacteria antimicrobial therapy. The number of articles was used as a reflection of scholarly activity. First, PubMed was searched using the following Medical Subject Headings (MeSH): antibacterial agents, Enterobacteriaceae, Acinetobacter, and Pseudomonas. A total of 12 643 articles were identified within PubMed, and 77 862 articles were identified within ISI Web of Science that included these terms. Second, these articles were categorized by antibiotic class to identify relative contributions to the literature by drug category. Third, these studies were used to identify key trends in the treatment of gram-negative bacterial infections from the past decade. This review highlights advances made in the past 10 years in antibacterial pharmacotherapy and some of the challenges that await the next decade of practice.

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.

Calculated parenteral initial treatment of bacterial infections: Infections with multi-resistant Gram-negative rods - ESBL producers, carbapenemase-producing Enterobacteriaceae, carbapenem-resistant Acinetobacter baumannii

This is the sixteenth chapter of the guideline "Calculated initial parenteral treatment of bacterial infections in adults - update 2018" in the 2nd updated version. The German guideline by the Paul-Ehrlich-Gesellschaft für Chemotherapie e.V. (PEG) has been translated to address an international audience. Infections due to multiresistant Gram-negative rods are challenging. In this chapter recommendations for targeted therapy for infections caused by ESBL-producing Enterobacteriaceae, carbapenemase-producing Enterobacteriaceae and carbapenem-resistant Acinetobacter baumannii are given, based on the limited available evidence.

Ceftazidime-avibactam and ceftolozane-tazobactam susceptibility of multidrug resistant Pseudomonas aeruginosa strains in Hungary

Our objective was to compare the activity ceftazidime-avibactam (C/A) and ceftolozane-tazobactam (C/T) against multidrug (including carbapenem) resistant Pseudomonas aeruginosa clinical isolates collected from six diagnostic centers in Hungary and to reveal the genetic background of their carbapenem resistance. Two hundred and fifty consecutive, non-duplicate, carbapenem-resistant multidrug resistant (MDR) P. aeruginosa isolates were collected in 2017. Minimal inhibitory concentration values of ceftazidime, cefepime, piperacillin/tazobactam, C/A and C/T were determined by broth microdilution method and gradient diffusion test. Carbapenem inactivation method (CIM) test was performed on all isolates. Carbapenemase-encoding blaVIM, blaIMP, blaKPC, blaOXA-48-like and blaNDM genes were identified by multiplex PCR. Of the isolates tested, 33.6% and 32.4% showed resistance to C/A and C/T, respectively. According to the CIM test results, 26% of the isolates were classified as carbapenemase producers. The susceptibility of P. aeruginosa isolates to C/A and C/T without carbapenemase production was 89% and 91%, respectively. Of the CIM-positive isolates, 80% were positive for blaVIM and 11% for blaNDM. The prevalence of Verona integron-encoded metallo-beta-lactamase (VIM)-type carbapenemase was 20.8%. NDM was present in 2.8% of the isolates. Although the rate of carbapenemase-producing P. aeruginosa strains is high, a negative CIM result indicates that either C/A or C/T could be effective even if carbapenem resistance has been observed.

Ceftazidime/Avibactam and Ceftolozane/Tazobactam for Multidrug-Resistant Gram Negatives in Patients with Hematological Malignancies: Current Experiences

Patients suffering from hematological malignancies are at high risk for severe infections, including in particular bloodstream infections, which represent one of the most frequent life-threatening complications for these patients, with reported mortality rates reaching 40%. Furthermore, a worrisome increase in antimicrobial resistance of Gram-negative bacteria (e.g., cephalosporin- and/or carbapenem-resistant Enterobacteriaceae and multidrug-resistant (MDR) Pseudomonas aeruginosa) involved in severe infectious complications among patients with hematological malignancies has been reported during the last years. The two novel combination of cephalosporins and β-lactamase inhibitors, ceftolozane/tazobactam and ceftazidime/avibactam, were recently approved for treatment of complicated intra-abdominal and urinary tract infections and nosocomial pneumonia and display activity against several MDR Gram-negative strains. Although not specifically approved for neutropenic and/or cancer patients, these drugs are used in this setting due to increasing rates of infections caused by MDR Gram-negative bacteria. The aim of this review is to describe the actual evidence from scientific literature about the "real-life" use of these two novel drugs in patients with hematological malignancies and infections caused by MDR Gram-negative bacteria.

Ceftolozane/Tazobactam for Treating Children With Exacerbations of Cystic Fibrosis Due to Pseudomonas aeruginosa: A Review of Available Data

Ceftolozane-tazobactam is a novel fifth-generation cephalosporin/β-lactamase inhibitor combination recently approved for treatment of both complicated intra-abdominal and urinary tract infections in adults. Considering its potent bactericidal activity against Pseudomonas aeruginosa, it might represent an important option also for treating children with exacerbations of cystic fibrosis due to Pseudomonas aeruginosa when other alternative treatments have been exhausted. We hereby review available data on the use of ceftolozane-tazobactam in children, focusing on cystic fibrosis.

Use of Ceftolozane-Tazobactam in Patient with Severe Medium Chronic Purulent Otitis by XDR Pseudomonas aeruginosa

We present a case of a male Italian patient of 66 years with a history of kidney transplantation in treatment with cyclosporine and methylprednisolone. He visited an ENT clinic and was diagnosed as chronic left purulent otitis media. He began at-home antibiotic therapy with poor benefit. On 09/13/18, he was admitted to the hospital "S. Maria "of Terni for persistence of left ear pain and complete hearing loss. Magnetic resonance imaging (MRI) of the brain showed "in correspondence of the petrous rock and the mastoid…presence of flogistic tissue." Auricular swabs and later surgical drainage of the purulent material were performed and both were positive for extensively drug-resistant (XDR) Pseudomonas aeruginosa sensitive only to colistin in absence of synergism with rifampin. The patient underwent antibiotic therapy with ceftolozane-tazobactam, a new generation cephalosporin with anti-Pseudomonas activity and a β-lactamase inhibitor, that currently is indicated for the treatment of complicated urinary tract infections and complicated intra-abdominal infections, with complete healing. In literature, it is described a series of 12 patients with severe MDR (multidrug-resistant) Pseudomonas aeruginosa infections (6 pneumonia) who received salvage therapy with ceftolozane-tazobactam after inappropriate empirical and/or suboptimal treatment. This study included a case of a male patient of 45 years, affected by Burkitt lymphoma and severe neutropenia, who presented with otitis and mastoiditis, and isolation of Pseudomonas aeruginosa in surgical drainage of the purulent material of the ear (blood cultures were negative). He underwent antibiotic therapy with ceftolozane-tazobactam at a dosage of 3 g/8 h for 21.3 days. The patient was healed, but a late recurrence was described because of isolation of ceftolozane-tazobactam-resistant Pseudomonas after therapy. The possibility of acquiring resistance to ceftolozane-tazobactam should be considered in patients with previous exposure to beta-lactams and with poor response to these antibiotics.

Ceftolozane/tazobactam for the treatment of complicated intra-abdominal and urinary tract infections: current perspectives and place in therapy

The current prevalence of infections caused by multidrug-resistant (MDR) organisms is a global threat, and thus, the development of new antimicrobial agents with activity against these pathogens is a healthcare priority. Ceftolozane-tazobactam (C/T) is a new combination of a cephalosporin with a β-lactamase inhibitor that shows excellent in vitro activity against a broad spectrum of Enterobacteriaceae and Pseudomonas aeruginosa, including extended spectrum β-lactamase-producing (ESBL) strains and MDR or extensively drug-resistant (XDR) P. aeruginosa. In phase III randomized clinical trials, C/T demonstrated similar efficacy to meropenem for the treatment of complicated intra-abdominal infections (cIAIs) and superior efficacy to levofloxacin for the treatment of complicated urinary tract infections (cUTIs), including pyelonephritis. The drug is generally safe and well tolerated and its PK/PD profile is very favorable. Observational studies with C/T have revealed good efficacy for the treatment of different types of infection caused by MDR or XDR P. aeruginosa, including some that originated from the digestive or urinary tracts. The place of C/T in therapy is not well defined, but its use could be recommended in a carbapenem-sparing approach for the treatment of infections caused by ESBL-producing strains or for the treatment of infections caused by P. aeruginosa if there are no other more favorable therapeutic options. Further clinical experience is needed to position this new antimicrobial drug for the empirical treatment of cIAIs or cUTIs.

Dual β-lactam combination therapy for multi-drug resistant Pseudomonas aeruginosa infection: enhanced efficacy in vivo and comparison with monotherapies of penicillin-binding protein inhibition

The aim of the study was to determine the efficacy of dual β-lactam combination treatments derived from eight approved drugs against Galleria mellonella larvae infected with MDR strains of P. aeruginosa. Carbapenem-resistant P. aeruginosa NCTC 13437 and an unrelated clinical isolate were used to infect G. mellonella larvae and the efficacy of twenty-eight dual β-lactam combination therapies were compared to their constituent monotherapies. For the most potent combinations identified, penicillin-binding protein (PBP) inhibition profiles were measured and compared with each constituent antibiotic. Five of the dual β-lactam combinations resulted in greater than 70% survival of infected G. mellonella. Two combinations showed potent, enhanced efficacy versus both strains − ceftazidime + meropenem and aztreonam + meropenem. Comparison of PBP inhibition profiles revealed that the enhanced efficacy of these two dual β-lactam combinations could not be explained by more potent inhibition of PBPs or inhibition of a broader range of PBPs. A possible contribution to the enhanced efficacy of the combinations could be stimulation of innate immunity via increased haemocyte numbers compared to their constituent monotherapies. Combinations of β-lactam antibiotics show promise in overcoming MDR P. aeruginosa and are worthy of additional study and development.

The "Old" and the "New" Antibiotics for MDR Gram-Negative Pathogens: For Whom, When, and How

The recent expansion of multidrug resistant and pan-drug-resistant pathogens poses significant challenges in the treatment of healthcare associated infections. An important advancement, is a handful of recently launched new antibiotics targeting some of the current most problematic Gram-negative pathogens, namely carbapenem-producing Enterobacteriaceae (CRE) and carbapenem-resistant P. aeruginosa (CRPA). Less options are available against carbapenem-resistant Acinetobacter baumannii (CRAB) and strains producing metallo-beta lactamases (MBL). Ceftazidime-avibactam signaled a turning point in the treatment of KPC and partly OXA- type carbapenemases, whereas meropenem-vaborbactam was added as a potent combination against KPC-producers. Ceftolozane-tazobactam could be seen as an ideal beta-lactam backbone for the treatment of CRPA. Plazomicin, an aminoglycoside with better pharmacokinetics and less toxicity compared to other class members, will cover important proportions of multi-drug resistant pathogens. Eravacycline holds promise in the treatment of infections by CRAB, with a broad spectrum of activity similar to tigecycline, and improved pharmacokinetics. Novel drugs and combinations are not to be considered "panacea" for the ongoing crisis in the therapy of XDR Gram-negative bacteria and colistin will continue to be considered as a fundamental companion drug for the treatment of carbapenem-resistant Enterobacteriaceae (particularly in areas where MBL predominate), for the treatment of CRPA (in many cases being the only in vitro active drug) as well as CRAB. Aminoglycosides are still important companion antibiotics. Finally, fosfomycin as part of combination treatment for CRE infections and P. aeruginosa, deserves a greater attention. Optimal conditions for monotherapy and the "when and how" of combination treatments integrating the novel agents will be discussed.

In vitro activity of ceftolozane/tazobactam versus antimicrobial non-susceptible Pseudomonas aeruginosa clinical isolates including MDR and XDR isolates obtained from across Canada as part of the CANWARD study, 2008-16

Objectives

Ceftolozane/tazobactam is a novel β-lactam β-lactamase inhibitor combination with a broad spectrum of activity that includes Pseudomonas aeruginosa. The purpose of this study was to evaluate the in vitro activity of ceftolozane/tazobactam and relevant comparators versus a large collection of antimicrobial non-susceptible P. aeruginosa clinical isolates recovered from patients across Canada (CANWARD, 2008-16).

Methods

Susceptibility testing was performed on P. aeruginosa clinical isolates obtained from sentinel hospitals across Canada between January 2008 and December 2016 using broth microdilution, as described by the CLSI. MDR P. aeruginosa were defined as isolates that tested non-susceptible to at least one antimicrobial from ≥3 classes. XDR P. aeruginosa were defined as isolates that tested non-susceptible to at least one antimicrobial from ≥5 classes.

Results

In total, 3229 P. aeruginosa isolates were obtained as a part of CANWARD. Ceftolozane/tazobactam was the most active antimicrobial evaluated, with 98.3% of isolates testing susceptible. The percentage of antimicrobial non-susceptible isolates that remained susceptible to ceftolozane/tazobactam ranged from 85.3% (amikacin non-susceptible subset) to 95.0% (ciprofloxacin non-susceptible subset). Four-hundred and sixty-two P. aeruginosa isolates were MDR (14.3% of all isolates tested) and 84 were XDR (2.6% of all isolates tested). Ceftolozane/tazobactam demonstrated excellent in vitro activity versus the MDR and XDR isolates, with 90.5% and 78.6% remaining susceptible, respectively.

Conclusions

Ceftolozane/tazobactam demonstrated excellent in vitro activity against antimicrobial non-susceptible P. aeruginosa clinical isolates, including MDR and XDR subsets. It may prove useful in the treatment of infections caused by these organisms.

Results from the China Antimicrobial Surveillance Network (CHINET) in 2017 of the In Vitro Activities of Ceftazidime-Avibactam and Ceftolozane-Tazobactam against Clinical Isolates of Enterobacteriaceae and Pseudomonas aeruginosa

The in vitro activities of ceftazidime-avibactam (CZA), ceftolozane-tazobactam (C-T), and comparators were determined for 1,774 isolates of Enterobacteriaceae and 524 isolates of Pseudomonas aeruginosa collected by 30 medical centers from the China Antimicrobial Surveillance Network (CHINET) in 2017. Antimicrobial susceptibility testing was performed by the CLSI broth microdilution method, and blaKPC and blaNDM were detected by PCR for all carbapenem-resistant Enterobacteriaceae (CRE). Ceftazidime-avibactam demonstrated potent activity against almost all Enterobacteriaceae (94.6% susceptibility; MIC50, ≤0.25 mg/liter; MIC90, ≤0.25 to >32 mg/liter) and good activity against P. aeruginosa (86.5% susceptibility; MIC50/90, 2/16 mg/liter). Among the CRE, 50.8% (189/372 isolates) were positive for blaKPC-2, which mainly existed in ceftazidime-avibactam-susceptible Klebsiella pneumoniae isolates (92.1%, 174/189). Among the CRE, 17.7% (66/372 isolates) were positive for blaNDM, which mainly existed in strains resistant to ceftazidime-avibactam (71.7%, 66/92). Ceftolozane-tazobactam showed good in vitro activity against Escherichia coli and Proteus mirabilis (MIC50/90, ≤0.5/2 mg/liter; 90.5 and 93.8% susceptibility, respectively), and the rates of susceptibility of K. pneumoniae (MIC50/90, 2/>64 mg/liter) and P. aeruginosa (MIC50/90, 1/8 mg/liter) were 52.7% and 88.5%, respectively. Among the CRE strains, 28.6% of E. coli isolates and 85% of K. pneumoniae isolates were still susceptible to ceftazidime-avibactam, but only 7.1% and 1.9% of them, respectively, were susceptible to ceftolozane-tazobactam. The rates of susceptibility of the carbapenem-resistant P. aeruginosa isolates to ceftazidime-avibactam (65.7%) and ceftolozane-tazobactam (68%) were similar. Overall, both ceftazidime-avibactam and ceftolozane-tazobactam were highly active against clinical isolates of Enterobacteriaceae and P. aeruginosa recently collected across China, and ceftazidime-avibactam showed activity superior to that of ceftolozane-tazobactam against Enterobacteriaceae, whereas ceftolozane-tazobactam showed a better effect against P. aeruginosa.

Activity of Ceftolozane/Tazobactam Against Gram-Negative Rods of the Family Enterobacteriaceae and Pseudomonas Spp. Isolated from Onco-Hematological Patients Hospitalized in a Clinical Hospital in Poland

Background

The most common etiological agents of infections in onco-hematological patients are Gram-negative rods resistant to many antimicrobials, including carbapenems. Recently, ceftolozane combined with tazobactam became a novel therapeutic option. The aim of the present study was to analyze the susceptibility to ceftolozane/tazobactam of the clinical strains of these bacteria.

Material/Methods

Material comprised rectal swabs, urine, and bronchoalveolar lavage fluid obtained from onco-hematological patients hospitalized in a clinical hospital (1050 beds) in Poland. Identification of the isolated bacteria was done by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) using the MALDI Biotyper (Bruker). Ceftolozane/tazobactam susceptibility of the isolates was assessed using antimicrobial gradient strips (E-test, BioMérieux). Antimicrobial susceptibility testing and interpretation of the results was done according to the current recommendations of the European Committee on Antimicrobial Susceptibility Testing (EUCAST).

Results

In total, 281 rectal swabs and 116 urine samples were tested for the presence of Gram-negative rods producing ESBL, and 531 rectal swabs and 8 bronchoalveolar lavage fluid samples were tested for the presence of Gram-negative rods resistant to carbapenems. In the analyzed period, 69 non-repetitive strains of bacteria were isolated that were in the spectrum of activity of ceftolozane/tazobactam. Among 44 clinical strains of ESBL(+) Enterobacteriaceae rods, 76% were susceptible to ceftolozane/tazobactam. All 9 strains of non-carbapenemase-producing P. aeruginosa resistant or with decreased susceptibility to carbapenems were susceptible to ceftolozane/tazobactam.

Conclusions

Ceftolozane/tazobactam may be an option in the therapy of infections caused by ESBL(+) strains of Enterobacteriaceae as well as non-carbapenemase-producing carbapenem-resistant strains of P. aeruginosa.

New treatments of multidrug-resistant Gram-negative ventilator-associated pneumonia

Ventilator-associated pneumonia (VAP) remains an important clinical problem globally, being associated with significant morbidity and mortality. As management of VAP requires adequate and timely antibiotic administration, global emergence of antimicrobial resistance poses serious challenges over our ability to maintain this axiom. Development of antimicrobials against MDR Gram-negative pathogens has therefore emerged as a priority and some new antibiotics have been marketed or approach late stage of development. The aim of this review is to analyse new therapeutic options from the point view of potential treatment of VAP. Among recently developed antimicrobials presented herein, it is obvious that we will have promising therapeutic options against VAP caused by Enterobacteriaceae excluding those producing metallo-β-lactamases, against which only cefiderocol and aztreonam/avibactam are expected to be active. Against infections caused by carbapenem non-susceptible Pseudomonas aeruginosa, ceftolozane/tazobactam and to a lesser extend ceftazidime/avibactam may cover a proportion of current medical needs, but there still remain a considerable proportion of strains which harbor other resistance mechanisms. Murepavadin and cefiderocol hold promise against this particularly notorious pathogen. Finally, Acinetobacter baummannii remains a treatment-challenge. Eravacycline, cefiderocol and probably plazomicin seem to be the most promising agents against this difficult-to treat pathogen, but we have still a long road ahead, to see their position in clinical practice and particularly in VAP. In summary, despite persisting and increasing unmet medical needs, several newly approved and forthcoming agents hold promise for the treatment of VAP and hopefully will enrich our antimicrobial arsenal in the next few years. Targeted pharmacokinetic and clinical studies in real-life scenario of VAP are important to position these new agents in clinical practice, whereas vigilant use will ensure their longevity in our armamentarium.

Infections by multidrug-resistant Gram-negative Bacteria: What's new in our arsenal and what's in the pipeline?

The spread of multidrug-resistant bacteria is an ever-growing concern, particularly among Gram-negative bacteria because of their intrinsic resistance and how quickly they acquire and spread new resistance mechanisms. Treating infections caused by Gram-negative bacteria is a challenge for medical practitioners and increases patient mortality and cost of care globally. This vulnerability, along with strategies to tackle antimicrobial resistance development, prompts the development of new antibiotic agents and exploration of alternative treatment options. This article summarises the new antibiotics that have recently been approved for Gram-negative bacterial infections, looks down the pipeline at promising agents currently in phase I, II, or III clinical trials, and introduces new alternative avenues that show potential in combating multidrug-resistant Gram-negative bacteria.

Multidrug-Resistant Pseudomonas Infections: Hard to Treat, But Hope on the Horizon?

PURPOSE OF REVIEW

As the sixth most common nosocomial pathogen in the USA, Pseudomonas aeruginosa poses a significant threat to patients within the healthcare system. Its intrinsic and acquired resistance mechanisms also significantly limit the choices for antimicrobial therapy, prompting an increase in the research and development of antibacterial agents with enhanced activity against multidrug-resistant (MDR) P. aeruginosa. While many approved and pipeline antibiotics have activity against wild-type P. aeruginosa, only four new antibiotics have promising activity against MDR P. aeruginosa: ceftazidime-avibactam (Avycaz®), ceftolozane-tazobactam (Zerbaxa®), cefiderocol, and imipenem-cilastatin/relebactam. The goal of this paper is to review the epidemiology and mechanisms of resistance in P. aeruginosa as well as explore the newly approved and pipeline agents that overcome these mechanisms of resistance.

RECENT FINDINGS

Ceftazidime-avibactam and ceftolozane-tazobactam are currently FDA-approved and available for use, while cefiderocol and imipenem-cilastatin/relebactam are in development. Current evidence suggests ceftazidime-avibactam and ceftolozane-tazobactam both may have a role in treatment of MDR P. aeruginosa infections. Ceftolozane-tazobactam appears to be modestly more potent against P. aeruginosa, but emergence of resistance has been noted in various reported cases. Trials are ongoing for cefiderocol and imipenem-cilastatin/relebactam and early results appear promising. The aforementioned agents fill important gaps in the antibiotic armamentarium, particularly for patients with MDR P. aeruginosa infections who otherwise have extremely limited and often toxic antibiotic options. However, resistance to all of these agents will likely emerge, and additional antibiotic development is warranted to provide sufficient options to successfully manage MDR P. aeruginosa infections.

First Penicillin-Binding Protein Occupancy Patterns of β-Lactams and β-Lactamase Inhibitors in Klebsiella pneumoniae

Penicillin-binding proteins (PBPs) are the high-affinity target sites of all β-lactam antibiotics in bacteria. It is well known that each β-lactam covalently binds to and thereby inactivates different PBPs with various affinities. Despite β-lactams serving as the cornerstone of our therapeutic armamentarium against Klebsiella pneumoniae, PBP binding data are missing for this pathogen. We aimed to generate the first PBP binding data on 13 chemically diverse and clinically relevant β-lactams and β-lactamase inhibitors in K. pneumoniae PBP binding was determined using isolated membrane fractions from K. pneumoniae strains ATCC 43816 and ATCC 13883. Binding reactions were conducted using β-lactam concentrations from 0.0075 to 256 mg/liter (or 128 mg/liter). After β-lactam exposure, unbound PBPs were labeled by Bocillin FL. Binding affinities (50% inhibitory concentrations [IC50]) were reported as the β-lactam concentrations that half-maximally inhibited Bocillin FL binding. PBP occupancy patterns by β-lactams were consistent across both strains. Carbapenems bound to all PBPs, with PBP2 and PBP4 as the highest-affinity targets (IC50, <0.0075 mg/liter). Preferential PBP2 binding was observed by mecillinam (amdinocillin; IC50, <0.0075 mg/liter) and avibactam (IC50, 2 mg/liter). Aztreonam showed high affinity for PBP3 (IC50, 0.06 to 0.12 mg/liter). Ceftazidime bound PBP3 at low concentrations (IC50, 0.06 to 0.25 mg/liter) and PBP1a/b at higher concentrations (4 mg/liter), whereas cefepime bound PBPs 1 to 4 at more even concentrations (IC50, 0.015 to 2 mg/liter). These PBP binding data on a comprehensive set of 13 clinically relevant β-lactams and β-lactamase inhibitors in K. pneumoniae enable, for the first time, the rational design and optimization of double β-lactam and β-lactam-β-lactamase inhibitor combinations.

Mobile genetic elements and antibiotic resistance in mine soil amended with organic wastes

Metal resistance has been associated with antibiotic resistance due to co- or cross-resistance mechanisms. Here, metal contaminated mine soil treated with organic wastes was screened for the presence of mobile genetic elements (MGEs). The occurrence of conjugative IncP-1 and mobilizable IncQ plasmids, as well as of class 1 integrons, was confirmed by PCR and Southern blot hybridization, suggesting that bacteria from these soils have gene-mobilizing capacity with implications for the dissemination of resistance factors. Moreover, exogenous isolation of MGEs from the soil bacterial community was attempted under antibiotic selection pressure by using Escherichia coli as recipient. Seventeen putative transconjugants were identified based on increased antibiotic resistance. Metabolic traits and metal resistance of putative transconjugants were investigated, and whole genome sequencing was carried out for two of them. Most putative transconjugants displayed a multi-resistant phenotype for a broad spectrum of antibiotics. They also displayed changes regarding the ability to metabolise different carbon sources, RNA: DNA ratio, growth rate and biofilm formation. Genome sequencing of putative transconjugants failed to detect genes acquired by horizontal gene transfer, but instead revealed a number of nonsense mutations, including in ubiH, whose inactivation was linked to the observed resistance to aminoglycosides. Our results confirm that mine soils contain MGEs encoding antibiotic resistance. Moreover, they point out the role of spontaneous mutations in achieving low-level antibiotic resistance in a short time, which was associated with a trade-off in the capability to metabolise specific carbon sources.

WCK 5107 (Zidebactam) and WCK 5153 Are Novel Inhibitors of PBP2 Showing Potent "β-Lactam Enhancer" Activity against Pseudomonas aeruginosa, Including Multidrug-Resistant Metallo-β-Lactamase-Producing High-Risk Clones

Zidebactam and WCK 5153 are novel β-lactam enhancers that are bicyclo-acyl hydrazides (BCH), derivatives of the diazabicyclooctane (DBO) scaffold, targeted for the treatment of serious infections caused by highly drug-resistant Gram-negative pathogens. In this study, we determined the penicillin-binding protein (PBP) inhibition profiles and the antimicrobial activities of zidebactam and WCK 5153 against Pseudomonas aeruginosa, including multidrug-resistant (MDR) metallo-β-lactamase (MBL)-producing high-risk clones. MIC determinations and time-kill assays were conducted for zidebactam, WCK 5153, and antipseudomonal β-lactams using wild-type PAO1, MexAB-OprM-hyperproducing (mexR), porin-deficient (oprD), and AmpC-hyperproducing (dacB) derivatives of PAO1, and MBL-expressing clinical strains ST175 (bla_VIM-2) and ST111 (bla_VIM-1). Furthermore, steady-state kinetics was used to assess the inhibitory potential of these compounds against the purified VIM-2 MBL. Zidebactam and WCK 5153 showed specific PBP2 inhibition and did not inhibit VIM-2 (apparent K_i [K_iapp] > 100 μM). MICs for zidebactam and WCK 5153 ranged from 2 to 32 μg/ml (amdinocillin MICs > 32 μg/ml). Time-kill assays revealed bactericidal activity of zidebactam and WCK 5153. LIVE-DEAD staining further supported the bactericidal activity of both compounds, showing spheroplast formation. Fixed concentrations (4 or 8 μg/ml) of zidebactam and WCK 5153 restored susceptibility to all of the tested β-lactams for each of the P. aeruginosa mutant strains. Likewise, antipseudomonal β-lactams (CLSI breakpoints), in combination with 4 or 8 μg/ml of zidebactam or WCK 5153, resulted in enhanced killing. Certain combinations determined full bacterial eradication, even with MDR MBL-producing high-risk clones. β-Lactam-WCK enhancer combinations represent a promising β-lactam "enhancer-based" approach to treat MDR P. aeruginosa infections, bypassing the need for MBL inhibition.

Ceftolozane/Tazobactam: A Review in Complicated Intra-Abdominal and Urinary Tract Infections

Globally, the increasing prevalence of multidrug-resistant pathogens continues to pose major problems in healthcare systems and, at least in part, is driving an initiative to develop new antibacterials, such as ceftolozane (a cephalosporin β-lactam). Adding a β-lactamase inhibitor (e.g. tazobactam) to a β-lactam extends its spectrum of activity against β-lactamase-producing microorganisms (a key mechanism of resistance to β-lactams). Ceftolozane/tazobactam (Zerbaxa™), a β-lactam/β-lactamase inhibitor combination, is indicated for the treatment of adults with complicated intra-abdominal infections (cIAI) or complicated urinary tract infections (cUTI), including pyelonephritis. In multinational, phase 3 noninferiority trials, intravenous ceftolozane/tazobactam was an effective and generally well tolerated treatment in patients with cIAI or cUTI. In the ASPECT-cIAI trial, ceftolozane/tazobactam plus metronidazole was noninferior to meropenem in terms of clinical cure rates at the test-of-cure (TOC) visit, with clinical cure rates in subgroup analyses consistent with those in the primary analysis. In the ASPECT-cUTI trial, ceftolozane/tazobactam was superior to levofloxacin in terms of composite cure rates (clinical cure plus microbiological eradiation) at the TOC visit. Further clinical experience should help to more definitively position ceftolozane/tazobactam in the treatment of cIAI and cUTI, including in patients with renal impairment. In the meantime, given its very good in vitro activity against extended-spectrum β-lactamase-producing Enterobacteriaceae and drug-resistant Pseudomonas aeruginosa isolates, ceftolozane/tazobactam provides a potential alternative to currently approved antibacterials for empirical treatment of cIAI and cUTI in adults.