Ceftolozane/tazobactam pharmacokinetic/pharmacodynamic-derived dose justification for phase 3 studies in patients with nosocomial pneumonia

Suggested Dosing of Select Beta-lactam Agents for the Treatment of Antimicrobial-Resistant Gram-Negative Infections in Children

The Infectious Diseases Society of America (IDSA) publishes annual guidance on the treatment of antimicrobial-resistant (AMR) gram-negative infections. Within the AMR guidance, suggested dosages of antibiotics for adults infected with AMR pathogens are provided. This document serves as a companion document to the IDSA guidance to assist pediatric specialists with dosing β-lactam agents for the treatment of AMR infections in children. A panel of 13 pediatric infectious diseases specialists, including 11 pharmacists and 2 physicians, reviewed existing pharmacokinetic/pharmacodynamic, animal, and clinical data for newer β-lactam agents that are available in the United States and suggested for the treatment of AMR infections (ie, cefiderocol, ceftazidime-avibactam, ceftazidime-avibactam and aztreonam, ceftolozane-tazobactam, imipenem-cilastatin-relebactam, meropenem-vaborbactam, sulbactam-durlobactam). Suggested dosing for ampicillin-sulbactam is also provided, given complexities in dosing for carbapenem-resistant Acinetobacter baumannii infections. Consensus-based suggested dosing for β-lactam agents used to treat AMR infections in neonates, infants, children, and adolescents and relevant supporting evidence are provided. Content is up to date as of December 1, 2024. Gaps and limitations to existing data are discussed. Optimizing antibiotic dosing is critical to improving the outcomes of children with AMR infections.

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.

A Systematic Review of the Pharmacokinetics and Pharmacodynamics of Novel Beta-Lactams and Beta-Lactam with Beta-Lactamase Inhibitor Combinations for the Treatment of Pneumonia Caused by Carbapenem-Resistant Gram-Negative Bacteria

BACKGROUND

Novel beta-lactams show activity against many multidrug-resistant Gram-negative bacteria that cause severe lung infections. Understanding pharmacokinetic/pharmacodynamic characteristics of these agents may help optimise outcomes in the treatment of pneumonia.

OBJECTIVES

To describe and appraise studies that report pulmonary pharmacokinetic and pharmacodynamic data of cefiderocol, ceftazidime/avibactam, ceftolozane/tazobactam, imipenem/cilastatin/relebactam and meropenem/vaborbactam.

METHODS

MEDLINE (PubMed), Embase, Web of Science and Scopus libraries were used for the literature search. Pulmonary population pharmacokinetic and pharmacokinetic/pharmacodynamic studies on adult patients receiving cefiderocol, ceftazidime/avibactam, ceftolozane/tazobactam, imipenem/cilastatin/relebactam, and meropenem/vaborbactam published in peer-reviewed journals were included. Two independent authors screened, reviewed and extracted data from included articles. A reporting guideline for clinical pharmacokinetic studies (ClinPK statement) was used for bias assessment. Relevant outcomes were included, such as population pharmacokinetic parameters and probability of target attainment of dosing regimens.

RESULTS

Twenty-four articles were included. There was heterogeneity in study methods and reporting of results, with diversity across studies in adhering to the ClinPK statement checklist. Ceftolozane/tazobactam was the most studied agent. Only two studies collected epithelial lining fluid samples from patients with pneumonia. All the other phase I studies enrolled healthy subjects. Significant population heterogeneity was evident among available population pharmacokinetic models. Probabilities of target attainment rates above 90% using current licensed dosing regiments were reported in most studies.

CONCLUSIONS

Although lung pharmacokinetics was rarely described, this review observed high target attainment using plasma pharmacokinetic data for all novel beta-lactams. Future studies should describe lung pharmacokinetics in patient populations at risk of carbapenem-resistant pathogen infections.

Translational PK/PD for the Development of Novel Antibiotics-A Drug Developer's Perspective

Antibiotic development traditionally involved large Phase 3 programs, preceded by Phase 2 studies. Recognizing the high unmet medical need for new antibiotics and, in some cases, challenges to conducting large clinical trials, regulators created a streamlined clinical development pathway in which a lean clinical efficacy dataset is complemented by nonclinical data as supportive evidence of efficacy. In this context, translational Pharmacokinetic/Pharmacodynamic (PK/PD) plays a key role and is a major contributor to a "robust" nonclinical package. The classical PK/PD index approach, proven successful for established classes of antibiotics, is at the core of recent antibiotic approvals and the current antibacterial PK/PD guidelines by regulators. Nevertheless, in the case of novel antibiotics with a novel Mechanism of Action (MoA), there is no prior experience with the PK/PD index approach as the basis for translating nonclinical efficacy to clinical outcome, and additional nonclinical studies and PK/PD analyses might be considered to increase confidence. In this review, we discuss the value and limitations of the classical PK/PD approach and present potential risk mitigation activities, including the introduction of a semi-mechanism-based PK/PD modeling approach. We propose a general nonclinical PK/PD package from which drug developers might choose the studies most relevant for each individual candidate in order to build up a "robust" nonclinical PK/PD understanding.

Nosocomial pneumonia: Current etiology and impact on antimicrobial therapy

Nosocomial pneumonia is an infection with high clinical impact and high morbimortality in which Pseudomonas aeruginosa plays a priority role, especially in the critically ill patient. Conventional antipseudomonal treatments, historically considered as standard, are currently facing important challenges due to the increase of antimicrobial resistance. In recent years, new antimicrobials have been developed with attractive sensitivity profiles and remarkable efficacy in clinical scenarios of nosocomial pneumonia including bacteremia, mechanical ventilation, infections with multidrug-resistant organisms or situations of therapeutic failure. This new evidence underscores the need to update current clinical guidelines for the antimicrobial treatment of nosocomial pneumonia, especially in the most critically ill patients.

Antibacterial effect of seven days exposure to ceftolozane-tazobactam as monotherapy and in combination with fosfomycin or tobramycin against Pseudomonas aeruginosa with ceftolozane-tazobactam MICs at or above 4 mg/l in an in vitro pharmacokinetic model

OBJECTIVES

To use a pre-clinical pharmacokinetic infection model to assess the antibacterial effect of ceftolozane/tazobactam alone or in combination with fosfomycin or tobramycin against Pseudomonas aeruginosa strains with MICs at or higher than the clinical breakpoint (MIC ≥ 4 mg/L).

METHODS

An in vitro model was used to assess changes in bacterial load and population profiles after exposure to mean human serum concentrations of ceftolozane/tazobactam associated with doses of 2 g/1 g q8h, fosfomycin concentrations associated with doses of 8 g q8h or tobramycin at doses of 7 mg/kg q24 h over 168 h.

RESULTS

Simulations of ceftolozane/tazobactam at 2 g/1 g q8h alone produced 3.5-4.5 log reductions in count by 6 h post drug exposure for strains with MIC ≤32 mg/L. The antibacterial effect over the first 24 h was related to ceftolozane/tazobactam MIC. There was subsequent regrowth with most strains to bacterial densities of >106 CFU/mL. Addition of either fosfomycin or tobramycin resulted in suppression of regrowth and in the case of tobramycin more rapid initial bacterial killing up to 6 h. These effects could not be related to either fosfomycin or tobramycin MICs. Changes in population profiles were noted with ceftolozane/tazobactam alone often after 96 h exposure but such changes were suppressed by fosfomycin and almost abolished by the addition of tobramycin.

CONCLUSIONS

The addition of either fosfomycin or tobramycin to ceftolozane/tazobactam at simulated human clinically observed concentrations reduced P. aeruginosa bacterial loads and the risk of resistance to ceftolozane/tazobactam when strains had ceftolozane/tazobactam MIC values at or above the clinical breakpoint.

Ceftolozane-Tazobactam Versus Ceftazidime-Avibactam for the Treatment of Infections Caused by Multidrug-Resistant Pseudomonas aeruginosa: a Multicenter Cohort Study

Ceftolozane-tazobactam (C-T) and ceftazidime-avibactam (CAZ-AVI) are two novel antimicrobials that retain activity against resistant Pseudomonas aeruginosa. The comparative effectiveness and safety of C-T versus CAZ-AVI remain unknown. A retrospective, multicenter cohort study was performed in six tertiary centers in Saudi Arabia and included patients who received either C-T or CAZ-AVI for infections due to multidrug-resistant (MDR) P. aeruginosa. Overall in-hospital mortality, 30-day mortality, and clinical cure were the main study outcomes. Safety outcomes were also evaluated. A multivariate analysis using logistic regression was used to determine the independent impact of treatment on the main outcomes of interest. We enrolled 200 patients in the study (100 in each treatment arm). A total of 56% were in the intensive care unit, 48% were mechanically ventilated, and 37% were in septic shock. Approximately 19% of patients had bacteremia. Combination therapy was administered to 41% of the patients. The differences between the C-T and CAZ-AVI groups did not reach statistical significance in the overall in-hospital mortality (44% versus 37%; P = 0.314; OR, 1.34; 95% CI, 0.76 to 2.36), 30-day mortality (27% versus 23%; P = 0.514; OR, 1.24; 95% CI, 0.65 to 2.35), clinical cure (61% versus 66%; P = 0.463; OR, 0.81; 95% CI, 0.43 to 1.49), or acute kidney injury (23% versus 17%; P = 0.289; OR, 1.46; 95% CI, 0.69 to 3.14), even after adjusting for differences between the two groups. C-T and CAZ-AVI did not significantly differ in terms of safety and effectiveness, and they serve as potential options for the treatment of infections caused by MDR P. aeruginosa.

Rationale and evidence for the use of new beta-lactam/beta-lactamase inhibitor combinations and cefiderocol in critically ill patients

BACKGROUND

Healthcare-associated infections involving Gram-negative bacteria (GNB) with difficult-to-treat resistance (DTR) phenotype are associated with impaired patient-centered outcomes and poses daily therapeutic challenges in most of intensive care units worldwide. Over the recent years, four innovative β-lactam/β-lactamase inhibitor (BL/BLI) combinations (ceftolozane-tazobactam, ceftazidime-avibactam, imipenem-relebactam and meropenem-vaborbactam) and a new siderophore cephalosporin (cefiderocol) have been approved for the treatment of certain DTR-GNB infections. The literature addressing their microbiological spectrum, pharmacokinetics, clinical efficacy and safety was exhaustively audited by our group to support the recent guidelines of the French Intensive Care Society on their utilization in critically ill patients. This narrative review summarizes the available evidence and unanswered questions on these issues.

METHODS

A systematic search for English-language publications in PUBMED and the Cochrane Library database from inception to November 15, 2022.

RESULTS

These drugs have demonstrated relevant clinical success rates and a reduced renal risk in most of severe infections for whom polymyxin- and/or aminoglycoside-based regimen were historically used as last-resort strategies-namely, ceftazidime-avibactam for infections due to Klebsiella pneumoniae carbapenemase (KPC)- or OXA-48-like-producing Enterobacterales, meropenem-vaborbactam for KPC-producing Enterobacterales, ceftazidime-avibactam/aztreonam combination or cefiderocol for metallo-β-lactamase (MBL)-producing Enterobacterales, and ceftolozane-tazobactam, ceftazidime-avibactam and imipenem-relebactam for non-MBL-producing DTR Pseudomonas aeruginosa. However, limited clinical evidence exists in critically ill patients. Extended-infusion scheme (except for imipenem-relebactam) may be indicated for DTR-GNB with high minimal inhibitory concentrations and/or in case of augmented renal clearance. The potential benefit of combining these agents with other antimicrobials remains under-investigated, notably for the most severe presentations. Other important knowledge gaps include pharmacokinetic information in particular situations (e.g., pneumonia, other deep-seated infections, and renal replacement therapy), the hazard of treatment-emergent resistance and possible preventive measures, the safety of high-dose regimen, the potential usefulness of rapid molecular diagnostic tools to rationalize their empirical utilization, and optimal treatment durations. Comparative clinical, ecological, and medico-economic data are needed for infections in whom two or more of these agents exhibit in vitro activity against the causative pathogen.

CONCLUSIONS

New BL/BLI combinations and cefiderocol represent long-awaited options for improving the management of DTR-GNB infections. Several research axes must be explored to better define the positioning and appropriate administration scheme of these drugs in critically ill patients.

Effectiveness of First-Line Therapy with Old and Novel Antibiotics in Ventilator-Associated Pneumonia Caused by Carbapenem-Resistant Acinetobacter baumannii: A Real Life, Prospective, Observational, Single-Center Study

Evidence-based, standard antibiotic therapy for ventilator-associated pneumonia (VAP) caused by carbapenem-resistant Acinetobacter baumannii (CRAB) is a relevant unmet clinical need in the intensive care unit (ICU). We aimed to evaluate the effectiveness of first-line therapy with old and novel CRAB active antibiotics in monomicrobial VAP caused by CRAB. A prospective, observational study was performed in a mixed non-COVID-19 ICU. The primary outcome measure was clinical failure upon first-line targeted therapy. Features independently influencing failure occurrence were also investigated via Cox proportional multivariable analysis. To account for the imbalance in antibiotic treatment allocation, a propensity score analysis with an inverse probability treatment weighting approach was adopted. Of the 90 enrolled patients, 34 (38%) experienced clinical failure. Compared to patients who experienced a clinical resolution of VAP, those who had clinical failure were of an older age (median age 71 (IQR 64-78) vs. 62 (IQR 52-69) years), and showed greater burden of comorbidities (median Charlson comorbidity index 8 (IQR 6-8) vs. 4 (IQR 2-6)), higher frequency of immunodepression (44% vs. 21%), and greater clinical severity at VAP onset (median SOFA score 10 (IQR 9-11) vs. 9 (IQR 7-11)). Lower rates of use of fast molecular diagnostics for nosocomial pneumonia (8.8% vs. 30.3%) and of timely CRAB active therapy administration (65% vs. 89%), and higher rates of colistin-based targeted therapy (71% vs. 46%) were also observed in patients who failed first-line therapy. Overall, CRAB active iv regimens were colistin-based in 50 patients and cefiderocol-based in 40 patients, both always combined with inhaled colistin. According to the backbone agent of first-line regimens, clinical failure was lower in the cefiderocol group, compared to that in the colistin group (25% vs. 48%, respectively). In multivariable Cox regression analysis, the burden of comorbid conditions independently predicted clinical failure occurrence (Charlson index aHR = 1.21, 95% CI = 1.04-1.42, p = 0.01), while timely targeted antibiotic treatment (aHR = 0.40, 95% CI = 0.19-0.84, p = 0.01) and cefiderocol-based first-line regimens (aHR = 0.38, 95% CI = 0.17-0.85, p = 0.02) strongly reduced failure risk. In patients with VAP caused by CRAB, timely active therapy improves infection outcomes and cefiderocol holds promise as a first-line therapeutic option.

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.

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.

Optimizing antibiotic dosing regimens for nosocomial pneumonia: a window of opportunity for pharmacokinetic and pharmacodynamic modeling

INTRODUCTION

Determining antibiotic exposure in the lung and the threshold(s) needed for effective antibacterial killing is paramount during development of new antibiotics for the treatment of nosocomial pneumonia, as these exposures directly affect clinical outcomes and resistance development. The use of pharmacokinetic and pharmacodynamic modeling is recommended by regulatory agencies to evaluate antibiotic pulmonary exposure and optimize dosage regimen selection. This process has been implemented in newer antibiotic development.

AREAS COVERED

This review will discuss the basis for conducting pharmacokinetic and pharmacodynamic studies to support dosage regimen selection and optimization for the treatment of nosocomial pneumonia. Pharmacokinetic/pharmacodynamic data that supported recent hospital-acquired bacterial pneumonia/ventilator-associated bacterial pneumonia indications for ceftolozane/tazobactam, ceftazidime/avibactam, imipenem/cilastatin/relebactam, and cefiderocol will be reviewed.

EXPERT OPINION

Optimal drug development requires the integration of preclinical pharmacodynamic studies, healthy volunteers and ideally patient bronchoalveolar lavage pharmacokinetic studies, Monte-Carlo simulation, and clinical trials. Currently, plasma exposure has been successfully used as a surrogate for lung exposure threshold. Future studies are needed to identify the value of lung pharmacodynamic thresholds in nosocomial pneumonia antibiotic dosage optimization.

Outcomes in participants with ventilated nosocomial pneumonia and organ failure treated with ceftolozane/tazobactam versus meropenem: a subset analysis of the phase 3, randomized, controlled ASPECT-NP trial

BACKGROUND

The pivotal ASPECT-NP trial showed ceftolozane/tazobactam was non-inferior to meropenem for the treatment of ventilated hospital-acquired/ventilator-associated bacterial pneumonia (vHABP/VABP). Here, we evaluated treatment outcomes by degree of respiratory or cardiovascular dysfunction.

METHODS

This was a subset analysis of data from ASPECT-NP, a randomized, double-blind, non-inferiority trial (ClinicalTrials.gov NCT02070757). Adults with vHABP/VABP were randomized 1:1 to 3 g ceftolozane/tazobactam or 1 g meropenem every 8 h for 8-14 days. Outcomes in participants with a baseline respiratory component of the Sequential Organ Failure Assessment (SOFA) score (R-SOFA) ≥ 2 (indicative of severe respiratory failure), cardiovascular component of the SOFA score (CV-SOFA) ≥ 2 (indicative of shock), or R-SOFA ≥ 2 plus CV-SOFA ≥ 2 were compared by treatment arm. The efficacy endpoint of primary interest was 28-day all-cause mortality. Clinical response, time to death, and microbiologic response were also evaluated.

RESULTS

There were 726 participants in the intention-to-treat population; 633 with R-SOFA ≥ 2 (312 ceftolozane/tazobactam, 321 meropenem), 183 with CV-SOFA ≥ 2 (84 ceftolozane/tazobactam, 99 meropenem), and 160 with R-SOFA ≥ 2 plus CV-SOFA ≥ 2 (69 ceftolozane/tazobactam, 91 meropenem). Baseline characteristics, including causative pathogens, were generally similar in participants with R-SOFA ≥ 2 or CV-SOFA ≥ 2 across treatment arms. The 28-day all-cause mortality rate was 23.7% and 24.0% [difference: 0.3%, 95% confidence interval (CI) - 6.4, 6.9] for R-SOFA ≥ 2, 33.3% and 30.3% (difference: - 3.0%, 95% CI - 16.4, 10.3) for CV-SOFA ≥ 2, and 34.8% and 30.8% (difference: - 4.0%, 95% CI - 18.6, 10.3), respectively, for R-SOFA ≥ 2 plus CV-SOFA ≥ 2. Clinical cure rates were as follows: 55.8% and 54.2% (difference: 1.6%, 95% CI - 6.2, 9.3) for R-SOFA ≥ 2, 53.6% and 55.6% (difference: - 2.0%, 95% CI - 16.1, 12.2) for CV-SOFA ≥ 2, and 53.6% and 56.0% (difference: - 2.4%, 95% CI - 17.6, 12.8), respectively, for R-SOFA ≥ 2 plus CV-SOFA ≥ 2. Time to death was comparable in all SOFA groups across both treatment arms. A higher rate of microbiologic eradication/presumed eradication was observed for CV-SOFA ≥ 2 and R-SOFA ≥ 2 plus CV-SOFA ≥ 2 with ceftolozane/tazobactam compared to meropenem.

CONCLUSIONS

The presence of severe respiratory failure or shock did not affect the relative efficacy of ceftolozane/tazobactam versus meropenem; either agent may be used to treat critically ill patients with vHABP/VABP.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02070757. Registered 25 February 2014, https://clinicaltrials.gov/ct2/show/NCT02070757.

Clinical characteristics, microbiology and outcomes of a cohort of patients treated with ceftolozane/tazobactam in acute care inpatient facilities, Houston, Texas, USA

Background

Ceftolozane/tazobactam is a β-lactam/β-lactamase inhibitor combination with activity against a variety of Gram-negative bacteria, including MDR Pseudomonas aeruginosa. This agent is approved for hospital-acquired and ventilator-associated bacterial pneumonia. However, most real-world outcome data come from small observational cohorts. Thus, we sought to evaluate the utilization of ceftolozane/tazobactam at multiple tertiary hospitals in Houston, TX, USA.

Methods

We conducted a multicentre retrospective study of patients receiving at least 48 h of ceftolozane/tazobactam therapy from January 2016 through to September 2019 at two hospital systems in Houston. Demographic, clinical and microbiological data were collected, including the infecting bacterial isolate, when available. The primary outcome was composite clinical success at hospital discharge. Secondary outcomes included in-hospital mortality and clinical disposition at 14 and 30 days post ceftolozane/tazobactam initiation. Multivariable logistic regression analysis was used to identify predictors of the primary outcome and mortality. Recovered isolates were tested for susceptibility to ceftolozane/tazobactam and underwent WGS.

Results

A total of 263 patients were enrolled, and composite clinical success was achieved in 185 patients (70.3%). Severity of illness was the most consistent predictor of clinical success. Combination therapy with ceftolozane/tazobactam and another Gram-negative-active agent was associated with reduced odds of clinical success (OR 0.32, 95% CI 0.16-0.63). Resistance to ceftolozane/tazobactam was noted in 15.4% of isolates available for WGS; mutations in ampC and ftsI were common but did not cluster with a particular ST.

Conclusions

Clinical success rate among this patient cohort treated with ceftolozane/tazobactam was similar compared with previous experiences. Ceftolozane/tazobactam remains an alternative agent for treatment of susceptible isolates of P. aeruginosa.

Antimicrobial Treatment of Pseudomonas aeruginosa Severe Sepsis

Pseudomonas aeruginosa is a pathogen often encountered in a healthcare setting. It has consistently ranked among the most frequent pathogens seen in nosocomial infections, particularly bloodstream and respiratory tract infections. Aside from having intrinsic resistance to many antibiotics, it rapidly acquires resistance to novel agents. Given the high mortality of pseudomonal infections generally, and pseudomonal sepsis particularly, and with the rise of resistant strains, treatment can be very challenging for the clinician. In this paper, we will review the latest evidence for the optimal treatment of P. aeruginosa sepsis caused by susceptible as well as multidrug-resistant strains including the difficult to treat pathogens. We will also discuss the mode of drug infusion, indications for combination therapy, along with the proper dosing and duration of treatment for various conditions with a brief discussion of the use of non-antimicrobial agents.

Population Pharmacokinetic Modeling and Probability of Target Attainment of Ceftaroline in Brain and Soft Tissues

Ceftaroline, approved to treat skin infections and pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA), has been considered for the treatment of central nervous system (CNS) infections. A population pharmacokinetic (popPK) model was developed to describe ceftaroline soft tissue and cerebrospinal fluid (CSF) distributions and investigate the probability of target attainment (PTA) of the percentage of the dosing interval that the unbound drug concentration exceeded the MIC (%fT_>MIC) to treat MRSA infections. Healthy subjects' plasma and microdialysate concentrations from muscle and subcutaneous tissue following 600 mg every 12 h (q12h) and q8h and neurosurgical patients' plasma and CSF concentrations following single 600-mg dosing were used. Plasma concentrations were described by a two-compartment model, and tissue concentrations were incorporated as three independent compartments linked to the central compartment by bidirectional transport (clearance in [CL_in] and CL_out). Apparent volumes were fixed to physiological interstitial values. Healthy status and body weight were identified as covariates for the volume of the central compartment, and creatinine clearance was identified for clearance. The CSF glucose concentration (GLUC) was inversely correlated with CL_in,CSF. Simulations showed a PTA of >90% in plasma and soft tissues for both regimens assuming an MIC of 1 mg/L and a %fT_>MIC of 28.8%. Using the same target, patients with inflamed meninges (0.5 < GLUC ≤ 2 mmol/L) would reach PTAs of 99.8% and 97.2% for 600 mg q8h and q12h, respectively. For brain infection with mild inflammation (2 < GLUC ≤ 3.5 mmol/L), the PTAs would be reduced to 34.3% and 9.1%, respectively. Ceftaroline's penetration enhanced by meningeal inflammation suggests that the drug could be a candidate to treat MRSA CNS infections.

Drug Regimens of Novel Antibiotics in Critically Ill Patients with Varying Renal Functions: A Rapid Review

There is currently an increase in the emergence of multidrug-resistant bacteria (MDR) worldwide, requiring the development of novel antibiotics. However, it is not only the choice of antibiotic that is important in treating an infection; the drug regimen also deserves special attention to avoid underdosing and excessive concentrations. Critically ill patients often have marked variation in renal function, ranging from augmented renal clearance (ARC), defined as a measured creatinine clearance (CrCL) ≥ 130 mL/min*1.73 m², to acute kidney injury (AKI), eventually requiring renal replacement therapy (RRT), which can affect antibiotic exposure. All novel beta-lactam (BLs) and/or beta-lactam/beta-lactamases inhibitors (BL/BLIs) antibiotics have specific pharmacokinetic properties, such as hydrophilicity, low plasma–protein binding, small volume of distribution, low molecular weight, and predominant renal clearance, which require adaptation of dosage regimens in the presence of abnormal renal function or RRT. However, there are limited data on the topic. The aim of this review was therefore to summarize available PK studies on these novel antibiotics performed in patients with ARC or AKI, or requiring RRT, in order to provide a practical approach to guide clinicians in the choice of the best dosage regimens in critically ill patients.

Beta-Lactams Therapeutic Monitoring in Septic Children-What Target Are We Aiming for? A Scoping Review

The antimicrobial therapy of sepsis and septic shock should be individualized based on pharmacokinetic/pharmacodynamic (PK/PD) parameters to deliver effective and timely treatment of life-threatening infections. We conducted a literature scoping review to identify therapeutic targets of beta-lactam antibiotics in septic pediatric patients and the strategies that have been applied to overcome sepsis-related altered pharmacokinetics and increase target attainment against susceptible pathogens. A systematic search was conducted in the MEDLINE, EMBASE and Web of Science databases to select studies conducted since 2010 with therapeutic monitoring data of beta-lactams in septic children. Last searches were performed on 02 September 2021. Two independent authors selected the studies and extracted the data. A narrative and qualitative approach was used to summarize the findings. Out of the 118 identified articles, 21 met the eligibility criteria. Population pharmacokinetic modeling was performed in 12 studies, while nine studies reported data from bedside monitoring of beta-lactams. Most studies were conducted in the United States of America (n = 9) and France (n = 5) and reported PK/PD data of amoxicillin, ampicillin, azlocillin, aztreonam, cefazolin, cefepime, cefotaxime, ceftaroline, ceftazidime, doripenem, meropenem and piperacillin/tazobactam. Therapeutic targets ranged from to 40% fT> MIC to 100% fT> 6 × MIC. Prolonging the infusion time and frequency were most described strategies to increase target attainment. Monitoring beta-lactam serum concentrations in clinical practice may potentially maximize therapeutic target attainment. Further studies are required to define the therapeutic target associated with the best clinical outcomes.

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.

The Unfulfilled Promise of Inhaled Therapy in Ventilator-Associated Infections: Where Do We Go from Here?

Respiratory infection is common in intubated/tracheotomized patients and systemic antibiotic therapy is often unrewarding. In 1967, the difficulty in treating Gram-negative respiratory infections led to the use of inhaled gentamicin, targeting therapy directly to the lungs. Fifty-three years later, the effects of topical therapy in the intubated patient remain undefined. Clinical failures with intravenous antibiotics persist and instrumented patients are now infected by many more multidrug-resistant Gram-negative species as well as methicillin-resistant Staphylococcus aureus. Multiple systematic reviews and meta-analyses suggest that there may be a role for inhaled delivery but “more research is needed.” Yet there is still no Food and Drug Administration (FDA) approved inhaled antibiotic for the treatment of ventilator-associated infection, the hallmark of which is the foreign body in the upper airway. Current pulmonary and infectious disease guidelines suggest using aerosols only in the setting of Gram-negative infections that are resistant to all systemic antibiotics or not to use them at all. Recently two seemingly well-designed large randomized placebo-controlled Phase 2 and Phase 3 clinical trials of adjunctive inhaled therapy for the treatment of ventilator-associated pneumonia failed to show more rapid resolution of pneumonia symptoms or effect on mortality. Despite evolving technology of delivery devices and more detailed understanding of the factors affecting delivery, treatment effects were no better than placebo. What is wrong with our approach to ventilator- associated infection? Is there a message from the large meta-analyses and these two large recent multisite trials? This review will suggest why current therapies are unpredictable and have not fulfilled the promise of better outcomes. Data suggest that future studies of inhaled therapy, in the milieu of worsening bacterial resistance, require new approaches with completely different indications and endpoints to determine whether inhaled therapy indeed has an important role in the treatment of ventilated patients.

Pharmacokinetic/Pharmacodynamic Optimization of Hospital-Acquired and Ventilator-Associated Pneumonia: Challenges and Strategies

Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) are correlated with high mortality rates worldwide. Thus, the administration of antibiotic therapy with appropriate dosing regimen is critical. An efficient antibiotic is needed to maintain an adequate concentration at the infection site, for a sufficient period of time, to achieve the best therapeutic outcome. It can, however, be challenging for antibiotics to penetrate the pulmonary system due to the complexity of its structure. Crossing the blood alveolar barrier is a difficult process determined by multiple factors that are either drug related or infection related. Thus, the understanding of pharmacokinetics/pharmacodynamics (PK/PD) of antibiotics identifies the optimum dosing regimens to achieve drug penetration into the epithelial lining fluid at adequate therapeutic concentrations. Critically ill patients in the ICU can express augmented renal clearance (ARC), characterized by enhanced renal function, or may have renal dysfunction necessitating supportive care such as continuous renal replacement therapy (CRRT). Both ARC and CRRT can alter drug elimination, thus affecting drug concentrations. PK of critically ill patients is less clear due to the multiple variabilities associated with their condition. Therefore, conventional dosing regimens often lead to therapeutic failure. Another major hurdle faced in optimizing treatment for HAP/VAP is the reduction of the in vitro potency. Therapeutic drug monitoring (TDM), if available, may allow health care providers to personalize treatment to maximize efficacy of the drug exposures while minimizing toxicity. TDM can be of significant importance in populations whom PK are less defined and for resistant infections to achieve the best therapeutic outcome.

Pharmacokinetic/pharmacodynamic simulations of cost-effective dosage regimens of ceftolozane/tazobactam and ceftazidime/avibactam in patients with renal impairment

The pharmacokinetics of ceftolozane/tazobactam (TOL/TAZ) and ceftazidime/avibactam (CEF/AVI) is influenced by renal function. Application of recommended dosages in patients with renal impairment require to use fractions of the full dose, as only one dosage is available for both antibiotics. The objective of this study was to evaluate the adequacy of alternative dosage regimens based on the full dose. We performed pharmacokinetic/pharmacodynamic (PK/PD) simulations of recommended and alternative dosage regimens in patients with various degrees of renal impairment, by using the Pmetrics program. Alternative regimens included longer dosage interval and prolonged infusions of the full dose for both drugs. Probabilities of target attainment (PTA) were assessed considering PK/PD targets defined for cephalosporins and beta-lactamase inhibitors as well as MIC breakpoints. The risk of overexposure was also assessed. Results showed that alternative dosage regimens based on a full dose of TOL/TAZ and CEF/AVI administered every 12 or 24h were associated with PTA similar to that of recommended dosages, especially when administered as prolonged infusion. The alternative dosage regimens were not associated with overexposure in most cases. In addition, those regimens could reduce dosing errors, drug cost and nurse labor. Clinical investigation of those alternative dosage regimens would be required before implementation.

Clinical and microbiological outcomes, by causative pathogen, in the ASPECT-NP randomized, controlled, Phase 3 trial comparing ceftolozane/tazobactam and meropenem for treatment of hospital-acquired/ventilator-associated bacterial pneumonia

OBJECTIVES

In the ASPECT-NP trial, ceftolozane/tazobactam was non-inferior to meropenem for treating nosocomial pneumonia; efficacy outcomes by causative pathogen were to be evaluated.

METHODS

Mechanically ventilated participants with hospital-acquired/ventilator-associated bacterial pneumonia were randomized to 3 g ceftolozane/tazobactam (2 g ceftolozane/1 g tazobactam) q8h or 1 g meropenem q8h. Lower respiratory tract (LRT) cultures were obtained ≤36 h before first dose; pathogen identification and susceptibility were confirmed at a central laboratory. Prospective secondary per-pathogen endpoints included 28 day all-cause mortality (ACM), and clinical and microbiological response at test of cure (7-14 days after the end of therapy) in the microbiological ITT (mITT) population.

RESULTS

The mITT population comprised 511 participants (264 ceftolozane/tazobactam, 247 meropenem). Baseline LRT pathogens included Klebsiella pneumoniae (34.6%), Pseudomonas aeruginosa (25.0%) and Escherichia coli (18.2%). Among baseline Enterobacterales isolates, 171/456 (37.5%) were ESBL positive. For Gram-negative baseline LRT pathogens, susceptibility rates were 87.0% for ceftolozane/tazobactam and 93.3% for meropenem. For Gram-negative pathogens, 28 day ACM [52/259 (20.1%) and 62/240 (25.8%)], clinical cure rates [157/259 (60.6%) and 137/240 (57.1%)] and microbiological eradication rates [189/259 (73.0%) and 163/240 (67.9%)] were comparable with ceftolozane/tazobactam and meropenem, respectively. Per-pathogen microbiological eradication for Enterobacterales [145/195 (74.4%) and 129/185 (69.7%); 95% CI: -4.37 to 13.58], ESBL-producing Enterobacterales [56/84 (66.7%) and 52/73 (71.2%); 95% CI: -18.56 to 9.93] and P. aeruginosa [47/63 (74.6%) and 41/65 (63.1%); 95% CI: -4.51 to 19.38], respectively, were also comparable.

CONCLUSIONS

In mechanically ventilated participants with nosocomial pneumonia owing to Gram-negative pathogens, ceftolozane/tazobactam was comparable with meropenem for per-pathogen 28 day ACM and clinical and microbiological response.

Assessment of rationality of available fixed dose combinations of antibiotics in India

OBJECTIVE

India is among the largest consumers of antibiotics. Easy availability and growing sales of Fixed Dose Combinations (FDCs) of antibiotics can worsen Antimicrobial Resistance (AMR). There is lack of comprehensive data on available antibiotic FDC formulations, their dose strengths and adequacy of scientific evidence regarding their efficacy, safety and suitability for human use. In the present work, we aimed at addressing this knowledge gap.

METHODS

Availability of FDCs was ascertained from the Current Index of Medical Specialties (CIMS) [Issue Jan-April 2020]. Customized data abstraction form was used to capture pertinent information for these FDCs. Assessment of rationality was done based on standard parameters.

RESULTS

More than 90% of the existing FDCs were found to be irrational; with two third of them being unapproved and or banned from use in the country.

CONCLUSIONS

Although the regulatory agency has already taken cognizance of the seriousness of the matter; there is an urgent need to revisit these FDCs to promote prudent antibiotic use.

EXPERT OPINION

High antibiotic use is associated with antimicrobial resistance; it is imperative that all factors which lead to high antibiotic use are adequately addressed. Easy availability of fixed dose combinations (FDCs) has begun to catch the attention of regulators in developing economies like India leading to a ban of 330 FDCs of which 19% were antibiotic combinations. The continuing presence and increasing sales of these irrational FDCs is a concern for effective antimicrobial stewardship.

The role of tazobactam-based combinations for the management of infections due to extended-spectrum β-lactamase-producing Enterobacterales: Insights from the Society of Infectious Diseases Pharmacists

Extended-spectrum β-lactamase (ESBL)-producing Enterobacterales are a global threat to public health due to their antimicrobial resistance profile and, consequently, their limited available treatment options. Tazobactam is a sulfone β-lactamase inhibitor with in vitro inhibitory activity against common ESBLs in Enterobacterales, including CTX-M. However, the role of tazobactam-based combinations in treating infections caused by ESBL-producing Enterobacterales remains unclear. In the United States, two tazobactam-based combinations are available, piperacillin-tazobactam and ceftolozane-tazobactam. We evaluated and compared the roles of tazobactam-based combinations against ESBL-producing organisms with emphasis on pharmacokinetic/pharmacodynamic exposures in relation to MIC distributions and established breakpoints, clinical outcomes data specific to infection site, and considerations for downstream effects with these agents regarding antimicrobial resistance development. While limited data with ceftolozane-tazobactam are encouraging for its potential role in infections due to ESBL-producing Enterobacterales, further evidence is needed to determine its place in therapy. Conversely, currently available microbiologic, pharmacokinetic, pharmacodynamic, and clinical data do not suggest a role for piperacillin-tazobactam, and we caution clinicians against its usage for these infections.

Penetration of Antibacterial Agents into Pulmonary Epithelial Lining Fluid: An Update

A comprehensive review of drug penetration into pulmonary epithelial lining fluid (ELF) was previously published in 2011. Since then, an extensive number of studies comparing plasma and ELF concentrations of antibacterial agents have been published and are summarized in this review. The majority of the studies included in this review determined ELF concentrations of antibacterial agents using bronchoscopy and bronchoalveolar lavage, and this review focuses on intrapulmonary penetration ratios determined with area under the concentration-time curve from healthy human adult studies or pharmacokinetic modeling of various antibacterial agents. If available, pharmacokinetic/pharmacodynamic parameters determined from preclinical murine infection models that evaluated ELF concentrations are also provided. There are also a limited number of recently published investigations of intrapulmonary penetration in critically ill patients with lower respiratory tract infections, where greater variability in ELF concentrations may exist. The significance of these changes may impact the intrapulmonary penetration in the setting of infection, and further studies relating ELF concentrations to clinical response are needed. Phase I drug development programs now include assessment of initial pharmacodynamic target values for pertinent organisms in animal models, followed by evaluation of antibacterial penetration into the human lung to assist in dosage selection for clinical trials in infected patients. The recent focus has been on β-lactam agents, including those in combination with β-lactamase inhibitors, particularly due to the rise of multidrug-resistant infections. This manifests as a large portion of the review focusing on cephalosporins and carbapenems, with or without β-lactamase inhibitors, in both healthy adult subjects and critically ill patients with lower respiratory tract infections. Further studies are warranted in critically ill patients with lower respiratory tract infections to evaluate the relationship between intrapulmonary penetration and clinical and microbiological outcomes. Our clinical research experience with these studies, along with this literature review, has allowed us to outline key steps in developing and evaluating dosage regimens to treat extracellular bacteria in lower respiratory tract infections.

Ceftolozane/tazobactam probability of target attainment and outcomes in participants with augmented renal clearance from the randomized phase 3 ASPECT-NP trial

Background

The randomized, double-blind, phase 3 ASPECT-NP trial evaluated the efficacy of 3 g of ceftolozane/tazobactam (C/T) versus 1 g of meropenem infused every 8 h for 8 to 14 days for treatment of adults with hospital-acquired bacterial pneumonia (HABP) or ventilator-associated bacterial pneumonia (VABP). We assessed the probability of target attainment and compared efficacy outcomes from ASPECT-NP in participants with augmented renal clearance (ARC) versus those with normal renal function.

Methods

Baseline renal function was categorized as normal renal function (creatinine clearance 80–130 mL/min) or ARC (creatinine clearance > 130 mL/min). Population pharmacokinetic models informed Monte Carlo simulations to assess probability of target attainment in plasma and pulmonary epithelial lining fluid. Outcomes included 28-day all-cause mortality and clinical cure and per-participant microbiologic cure rates at the test-of-cure visit.

Results

A > 99% and > 80% probability of target attainment was demonstrated for ceftolozane and tazobactam, respectively, in simulated plasma and epithelial lining fluid. Within treatment arms, 28-day all-cause mortality rates in participants with normal renal function (C/T, n = 131; meropenem, n = 123) and ARC (C/T, n = 96; meropenem, n = 113) were comparable (data comparisons presented as rate; treatment difference [95% CI]) (C/T: normal renal function, 17.6%; ARC, 17.7%; 0.2 [− 9.6 to 10.6]; meropenem: normal renal function, 20.3%; ARC, 17.7%; − 2.6 [− 12.6 to 7.5]). Clinical cure rates at test-of-cure were also comparable across renal function groups within treatment arms (C/T: normal renal function, 57.3%; ARC, 59.4%; − 2.1 [− 14.8 to 10.8]; meropenem: normal renal function, 59.3%; ARC, 57.5%; 1.8 [− 10.6 to 14.2]). Per-participant microbiologic cure rates at test-of-cure were consistent across renal function groups within treatment arms (C/T: normal renal function, 72.2% [n/N = 70/97]; ARC, 71.4% [n/N = 55/77]; 0.7 [− 12.4 to 14.2]; meropenem: normal renal function, 75.0% [n/N = 66/88]; ARC, 70.0% [n/N = 49/70]; 5.0 [− 8.7 to 19.0]).

Conclusions

C/T and meropenem resulted in 28-day all-cause mortality, clinical cure, and microbiologic cure rates that were comparable between participants with ARC or normal renal function. In conjunction with high probability of target attainment, these results confirm that C/T (3 g) every 8 h is appropriate in patients with HABP/VABP and ARC.

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

Lung penetration, bronchopulmonary pharmacokinetic/pharmacodynamic profile and safety of 3 g of ceftolozane/tazobactam administered to ventilated, critically ill patients with pneumonia

Objectives

Ceftolozane/tazobactam is approved for hospital-acquired/ventilator-associated bacterial pneumonia at double the dose (i.e. 2 g/1 g) recommended for other indications. We evaluated the bronchopulmonary pharmacokinetic/pharmacodynamic profile of this 3 g ceftolozane/tazobactam regimen in ventilated pneumonia patients.

Methods

This was an open-label, multicentre, Phase 1 trial (clinicaltrials.gov: NCT02387372). Mechanically ventilated patients with proven/suspected pneumonia received four to six doses of 3 g of ceftolozane/tazobactam (adjusted for renal function) q8h. Serial plasma samples were collected after the first and last doses. One bronchoalveolar lavage sample per patient was collected at 1, 2, 4, 6 or 8 h after the last dose and epithelial lining fluid (ELF) drug concentrations were determined. Pharmacokinetic parameters were estimated by non-compartmental analysis and pharmacodynamic analyses were conducted to graphically evaluate achievement of target exposures (plasma and ELF ceftolozane concentrations >4 mg/L and tazobactam concentrations >1 mg/L; target in plasma: ≥30% and ≥20% of the dosing interval, respectively).

Results

Twenty-six patients received four to six doses of study drug; 22 were included in the ELF analyses. Ceftolozane and tazobactam T_max (6 and 2 h, respectively) were delayed in ELF compared with plasma (1 h). Lung penetration, expressed as the ratio of mean drug exposure (AUC) in ELF to plasma, was 50% (ceftolozane) and 62% (tazobactam). Mean ceftolozane and tazobactam ELF concentrations remained >4 mg/L and >1 mg/L, respectively, for 100% of the dosing interval. There were no deaths or adverse event-related study discontinuations.

Conclusions

In ventilated pneumonia patients, 3 g of ceftolozane/tazobactam q8h yielded ELF exposures considered adequate to cover ceftolozane/tazobactam-susceptible respiratory pathogens.

Pharmacokinetics and pharmacodynamics of antibiotics in cystic fibrosis: a narrative review

Cystic fibrosis affects several organs, predisposing patients to severe bacterial respiratory infections, including those caused by methicillin-resistant Staphylococcus aureus. Cystic fibrosis is also associated with a wide spectrum of pathological changes that can significantly affect the absorption, distribution, metabolism, and/or elimination of several drugs, including antibacterial agents. Therefore, awareness of the pharmacokinetic derangements in patients with cystic fibrosis is mandatory for the optimisation of antibiotic therapy. This review discusses the basic principles of pharmacokinetics and the pathophysiology of the pharmacokinetics changes associated with cystic fibrosis; it also provides an update of available data for the most widely used antibiotics. Evidence accumulated in the last few years has clearly shown that a significant number of cystic fibrosis patients treated with conventional dosing schemes have sub-therapeutic antibiotic concentrations, increasing their risk of therapeutic failure and/or the emergence of resistant pathogens. Some proposals to optimise antibiotic therapies in this clinical setting based on therapeutic drug monitoring are also discussed.

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.

Real-world evaluation of ceftolozane/tazobactam therapy and clinical outcomes in France

OBJECTIVES

To describe the real-world clinical use of ceftolozane/tazobactam (C/T) and associated outcomes in France.

PATIENTS AND METHODS

Multicenter, prospective cohort study conducted in 22 hospitals. All adult patients who received at least one dose of C/T were asked to participate (2018-2019). Patients were treated according to standard hospital practice and followed up until C/T stop.

RESULTS

At the time of the analysis, 84 patients were evaluated. The median age was 64.8 years, and 67.9% (57/84) of patients were males. Fifty-seven patients (57/82, 69.5%) had one or more risk factors for multidrug-resistant (MDR) infections (missing MDR risk factor data for two patients). Most patients were critically ill and had several comorbidities. A majority (59/84, 70.2%) of patients had nosocomial infections. Half of all patients (n=42) had a diagnosis of pneumonia, of which 69% (29/42) were hospital acquired. Overall, 90.5% (76/84) of patients had MDR bacteria. Pseudomonas aeruginosa was the most frequently isolated bacterium (71/80, 88.8%), including 93% (80/86) of C/T-susceptible strains. C/T was prescribed as the first-line treatment to 29.8% (25/84) of patients. A concomitant antibiotic treatment was prescribed to 48.8% (41/84) of patients, of whom 65.9% (27/41) were prescribed concomitant antibiotics at the same time as C/T initiation. Empirical C/T prescription was microbiologically appropriate in 11/16 patients after susceptibility testing. Most patients (44/72, 61.1%) were cured and four (4/72, 5.6%) deaths were reported.

CONCLUSIONS

The results showed that C/T was most frequently prescribed for documented cases of P. aeruginosa infections. Most outcomes were positive, including among pneumonia patients.

A Novel Dosing Strategy of Ceftolozane/Tazobactam in a Patient Receiving Intermittent Hemodialysis

We describe the case of a 54-year-old male receiving intermittent hemodialysis (iHD) who was found to have Pseudomonas aeruginosa bacteremia secondary to osteomyelitis of the calcaneus bone. The patient was clinically cured without recurrence using a ceftolozane/tazobactam (CTZ) dosing strategy of 100/50 mg every 8 hours (standard dosing) and 1000/500 mg thrice weekly following iHD. Utilizing a susceptibility breakpoint of ≤4 µg/mL for P. aeruginosa, the T > MIC for standard dosing and the 1000/500-mg thrice-weekly following iHD regimen were calculated to be 92.7% and 94.1%, respectively. Ceftolozane total body clearance for the standard q 8 h dosing and the 1000/500-mg thrice-weekly following iHD regimen were calculated to be 0.196 L/h and 0.199 L/h, respectively. To our knowledge, this is the first report to illustrate the administration of CTZ at a dose of 1000/500 mg thrice weekly following iHD.

Pharmacokinetic/pharmacodynamic target attainment in critically ill renal patients on antimicrobial usage: focus on novel beta-lactams and beta lactams/beta-lactamase inhibitors

INTRODUCTION

Several novel beta-lactams (BLs) and/or beta lactams/beta-lactamase inhibitors (BL/BLIs) have been recently developed for the management of multidrug-resistant bacterial infections. Data concerning dose optimization in critically ill patients with altered renal function are scanty.

AREAS COVERED

This article provides a critical reappraisal of pharmacokinetic and clinical issues emerged with novel BLs and/or BL/BLIs in renal critically ill patients. Clinical and pharmacokinetic studies published in English until December 2020 were searched on the PubMed-MEDLINE database.

EXPERT OPINION

Several issues emerged with the use of novel BLs and/or BL/BLIs in critically ill renal patients. Suboptimal clinical response rate with ceftazidime-avibactam and ceftolozane-tazobactam was reported in phase II-III trials in patients with moderate kidney injury; data on patients undergoing renal replacement therapy are limited to some case reports; dose adjustment in augmented renal clearance is provided only for cefiderocol. Implementation of altered dosing strategies (prolonged infusion and/or higher dosage) coupled with adaptive real-time therapeutic drug monitoring could represent the most effective approach in warranting optimal pharmacokinetic/pharmacodynamic targets with novel BLs and/or BL/BLIs in challenging scenarios, thus minimizing the risk of clinical failure and/or of resistance selection.

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.

Pharmacokinetics and Pharmacodynamics of Ceftolozane/Tazobactam in Critically Ill Patients With Augmented Renal Clearance

OBJECTIVE

To determine whether established ceftolozane/tazobactam (C/T) dosing is adequate for patients with augmented renal clearance (ARC) and bacterial infection.

METHODS

ARC (creatinine clearance [CrCl] ≥ 130 mL/min) was confirmed by directly measured CrCl in 11 critically ill patients in a phase 1 pharmacokinetics study. Patients received 3 g C/T (ceftolozane 2 g/tazobactam 1 g) as a 60-minute intravenous infusion. Pharmacokinetic sampling occurred at 0 (predose), 1, 2, 4, 6, and 8 hours after the start of the infusion. Noncompartmental analyses were conducted on concentration data. The following pharmacodynamic targets were evaluated: time that free (unbound) drug concentrations exceeded the minimum inhibitory concentration (fT>MIC) of 4 μg/mL for ceftolozane and time that the unbound concentration exceeded the 1 μg/mL target threshold (fT>threshold = 1 µg/mL) for > 20% of the dosing interval for tazobactam. Safety was evaluated.

RESULTS

Mean (SD) area under the plasma concentration-time curve from 0 to infinity, clearance and volume of distribution at steady state (V_ss) were 236 (118) h*µg/mL, 10.4 (4.5) L/h and 30.8 (10.8) L, respectively, for ceftolozane; and 35.5 (18.5) h*µg/mL, 35.3 (16.5) L/h and 54.8 (20.1) L, respectively, for tazobactam. Clearance and V_ss were higher for both ceftolozane and tazobactam in patients with ARC compared with healthy individuals. The mean estimated ceftolozane fT>MIC at 4 µg/mL was 86.4%; the mean estimated tazobactam fT>threshold = 1 µg/mL was 54.9%. Treatment-emergent adverse events were mild to moderate.

CONCLUSIONS

In patients with ARC, a 3 g C/T dose met respective pharmacodynamic targets for ceftolozane and tazobactam. CLINICALTRIALS.

GOV IDENTIFIER

NCT02387372.

Ceftolozane/Tazobactam-Induced Leukocytosis and Clinical Failure in a Patient Being Treated for Ventilator-Associated Pneumonia Caused by Carbapenem-Resistant Pseudomonas aeruginosa: a Case Report

Ceftolozane/tazobactam is an intravenous beta-lactam/beta-lactamase inhibitor that utilizes a novel oxyimino-cephalosporin with a traditional beta-lactamase inhibitor. It is approved by the Food and Drug Administration to treat complicated intra-abdominal infections in combination with metronidazole, complicated urinary tract infections, and, most recently, hospital-acquired bacterial and ventilator-associated bacterial pneumonias. It is commonly utilized to treat infections caused by multidrug-resistant Pseudomonas aeruginosa. This case report delineates the first published case of ceftolozane/tazobactam-induced leukocytosis (up to 36.9 × 10⁹ cells/L) and clinical failure when utilized in a high-dose regimen for a patient being treated for ventilator-associated pneumonia secondary to carbapenem-resistant P. aeruginosa. The reaction occurred during initial challenge, resolved after discontinuation, and recurred during re-challenge. In patients who are appropriately being treated with ceftolozane/tazobactam for susceptible infections, consider a drug-induced reaction as a potential cause of rising leukocytosis; this should be differentiated from clinical failure if the patient is clinically stable.

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.

Multicenter study of ceftolozane/tazobactam for treatment of Pseudomonas aeruginosa infections in critically ill patients

BACKGROUND

This study aimed to assess the efficacy of ceftolozane-tazobactam (C/T) for treating infections due to Pseudomonas aeruginosa (P. aeruginosa) in critically ill patients.

PATIENTS AND METHODS

A multicenter, retrospective and observational study was conducted in critically ill patients receiving different C/T dosages and antibiotic combinations for P. aeruginosa infections. Demographic data, localisation and severity of infection, clinical and microbiological outcome, and mortality were evaluated.

RESULTS

Ninety-five patients received C/T for P. aeruginosa serious infections. The main infections were nosocomial pneumonia (56.2%), intra-abdominal infection (10.5%), tracheobronchitis (8.4%), and urinary tract infection (6.3%). Most infections were complicated with sepsis (49.5%) or septic shock (45.3%), and bacteraemia (10.5%). Forty-six episodes were treated with high-dose C/T (3 g every 8 hours) and 38 episodes were treated with standard dosage (1.5 g every 8 hours). Almost half (44.2%) of the patients were treated with C/T monotherapy, and the remaining group received combination therapy with other antibiotics. Sixty-eight (71.6%) patients presented a favourable clinical response. Microbiological eradication was documented in 42.1% (40/95) of the episodes. The global ICU mortality was 36.5%. Univariate analysis showed that 30-day mortality was significantly associated (P < 0.05) with Charlson Index at ICU admission and the need of life-supporting therapies.

CONCLUSIONS

C/T appeared to be an effective therapy for severe infections due to P. aeruginosa in critically ill patients. Mortality was mainly related to the severity of the infection. No benefit was observed with high-dose C/T or combination therapy with other antibiotics.

Evaluating the emergence of nonsusceptibility among Pseudomonas aeruginosa respiratory isolates from a phase-3 clinical trial for treatment of nosocomial pneumonia (ASPECT-NP)

OBJECTIVES

The emergence of nonsusceptibility to ceftolozane/tazobactam and meropenem was evaluated among Pseudomonas aeruginosa (P. aeruginosa) lower respiratory tract isolates obtained from participants in the ASPECT-NP clinical trial.

METHODS

ASPECT-NP was a phase-3, randomised, double-blind, multicentre trial that demonstrated noninferiority of 3 g ceftolozane/tazobactam q8h versus 1 g meropenem q8h for treatment of ventilated hospital-acquired/ventilator-associated bacterial pneumonia. Molecular resistance mechanisms among postbaseline nonsusceptible P. aeruginosa isolates and clinical outcomes associated with participants with emergence of nonsusceptibility were examined. Baseline susceptible and postbaseline nonsusceptible P. aeruginosa isolate pairs from the same participant underwent molecular typing.

RESULTS

Emergence of nonsusceptibility was not observed among the 59 participants with baseline susceptible P. aeruginosa isolates in the ceftolozane/tazobactam arm. Among 58 participants with baseline susceptible P. aeruginosa isolates in the meropenem arm, emergence of nonsusceptibility was observed in 13 (22.4%). Among participants who received ceftolozane/tazobactam and meropenem, 5.1% and 3.4% had a new infection with a nonsusceptible strain, respectively. None of the isolates with emergence of nonsusceptibility to meropenem developed co-resistance to ceftolozane/tazobactam. The molecular mechanisms associated with emergence of nonsusceptibility to meropenem were decreased expression or loss of OprD and overexpression of MexXY.

CONCLUSIONS

Among participants with emergence of nonsusceptibility to meropenem, clinical outcomes were similar to overall clinical outcomes in the ASPECT-NP meropenem arm. Ceftolozane/tazobactam was more stable to emergence of nonsusceptibility versus meropenem; emergence of nonsusceptibility was not observed in any participants with baseline susceptible P. aeruginosa who received ceftolozane/tazobactam in ASPECT-NP.

New perspectives in the antibiotic treatment of mechanically ventilated patients with infections from Gram-negatives

Introduction: Ventilator-associated pneumonia (VAP) is a common and potentially fatal complication of mechanical ventilation that is often caused by multidrug-resistant (MDR) Gram-negative bacteria (GNB). Despite the repurposing of older treatments and the novel antimicrobials, many resistance mechanisms cannot be confronted, and novel therapies are needed.Areas covered: We searched the literature for keywords regarding the treatment of GNB infections in mechanically ventilated patients. This narrative review presents new data on antibiotics and non-antibiotic approaches focusing on Phase 3 trials against clinically significant GNB that cause VAP.Expert opinion: Ceftazidime-avibactam, meropenem-vaborbactam, and imipenem-relebactam stand out as new options for infections by Klebsiella pneumoniae carbapenemase-producing bacteria, whereas ceftolozane-tazobactam adds therapeutic flexibility in Pseudomonas aeruginosa infections with multiple resistance mechanisms. Ceftazidime-avibactam and ceftolozane-tazobactam have relevant literature. Aztreonam-avibactam holds promise for the treatment of infections by metallo-β-lactamase (MBL)-producing organisms. Recently approved cefiderocol possesses an extended antibacterial spectrum, including KPC- and MBL-producers. However, recently published data have toned down optimism about treating VAP caused by carbapenem-resistant Acinetobacter baumannii. For the latter, eravacycline may provide additional hope, pending pertinent data. Non-antibiotic treatments currently being considered as adjunct therapeutic approaches are welcome. Nevertheless, they will hopefully substitute current antimicrobials in the future.

Spotlight on New Antibiotics for the Treatment of Pneumonia

In the last years, the presence of multidrug-resistant (MDR) Gram-negative (like Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii) and Gram-positive bacteria (mostly methicillin-resistant Staphylococcus aureus) was worldwide reported, limiting the options for an effective antibiotic therapy. For these reasons, inappropriate antimicrobial therapy and delayed prescription can lead to an unfavorable outcome, especially in patients with pneumonia. New antibiotics approved belong to classes of antimicrobials, like beta-lactams with or without beta-lactamase inhibitors, aminoglycosides, oxazolidinones, quinolones, and tetracyclines, or based on new mechanisms of action. These new compounds show many advantages, including a broad spectrum of activity against MDR pathogens, good lung penetration, safety and tolerability, and finally the possibility of intravenous and/or oral formulations. However, the new antibiotics under development represent an important possible armamentarium against difficult-to-treat strains. The safety and clinical efficacy of these future drugs should be tested in clinical practice. In this review, there are reported characteristics of newly approved antibiotics that represent potential future options for the treatment of respiratory tract infections, including those caused by multidrug-resistant bacteria. Finally, the characteristics of the drugs under development are briefly reported.

Outcomes in Participants with Renal Impairment from a Phase 3 Clinical Trial for Ceftolozane/Tazobactam Treatment of Nosocomial Pneumonia (ASPECT-NP)

In the phase 3 ASPECT-NP trial (NCT02070757), ceftolozane/tazobactam (C/T) was noninferior to meropenem for treatment of Gram-negative ventilated hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia (vHABP/VABP). Here, we report outcomes in participants from ASPECT-NP with renal impairment (RI). Participants were categorized by their baseline renal function as follows: normal renal function (NRF; creatinine clearance [CL_CR], ≥80 ml/min), mild RI (CL_CR, >50 to <80 ml/min), moderate RI (CL_CR, ≥30 to ≤50 ml/min), and severe RI (CL_CR, ≥15 to <30 ml/min). Dosing of both study drugs was adjusted based on renal function. The following C/T doses were administered every 8 h: NRF or mild RI, 3 g; moderate RI, 1.5 g; and severe RI, 0.75 g. The primary and key secondary endpoints were day 28 all-cause mortality (ACM) and clinical response at the test-of-cure visit in the intention-to-treat (ITT) population, respectively. In the ITT population, day 28 ACM rates for the C/T arm versus the meropenem arm were 17.6% versus 19.1% (NRF), 36.6% versus 28.6% (mild RI), 31.4% versus 38.5% (moderate RI), and 35.3% versus 61.9% (severe RI). Rates of clinical cure in the ITT population for the C/T arm versus the meropenem arm were 58.1% versus 58.5% (NRF), 54.9% versus 45.5% (mild RI), 37.1% versus 42.3% (moderate RI), and 41.2% versus 47.6% (severe RI). Small sample sizes in the RI groups resulted in large 95% confidence intervals (CIs), limiting conclusive interpretation of the analysis. Both drugs were well tolerated across all renal function groups. Overall, these results support the use of the study dosing regimens of C/T for treatment of vHABP/VABP in patients with RI. (This study has been registered at ClinicalTrials.gov under identifier NCT02070757.).

In vitro synergy of β-lactam combinations against KPC-producing Klebsiella pneumoniae strains

BACKGROUND

Double carbapenem therapy has been promoted as an alternative treatment for infections due to carbapenemase-producing Enterobacteriaceae where carbapenemase inhibitors are unavailable or when other agents have demonstrated toxicity with equally limited evidence. The capacity of other β-lactams and β-lactamase inhibitors to provide synergistic activity with carbapenems is unclear.

OBJECTIVES

This study sought to investigate the in vitro synergistic potential of other β-lactam/β-lactamase combinations with meropenem against KPC producers.

METHODS

Time-kill assays were performed on 24 unique strains of KPC-producing Klebsiella pneumoniae. Combinations evaluated included meropenem or imipenem with one of the following: ertapenem, piperacillin/tazobactam or ceftolozane/tazobactam. Concentrations used for each drug were those considered physiologically attainable in patients with a time above the concentration exceeding 40%-50% of the dose interval. Combinations were considered to be synergistic when they reduced bacterial cfu/mL by ≥2 log10 at 24 h as compared with the single most active agent.

RESULTS

The combination of piperacillin/tazobactam with meropenem was found to be synergistic against 70.8% of the isolates, followed by ertapenem with meropenem (58.3%) and ceftolozane/tazobactam with meropenem (41.7%). The piperacillin/tazobactam combination was found to be more bactericidal than the other combinations, with 58.3% of isolates demonstrating a ≥4 log10 cfu/mL reduction at 24 h, as compared with 37.5% for ertapenem and 20.8% for ceftolozane/tazobactam combinations.

CONCLUSIONS

The combination of piperacillin/tazobactam with meropenem may be a potential therapy against KPC-producing K. pneumoniae when other therapies are unavailable or prohibitively toxic.

Population Pharmacokinetic Analysis for Plasma and Epithelial Lining Fluid Ceftolozane/Tazobactam Concentrations in Patients With Ventilated Nosocomial Pneumonia

Ceftolozane/tazobactam (C/T) is a combination of a novel cephalosporin with tazobactam, recently approved for the treatment of hospital-acquired and ventilator-associated pneumonia. The plasma pharmacokinetics (PK) of a 3-g dose of C/T (2 g ceftolozane and 1 g tazobactam) administered via a 1-hour infusion every 8 hours in adult patients with nosocomial pneumonia (NP) were evaluated in a phase 3 study (ASPECT-NP; NCT02070757). The present work describes the development of population PK models for ceftolozane and tazobactam in plasma and pulmonary epithelial lining fluid (ELF). The concentration-time profiles of both agents were well characterized by 2-compartment models with zero-order input and first-order elimination. Consistent with the elimination pathway, renal function estimated by creatinine clearance significantly affected the clearance of ceftolozane and tazobactam. The central volumes of distribution for both agents and the peripheral volume of distribution for tazobactam were approximately 2-fold higher in patients with pneumonia compared with healthy participants. A hypothetical link model was developed to describe ceftolozane and tazobactam disposition in ELF in healthy participants and patients with pneumonia. Influx (from plasma to the ELF compartment) and elimination (from the ELF compartment) rate constants were approximately 97% lower for ceftolozane and 52% lower for tazobactam in patients with pneumonia versus healthy participants. These population PK models adequately described the plasma and ELF concentrations of ceftolozane and tazobactam, thus providing a foundation for further modeling and simulation, including the probability of target attainment assessments to support dose recommendations of C/T in adult patients with NP.

Pharmacologic optimization of antibiotics for Gram-negative infections

PURPOSE OF REVIEW

Antimicrobial resistance among Gram-negative organisms is a rapidly escalating global challenge. Pharmacologic dose optimization based on pharmacokinetic/pharmacodynamic principles is essential for managing Gram-negative infections. High-risk patient populations may receive nonoptimized antimicrobial dosing because pf physiologic changes in acute illness and/or medical interventions. The purpose of this review is to discuss opportunities for pharmacologic optimization of new agents and highlight patient populations that are often associated with poor drug exposure profiles.

RECENT FINDINGS

Dose optimization of the novel β-lactam-β-lactamase inhibitor combinations has been evaluated through optimizing exposure at the site of infection, evaluating target attainment of both the β-lactam and the β-lactamase-inhibitor in critically ill patients, and evaluating drug exposure to prevent the development of resistance. Plazomicin, a novel aminoglycoside, has pharmacodynamic optimization potential via therapeutic drug monitoring and nomogram-based dosing. Recent studies have evaluated the adequacy of dosing in varying degrees of renal function specifically acute kidney injury, continuous renal replacement therapy (CRRT), and augmented renal clearance (ARC).

SUMMARY

The application of fundamental pharmacokinetic/pharmacodynamic principles is required to optimize new antimicrobials in the treatment of serious Gram-negative infections. Exposure at the site of infection, pharmacokinetics in critically ill patients, and exposures to prevent resistance are all considerations to improve microbiologic and clinical outcomes. Therapeutic drug monitoring may be needed for high-risk patients.

Plasma pharmacokinetics of ceftolozane/tazobactam in pediatric patients with cystic fibrosis

BACKGROUND

The antipseudomonal cephalosporin/β-lactamase inhibitor combination ceftolozane/tazobactam could be a potential treatment option for cystic fibrosis (CF) pulmonary exacerbations. The pharmacokinetics (PK) of ceftolozane/tazobactam in children with CF merits further evaluation.

METHODS

This is a retrospective subgroup analysis of a phase 1, noncomparative trial that characterized PK, safety, and tolerability of single intravenous doses of ceftolozane/tazobactam in pediatric patients. This analysis compares ceftolozane and tazobactam plasma PK parameters, estimated from a population PK model, between patients with and without CF enrolled in that trial. Individual attainment of PK/pharmacodynamic (PD) targets of ceftolozane and tazobactam (free ceftolozane concentration >4 µg/mL for >30% and free tazobactam concentration >1 µg/mL for 20% of the dosing interval) in patients with and without CF were evaluated.

RESULTS

The study enrolled 18 patients aged greater than or equal to 2 to less than 18 years old, which included 9 with CF. Weight-normalized ceftolozane PK parameters were similar between patients with CF (clearance: 0.16 L/h/kg, half-life: 1.54 hours, volume of distribution: 0.26 L/kg) and without CF (clearance: 0.15 L/h/kg, half-life: 1.62 hours, volume of distribution: 0.26 L/kg), as were most weight-normalized tazobactam PK parameters. Weight-normalized tazobactam clearance was higher in patients with CF (0.73 L/h/kg) than patients without CF (0.42 L/h/kg). All patients achieved the prespecified PK/PD targets for ceftolozane and tazobactam.

CONCLUSIONS

This retrospective analysis demonstrated generally similar weight-normalized plasma PK parameters for ceftolozane and tazobactam among children with and without CF; thus, projected doses for treatment of pediatric hospital-acquired/ventilator-associated pneumonia, which are higher than the pediatric complicated urinary tract infection/intra-abdominal infection doses, may be appropriate for treatment of CF pulmonary exacerbation.