Ceftolozane/tazobactam: place in therapy

Ceftolozane/tazobactam use and emergence of resistance: a 4-year analysis of antimicrobial susceptibility in Pseudomonas aeruginosa isolates in a tertiary hospital

Background

Ceftolozane/tazobactam (C/T) was temporarily withdrawn from December 2020 to February 2022: this forced unavailability created the conditions to study how drug discontinuation might influence Pseudomonas aeruginosa (PA) resistance reversibility in a real-life setting.

Methods

Clinically relevant PA isolates collected between January 1st 2019 and February 22nd 2023 with a C/T susceptibility test available were included. Changes in PA antibiotic susceptibility towards C/T and other antibiotics were examined in three different periods (period A, March-December 2019 and March-December 2020, C/T available; period B, March-December 2021, C/T withdrawn; period C, March-December 2022, C/T reintroduced), also considering the overall consumption rate through the Defined Daily Dose per 100 bed-days per year.

Results

Seven hundred and fifty-one PA isolates were included. A statistically significant reduction of C/T resistance rate was observed when C/T became unavailable, followed by a subsequent increase with its reintroduction (period A 25.1% vs. period B 5.3% vs. period C 10.0%, p < 0.001). A concomitant reduction of resistance rates towards other antibiotics was recorded, consistent with antibiotic consumptions and antimicrobial stewardship programs implementation. A subgroup of 22 patients presented a C/T-resistant isolate after a previous susceptible one; only 4 patients had received a prior C/T treatment.

Conclusion

The unavailability of C/T created the conditions to analyze the practical application of the theory of fitness cost to maintain resistance. A subsequent increase after a first reduction in C/T resistance rate was observed, probably due to persistence of resistant isolates and antibiotic selective pressure. Continuous monitoring of antibiotic use and evolving resistance is essential.

Ceftolozane/tazobactam disrupts Pseudomonas aeruginosa biofilms under static and dynamic conditions

BACKGROUND

Pseudomonas aeruginosa biofilms limit the efficacy of currently available antibacterial therapies and pose significant clinical challenges. Pseudomonal biofilms are complicated further when other markers of persistence such as mucoid and hypermutable phenotypes are present. There is currently a paucity of data regarding the activity of the newer β-lactam/β-lactamase inhibitor combination ceftolozane/tazobactam against P. aeruginosa biofilms.

METHODS

We evaluated the efficacy of ceftolozane/tazobactam against clinical P. aeruginosa isolates, the laboratory isolate PAO1 and its isogenic mutS-deficient hypermutator derivative (PAOMS) grown under static and dynamic biofilm conditions. The clinical isolate collection included strains with mucoid and hypermutable phenotypes.

RESULTS

Ceftolozane/tazobactam exposure led to a bactericidal (≥3 log cfu/cm2) biofilm reduction in 15/18 (83%) clinical isolates grown under static conditions, irrespective of carbapenem susceptibility or mucoid phenotype, with greater activity compared with colistin (P < 0.05). Dynamically grown biofilms were less susceptible to ceftolozane/tazobactam with active biofilm reduction (≥1 log cfu/cm2) observed in 2/3 isolates. Hypermutability did not affect the antibiofilm efficacy of ceftolozane/tazobactam in either static or dynamic conditions when comparing PAO1 and PAOMS. Consistent with the activity of ceftolozane/tazobactam as a potent inhibitor of PBP3, dramatic impacts on P. aeruginosa morphology were observed.

CONCLUSIONS

Our data demonstrate that ceftolozane/tazobactam has encouraging properties in the treatment of P. aeruginosa biofilm infections, and its activity is not diminished against mucoid or hypermutable variants at the timepoints examined.

Cefepime/Enmetazobactam: a microbiological, pharmacokinetic, pharmacodynamic, and clinical evaluation

INTRODUCTION

Cefepime/enmetazobactam is a novel β-lactam/β-lactamase inhibitor (BL-BLI) combination with broad Gram-positive and -negative activity. Cefepime is relatively resistant to hydrolysis by AmpC, and enmetazobactam inhibits all Ambler Class A extended spectrum β-lactamases (ESBLs). Hence, the combination is resistant to hydrolysis by many ESBLs. Important spectrum gaps are MRSA, enterococci, Acinetobacter spp. and anaerobes. There is no completely reliable activity against carbapenem-resistant organisms.

AREAS COVERED

We describe the chemistry, pharmacodynamics, pharmacokinetics, toxicities, drug-drug interactions, clinical efficacy, and current regulatory position of cefepime/enmetazobactam, following a review of available published literature relating to cefepime/enmetazobactam.

EXPERT OPINION

The main potential role for cefepime/enmetazobactam is as a carbapenem-sparing agent for the treatment of infections caused by ESBL-producing Enterobacterales to prevent the use of carbapenems and to avoid the toxicities of non-β-lactam alternatives.There may be potential uses for cefepime/enmetazobactam for the treatment of reproductive tract infections, abdominal infections and neonatal sepsis, given the spectrum of activity and pharmacokinetic properties. However, additional non-clinical and clinical studies are required before use in these settings.

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.

The Molecular Mouse System: A New Useful Tool for Guiding Antimicrobial Therapy in Critically Ill Septic Patients

Bloodstream infections (BSI) caused by multidrug-resistant (MDR) bacteria, pose a major threat for patients, especially for those who are immunosuppressed. Rapid pathogen detection and characterization from positive blood cultures are crucial in the management of patients with BSI to enable an adequate and timely antimicrobial therapy. This study aimed to investigate the potential role of the Molecular Mouse system, a new CE IVD molecular test designed to rapidly detect the causative agents of bacteremia and their resistance determinants, in the management of the therapy in critically ill patients. Agreement between the results of the Molecular Mouse and the conventional routine method was also considered. Overall, 100 positive blood cultures were collected from septic critically ill patients from May 2023 to January 2024 and analyzed with Molecular Mouse and routine protocols. The new instrument consistently agreed with the routine protocols in the case of monomicrobial blood cultures, while some discrepancies were obtained in the polymicrobial samples. Antimicrobial resistance genes were detected in 35 samples, with vanA and CTX-M-1/9 groups being the most frequently detected targets. Therapy was adjusted in 42 critically ill patients confirming the importance of new rapid molecular tests in the management of positive blood cultures, to adjust empirical therapy and use new antibiotics accurately.

Novel Siderophore Cephalosporin and Combinations of Cephalosporins with β-Lactamase Inhibitors as an Advancement in Treatment of Ventilator-Associated Pneumonia

In an era of increasing antibiotic resistance among pathogens, the treatment options for infectious diseases are diminishing. One of the clinical groups especially vulnerable to this threat are patients who are hospitalized in intensive care units due to ventilator-associated pneumonia caused by multidrug-resistant/extensively drug-resistant Gram-negative bacteria. In order to prevent the exhaustion of therapeutic options for this life-threatening condition, there is an urgent need for new pharmaceuticals. Novel β-lactam antibiotics, including combinations of cephalosporins with β-lactamase inhibitors, are proposed as a solution to this escalating problem. The unique mechanism of action, distinctive to this new group of siderophore cephalosporins, can overcome multidrug resistance, which is raising high expectations. In this review, we present the summarized results of clinical trials, in vitro studies, and case studies on the therapeutic efficacy of cefoperazone-sulbactam, ceftolozane-tazobactam, ceftazidime-avibactam, and cefiderocol in the treatment of ventilator-associated pneumonia. We demonstrate that treatment strategies based on siderophore cephalosporins and combinations of β-lactams with β-lactamases inhibitors show comparable or higher clinical efficacy than those used with classic pharmaceuticals, like carbapenems, colistin, or tigecycline, and are often associated with a lower risk of adverse events.

Role of β-Lactamase Inhibitors as Potentiators in Antimicrobial Chemotherapy Targeting Gram-Negative Bacteria

Since the discovery of penicillin, β-lactam antibiotics have commonly been used to treat bacterial infections. Unfortunately, at the same time, pathogens can develop resistance to β-lactam antibiotics such as penicillins, cephalosporins, monobactams, and carbapenems by producing β-lactamases. Therefore, a combination of β-lactam antibiotics with β-lactamase inhibitors has been a promising approach to controlling β-lactam-resistant bacteria. The discovery of novel β-lactamase inhibitors (BLIs) is essential for effectively treating antibiotic-resistant bacterial infections. Therefore, this review discusses the development of innovative inhibitors meant to enhance the activity of β-lactam antibiotics. Specifically, this review describes the classification and characteristics of different classes of β-lactamases and the synergistic mechanisms of β-lactams and BLIs. In addition, we introduce potential sources of compounds for use as novel BLIs. This provides insights into overcoming current challenges in β-lactamase-producing bacteria and designing effective treatment options in combination with BLIs.

The burden of antibiotic resistance of the main microorganisms causing infections in humans - review of the literature

One of the biggest threats to human well-being and public health is antibiotic resistance. If allowed to spread unchecked, it might become a major health risk and trigger another pandemic. This proves the need to develop antibiotic resistance-related global health solutions that take into consideration microdata from various global locations. Establishing positive social norms, guiding individual and group behavioral habits that support global human health, and ultimately raising public awareness of the need for such action could all have a positive impact. Antibiotic resistance is not just a growing clinical concern but also complicates therapy, making adherence to current guidelines for managing antibiotic resistance extremely difficult. Numerous genetic components have been connected to the development of resistance; some of these components have intricate paths of transfer between microorganisms. Beyond this, the subject of antibiotic resistance is becoming increasingly significant in medical microbiology as new mechanisms underpinning its development are identified. In addition to genetic factors, behaviors such as misdiagnosis, exposure to broad-spectrum antibiotics, and delayed diagnosis contribute to the development of resistance. However, advancements in bioinformatics and DNA sequencing technology have completely transformed the diagnostic sector, enabling real-time identification of the components and causes of antibiotic resistance. This information is crucial for developing effective control and prevention strategies to counter the threat.

Construction of C-S and C-Se Bonds from Unstrained Ketone Precursors under Photoredox Catalysis

A mild photoredox catalyzed construction of sulfides, disulfides, selenides, sulfoxides and sulfones from unstrained ketone precursors is introduced. Combination of this deacylative process with SN 2 or coupling reactions provides novel and convenient modular strategies toward unsymmetrical or symmetric disulfides. Reactivity studies favor a bromine radical that initiates a HAT (Hydrogen Atom Transfer) from the aminal intermediate resulting in expulsion of a C-centered radical that is intercepted to make C-S and C-Se bonds. Gram scale reactions, broad substrate scope and tolerance towards various functional groups render this method appealing for future applications in the synthesis of organosulfur and selenium complexes.

New Antibiotics Against Multidrug-Resistant Gram-Negative Bacteria in Liver Transplantation: Clinical Perspectives, Toxicity, and PK/PD Properties

Antimicrobial resistance is a growing global health problem, and it is especially relevant among liver transplant recipients where infections, particularly when caused by microorganisms with a difficult-to-treat profile, are a significant cause of morbidity and mortality. We provide here a complete dissection of the antibiotics active against multidrug-resistant Gram-negative bacteria approved over the last years, focusing on their activity spectrum, toxicity profile and PK/PD properties, including therapeutic drug monitoring, in the setting of liver transplantation. Specifically, the following drugs are presented: ceftolozane/tazobactam, ceftazidime/avibactam, meropenem/vaborbactam, imipenem/relebactam, cefiderocol, and eravacycline. Overall, studies on the safety and optimal employment of these drugs in liver transplant recipients are limited and especially needed. Nevertheless, these pharmaceuticals have undeniably enhanced therapeutic options for infected liver transplant recipients.

Extended-Spectrum β-Lactamases (ESBL): Challenges and Opportunities

The rise of antimicrobial resistance, particularly from extended-spectrum β-lactamase producing Enterobacteriaceae (ESBL-E), poses a significant global health challenge as it frequently causes the failure of empirical antibiotic therapy, leading to morbidity and mortality. The E. coli- and K. pneumoniae-derived CTX-M genotype is one of the major types of ESBL. Mobile genetic elements (MGEs) are involved in spreading ESBL genes among the bacterial population. Due to the rapidly evolving nature of ESBL-E, there is a lack of specific standard examination methods. Carbapenem has been considered the drug of first choice against ESBL-E. However, carbapenem-sparing strategies and alternative treatment options are needed due to the emergence of carbapenem resistance. In South Asian countries, the irrational use of antibiotics might have played a significant role in aggravating the problem of ESBL-induced AMR. Superbugs showing resistance to last-resort antibiotics carbapenem and colistin have been reported in South Asian regions, indicating a future bleak picture if no urgent action is taken. To counteract the crisis, we need rapid diagnostic tools along with efficient treatment options. Detailed studies on ESBL and the implementation of the One Health approach including systematic surveillance across the public and animal health sectors are strongly recommended. This review provides an overview of the background, associated risk factors, transmission, and therapy of ESBL with a focus on the current situation and future threat in the developing countries of the South Asian region and beyond.

Pharmacokinetic and Pharmacodynamic Considerations of Novel Antibiotic Agents for Pediatric Infections: A Narrative Review

Background: Currently, the escalation of microbial resistance poses a significant global challenge. Children are more susceptible to develop infections and therefore are prescribed antibiotics more frequently. The overuse and misuse of antibiotics in pediatric patients can play a considerable role in developing microbial resistance. Accordingly, many policies, including research into new antibiotic agents have been recommended to combat microbial resistance. Recent developments in novel antibiotics have shown promising results against multi-drug resistant (MDR) and extensive drug resistance (XDR) pathogens. However, as pediatric patients are typically excluded from the clinical trials of new medications, labeling and information about approved antibiotics should be improved. This study aimed to evaluate antibiotics having been introduced to the market in the last decade focusing on pediatric population. Methods: This study reviewed the published literatures on novel FDA-approved antibiotics released between 2010 and 2022. Results: Finally, seven newly approved antibiotics including ceftaroline fosamil, ceftazidime-avibactam, ceftolozane-tazobactam, ceftobiprole, imipenem-cilastatin-relebactam, meropenem-vaborbactam, and tedizolid were considered in the present review-article. All relevant data extracted from literatures, were discussed in different subtitles of "Pharmacology", "Mechanism of action", "Indication", "Dosage regimen and pharmacokinetic and pharmacodynamic properties", "Dosage adjustment in renal/liver failure", "Resistance pattern", and "Adverse drug events". Conclusion: This study reviewed available data on seven new antibiotic agents and their pharmacodynamic and pharmacokinetic properties, with a particular focus on their use in pediatric patients. The information presented in this review will be useful for healthcare professionals in selecting appropriate antibiotics for pediatric patients and for researchers in achieving the ideal therapeutic regimens.

Age of Antibiotic Resistance in MDR/XDR Clinical Pathogen of Pseudomonas aeruginosa

Antibiotic resistance in Pseudomonas aeruginosa remains one of the most challenging phenomena of everyday medical science. The universal spread of high-risk clones of multidrug-resistant/extensively drug-resistant (MDR/XDR) clinical P. aeruginosa has become a public health threat. The P. aeruginosa bacteria exhibits remarkable genome plasticity that utilizes highly acquired and intrinsic resistance mechanisms to counter most antibiotic challenges. In addition, the adaptive antibiotic resistance of P. aeruginosa, including biofilm-mediated resistance and the formation of multidrug-tolerant persisted cells, are accountable for recalcitrance and relapse of infections. We highlighted the AMR mechanism considering the most common pathogen P. aeruginosa, its clinical impact, epidemiology, and save our souls (SOS)-mediated resistance. We further discussed the current therapeutic options against MDR/XDR P. aeruginosa infections, and described those treatment options in clinical practice. Finally, other therapeutic strategies, such as bacteriophage-based therapy and antimicrobial peptides, were described with clinical relevance.

Antibiotic Therapy Strategies for Treating Gram-Negative Severe Infections in the Critically Ill: A Narrative Review

INTRODUCTION

Not enough data exist to inform the optimal duration and type of antimicrobial therapy against GN infections in critically ill patients.

METHODS

Narrative review based on a literature search through PubMed and Cochrane using the following keywords: "multi-drug resistant (MDR)", "extensively drug resistant (XDR)", "pan-drug-resistant (PDR)", "difficult-to-treat (DTR) Gram-negative infection," "antibiotic duration therapy", "antibiotic combination therapy" "antibiotic monotherapy" "Gram-negative bacteremia", "Gram-negative pneumonia", and "Gram-negative intra-abdominal infection".

RESULTS

Current literature data suggest adopting longer (≥10-14 days) courses of synergistic combination therapy due to the high global prevalence of ESBL-producing (45-50%), MDR (35%), XDR (15-20%), PDR (5.9-6.2%), and carbapenemases (CP)/metallo-β-lactamases (MBL)-producing (12.5-20%) Gram-negative (GN) microorganisms (i.e., Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumanii). On the other hand, shorter courses (≤5-7 days) of monotherapy should be limited to treating infections caused by GN with higher (≥3 antibiotic classes) antibiotic susceptibility. A general approach should be based on (i) third or further generation cephalosporins ± quinolones/aminoglycosides in the case of MDR-GN; (ii) carbapenems ± fosfomycin/aminoglycosides for extended-spectrum β-lactamases (ESBLs); and (iii) the association of old drugs with new expanded-spectrum β-lactamase inhibitors for XDR, PDR, and CP microorganisms. Therapeutic drug monitoring (TDM) in combination with minimum inhibitory concentration (MIC), bactericidal vs. bacteriostatic antibiotics, and the presence of resistance risk predictors (linked to patient, antibiotic, and microorganism) should represent variables affecting the antimicrobial strategies for treating GN infections.

CONCLUSIONS

Despite the strategies of therapy described in the results, clinicians must remember that all treatment decisions are dynamic, requiring frequent reassessments depending on both the clinical and microbiological responses of the patient.

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.

The safety of ceftolozane/tazobactam for the treatment of complicated urinary tract infections

INTRODUCTION

Ceftolozane is a cephalosporin similar to ceftazidime in its structure, which is marketed in combination with tazobactam, a well-known β-lactamase inhibitor.

AREAS COVERED

After a brief introduction on the drug characteristics and efficacy, we focused on available data from randomized controlled trials and post-marketing observational studies pertaining to the safety of ceftolozane/tazobactam (C/T) for the treatment of complicated urinary tract infections (cUTI). A search was conducted in PubMed from January 2010 to February 2023.

EXPERT OPINION

The use of C/T for the treatment of cUTI is supported by solid efficacy and safety data, especially for the treatment of those pathogens where it can represent a first-line approach due to some peculiar characteristics: (i) treatment of cUTI caused by multidrug-resistant Pseudomonas aeruginosa, in view of its frequent activity against carbapenem-resistant isolates when resistance mechanisms other than production of carbapenemases are concerned; (ii) treatment of cUTI caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacterales in those settings where the selective pressure for carbapenem resistance needs to be relieved, as a suitable and effective carbapenem-sparing option. Although development of resistance to C/T during or after treatment has been reported, this has been reported very rarely in patients receiving C/T for the treatment of cUTI.

Extended and Continuous Infusion of Novel Protected β-Lactam Antibiotics: A Narrative Review

Consolidated data from pharmacokinetic and pharmacodynamic studies support the administration of β-lactam antibiotics in prolonged infusion (i.e., extended or continuous) to optimize therapeutic efficacy by increasing the probability of attaining maximal bactericidal activity. This is the longest possible time during which the free drug concentrations are approximately four-fold the minimum inhibitory concentration between dosing intervals. In the context of antimicrobial stewardship strategies, achieving aggressive pharmacokinetic and pharmacodynamic targets is an important tool in the management of multi-drug resistant (MDR) bacterial infections and in the attainment of mutant preventing concentrations. However, prolonged infusion remains an unexploited resource. Novel β-lactam/β-lactamase inhibitor (βL/βLI) combinations (ceftolozane-tazobactam, ceftazidime-avibactam, meropenem-vaborbactam, and imipenem-cilastatin-relebactam) have been released in recent years to face the emerging challenge of MDR Gram-negative bacteria. Pre-clinical and real-life evidence has confirmed the promising role of prolonged infusion of these molecules in specific settings and clinical populations. In this narrative review we have summarized available pharmacological and clinical data, future perspectives, and current limitations of prolonged infusion of the novel protected β-lactams, their application in hospital settings and in the context of outpatient parenteral antimicrobial therapy.

Antimicrobial susceptibility of ceftolozane-tazobactam against multidrug-resistant Pseudomonas aeruginosa isolates from Melbourne, Australia

We collected 163 clinical Pseudomonas aeruginosa isolates at a tertiary hospital specialising in adult cystic fibrosis (CF) and lung transplantation (LTx) in Melbourne, Australia, to explore the activity of ceftolozane-tazobactam (C/T) in populations at high-risk for antimicrobial resistance. Of these, 144 (88.3%) were collected from sputum, and 19 (11.7%) from bronchoalveolar lavage. Most (85.3%) were derived from patients with cystic fibrosis and included a subset of patients that had undergone LTx. These isolates were tested against 11 antibiotics, including C/T, using Sensititre plates for broth microdilution (BMD) testing. Sixty (36.8%) isolates were classified as multidrug resistant (MDR) and 32 (19.6%) were extensively drug resistant (XDR). Overall, 133/163 (81.6%) isolates were susceptible to C/T. For MDR and XDR isolates, 88.3% and 28.1% were C/T susceptible, respectively. Among the non-MDR/XDR isolates, 100% remained susceptible to C/T. Comparisons of C/T susceptibility were made using BioMérieux Etests and Liofilchem MIC test strips (MTS). Categorical agreement to BMD was >93% for both test strips, but essential agreement to BMD was slightly higher with Etest (89.0%) compared to Liofilchem (74.8%). In conclusion, C/T retained activity against most MDR and over a quarter of XDR P. aeruginosa isolates from complex patients with CF and post-LTx.

Comparative in vitro antipseudomonal activity of ceftolozane/tazobactam against Pseudomonas aeruginosa isolates from children with cystic fibrosis

This study evaluated the in vitro activity of Ceftolozane/tazobactam (C/T) vs 10 comparator agents against Pseudomonas aeruginosa isolates obtained from clinical respiratory samples from pediatric patients with cystic fibrosis at three hospitals during 2015 to 2020. Antimicrobial susceptibility testing was performed using microbroth dilution technique with custom prepared Sensititre® MIC plates. MICs were determined via Sensititre Vizion® system and results were interpreted using current CLSI and EUCAST (2022) breakpoint criteria. C/T was the most potent agent as compared with other antipseudomonal drugs against 291 isolates with MIC₅₀ = 1 μg/mL and MIC₉₀ = 2 μg/mL with percent susceptibility as 95.2%. C/T remained active against majority of ß-lactam non-susceptible isolates; percent susceptibility ranging from 61.2% to 80% including 65.9% ceftazidime non-susceptible isolates. C/T had high activity against P. aeruginosa from 3 geographically diverse pediatric medical centers. Study results suggest that C/T may be used as a potential therapeutic option for treating pediatric patients with CF.

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.

Ceftolozane/Tazobactam In-Vitro Activity against Clinical Isolates from Complicated Intra-Abdominal Infection Patients in Three Indonesian Referral Hospitals

Complicated intra-abdominal infections (cIAIs) lead to high morbidity and mortality, especially if poorly managed. However, Indonesia's microbial pattern and susceptibility data are limited, especially for new antibiotics. Ceftolozane/tazobactam (C/T) is reported to be a new potent antibiotic against various pathogens. Thus, we aim to investigate C/T in vitro activity against clinical isolates from cIAI patients. This prospective cross-sectional study was conducted in three major referral hospitals in Indonesia, including Dr. Cipto Mangunkusumo Hospital (Jakarta), Dr. Kariadi Hospital (Semarang), and Dr. Soetomo Hospital (Surabaya), enrolling those diagnosed with cIAIs. Blood specimens were collected before or after at least 72 h of the last antibiotic administration. Meanwhile, tissue biopsy/aspirate specimens were collected intraoperatively. These specimens were cultured, followed by a susceptibility test for specific pathogens. The minimum inhibitory concentration (MIC) of isolates was determined according to CLSI M100. Two-hundred-and-eighty-four patients were enrolled from 2019-2021. Blood culture was dominated by Gram-positive bacteria (GPB, n = 25, 52.1%), whereas abdominal tissue culture was dominated by Gram-negative bacteria (GNB, n = 268, 79.5%). The three most common organisms were GNB, including E. coli, K. pneumoniae, and P. aeruginosa. C/T was susceptible in 96.7%, 70.2%, and 94.1% of the E. coli, K. pneumoniae, and P. aeruginosa isolates, respectively. In addition, C/T also remained active against ESBL Enterobacterales and carbapenem-non-susceptible P. aeruginosa. Overall, C/T demonstrates a high potency against GNB isolates and can be considered an agent for carbapenem-sparing strategy for cIAI patients as the susceptibility is proven.

Alternatives Therapeutic Approaches to Conventional Antibiotics: Advantages, Limitations and Potential Application in Medicine

Resistance to antimicrobials and particularly multidrug resistance is one of the greatest challenges in the health system nowadays. The continual increase in the rates of antimicrobial resistance worldwide boosted by the ongoing COVID-19 pandemic poses a major public health threat. Different approaches have been employed to minimize the effect of resistance and control this threat, but the question still lingers as to their safety and efficiency. In this context, new anti-infectious approaches against multidrug resistance are being examined. Use of new antibiotics and their combination with new β-lactamase inhibitors, phage therapy, antimicrobial peptides, nanoparticles, and antisense antimicrobial therapeutics are considered as one such promising approach for overcoming bacterial resistance. In this review, we provide insights into these emerging alternative therapies that are currently being evaluated and which may be developed in the future to break the progression of antimicrobial resistance. We focus on their advantages and limitations and potential application in medicine. We further highlight the importance of the combination therapy approach, wherein two or more therapies are used in combination in order to more effectively combat infectious disease and increasing access to quality healthcare. These advances could give an alternate solution to overcome antimicrobial drug resistance. We eventually hope to provide useful information for clinicians who are seeking solutions to the problems caused by antimicrobial resistance.

A minireview of 1,2,3-triazole hybrids with O-heterocycles as leads in medicinal chemistry

Over the past few decades, the dynamic progress in the synthesis and screening of heterocyclic compounds against various targets has made a significant contribution in the field of medicinal chemistry. Among the wide array of heterocyclic compounds, triazole moiety has attracted the attention of researchers owing to its vast therapeutic potential and easy preparation via copper and ruthenium-catalyzed azide-alkyne cycloaddition reactions. Triazole skeletons are found as major structural components in a different class of drugs possessing diverse pharmacological profiles including anti-cancer, anti-bacterial, anti-fungal, anti-viral, anti-oxidant, anti-inflammatory, anti-diabetic, anti-tubercular, and anti-depressant among various others. Furthermore, in the past few years, a significantly large number of triazole hybrids were synthesized with various heterocyclic moieties in order to gain the added advantage of the improved pharmacological profile, overcoming the multiple drug resistance and reduced toxicity from molecular hybridization. Among these synthesized triazole hybrids, many compounds are available commercially and used for treating different infections/disorders like tazobactam and cefatrizine as potent anti-bacterial agents while isavuconazole and ravuconazole as anti-fungal activities to name a few. In this review, we will summarize the biological activities of various 1,2,3-triazole hybrids with copious oxygen-containing heterocycles as lead compounds in medicinal chemistry. This review will be very helpful for researchers working in the field of molecular modeling, drug design and development, and medicinal chemistry.

Silver-Catalyzed Cascade Cyclization of Amino-NH-1,2,3-Triazoles with 2-Alkynylbenzaldehydes: An Access to Pentacyclic Fused Triazoles

An operationally simple Ag(I)-catalyzed approach for the synthesis of isoquinoline and quinazoline fused 1,2,3-triazoles was developed by a condensation and amination cyclization cascade of amino-NH-1,2,3-triazoles with 2-alkynylbenzaldehydes involving three new C-N bond formations in one manipulation, in which the group of -NH of the triazole ring serves as a nucleophile to form the quinazoline skeleton. The efficient protocol can be applied to a variety of substrates containing a range of functional groups, delivering novel pentacyclic fused 1,2,3-triazoles in good-to-excellent yields.

New antimicrobial treatment options for severe Gram-negative infections

PURPOSE OF REVIEW

This review will provide rationale for the development of new antibiotics to treat severe or multidrug-resistant (MDR) Gram-negative infections. It will also provide an overview of recently approved and pipeline antibiotics for severe/MDR Gram-negative infections.

RECENT FINDINGS

MDR Gram-negative infections are recognized as critical threats by global and national organizations and carry a significant morbidity and mortality risk. Increasing antibiotic resistance amongst Gram-negative bacteria, including carbapenem-resistant Acinetobacter baumannii , extended-spectrum β-lactamase-producing Enterobacterales, carbapenem-resistant Enterobacterales and Pseudomonas aeruginosa , with difficult-to-treat-resistance has made both empiric and definitive treatment of these infections increasingly problematic. In recent years, several antibiotics have been approved for treatment of MDR Gram-negative infections and ongoing clinical trials are poised to provide additional options to clinicians' armamentarium. These agents include various β-lactam/β-lactamase inhibitor combinations, eravacycline, plazomicin and cefiderocol.

SUMMARY

Severe/MDR Gram-negative infections continue to be important infections due to their impact on patient outcomes, especially in critically ill and immunocompromised hosts. The availability of new antibiotics offers an opportunity to improve empiric and definitive treatment of these infections.

Current and Potential Therapeutic Options for Infections Caused by Difficult-to-Treat and Pandrug Resistant Gram-Negative Bacteria in Critically Ill Patients

Carbapenem resistance in Gram-negative bacteria has come into sight as a serious global threat. Carbapenem-resistant Gram-negative pathogens and their main representatives Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa are ranked in the highest priority category for new treatments. The worrisome phenomenon of the recent years is the presence of difficult-to-treat resistance (DTR) and pandrug-resistant (PDR) Gram-negative bacteria, characterized as non-susceptible to all conventional antimicrobial agents. DTR and PDR Gram-negative infections are linked with high mortality and associated with nosocomial infections, mainly in critically ill and ICU patients. Therapeutic options for infections caused by DTR and PDR Gram-negative organisms are extremely limited and are based on case reports and series. Herein, the current available knowledge regarding treatment of DTR and PDR infections is discussed. A focal point of the review focuses on salvage treatment, synergistic combinations (double and triple combinations), as well as increased exposure regimen adapted to the MIC of the pathogen. The most available data regarding novel antimicrobials, including novel β-lactam-β-lactamase inhibitor combinations, cefiderocol, and eravacycline as potential agents against DTR and PDR Gram-negative strains in critically ill patients are thoroughly presented.

Ceftolozane/tazobactam for hospital-acquired/ventilator-associated bacterial pneumonia due to ESBL-producing Enterobacterales: a subgroup analysis of the ASPECT-NP clinical trial

BACKGROUND

After the MERINO trial with piperacillin/tazobactam, the efficacy of β-lactam/tazobactam combinations in serious infections involving extended-spectrum β-lactamase (ESBL)-producing pathogens merits special evaluation.

OBJECTIVES

To further confirm the efficacy of ceftolozane/tazobactam in treating hospital-acquired/ventilator-associated bacterial pneumonia (HABP/VABP) involving ESBL-positive and/or AmpC-producing Enterobacterales.

METHODS

Retrospective subgroup analysis of the ASPECT-NP trial comparing ceftolozane/tazobactam with meropenem for treating HABP/VABP in mechanically ventilated adults (ClinicalTrials.gov NCT02070757). ESBLs were identified using whole genome sequencing. Chromosomal AmpC production was quantified employing a high-sensitivity mRNA transcription assay.

RESULTS

Overall, 61/726 (8.4%) participants had all baseline lower respiratory tract (LRT) isolates susceptible to both study treatments and ≥1 baseline ESBL-positive/AmpC-overproducing Enterobacterales isolate. In this subgroup (ceftolozane/tazobactam n = 30, meropenem n = 31), baseline characteristics were generally comparable between treatment arms. The most frequent ESBL-positive and/or AmpC-overproducing Enterobacterales isolates (ceftolozane/tazobactam n = 31, meropenem n = 35) overall were Klebsiella pneumoniae (50.0%), Escherichia coli (22.7%), and Proteus mirabilis (7.6%). The most prevalent ESBLs were CTX-M-15 (75.8%), other CTX-M (19.7%), and SHV (4.5%); 10.6% of isolates overproduced chromosomal AmpC. Overall, 28 day all-cause mortality was 6.7% (2/30) with ceftolozane/tazobactam and 32.3% (10/31) with meropenem (25.6% difference, 95% CI: 5.54 to 43.84). Clinical cure rate at test-of-cure, 7-14 days after end of therapy, was 73.3% (22/30) with ceftolozane/tazobactam and 61.3% (19/31) with meropenem (12.0% difference, 95% CI: -11.21 to +33.51). Per-isolate microbiological response at test-of-cure was 64.5% (20/31) with ceftolozane/tazobactam and 74.3% (26/35) with meropenem (-9.8% difference, 95% CI: -30.80 to +12.00).

CONCLUSIONS

These data confirm ceftolozane/tazobactam as an effective treatment option for HABP/VABP involving ceftolozane/tazobactam-susceptible ESBL-positive and/or AmpC-producing Enterobacterales.

Genomic Characterization of Mutli-Drug Resistant Pseudomonas aeruginosa Clinical Isolates: Evaluation and Determination of Ceftolozane/Tazobactam Activity and Resistance Mechanisms

Resistance to ceftolozane/tazobactam (C/T) in Pseudomonas aeruginosa is a health concern. In this study, we conducted a whole-genome-based molecular characterization to correlate resistance patterns and β-lactamases with C/T resistance among multi-drug resistant P. aeruginosa clinical isolates. Resistance profiles for 25 P. aeruginosa clinical isolates were examined using disk diffusion assay. Minimal inhibitory concentrations (MIC) for C/T were determined by broth microdilution. Whole-genome sequencing was used to check for antimicrobial resistance determinants and reveal their genetic context. The clonal relatedness was evaluated using MLST, PFGE, and serotyping. All the isolates were resistant to C/T. At least two β-lactamases were detected in each with the bla_OXA-4, bla_OXA-10, bla_OXA-50, and bla_OXA-395 being the most common. bla_IMP-15, bla_NDM-1, or bla_VIM-2, metallo-β-lactamases, were associated with C/T MIC >256 μg/mL. Eight AmpC variants were identified, and PDC-3 was the most common. We also determined the clonal relatedness of the isolates and showed that they grouped into 11 sequence types (STs) some corresponding to widespread clonal complexes (ST111, ST233, and ST357). C/T resistance was likely driven by the acquired OXA β-lactamases such as OXA-10, and OXA-50, ESBLs GES-1, GES-15, and VEB-1, and metallo- β-lactamases IMP-15, NDM-1, and VIM-2. Collectively, our results revealed C/T resistance determinants and patterns in multi-drug resistant P. aeruginosa clinical isolates. Surveillance programs should be implemented and maintained to better track and define resistance mechanisms and how they accumulate and interact.

Fighting Back against Antimicrobial Resistance with Comprehensive Policy and Education: A Narrative Review

Globally, antimicrobial resistance has emerged as a significant threat. A comprehensive plan is required to combat antimicrobial resistance. There have been national and international efforts to address this global health problem, but much work remains. Enhanced funding and regulations to support antimicrobial stewardship policy and program development, reforms to incentivize drug development to treat resistant pathogens, and efforts to strengthen One Health programs are areas for collaboration and innovation. Finally, implementation of educational interventions for trainees encompassing these key areas along with training on policy and leadership development is critical to enable sustainability of these efforts to fight back against antimicrobial resistance.

New Drugs for the Treatment of Pseudomonas aeruginosa Infections with Limited Treatment Options: A Narrative Review

P. aeruginosa is still one of the most threatening pathogens responsible for serious hospital-acquired infections. It is intrinsically resistant to many antimicrobial agents and additional acquired resistance further complicates the management of such infections. High rates of combined antimicrobial resistance persist in many countries, especially in the eastern and south-eastern parts of Europe. The aim of this narrative review is to provide a comprehensive assessment of the epidemiology, latest data, and clinical evidence on the current and new available drugs active against P. aeruginosa isolates with limited treatment options. The latest evidence and recommendations supporting the use of ceftolozane-tazobactam and ceftazidime-avibactam, characterized by targeted clinical activity against a significant proportion of P. aeruginosa strains with limited treatment options, are described based on a review of the latest microbiological and clinical studies. Cefiderocol, with excellent in vitro activity against P. aeruginosa isolates, good stability to all β-lactamases and against porin and efflux pumps mutations, is also examined. New carbapenem combinations are explored, reviewing the latest experimental and initial clinical evidence. One section is devoted to a review of new anti-pseudomonal antibiotics in the pipeline, such as cefepime-taniborbactam and cefepime-zidebactam. Finally, other “old” antimicrobials, mainly fosfomycin, that can be used as combination strategies, are described.

β-Lactam Antibiotics and β-Lactamase Enzymes Inhibitors, Part 2: Our Limited Resources

β-lactam antibiotics (BLAs) are crucial molecules among antibacterial drugs, but the increasing emergence of resistance to them, developed by bacteria producing β-lactamase enzymes (BLEs), is becoming one of the major warnings to the global public health. Since only a small number of novel antibiotics are in development, a current clinical approach to limit this phenomenon consists of administering proper combinations of β-lactam antibiotics (BLAs) and β-lactamase inhibitors (BLEsIs). Unfortunately, while few clinically approved BLEsIs are capable of inhibiting most class-A and -C serine β-lactamases (SBLEs) and some carbapenemases of class D, they are unable to inhibit most part of the carbapenem hydrolyzing enzymes of class D and the worrying metallo-β-lactamases (MBLEs) of class B. Particularly, MBLEs are a set of enzymes that catalyzes the hydrolysis of a broad range of BLAs by a zinc-mediated mechanism, and currently no clinically available molecule capable of inhibiting MBLEs exists. Additionally, new types of alarming "superbugs", were found to produce the New Delhi metallo-β-lactamases (NDMs) encoded by increasing variants of a plasmid-mediated gene capable of rapidly spreading among bacteria of the same species and even among different species. Particularly, NDM-1 possesses a flexible hydrolysis mechanism that inactivates all BLAs, except for aztreonam. The present review provides first an overview of existing BLAs and the most clinically relevant BLEs detected so far. Then, the BLEsIs and their most common associations with BLAs already clinically applied and those still in development are reviewed.

Ceftolozane/tazobactam for difficult-to-treat Gram-negative infections: A real-world tertiary hospital experience

OBJECTIVE

To evaluate the real-world clinical efficacy of ceftolozane/tazobactam (C/T) in difficult-to-treat infections caused by multi-drug resistant Gram-negative microorganisms, including carbapenem-resistant Pseudomonas aeruginosa.

METHODS

Retrospective cohort study of adult patients treated with C/T for at least 48 hours for infections caused by multi-drug resistant Gram-negative bacteria in a tertiary hospital from May 2016 until August 2019. The primary outcome analysed was clinical failure, defined as a composite of symptomatology persistence after 7 days of C/T treatment, infection recurrence, and/or all-cause mortality within 30 days of follow-up.

RESULTS AND DISCUSSION

96 episodes of C/T treatment were included, mostly consisting of targeted treatments (83.9%) for the following sources of infection: intra-abdominal (22.6%), urinary tract (25.8%), skin and soft tissue (19.4%), hospital-acquired pneumonia (14%), and other (6.4%). The most frequently isolated bacteria were carbapenem-resistant (88, 94.6%). Clinical failure rate was 30.1%, due to persistent infection at day 7 (4.3%), recurrence of the initial infection (16.1%), or 30-day all-cause mortality (8.6%). Adverse events most frequently reported were Clostridium difficile infection (9%) and cholestasis (8%).

WHAT IS NEW AND CONCLUSION

C/T showed a favourable clinical profile for difficult-to-treat multidrug-resistant and carbapenem-resistant Gram-negative infections, regardless of the source of infection.

New Antibiotics for Hospital-Acquired Pneumonia and Ventilator-Associated Pneumonia

Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) represent one of the most common hospital-acquired infections, carrying a significant morbidity and risk of mortality. Increasing antibiotic resistance among the common bacterial pathogens associated with HAP and VAP, especially Enterobacterales and nonfermenting gram-negative bacteria, has made the choice of empiric treatment of these infections increasingly challenging. Moreover, failure of initial empiric therapy to cover the causative agents associated with HAP and VAP has been associated with worse clinical outcomes. This review provides an overview of antibiotics newly approved or in development for the treatment of HAP and VAP. The approved antibiotics include ceftobiprole, ceftolozane-tazobactam, ceftazidime-avibactam, meropenem-vaborbactam, imipenem-relebactam, and cefiderocol. Their major advantages include their high activity against multidrug-resistant gram-negative pathogens.

New β-Lactam Antibiotics and Ceragenins - A Study to Assess Their Potential in Treatment of Infections Caused by Multidrug-Resistant Strains of Pseudomonas aeruginosa

Background

The increasing number of infections caused by antibiotic resistant strains of Pseudomonas aeruginosa posed a very serious challenge for clinical practice. This standing is driving scientists to develop new antibiotics against these microorganisms.

Methods

In this study, we measured the MIC/MBC values and estimated the ability of tested molecules to prevent bacterial biofilm formation to explore the effectiveness of β-lactam antibiotics ceftolozane/tazobactam, ceftazidime/avibactam, meropenem/vaborbactam, and ceragenins CSA-13, CSA-44, and CSA-131 against 150 clinical isolates of Pseudomonas aeruginosa that were divided into five groups, based on their antibiotic resistance profiles to beta-lactams. Selected strains of microorganisms from each group were also subjected to prolonged incubations (20 passages) with ceragenins to probe the development of resistance towards those molecules. Cytotoxicity of tested ceragenins was evaluated using human red blood cell (RBCs) hemolysis and microscopy observations of human lung epithelial A549 cells after ceragenin treatment. Poloxamer 407 (pluronic F-127) at concentrations ranging from 0.5% to 5% was tested as a potential drug delivery substrate to reduce ceragenin toxicity.

Results

Collected data proved that ceragenins at low concentrations are highly active against clinical strains of Pseudomonas aeruginosa regardless of their resistance mechanisms to conventional antibiotics. Ceragenins also show low potential for resistance development, high antibiofilm activity, and controlled toxicity when used together with poloxamer 407.

Conclusion

This data strongly supports the need for further study directed to develop this group of molecules as new antibiotics to fighting infections caused by antibiotic resistant strains of Pseudomonas aeruginosa.

Discovery and Development of Antibacterial Agents: Fortuitous and Designed

Today, antibacterial drug resistance has turned into a significant public health issue. Repeated intake, suboptimal and/or unnecessary use of antibiotics, and, additionally, the transfer of resistance genes are the critical elements that make microorganisms resistant to conventional antibiotics. A substantial number of antibacterials that were successfully utilized earlier for prophylaxis and therapeutic purposes have been rendered inadequate due to this phenomenon. Therefore, the exploration of new molecules has become a continuous endeavour. Many such molecules are at various stages of investigation. A surprisingly high number of new molecules are currently in the stage of phase 3 clinical trials. A few new agents have been commercialized in the last decade. These include solithromycin, plazomicin, lefamulin, omadacycline, eravacycline, delafloxacin, zabofloxacin, finafloxacin, nemonoxacin, gepotidacin, zoliflodacin, cefiderocol, BAL30072, avycaz, zerbaxa, vabomere, relebactam, tedizolid, cadazolid, sutezolid, triclosan and afabiacin. This article aims to review the investigational and recently approved antibacterials with a focus on their structure, mechanisms of action/resistance, and spectrum of activity. Delving deep, their success or otherwise in various phases of clinical trials is also discussed while attributing the same to various causal factors.

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.

Role of new antibiotics in extended-spectrum β-lactamase-, AmpC- infections

PURPOSE OF REVIEW

Extended-spectrum β-lactamases (ESBL)- and ampicillinase class C (AmpC)-producing Enterobacterales represent one of the major public threats of the current era. As a consequence, during the last decades there have been great efforts to develop new therapeutic agents against these microorganisms. The aim of this review is to summarize the clinical features associated with novel antibiotics with activity against ESBL- and AmpC-producing isolates.

RECENT FINDINGS

There a number of therapeutic agents with activity against ESBL and AmpC than have been introduced and approved over the past few years. Ceftazidime-avibactam and ceftolozane-tazobactam are both carbapenem sparing agents that appear interesting alternatives for treatment of serious Gram-negative infections. Other new β-lactams/ β-lactamase inhibitors (e.g. cefepime-enmetazobactam; ceftaroline fosamil-avibactam; aztreonam-avibactam and cefepime-zidebactam) as well as eravacycline, omadacycline, and plazomicin are also promising agents for treatment of ESBL- and AmpC- infections, but further clinical data are needed to establish their efficacy in comparison to carbapenems. The role of carbapenems/ β-lactamase inhibitors remains to be clarified.

SUMMARY

New therapeutic agents against ESBL- and AmpC-producing Enterobacterales have distinctive specificities and limitations that require further investigations. Future randomized clinical trials are required to define the best strategy for their use in patients with serious infections due to ESBL- and/or AmpC- infections.

Novelty and nuance in the intensive care unit: new options to combat multidrug resistant pneumonia

PURPOSE OF REVIEW

To describe the increasing burden of multidrug resistant (MDR) Gram-negative pathogens in severe pneumonia and to examine the clinical trials supporting a role for novel agents for the treatment of this infection.

RECENT FINDINGS

MDR Gram-negative bacteria cause an increasing proportion of severe pneumonias. Although the epidemiology of resistance varies across the globe, all regions have seen an evolution in resistance, especially among Enterobacterales spp, Pseudomonas aeruginosa, and Acinetobacter bumannii. Fortunately, several clinical trials have established the role for multiple new antibiotics in pneumonia. Although these drugs all have different ranges of in vitro activity and potency, each helps to address the problem of MDR. These studies have varied based on the proportion of subjects undergoing mechanical ventilation and the comparator agents employed. Although all these trials have demonstrated noninferiority to the comparator, the mortality rates across the analyses ranged from <% to >20%. None of the recent investigations included immunocompromised subjects.

SUMMARY

Multiple new agents exist for treating MDR Gram-negative pneumonia. These agents are not interchangeable. Thus, one must approach their adoption with a nuanced eye.

Old and New Beta-Lactamase Inhibitors: Molecular Structure, Mechanism of Action, and Clinical Use

The β-lactams have a central place in the antibacterial armamentarium, but the increasing resistance to these drugs, especially among Gram-negative bacteria, is becoming one of the major threats to public health worldwide. Treatment options are limited, and only a small number of novel antibiotics are in development. However, one of the responses to this threat is the combination of β-lactam antibiotics with β-lactamase inhibitors, which are successfully used in the clinic for overcoming resistance by inhibiting β-lactamases. The existing inhibitors inactivate most of class A and C serine β-lactamases, but several of class D and B (metallo-β-lactamase) are resistant. The present review provides the status and knowledge concerning current β-lactamase inhibitors and an update on research efforts to identify and develop new and more efficient β-lactamase inhibitors.

New Perspectives on Antimicrobial Agents: Ceftolozane-Tazobactam

Ceftolozane-tazobactam (C/T) is a new fifth-generation cephalosporin/beta-lactamase inhibitor combination approved by the Food and Drug Administration and the European Medicines Agency for treatment of complicated intraabdominal infections, complicated urinary tract infections, and hospital-acquired pneumonia in adult patients. This review will briefly describe the pharmacology of C/T and focus on the emerging clinical trial and real-world data supporting its current utilization. Additionally, our synthesis of these data over time has set our current usage of C/T at Barnes-Jewish Hospital (BJH). C/T is primarily employed as directed monotherapy at BJH when Pseudomonas aeruginosa isolates are identified with resistance to other beta-lactams. C/T can also be used empirically in specific clinical situations at BJH prior to microbiological detection of an antibiotic-resistant P. aeruginosa isolate. These situations include critically ill patients in the intensive care unit (ICU) setting, where there is a high likelihood of infection with multidrug-resistant (MDR) P. aeruginosa; patients failing therapy with a carbapenem; specific patient populations known to be at high risk for infection with MDR P. aeruginosa (e.g., lung transplant and cystic fibrosis patients); and patients know to have previous infection or colonization with MDR P. aeruginosa.

Antimicrobial activity of ceftolozane-tazobactam against Enterobacterales and Pseudomonas aeruginosa recovered during the Study for Monitoring Antimicrobial Resistance Trends (SMART) program in Spain (2016-2018)

OBJECTIVE

To analyse the susceptibility to ceftolozane-tazobactam and comparators in Enterobacterales and Pseudomonas aeruginosa isolates recovered from intraabdominal (IAI), urinary (UTI), respiratory (RTI) and bloodstream infection (BSI) in the SMART (Study for Monitoring Antimicrobial Resistance Trends) study.

METHODS

The susceptibility of 5,351 isolates collected in 11 Spanish hospitals (2016-2018) were analysed (EUCAST-2020 criteria) by broth microdilution and were phenotypically studied for the presence of extended-spectrum beta-lactamases (ESBL). Ceftolozane-tazobactam and/or carbapenem resistant isolates were genetically characterized for ESBL and carbapenemases.

RESULTS

Escherichia coli was the most frequent pathogen (49.3% IAI, 54.9% UTI, 16.7% RTI and 50% BSI), followed by Klebsiella pneumoniae (11.9%, 19.1%, 13.1% and 15.4%, respectively). P. aeruginosa was isolated in 9.3%, 5.6%, 32% and 9%, respectively. The frequency of isolates with ESBLs (2016-2017) was: 30.5% K. pneumoniae, 8.6% E. coli, 2.3% Klebsiella oxytoca and 0.7% Proteus mirabilis. Ceftolozane-tazobactam was very active against non-ESBL-(99.3% susceptible) and ESBL-(95.2%) producing E. coli being less active against K. pneumoniae (98% and 43.1%, respectively) isolates. CTX-M-15 was the most prevalent ESBL in E. coli (27.5%) and K. pneumoniae (51.9%) frequently associated with OXA-48-like carbapenemase. Overall, 93% of P. aeruginosa isolates were susceptible to ceftolozane-tazobactam, preserving this activity (>75%) in isolates resistant to other beta-lactams except in those resistant to meropenen or ceftazidime-avibactam. GES-5, PER-1, VIM-1/2 were the most prevalent enzymes in isolates resistant to ceftolozane-tazobactam.

CONCLUSIONS

Ceftolozane-tazobactam showed high activity rates against isolates recovered in the SMART study although it was affected in K. pneumoniae and P. aeruginosa isolates with ESBL and/or carbapenemases.

Novel Cephalosporins in Septic Subjects and Severe Infections: Present Findings and Future Perspective

In past decade, cephalosporins have developed significantly, and data regarding novel cephalosporins (i.e., ceftobiprole, ceftaroline, ceftolozane/tazobactam, ceftazidime/avibactam, and cefiderocol) within septic and bacteremic subjects are rising. These compounds generally offer very promising in vitro microbiological susceptibility, although the variability among gram-negative and -positive strains of different cohorts is noticed in the literature. We require further pharmacological data to measure the best dose in order to prevent sub-therapeutic drug levels in critically ill patients. These new compounds in theory are the sparing solution in the Enterobacteriales infection group for different antimicrobial classes such as aminoglycosides notably within endovascular and GNB-bacteremias, as well as colistin and carbapenem-sparing strategies, favoring good safety profile molecules. Moreover, new cephalosporins are the basis for the actual indications to open up new and exciting prospects for serious infections in the future. In future, patients will be addressed with the desirable approach to sepsis and serious infections in terms of their clinical situation, inherent features of the host, the sensitivity profile, and local epidemiology, for which evidence of the use of new cephalosporin in the treatment of severe infections will fill the remaining gaps.

Ceftolozane/tazobactam for Pseudomonas aeruginosa pulmonary exacerbations in cystic fibrosis adult patients: a case series

Management of cystic fibrosis (CF) patients colonized with Pseudomonas aeruginosa is challenging due to its virulence and multi-drug resistance. Ceftolozane/tazobactam (C/T) is a promising new antipseudomonal agent, and clinical data on CF are limited. We describe our experience in the use of C/T for P. aeruginosa-related pulmonary exacerbations (PE) in CF adults admitted within 2016 and 2019 at Careggi Hospital, Florence, Italy. PE was diagnosed as deterioration of respiratory function, worsening cough, and increasing of sputum. C/T was given at the dose of 3 g every 8 h. C/T was used in ten patients. Mean length of C/T treatment was 16.3 days, and tobramycin was the most frequently combined antipseudomonal agent. All patients were successfully treated although susceptibility testing on sputum sample showed C/T resistance in two cases. No adverse effects related to C/T were reported. To our knowledge this is the largest case series on CF patients treated with C/T. Clinical responses were encouraging even where C/T resistant P. aeruginosa was isolated, probably due to multiple phenotypes colonizing CF lungs. C/T could play a promising role in combination therapy against P. aeruginosa as a part of a colistin-sparing regime.

Nosocomial Pneumonia in the Era of Multidrug-Resistance: Updates in Diagnosis and Management

Nosocomial pneumonia (NP), including hospital-acquired pneumonia in non-intubated patients and ventilator-associated pneumonia, is one of the most frequent hospital-acquired infections, especially in the intensive care unit. NP has a significant impact on morbidity, mortality and health care costs, especially when the implicated pathogens are multidrug-resistant ones. This narrative review aims to critically review what is new in the field of NP, specifically, diagnosis and antibiotic treatment. Regarding novel imaging modalities, the current role of lung ultrasound and low radiation computed tomography are discussed, while regarding etiological diagnosis, recent developments in rapid microbiological confirmation, such as syndromic rapid multiplex Polymerase Chain Reaction panels are presented and compared with conventional cultures. Additionally, the volatile compounds/electronic nose, a promising diagnostic tool for the future is briefly presented. With respect to NP management, antibiotics approved for the indication of NP during the last decade are discussed, namely, ceftobiprole medocaril, telavancin, ceftolozane/tazobactam, ceftazidime/avibactam, and meropenem/vaborbactam.

Comparative in vitro effectiveness of ceftolozane/tazobactam against pediatric gram-negative drug-resistant isolates

Ceftolozane/tazobactam (C/T), a cephalosporin/beta-lactamase inhibitor combination, was evaluated in vitro vs. 10 comparators against 299 pediatric extended-spectrum-cephalosporin-resistant or carbapenem-resistant (ESC-R/CR) Gram-negative Enterobacteriaceae from three freestanding pediatric centers. Isolates were from urine or other sterile sites of children and adolescents through 21 years of age. Susceptibilities were assayed by microbroth dilution via custom Sensititre plates (Thermo Fisher Scientific). Susceptibility was determined using the Sensititre Vizion® system (Thermo Fisher Scientific). Susceptibility breakpoint criteria were those of the Clinical and Laboratory Standards Institute (CLSI) for 2017, except for colistin (EUCAST 2019). Overall, 87.5% isolates were C/T susceptible (MIC ≤2 μg/ml; MIC_50/90, 0.25/4 μg/ml). Susceptibility to C/T was detected more frequently as compared to all other antimicrobials tested except for colistin (95.4%) and meropenem (97.4%). Percent susceptibility to C/T was high for E. coli (91%) and Klebsiella spp. (73.3%). C/T demonstrated good in-vitro activity and high potency against most beta-lactam resistant pediatric Enterobacteriaceae from three geographically diverse U.S. regions.

Short-Term Effects of Appropriate Empirical Antimicrobial Treatment with Ceftolozane/Tazobactam in a Swine Model of Nosocomial Pneumonia

The rising frequency of multidrug-resistant and extensively drug-resistant (MDR/XDR) pathogens is making more frequent the inappropriate empirical antimicrobial therapy (IEAT) in nosocomial pneumonia, which is associated with increased mortality. We aim to determine the short-term benefits of appropriate empirical antimicrobial treatment (AEAT) with ceftolozane/tazobactam (C/T) compared with IEAT with piperacillin/tazobactam (TZP) in MDR Pseudomonas aeruginosa pneumonia. Twenty-one pigs with pneumonia caused by an XDR P. aeruginosa strain (susceptible to C/T but resistant to TZP) were ventilated for up to 72 h. Twenty-four hours after bacterial challenge, animals were randomized to receive 2-day treatment with either intravenous saline (untreated) or 25 to 50 mg of C/T per kg body weight (AEAT) or 200 to 225 mg of TZP per kg (IEAT) every 8 h. The primary outcome was the P. aeruginosa burden in lung tissue and the histopathology injury. P. aeruginosa burden in tracheal secretions and bronchoalveolar lavage (BAL) fluid, the development of antibiotic resistance, and inflammatory markers were secondary outcomes. Overall, P. aeruginosa lung burden was 5.30 (range, 4.00 to 6.30), 4.04 (3.64 to 4.51), and 4.04 (3.05 to 4.88) log₁₀CFU/g in the untreated, AEAT, and IEAT groups, respectively (P = 0.299), without histopathological differences (P = 0.556). In contrast, in tracheal secretions (P < 0.001) and BAL fluid (P = 0.002), bactericidal efficacy was higher in the AEAT group. An increased MIC to TZP was found in 3 animals, while resistance to C/T did not develop. Interleukin-1β (IL-1β) was significantly downregulated by AEAT in comparison to other groups (P = 0.031). In a mechanically ventilated swine model of XDR P. aeruginosa pneumonia, appropriate initial treatment with C/T decreased respiratory secretions' bacterial burden, prevented development of resistance, achieved the pharmacodynamic target, and may have reduced systemic inflammation. However, after only 2 days of treatment, P. aeruginosa tissue concentrations were moderately affected.