Activity of Ceftolozane-Tazobactam against Pseudomonas aeruginosa and Enterobacteriaceae Isolates Collected from Respiratory Tract Specimens of Hospitalized Patients in the United States during 2013 to 2015

In vitro activity of plazomicin and other aminoglycosides against Klebsiella pneumoniae multidrug-resistant strains

Plazomicin is a new aminoglycoside with broad-spectrum activity against multidrug-resistant strains. The aim of this study was to assess the susceptibility of the K. pneumoniae strains to plazomicin and other aminoglycosides. The activity of plazomicin in combination with ceftazidim-avibactam or meropenem with selected strains was evaluated. The study involved 60 ESβL-positive K. pneumoniae isolates and 50 carbapenemase-positive. The susceptibility to aminoglycosides was tested using the gradient strip. The in vitro activities of plazomicin and ceftazidim-avibactam or meropenem were evaluated using the MTSTM cross synergy method. Plazomicin exhibited high activity against K. pneumoniae with MICs ranging from 0.19 to 4 µg ml-1 for ESβL-positive strains and from 0.25 to 256 µg ml-1 for carbapenemase-positive strains. No antagonism was identified with any combinations. Plazomicin demonstrated excellent in vitro activity against analyzed strains, suggesting that this antibiotic may be an effective therapeutic option in the treatment of infections caused by MDR K. pneumoniae strains.

Ceftolozane/tazobactam: Literature review of its activity on Taiwanese isolates before its launch in Taiwan (2012-2021)

Ceftolozane, a novel cephalosporin, combined with tazobactam, a known β-lactamase inhibitor, shows robust antipseudomonal activity, although it doesn't cover carbapenemases. Our review of data from 2012 to 2021 in Taiwan highlights TOL/TAZ's in-vitro performance. TOL/TAZ is most effective against Pseudomonas aeruginosa (91.3-94.4 % susceptible, with an MIC <4 μg/mL). It also demonstrates good activity against Enterobacterales, including Escherichia coli (88-94.3 % susceptible), Klebsiella pneumoniae (72.6-84.1 % susceptible), Citrobacter koseri (93.3 % susceptible), Klebsiella oxytoca (98.1-100 % susceptible), and Proteus mirabilis (100 % susceptible). However, its efficacy varies among species typically associated with chromosomally-mediated AmpC production, such as Morganella morganii (100 % susceptible), Serratia marcescens (81.3-90.0 % susceptible), Enterobacter cloacae species complex (76.6-76.7 % susceptible), Klebsiella aerogenes (66.7-89.6% susceptible), and Citrobacter freundii (60.0 % susceptible). For carbapenem-nonsusceptible isolates, TOL/TAZ is less effective against K. pneumoniae and E. coli (susceptibility <10 %) but remains useful for P. aeruginosa (susceptibility 81.3-91.8 %). In conclusion, TOL/TAZ shows potent activity against P. aeruginosa and carbapenem-susceptible Enterobacterales in Taiwan.

Activity of ceftolozane/tazobactam, imipenem/relebactam and ceftazidime/avibactam against clinical Gram-negative isolates-SMART United States 2019-21

Background

Ongoing national and international surveillance efforts are critical components of antimicrobial stewardship, resistance monitoring, and drug development programs. In this report, we summarize the results of ceftolozane/tazobactam, imipenem/relebactam, ceftazidime/avibactam and comparator agent testing against 10 509 Enterobacterales and 2524 Pseudomonas aeruginosa collected by USA clinical laboratories in 2019-21 as part of the SMART global surveillance programme.

Methods

MICs were determined by CLSI broth microdilution and interpreted using 2023 CLSI M100 breakpoints.

Results

Most Enterobacterales were ceftazidime/avibactam susceptible (>99%), meropenem susceptible (99%) and ceftolozane/tazobactam susceptible (94%). Non-Morganellaceae Enterobacterales were also highly susceptible to imipenem/relebactam (99%). Ceftolozane/tazobactam inhibited 94% of Escherichia coli and 89% of Klebsiella pneumoniae with ceftriaxone non-susceptible/non-carbapenem-resistant phenotypes. Against P. aeruginosa, ceftolozane/tazobactam (97% susceptible) was more active than ceftazidime/avibactam (95%) and imipenem/relebactam (91%). MDR and difficult-to-treat resistance (DTR) phenotypes were identified in 13% and 7% of P. aeruginosa isolates, respectively. Ceftolozane/tazobactam remained active against 78% of MDR P. aeruginosa (13% and 23% higher than ceftazidime/avibactam and imipenem/relebactam, respectively) and against 74% of DTR P. aeruginosa (24% and 37% higher than ceftazidime/avibactam and imipenem/relebactam, respectively). Length of hospital stay at the time of specimen collection, ward type and infection type resulted in percent susceptible value differences of >5% across isolate demographic strata for some antimicrobial agent/pathogen combinations.

Conclusions

We conclude that in the USA, in 2019-21, carbapenem (meropenem) resistance remained uncommon in Enterobacterales and ceftolozane/tazobactam was more active than both ceftazidime/avibactam and imipenem/relebactam against 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.

A single- and multiple-dose study to characterize the pharmacokinetics, safety, and tolerability of ceftolozane/tazobactam in healthy Chinese participants

Ceftolozane/tazobactam (C/T) is approved in several countries to treat complicated urinary tract infections, complicated intra-abdominal infections, and nosocomial pneumonia. There is a paucity of pharmacokinetics and safety data for C/T in Chinese participants. This study evaluated the pharmacokinetics, safety, and tolerability of C/T in 12 healthy Chinese participants after three single administrations of increasing doses (0.75 g, 1.5 g, and 3 g) and multiple administrations of 1.5 g C/T every 8 h for 3 days. After single doses, maximum concentrations of ceftolozane and tazobactam were reached by the end of the 1-h infusion and declined in a biphasic manner thereafter, with mean half-lives of 1.9-2.2 h and 0.74-0.95 h, respectively. Volume of distribution (V_d) and renal clearance (CL) were consistent across the three single-dose levels for ceftolozane (V_d, 15.8-19.5 L; CL, 5.68-6.09 L/h) and tazobactam (V_d, 23.3-28.6 L; CL, 20.8-23.5 L/h). Area under the concentration-time curve (AUC) extrapolated to infinity (ceftolozane, 88.1-328 h∙μg/mL; tazobactam, 10.7-48.0 h∙μg/mL) increased in a dose-dependent manner. After multiple doses over 3 days, AUC from time 0 to 8 h, and concentration at the end of infusion were similar to single-dose measurements (geometric mean ratios, 0.87-1.01 for both drugs). C/T was well tolerated, with no serious adverse events or discontinuations reported; all adverse events were mild. The pharmacokinetics and safety/tolerability of C/T in healthy Chinese participants was comparable to that in previous studies in other populations, supporting the use of C/T for the treatment of Chinese patients.

Ceftolozane-Tazobactam Pharmacokinetics in the Abdominal Tissue of Patients Undergoing Lower Gastrointestinal Surgery: Dosing Considerations Based on Site-Specific Pharmacodynamic Target Attainment

INTRODUCTION

Recently, complicated intra-abdominal infections (cIAI) have been caused not only by Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, and Pseudomonas aeruginosa, but also by extended-spectrum β-lactamase-producing Enterobacterales members. Ceftolozane-tazobactam (CTLZ-TAZ) is considered to exhibit therapeutic effects against cIAI. Studies on the concentrations of antibiotics in abdominal tissues directly affected by cIAI are limited. Therefore, in this study, we investigated the pharmacokinetics of CTLZ-TAZ in abdominal tissue and simulated the administration regimen required to achieve the pharmacodynamic target for cIAI-causing bacteria.

METHODS

Patients scheduled for elective lower gastrointestinal surgery were intravenously administered preoperative CTLZ-TAZ (1 g CTLZ and 0.5 g TAZ). Plasma, peritoneal fluid, peritoneum, and subcutaneous adipose tissue samples were collected during the surgery, and CTLZ as well as TAZ concentrations were measured. The noncompartmental and compartmental pharmacokinetic parameters were then estimated. Site-specific pharmacodynamic target attainment analysis using 1.5 g of CTLZ-TAZ was performed.

RESULTS

CTLZ-TAZ was administered to nine patients (once to five patients and twice to four patients). The mean peritoneal fluid-to-plasma ratio (one dose/two doses) for CTLZ was 0.74/1.15, which was slightly higher than the mean peritoneal fluid-to-plasma ratio for TAZ (0.95/1.13). The ratio for subcutaneous adipose was lower than those for peritoneal fluid and peritoneum tissues. We also discovered that the average ratio of CTLZ and TAZ concentrations in all tissues was maintained at or above 2:1. In our investigation of pharmacodynamic target attainment in each tissue, the desired bactericidal effect was attained with all CTLZ-TAZ (1.5 g) administration regimens [q12h (3 g/day), q8h (4.5 g/day), and q6h (6 g/day)].

CONCLUSION

To the best of our knowledge, this is the first study investigating the optimal pharmacodynamic level of CTLZ-TAZ in the abdominal tissue against cIAI-causing bacteria. This study also serves as a guideline for designing an optimal administration regimen based on pharmacodynamic target attainment for cIAI-causing bacteria.

DETAILS OF THE TRIAL REGISTRATION

The institutional review board of Hiroshima University Hospital, CRB6180006. The Japan Registry of Clinical Trials, jRCTs061190025.

New antibiotics for Gram-negative pneumonia

Pneumonia is frequently encountered in clinical practice, and Gram-negative bacilli constitute a significant proportion of its aetiology, especially when it is acquired in a hospital setting. With the alarming global rise in multidrug resistance in Gram-negative bacilli, antibiotic therapy for treating patients with pneumonia is challenging and must be guided by in vitro susceptibility results. In this review, we provide an overview of antibiotics newly approved for the treatment of pneumonia caused by Gram-negative bacilli. Ceftazidime-avibactam, imipenem-relebactam and meropenem-vaborbactam have potent activity against some of the carbapenem-resistant Enterobacterales, especially Klebsiella pneumoniae carbapenemase producers. Several novel antibiotics have potent activity against multidrug-resistant Pseudomonas aeruginosa, such as ceftazidime-avibactam, ceftolozane-tazobactam, imipenem-relabactam and cefiderocol. Cefiderocol may also play an important role in the management of pneumonia caused by Acinetobacter baumannii, along with plazomicin and eravacycline.

Outcomes in participants with failure of initial antibacterial therapy for hospital-acquired/ventilator-associated bacterial pneumonia prior to enrollment in the randomized, controlled phase 3 ASPECT-NP trial of ceftolozane/tazobactam versus meropenem

BACKGROUND

Ceftolozane/tazobactam, a combination antibacterial agent comprising an anti-pseudomonal cephalosporin and β-lactamase inhibitor, is approved for the treatment of hospital-acquired/ventilator-associated bacterial pneumonia (HABP/VABP) in adults. Participants in the ASPECT-NP trial received ceftolozane/tazobactam (3 g [2 g ceftolozane/1 g tazobactam] every 8 h) or meropenem (1 g every 8 h). Participants failing prior antibacterial therapy for the current HABP/VABP episode at study entry had lower 28-day all-cause mortality (ACM) rates with ceftolozane/tazobactam versus meropenem treatment. Here, we report a post hoc analysis examining this result.

METHODS

The phase 3, randomized, controlled, double-blind, multicenter, noninferiority trial compared ceftolozane/tazobactam versus meropenem for treatment of adults with ventilated HABP/VABP; eligibility included those failing prior antibacterial therapy for the current HABP/VABP episode at study entry. The primary and key secondary endpoints were 28-day ACM and clinical response at test of cure (TOC), respectively. Participants who were failing prior therapy were a prospectively defined subgroup; however, subgroup analyses were not designed for noninferiority testing. The 95% CIs for treatment differences were calculated as unstratified Newcombe CIs. Post hoc analyses were performed using multivariable logistic regression analysis to determine the impact of baseline characteristics and treatment on clinical outcomes in the subgroup who were failing prior antibacterial therapy.

RESULTS

In the ASPECT-NP trial, 12.8% of participants (93/726; ceftolozane/tazobactam, n = 53; meropenem, n = 40) were failing prior antibacterial therapy at study entry. In this subgroup, 28-day ACM was higher in participants who received meropenem versus ceftolozane/tazobactam (18/40 [45.0%] vs 12/53 [22.6%]; percentage difference [95% CI]: 22.4% [3.1 to 40.1]). Rates of clinical response at TOC were 26/53 [49.1%] for ceftolozane/tazobactam versus 15/40 [37.5%] for meropenem (percentage difference [95% CI]: 11.6% [- 8.6 to 30.2]). Multivariable regression analysis determined concomitant vasopressor use and treatment with meropenem were significant factors associated with risk of 28-day ACM. Adjusting for vasopressor use, the risk of dying after treatment with ceftolozane/tazobactam was approximately one-fourth the risk of dying after treatment with meropenem.

CONCLUSIONS

This post hoc analysis further supports the previously demonstrated lower ACM rate for ceftolozane/tazobactam versus meropenem among participants who were failing prior therapy, despite the lack of significant differences in clinical cure rates.

CLINICALTRIALS

gov registration NCT02070757 . Registered February 25, 2014, clinicaltrials.gov/ct2/show/NCT02070757 .

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.

In Vitro Activity of Ceftolozane-Tazobactam, Imipenem-Relebactam, Ceftazidime-Avibactam, and Comparators against Pseudomonas aeruginosa Isolates Collected in United States Hospitals According to Results from the SMART Surveillance Program, 2018 to 2020

Ceftolozane-tazobactam (C/T), imipenem-relebactam (IMR), and ceftazidime-avibactam (CZA) were tested against 2,531 P. aeruginosa strains isolated from patients in the United States from 2018 to 2020 as part of the SMART (Study for Monitoring Antimicrobial Resistance Trends) surveillance program. MICs were determined by CLSI broth microdilution and interpreted using CLSI M100 (2021) breakpoints. Imipenem-, IMR-, or C/T-nonsusceptible isolates were screened for β-lactamase genes: 96.4% of all isolates and ≥70% of multidrug-resistant (MDR), pan-β-lactam-nonsusceptible, and difficult-to-treat resistance (DTR) isolates were C/T-susceptible; 52.2% of C/T-nonsusceptible isolates remained susceptible to IMR compared to 38.9% for CZA; and 1.7% of isolates tested were nonsusceptible to both C/T and IMR versus 2.2% of isolates with a C/T-nonsusceptible and CZA-resistant phenotype (a difference of 12 isolates). C/T and IMR modal MICs for pan-β-lactam-nonsusceptible isolates remained at or below their respective susceptible MIC breakpoints from 2018 to 2020, while the modal MIC for CZA increased 2-fold from 2018 to 2019 and exceeded the CZA-susceptible MIC breakpoint in both 2019 and 2020. Only six of 802 molecularly characterized isolates carried a metallo-β-lactamase, and two isolates carried a GES carbapenemase. Most P. aeruginosa isolates were C/T-susceptible, including many with MDR, pan-β-lactam-nonsusceptible, DTR, CZA-resistant, and IMR-nonsusceptible phenotypes. While C/T was the most active antipseudomonal agent, IMR demonstrated greater activity than CZA against isolates nonsusceptible to C/T.

Exposure-Efficacy Analyses Support Optimal Dosing Regimens of Ceftolozane/Tazobactam in Participants with Hospital-Acquired/Ventilator-Associated Bacterial Pneumonia in ASPECT-NP

An exposure–efficacy analysis of the phase 3 ASPECT-NP trial was performed to evaluate the relationship between plasma exposure of ceftolozane and tazobactam and efficacy endpoints (primary: 28-day all-cause mortality; key secondary: clinical cure at test-of-cure visit) in adult participants with hospital-acquired or ventilator-associated bacterial pneumonia (HABP/VABP). Participants (N = 231) from the ceftolozane/tazobactam treatment group in the intention-to-treat population who had pharmacokinetic data available and relevant baseline lower respiratory tract (LRT) pathogen(s) susceptibility data were included. Population pharmacokinetic models were used to predict individual ceftolozane and tazobactam plasma exposure measures (percentage of the interdose interval with free drug concentrations above the MIC [%ƒT>MIC] and %ƒT above a threshold [%ƒT>C_T = 1 μg/mL], respectively) associated with the last dose using the highest ceftolozane/tazobactam MIC for the relevant baseline LRT pathogens. Efficacy measures were comparable between the baseline LRT pathogens and across MIC cutoffs (1–8 μg/mL). Most participants (82%) had 99% ƒT>MIC for ceftolozane; 9% (N = 21/231) had 0% ƒT>MIC due to high MICs of the LRT pathogen (64–256 μg/mL). The %ƒT>MIC for ceftolozane exceeded 73% for all participants with baseline LRT pathogen(s) MIC ≤4 μg/mL. All 231 participants achieved the tazobactam pharmacokinetic/pharmacodynamic target of >20% ƒT>C_T where C_T = 1 μg/mL. For either efficacy endpoint, median ceftolozane %ƒT>MIC was 99% in participants achieving efficacy. No exposure–efficacy trend was observed for ceftolozane or tazobactam. These results further support the recommended ceftolozane/tazobactam dosing regimens evaluated in ASPECT-NP for patients with HABP/VABP.

Activity of ceftolozane/tazobactam against Gram-negative isolates among different infections in Hong Kong: SMART 2017-2019

Introduction. Ceftolozane/tazobactam was approved by the Drug Office, Department of Health, Government of the Hong Kong Special Administrative Region in 2017.Hypothesis/Gap Statement. Currently the in vitro activity of ceftolozane/tazobactam against Gram-negative pathogens isolated from patients in Hong Kong is undocumented. It would be prudent to document the activity of ceftolozane/tazobactam against Pseudomonas aeruginosa and Enterobacterales isolated from hospitalized patients in Hong Kong.Aim. To describe the in vitro susceptibility of recent clinical isolates of P. aeruginosa and the two most common Enterobacterales species (Klebsiella pneumoniae, Escherichia coli) cultured from respiratory tract, intra-abdominal, urinary tract and bloodstream infection samples to ceftolozane/tazobactam and other commonly used antimicrobial agents.Methodology. CLSI-defined broth microdilution MICs were determined and interpreted for Gram-negative isolates collected in Hong Kong from 2017 to 2019 by the SMART surveillance programme.Results. For P. aeruginosa, 96.7 % of isolates (n=210) were susceptible to ceftolozane/tazobactam, while susceptibility rates were ≥14 % lower to meropenem (82.9 % susceptible), cefepime (82.4 %), ceftazidime (81.4 %), piperacillin/tazobactam (76.7 %) and levofloxacin (79.5 %). Ceftolozane/tazobactam inhibited 85.7 % of piperacillin/tazobactam-nonsusceptible isolates, 80.6-82.1 % of cefepime-, ceftazidime- or meropenem-nonsusceptible isolates, and 75.9 % of multidrug-resistant (MDR) isolates of P. aeruginosa. For K. pneumoniae, 96.1 % of isolates (n=308) were susceptible to ceftolozane/tazobactam compared with meropenem (99.0 % susceptible), piperacillin/tazobactam (93.8 %), cefepime (85.7 %) and ceftazidime (85.4 %). The majority (88.3 %) of ESBL (extended-spectrum β-lactamase) non-CRE (carbapenem-resistant Enterobacterales) phenotype isolates of K. pneumoniae were susceptible to ceftolozane/tazobactam, comparable to piperacillin/tazobactam (85.0 %) but lower than meropenem (100 %). For E. coli, 98.5 % of isolates (n=609) were susceptible to ceftolozane/tazobactam compared to meropenem (99.3 % susceptible), piperacillin/tazobactam (96.7 %), ceftazidime (82.3 %) and cefepime (76.5 %). The majority (96.7 %) of ESBL non-CRE phenotype isolates of E. coli were susceptible to ceftolozane/tazobactam, similar to both meropenem (100 %) and piperacillin/tazobactam (94.5 %).Conclusions. Overall, >96 % of clinical isolates of P. aeruginosa, K. pneumoniae and E. coli collected in Hong Kong in 2017-2019 were susceptible to ceftolozane/tazobactam, while the activity of several commonly prescribed β-lactams was reduced, especially for P. aeruginosa. Continued surveillance of ceftolozane/tazobactam and other agents is warranted.

Infectious Diseases Society of America 2022 Guidance on the Treatment of Extended-Spectrum β-lactamase Producing Enterobacterales (ESBL-E), Carbapenem-Resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with Difficult-to-Treat Resistance (DTR-P. aeruginosa)

BACKGROUND

The Infectious Diseases Society of America (IDSA) is committed to providing up-to-date guidance on the treatment of antimicrobial-resistant infections. The initial guidance document on infections caused by extended-spectrum β-lactamase producing Enterobacterales (ESBL-E), carbapenem-resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with difficult-to-treat resistance (DTR-P. aeruginosa) was published on 17 September 2020. Over the past year, there have been a number of important publications furthering our understanding of the management of ESBL-E, CRE, and DTR-P. aeruginosa infections, prompting a rereview of the literature and this updated guidance document.

METHODS

A panel of 6 infectious diseases specialists with expertise in managing antimicrobial-resistant infections reviewed, updated, and expanded previously developed questions and recommendations about the treatment of ESBL-E, CRE, and DTR-P. aeruginosa infections. Because of differences in the epidemiology of resistance and availability of specific anti-infectives internationally, this document focuses on the treatment of infections in the United States.

RESULTS

Preferred and alternative treatment recommendations are provided with accompanying rationales, assuming the causative organism has been identified and antibiotic susceptibility results are known. Approaches to empiric treatment, duration of therapy, and other management considerations are also discussed briefly. Recommendations apply for both adult and pediatric populations.

CONCLUSIONS

The field of antimicrobial resistance is highly dynamic. Consultation with an infectious diseases specialist is recommended for the treatment of antimicrobial-resistant infections. This document is current as of 24 October 2021. The most current versions of IDSA documents, including dates of publication, are available at www.idsociety.org/practice-guideline/amr-guidance/.

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.

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.

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.

Infectious Diseases Society of America Guidance on the Treatment of Extended-Spectrum β-lactamase Producing Enterobacterales (ESBL-E), Carbapenem-Resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with Difficult-to-Treat Resistance (DTR-P. aeruginosa)

BACKGROUND

Antimicrobial-resistant infections are commonly encountered in US hospitals and result in significant morbidity and mortality. This guidance document provides recommendations for the treatment of infections caused by extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E), carbapenem-resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with difficult-to-treat resistance (DTR-P. aeruginosa).

METHODS

A panel of 6 infectious diseases specialists with expertise in managing antimicrobial-resistant infections formulated common questions regarding the treatment of ESBL-E, CRE, and DTR-P. aeruginosa infections. Based on review of the published literature and clinical experience, the panel provide recommendations and associated rationale for each recommendation. Because of significant differences in the molecular epidemiology of resistance and the availability of specific anti-infective agents globally, this document focuses on treatment of antimicrobial-resistant infections in the United States.

RESULTS

Approaches to empiric treatment selection, duration of therapy, and other management considerations are briefly discussed. The majority of guidance focuses on preferred and alternative treatment recommendations for antimicrobial-resistant infections, assuming that the causative organism has been identified and antibiotic susceptibility testing results are known. Treatment recommendations apply to both adults and children.

CONCLUSIONS

The field of antimicrobial resistance is dynamic and rapidly evolving, and the treatment of antimicrobial-resistant infections will continue to challenge clinicians. This guidance document is current as of 17 September 2020. Updates to this guidance document will occur periodically as new data emerge. Furthermore, the panel will expand recommendations to include other problematic gram-negative pathogens in future versions. The most current version of the guidance including the date of publication can be found at www.idsociety.org/practice-guideline/amr-guidance/.

Present and Future Perspectives on Therapeutic Options for Carbapenemase-Producing Enterobacterales Infections

Carbapenem-resistant Enterobacterales (CRE) are included in the list of the most threatening antibiotic resistance microorganisms, being responsible for often insurmountable therapeutic issues, especially in hospitalized patients and immunocompromised individuals and patients in intensive care units. The enzymatic resistance to carbapenems is encoded by different β-lactamases belonging to A, B or D Ambler class. Besides compromising the activity of last-resort antibiotics, CRE have spread from the clinical to the environmental sectors, in all geographic regions. The purpose of this review is to present present and future perspectives on CRE-associated infections treatment.

Evaluation of in vitro activity of ceftolozane-tazobactam in combination with other classes of antibacterial agents against Enterobacterales and Pseudomonas aeruginosa-the EM200 study

Ceftolozane-tazobactam is a cephalosporin/β-lactamase inhibitor combination developed for use against some β-lactam- and multidrug-resistant Gram-negative organisms. This study aimed to evaluate the in vitro activity of ceftolozane-tazobactam against clinical bacterial isolates at the University Hospital of Marrakech. This is a descriptive and analytical prospective study. A total of 143 Enterobacterales and 48 Pseudomonas aeruginosa isolates were collected from January 2018 to December 2018 from patients with respiratory, urinary and intra-abdominal infections. The identification was made by Phoenix automated system (BioMérieux). MIC50/90 were tested by broth microdilution for ceftolozane-tazobactam, and other drugs using dried panels. Antimicrobial susceptibility results were interpreted according to CLSI guidelines. Ceftolozane-tazobactam inhibited 98% of Escherichia coli (MIC_50/90; 0.25/0.5 μg/mL). The susceptibility rate of Klebsiella pneumoniae to ceftolozane-tazobactam was 68.8% (MIC_50/90, 0.5/>32 μg/mL); other Enterobacterales have shown susceptibility rates of 80.4% (MIC_50/90; 0.5/8 μg/mL). In carbapenemase-producing K. pneumoniae, the bla _OXA-48 mutation was found in two isolates. Susceptibility of P. aeruginosa to ceftolozane-tazobactam was 91.7% (MIC_50/90, 0.5/>32 μg/mL). In non-carbapenemase-producing P. aeruginosa, AmpC mutations were found in all isolates. Ceftolozane-tazobactam was satisfactorily active against a wide range of tested isolates and offers clinicians a potential therapeutic option even against resistant strains in patients with intra-abdominal infections, urinary tract infections and nosocomial pneumonia.

Activity of ceftolozane/tazobactam against Gram-negative isolates from patients with lower respiratory tract infections - SMART United States 2018-2019

BACKGROUND

Ceftolozane/tazobactam (C/T) is approved in 70 countries, including the United States, for the treatment of patients with hospital-acquired and ventilator-associated bacterial pneumonia caused by susceptible Gram-negative pathogens. C/T is of particular importance as an agent for the treatment of multidrug-resistant (MDR) Pseudomonas aeruginosa infections. The current study summarizes 2018-2019 data from the United States on lower respiratory tract isolates of Gram-negative bacilli from the SMART global surveillance program. The CLSI reference broth microdilution method was used to determine in vitro susceptibility of C/T and comparators against isolates of P. aeruginosa and Enterobacterales.

RESULTS

C/T inhibited 96.0% of P. aeruginosa (n = 1237) at its susceptible MIC breakpoint (≤4 μg/ml), including > 85% of meropenem-nonsusceptible and piperacillin/tazobactam (P/T)-nonsusceptible isolates and 76.2% of MDR isolates. Comparator agents demonstrated lower activity than C/T against P. aeruginosa: meropenem (74.8% susceptible), cefepime (79.2%), ceftazidime (78.5%), P/T (74.4%), and levofloxacin (63.1%). C/T was equally active against ICU (96.0% susceptible) and non-ICU (96.7%) isolates of P. aeruginosa. C/T inhibited 91.8% of Enterobacterales (n = 1938) at its susceptible MIC breakpoint (≤2 μg/ml); 89.5% of isolates were susceptible to cefepime and 88.0% susceptible to P/T. 67.1 and 86.5% of extended-spectrum β-lactamase (ESBL) screen-positive isolates of Klebsiella pneumoniae (n = 85) and Escherichia coli (n = 74) and 49.6% of MDR Enterobacterales were susceptible to C/T. C/T was equally active against ICU (91.3% susceptible) and non-ICU (92.6%) Enterobacterales isolates.

CONCLUSION

Data from the current study support the use of C/T as an important treatment option for lower respiratory tract infections including those caused by MDR P. aeruginosa.

Molecular Characterization of Baseline Enterobacterales and Pseudomonas aeruginosa Isolates from a Phase 3 Nosocomial Pneumonia (ASPECT-NP) Clinical Trial

We reviewed β-lactam-resistant baseline Enterobacterales species and Pseudomonas aeruginosa lower respiratory tract isolates collected during the ASPECT-NP phase 3 clinical trial that evaluated the safety and efficacy of ceftolozane-tazobactam compared with meropenem for the treatment of nosocomial pneumonia in ventilated adults. Isolates were subjected to whole-genome sequencing, real-time PCR for the quantification of the expression levels of β-lactamase and efflux pump genes, and Western blot analysis for the detection of OprD (P. aeruginosa only). Extended-spectrum β-lactamase (ESBL) genes were detected in 168 of 262 Enterobacterales isolates, and among these, bla _CTX-M-15 was the most common, detected in 125 isolates. Sixty-one Enterobacterales isolates carried genes encoding carbapenemases, while 33 isolates did not carry ESBLs or carbapenemases. Carbapenemase-producing isolates carried mainly NDM and OXA-48 variants, with ceftolozane-tazobactam MIC values ranging from 4 to 128 µg/ml. Most ceftolozane-tazobactam-nonsusceptible Enterobacterales isolates that did not carry carbapenemases were Klebsiella pneumoniae isolates that exhibited disrupted OmpK35, specific mutations in OmpK36, and, in some isolates, elevated expression of bla _CTX-M-15 Among 89 P. aeruginosa isolates, carbapenemases and ESBL-encoding genes were observed in 12 and 22 isolates, respectively. P. aeruginosa isolates without acquired β-lactamases displaying elevated expression of AmpC (14 isolates), elevated expression of efflux pumps (11 isolates), and/or a decrease or loss of OprD (22 isolates) were susceptible to ceftolozane-tazobactam. Ceftolozane-tazobactam was active against >75% of the Enterobacterales isolates from the ASPECT-NP trial that did not carry carbapenemases. K. pneumoniae strains resistant to ceftolozane-tazobactam might represent a challenge for treatment due to their multiple resistance mechanisms. Ceftolozane-tazobactam was among the agents that displayed the greatest activity against P. aeruginosa isolates. (This study has been registered at ClinicalTrials.gov under registration no. NCT02070757.).

Susceptibility trends of ceftolozane/tazobactam and comparators when tested against U.S. gram-negative bacterial surveillance isolates (2012-2018)

Ceftolozane/tazobactam is an antipseudomonal cephalosporin combined with a β-lactamase inhibitor. Ceftolozane/tazobactam has been approved in >60 countries for treating complicated urinary tract infections, acute pyelonephritis, complicated intra-abdominal infections (with metronidazole), and hospital-acquired pneumonia, including ventilator-associated pneumonia in adults. We analyzed susceptibilities for 35,882 gram-negative isolates collected from patients in 35 US medical centers from 2012 to 2018. The rate of multi-drug resistant Enterobacterales was stable (9.5%-10.1%), while the P. aeruginosa multi-drug resistance rate increased from 15.5% in 2012 to 22.9% in 2018. The carbapenem-resistant Enterobacterales rates varied from 0.9% to 2.2% and extended-spectrum β-lactamase phenotypes increased from 10.5% to 16.8%. The most active drugs against P. aeruginosa were ceftolozane/tazobactam (95.8%-97.5% susceptible) and amikacin (93.9%-98.0%); against Enterobacterales, amikacin (97.9%-98.8%), meropenem (97.7%-98.8%), and ceftolozane/tazobactam (93.3%-95.6%) were the most active. These data suggest that ceftolozane/tazobactam has effective in vitro activity against organisms causing serious gram-negative infections.

New β-Lactam-β-Lactamase Inhibitor Combinations

The limited armamentarium against drug-resistant Gram-negative bacilli has led to the development of several novel β-lactam-β-lactamase inhibitor combinations (BLBLIs). In this review, we summarize their spectrum of in vitro activities, mechanisms of resistance, and pharmacokinetic-pharmacodynamic (PK-PD) characteristics. A summary of available clinical data is provided per drug. Four approved BLBLIs are discussed in detail. All are options for treating multidrug-resistant (MDR) Enterobacterales and Pseudomonas aeruginosa Ceftazidime-avibactam is a potential drug for treating Enterobacterales producing extended-spectrum β-lactamase (ESBL), Klebsiella pneumoniae carbapenemase (KPC), AmpC, and some class D β-lactamases (OXA-48) in addition to carbapenem-resistant Pseudomonas aeruginosa Ceftolozane-tazobactam is a treatment option mainly for carbapenem-resistant P. aeruginosa (non-carbapenemase producing), with some activity against ESBL-producing Enterobacterales Meropenem-vaborbactam has emerged as treatment option for Enterobacterales producing ESBL, KPC, or AmpC, with similar activity as meropenem against P. aeruginosa Imipenem-relebactam has documented activity against Enterobacterales producing ESBL, KPC, and AmpC, with the combination having some additional activity against P. aeruginosa relative to imipenem. None of these drugs present in vitro activity against Enterobacterales or P. aeruginosa producing metallo-β-lactamase (MBL) or against carbapenemase-producing Acinetobacter baumannii Clinical data regarding the use of these drugs to treat MDR bacteria are limited and rely mostly on nonrandomized studies. An overview on eight BLBLIs in development is also provided. These drugs provide various levels of in vitro coverage of carbapenem-resistant Enterobacterales, with several drugs presenting in vitro activity against MBLs (cefepime-zidebactam, aztreonam-avibactam, meropenem-nacubactam, and cefepime-taniborbactam). Among these drugs, some also present in vitro activity against carbapenem-resistant P. aeruginosa (cefepime-zidebactam and cefepime-taniborbactam) and A. baumannii (cefepime-zidebactam and sulbactam-durlobactam).

WGS characterization of MDR Enterobacterales with different ceftolozane/tazobactam susceptibility profiles during the SUPERIOR surveillance study in Spain

Objectives

To analyse by WGS the ceftolozane/tazobactam (C/T) resistance mechanisms in Escherichia coli and Klebsiella spp. isolates recovered from complicated intra-abdominal and urinary tract infections in patients from Spanish ICUs (SUPERIOR surveillance study, 2016-17).

Methods

The clonal relatedness, the resistome and the virulome of 45 E. coli and 43 Klebsiella spp. isolates with different C/T susceptibility profiles were characterized.

Results

In E. coli, two (C/T susceptible) carbapenemase producers (VIM-2-CC23, OXA-48-ST38) were detected. The most relevant clone was ST131-B2-O25:H4-H30 (17/45), particularly the CTX-M-15-ST131-H30-Rx sublineage (15/17). ST131 strains were mainly C/T susceptible (15/17) and showed an extensive virulome. In non-ST131 strains (28/45), CTX-M enzymes [CTX-M-14 (8/24); CTX-M-15 (6/24); CTX-M-1 (3/24); CTX-M-32 (2/24)] were found in different clones. C/T resistance was detected in non-clonal E. coli isolates (13%, 6/45) with ESBL (4/6) and non-ESBL (2/6) genotypes. Among Klebsiella spp., Klebsiella pneumoniae (42/43) and Klebsiella michiganensis (1/43) species were identified; 42% (18/43) were carbapenemase producers and 58% showed a C/T resistance phenotype (25/43). OXA-48-ST11 (12/18), OXA-48-ST392 (2/18), OXA-48-ST15 (2/18), NDM-1-ST101 (1/18) and OXA-48+VIM-2-ST15 (1/18) isolates were found, all C/T resistant. Correlation between carbapenemase detection and resistance to C/T was demonstrated (P < 0.001). In non-carbapenemase-producing K. pneumoniae (25/43), C/T resistance (28%, 7/25) was detected in ESBL (3/7) and AmpC (2/7) producers. Overall, an extensive virulome was found and was correlated with carbapenemase carriage (P < 0.001) and C/T resistance (P < 0.05), particularly in OXA-48-ST11 strains (P < 0.05).

Conclusions

Prediction of antimicrobial susceptibility profiles using WGS is challenging. Carbapenemase-encoding genes are associated with C/T resistance in K. pneumoniae, but other resistance mechanisms might be additionally involved.

Resistance to Novel β-Lactam-β-Lactamase Inhibitor Combinations: The "Price of Progress"

Significant advances were made in antibiotic development during the past 5 years. Novel agents were added to the arsenal that target critical priority pathogens, including multidrug-resistant Pseudomonas aeruginosa and carbapenem-resistant Enterobacterales. Of these, 4 novel β-lactam-β-lactamase inhibitor combinations (ceftolozane-tazobactam, ceftazidime-avibactam, meropenem-vaborbactam, and imipenem-cilastatin-relebactam) reached clinical approval in the United States. With these additions comes a significant responsibility to reduce the possibility of emergence of resistance. Reports in the rise of resistance toward ceftolozane-tazobactam and ceftazidime-avibactam are alarming. Clinicians and scientists must make every attempt to reverse or halt these setbacks.

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.

Activity of ceftolozane-tazobactam and comparators against gram-negative bacilli: Results from the study for monitoring antimicrobial resistance trends (SMART - Brazil; 2016-2017)

Multi-drug resistant Gram-negative bacilli (GNB) have been reported as cause of serious hospital-acquired infections worldwide. The aim of this study was to investigate the in vitro activity of ceftolozane-tazobactam compared to other agents against GNB isolated from patients admitted to Brazilian medical centers between the years 2016 and 2017. Presence of β-lactamase encoding genes was also evaluated.

Methods

Antimicrobial susceptibility testing of GNB isolated from intra-abdominal (IAI), respiratory (RTI), and urinary tract infections (UTI) was performed according to ISO 227-1 guidelines and interpreted following CLSI and BrCAST/EUCAST guidelines. Qualifying Enterobacteriaceae isolates were screened for the presence of β-lactamase genes by PCR followed by DNA sequencing.

Results

1748 GNB collected from UTI (45.2%), IAI (25.7%) and RTI (29.1%) were evaluated. Ceftolozane-tazobactam remained highly active (94.7%) against E. coli isolates. Among K. pneumoniae, susceptibility rates were 85.9% and 85.4% for amikacin and colistin, whereas ceftolozane-tazobactam (44.1% susceptible) and carbapenems (55.2-62.2% susceptible) showed poor activity due to bla_KPC-2. Against E. cloacae amikacin, imipenem, and meropenem retained good activity (>90%). Ceftolozane-tazobactam was the most potent β-lactam agent tested against P. aeruginosa (90.9% susceptible), including ceftazidime and imipenem resistant isolates. β-lactamase encoding genes testing was carried out in 433 isolates. bla_CTX-M variants were predominant in E. coli, P. mirabilis and E. cloacae. Among the K. pneumoniae molecularly tested, most carried bla_KPC (68.5%), with all harboring bla_KPC-2, except two isolates carrying bla_KPC-3 or bla_KPC-30. ESBL encoding genes, mainly CTX-M family, were frequently detected in K. pneumoniae, plasmid-mediated AmpC were rare. A variety of PDC encoding genes were detected in P. aeruginosa isolates with five isolates harboring MBL and one KPC encoding genes.

Conclusion

Ceftolozane-tazobactam was very active against E. coli, P. mirabilis and P. aeruginosa isolates and could constitute an excellent therapeutic option including for those isolates resistant to extended-spectrum cephalosporins and carbapenems but not producers of carbapenemases.

Multicentre study of the in vitro activity of ceftolozane/tazobactam and other commonly used antibiotics against Pseudomonas aeruginosa isolates from patients in the UK

Objectives

To evaluate the in vitro activity of ceftolozane/tazobactam and other commonly used antipseudomonal antibiotics against geographically spread Pseudomonas aeruginosa isolates in the UK using disc susceptibility testing.

Methods

The in vitro activity of ceftolozane/tazobactam and nine other commonly used antipseudomonal antibiotics was evaluated. Isolates were collected between January 2015 and April 2018. Susceptibility results were interpreted using EUCAST 2018 criteria.

Results

Overall, 1326 clinical isolates from 14 centres in the UK were tested. The majority of the isolates were collected from non-cystic fibrosis (non-CF) patients (n = 1123, 85.0%). In addition, 199 cystic fibrosis (CF) isolates were collected from 10 centres. Overall susceptibility to ceftolozane/tazobactam was 89.3% (n = 1181), which included 128 CF and 1053 non-CF isolates. The other antibacterial agents with the highest susceptibility were tobramycin (92.4%, n = 1221) and piperacillin/tazobactam (90.7%, n = 1199). Susceptibility to all antibacterial agents was lower for CF isolates. Piperacillin/tazobactam was the most active of the antibacterial agents tested, followed by ceftolozane/tazobactam (70.4% and 64.3%, respectively), and <60% of CF isolates were susceptible to ceftazidime and the carbapenems. The reason for the higher rates of susceptibility to piperacillin/tazobactam and lower susceptibility to ceftazidime compared with other studies is unclear.

Conclusions

The data presented here support the need to investigate the place of ceftolozane/tazobactam as a treatment option in the management of pseudomonal infections, particularly in patients with CF. The results highlight the importance of routine testing of new antibacterial agents and of making the data available to clinicians to make appropriate and informed treatment choices.

Antimicrobial Activity of Ceftolozane-Tazobactam and Comparators against Clinical Isolates of Haemophilus influenzae from the United States and Europe

Nine hundred Haemophilus influenzae clinical isolates from 83 U.S. and European medical centers were tested for susceptibility by reference broth microdilution methods against ceftolozane-tazobactam and comparators. Results were stratified by β-lactamase production and infection type. Overall, ceftolozane-tazobactam MIC_50/90 values were 0.12/0.25 mg/liter, and 99.0% of isolates were inhibited at the susceptible breakpoint of ≤0.5 mg/liter; the highest MIC value was only 2 mg/liter. Our results support using ceftolozane-tazobactam to treat H. influenzae infections.

First Study of Antimicrobial Activity of Ceftazidime-Avibactam and Ceftolozane-Tazobactam Against Pseudomonas aeruginosa Isolated from Patients with Urinary Tract Infection in Tehran, Iran

Purpose

Pseudomonas aeruginosa causes complicated and/or nosocomial UTI. These infections are usually associated with severe and multi-drug resistant P. aeruginosa isolates. As there is no study about the activity of novel antibiotics ceftazidime-avibactam (CZA) and ceftolozane-tazobactam (C/T) against P. aeruginosa isolates in Iran, we aimed to evaluate for the first time the efficacy of these agents against P. aeruginosa isolated from patients with UTI in Iran. Then, the genetic diversity of the resistant isolates was assayed.

Methods

In this study, a total of 200 P. aeruginosa isolates were collected from patients with UTI in Tehran, Iran. Disk diffusion and Minimum Inhibitory Concentration (MIC) methods were applied to determine the resistance of the isolates to CZA, C/T, and the other antibiotics. Extended-spectrum β-lactamases (ESBLs) and Metallo Beta Lactamase (MBL) production were assayed by Combination disk diffusion test (CDDT). Polymerase chain reaction (PCR) was carried out to detect the resistance genes, including beta-lactamases and carbapenemases genes. Finally, genomic analysis of the isolates was performed using the Pulse field gel electrophoresis (PFGE).

Results

Among the isolates, 16 (8%) were resistant to CZA and C/T that MIC confirmed it. The resistant isolates showed high resistance to the other classes of antibiotics. Among the resistant isolates, 31.2% and 75% were ESBL and MBL producers, respectively. The prevalence of bla_OXA10, bla_VIM, bla_OXA48, bla_OXA2, and bla_CTX-M was 100%, 50%, 31.2%, 25%, and 12.5%. Furthermore, two isolates (12.5%) harbored bla_PER and bla_NDM genes. The resistant isolates were grouped into 14 distinct pulsotypes and two shared pulsotypes were found.

Conclusion

Ceftazidime-avibactam and ceftolozane-tazobactam showed high activity against the P. aeruginosa isolated from patients with UTI in Iran. The low rate of resistance to the antibiotics is also alarming and should be considered to avoid further spreading of the antibiotic resistance among the P. aeruginosa and the other bacteria.

Experience With Ceftolozane-Tazobactam for the Treatment of Serious Pseudomonas aeruginosa Infections in Saudi Tertiary Care Center

Introduction:

Multidrug-resistant Pseudomonas aeruginosa isolates have multiple resistance mechanisms, and there are insufficient therapeutic options to target them. Ceftolozane-tazobactam is a novel antipseudomonal agent that contains a combination of an oxyimino-aminothiazolyl cephalosporin (ceftolozane) and a β-lactamase inhibitor (tazobactam).

Methods:

A single-center retrospective observational study between January 2017 and December 2018 for patients who had been diagnosed with carbapenem-resistant P aeruginosa infections and treated with ceftolozane-tazobactam for more than 72 hours. We assessed clinical success based on microbiological clearance as well as the clinical resolution of signs and symptoms of infection.

Results:

A total of 19 patients fit the inclusion criteria, with a median age was 57 years, and 53% were female. The types of infections were nosocomial pneumonia, acute bacterial skin, and skin structure infections; complicated intra-abdominal infections; and central line–associated bloodstream infections. All of the isolates were resistant to both meropenem and imipenem. The duration of therapy was variable (average of 14 days). At day 14 of starting ceftolozane-tazobactam, 18 of 19 patients had a resolution of signs and symptoms of the infection. Only 14 of 19 patients (74%) had proven microbiological eradication observed at the end of therapy. During therapy, there was no adverse event secondary to ceftolozane-tazobactam, and no Clostridium difficile infection was identified. The 30-day mortality rate was 21% (4/19).

Conclusions:

Multidrug-resistant P aeruginosa infection is associated with high mortality, which would potentially be improved using a new antibiotic such as ceftolozane-tazobactam. Studies are required to explain the role of combination therapy, define adequate dosing, and identify the proper duration of treatment.

Activity of ceftolozane-tazobactam against Gram-negative pathogens isolated from lower respiratory tract infections in the Asia-Pacific region: SMART 2015-2016

The aim of this study was to investigate the susceptibility of respiratory Gram-negative bacteria to ceftolozane/tazobactam and other antibiotics in the Asia-Pacific region during 2015-2016. MICs were determined using the CLSI standard broth microdilution method and interpreted accordingly. Pseudomonas aeruginosa (1574 isolates), Klebsiella pneumoniae (1226), Acinetobacter baumannii (627) and Escherichia coli (476) accounted for 73.1% of 5342 Gram-negative respiratory pathogens. Susceptibility to ceftolozane/tazobactam of individual Enterobacteriaceae was >80%, except for Enterobacter cloacae (76.6%). Ceftolozane/tazobactam inhibited 81.9% of K. pneumoniae and 91.9% of E. coli, with respective MIC₅₀/MIC₉₀ values of 0.5/>32 and 0.25/2 mg/L. For carbapenem-susceptible, ESBL-producing K. pneumoniae and E. coli, susceptibility was 65.5% and 93.3%, respectively, and respective MIC₅₀/MIC₉₀ values were 2/>32 and 0.5/2 mg/L. Bla_{CTX-M-1 group} was most prevalent in selected ESBL-producing K. pneumoniae (40 of 54 isolates) and E. coli (15 of 22 isolates), with ceftolozane/tazobactam susceptibility rates of 50% and 80%, respectively. Bla_SHV-ESBL was the second most prevalent, and ceftolozane/tazobactam inhibited 20% of 20 K. pneumoniae isolates with bla_SHV-ESBL. The only effective antibiotics for carbapenem-non-susceptible K. pneumoniae (111 isolates) and E. coli (24 isolates) were amikacin and colistin. Ceftolozane/tazobactam was effective against almost all tested P. aeruginosa and carbapenem-non-susceptible strains, with susceptibility of 92.3% and 72.8%, respectively; the respective MIC₅₀/MIC₉₀ values were 1/4 and 2/>32 mg/L. The high susceptibility of ceftolozane/tazobactam remained in different age groups, patient locations, recovery times and countries, except Vietnam. In conclusion, ceftolozane/tazobactam was effective against most respiratory Gram-negative pathogens in the Asia-Pacific region; however, the emergence of carbapenem resistance mandates ongoing surveillance.

The latest advances in β-lactam/β-lactamase inhibitor combinations for the treatment of Gram-negative bacterial infections

Introduction: Antimicrobial resistance in Gram-negative pathogens is a significant threat to global health. β-Lactams (BL) are one of the safest and most-prescribed classes of antibiotics on the market today. The acquisition of β-lactamases, especially those which hydrolyze carbapenems, is eroding the efficacy of BLs for the treatment of serious infections. During the past decade, significant advances were made in the development of novel BL-β-lactamase inhibitor (BLI) combinations to target β-lactamase-mediated resistant Gram-negatives.Areas covered: The latest progress in 20 different approved, developing, and preclinical BL-BLI combinations to target serine β-lactamases produced by Gram-negatives are reviewed based on primary literature, conference abstracts (when available), and US clinical trial searches within the last 5 years. The majority of the compounds that are discussed are being evaluated as part of a BL-BLI combination.Expert opinion: The current trajectory in BLI development is promising; however, a significant challenge resides in the selection of an appropriate BL partner as well as the development of resistance linked to the BL partner. In addition, dosing regimens for these BL-BLI combinations need to be critically evaluated. A revolution in bacterial diagnostics is essential to aid clinicians in the appropriate selection of novel BL-BLI combinations for the treatment of serious infections.

Multidrug-resistant Gram-negative bacterial infections in solid organ transplant recipients-Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of infections due to multidrug-resistant (MDR) Gram-negative bacilli in the pre- and post-transplant period. MDR Gram-negative bacilli, including carbapenem-resistant Enterobacteriaceae, MDR Pseudomonas aeruginosa, and carbapenem-resistant Acinetobacter baumannii, remain a threat to successful organ transplantation. Clinicians now have access to at least five novel agents with activity against some of these organisms, with others in the advanced stages of clinical development. No agent, however, provides universal and predictable activity against any of these pathogens, and very little is available to treat infections with MDR nonfermenting Gram-negative bacilli including A baumannii. Despite advances, empiric antibiotics should be tailored to local microbiology and targeted regimens should be tailored to susceptibilities. Source control remains an important part of the therapeutic armamentarium. Morbidity and mortality associated with infections due to MDR Gram-negative organisms remain unacceptably high. Heightened infection control and antimicrobial stewardship initiatives are needed to prevent these infections, curtail their transmission, and limit the evolution of MDR Gram-negative pathogens, especially in the setting of organ transplantation.

Incremental clinical and economic burden of suspected respiratory infections due to multi-drug-resistant Pseudomonas aeruginosa in the United States

BACKGROUND

Multi-drug resistant (MDR) Pseudomonas aeruginosa can negatively affect patients and hospitals.

AIM

To evaluate excess mortality and cost burden among patients hospitalized with suspected respiratory infections due to MDR P. aeruginosa vs patients with non-MDR P. aeruginosa in 78 United States (US) hospitals.

METHODS

This study analyzed electronically captured microbiological and outcomes data of patients hospitalized with non-duplicate P. aeruginosa isolates from respiratory sources collected ≥3 days after admission to identify hospital-onset MDR or non-MDR P. aeruginosa per the Centers for Disease Control and Prevention definition. The risk of multi-drug resistance was estimated on mortality, length of stay (LOS), cost, operation gain/loss, and 30-day readmission. A sensitivity analysis was conducted utilizing a cohort with pharmacy data available.

FINDINGS

Of 523 MDR and 1381 non-MDR P. aeruginosa cases, unadjusted mortality was 23.7% vs 18.0% and multi-variable-adjusted mortality was 20.0% (95% confidence interval (CI): 14.3-27.2%) vs 15.5% (95% CI: 11.2-20.9%; P=0.026), the average adjusted excess LOS was 6.7 days (P<0.001); excess cost per case was US$22,370 higher (P=0.002) and operational loss per case was US$10,661 (P=0.024) greater, and the multi-variable adjusted readmission rate was 16.2% (95% CI: 11.2-22.9%) vs 11.1% (95% CI: 7.8-15.6%; P=0.006). The sensitivity analysis yielded similar results.

CONCLUSIONS

Compared with suspected infections due to non-MDR P. aeruginosa, patients with MDR P. aeruginosa had higher risk of mortality, readmission, and longer LOS, as well as US$20,000 incremental cost and >US$10,000 incremental net loss per case after controlling for patient and hospital characteristics.

A Combination Antibiogram Evaluation for Pseudomonas aeruginosa in Respiratory and Blood Sources from Intensive Care Unit (ICU) and Non-ICU Settings in U.S. Hospitals

Pseudomonas aeruginosa is an important pathogen associated with significant morbidity and mortality. U.S. guidelines for the treatment of hospital-acquired and ventilator-associated pneumonia recommend the use of two antipseudomonal drugs for high-risk patients to ensure that ≥95% of patients receive active empirical therapy. We evaluated the utility of combination antibiograms in identifying optimal anti-P. aeruginosa drug regimens. We conducted a retrospective cross-sectional analysis of the antimicrobial susceptibility of all nonduplicate P. aeruginosa blood and respiratory isolates collected between 1 October 2016 and 30 September 2017 from 304 U.S. hospitals in the BD Insights Research Database. Combination antibiograms were used to determine in vitro rates of susceptibility to potential anti-P. aeruginosa combination regimens consisting of a backbone antibiotic (an extended-spectrum cephalosporin, carbapenem, or piperacillin-tazobactam) plus an aminoglycoside or fluoroquinolone. Single-agent susceptibility rates for the 11,701 nonduplicate P. aeruginosa isolates ranged from 72.7% for fluoroquinolones to 85.0% for piperacillin-tazobactam. Susceptibility rates were higher for blood isolates than for respiratory isolates (P < 0.05). Antibiotic combinations resulted in increased susceptibility rates but did not achieve the goal of 95% antibiotic coverage. Adding an aminoglycoside resulted in higher susceptibility rates than adding a fluoroquinolone; piperacillin-tazobactam plus an aminoglycoside resulted in the highest susceptibility rate (93.3%). Intensive care unit (ICU) isolates generally had lower susceptibility rates than non-ICU isolates. Commonly used antipseudomonal drugs, either alone or in combination, did not achieve 95% coverage against U.S. hospital P. aeruginosa isolates, suggesting that new drugs are needed to attain this goal. Local institutional use of combination antibiograms has the potential to optimize empirical therapy of infections caused by difficult-to-treat pathogens.

Activity of ceftolozane/tazobactam against Pseudomonas aeruginosa and Enterobacterales isolates recovered from intensive care unit patients in Spain: The SUPERIOR multicentre study

Patients in intensive care units (ICUs) present a high risk of developing an infection caused by multidrug-resistant bacteria. Consequently, new antimicrobials and combinations are required. In this study, the activity of ceftolozane/tazobactam (C/T) was evaluated against Enterobacterales (n = 400) and Pseudomonas aeruginosa (n = 80) clinical isolates collected from patients in Spanish ICUs with complicated urinary tract infections (cUTI) and complicated intra-abdominal infections (cIAI). Overall susceptibility to C/T in P. aeruginosa isolates by infection type was 95.7% in cUTI (MIC_50/90, 1/4 mg/L) and 85.3% in cIAI (MIC_50/90, 1/64 mg/L). Activity against P. aeruginosa was maintained regardless of its resistance pattern, confirming that C/T is one of the best antipseudomonal agents along with colistin and amikacin. Susceptibility to C/T in Enterobacterales by infection type was 79.5/81.9% and 89.3/92.3% (EUCAST/CLSI) in cIAI and cUTI isolates, respectively. Activity was excellent against wild-type organisms, with 100% susceptible and inhibited at MIC ≤1 mg/L. Nevertheless, C/T susceptibility decreased against extended-spectrum β-lactamase (ESBL)-producing isolates: Escherichia coli (80.4/84.8% susceptible by EUCAST/CLSI) and Klebsiella pneumoniae (59.1/77.3% susceptible by EUCAST/CLSI). No activity of C/T was observed in carbapenemase-producing isolates. The in vitro activity of C/T observed in this surveillance study suggests that this agent can be considered as a therapeutic option for cUTI and cIAI due to Enterobacterales and P. aeruginosa in ICU patients, particularly when carbapenemase-producing isolates are not involved.

Acquisition of Extended-Spectrum β-Lactamase GES-6 Leading to Resistance to Ceftolozane-Tazobactam Combination in Pseudomonas aeruginosa

A clinical Pseudomonas aeruginosa isolate resistant to all β-lactams, including ceftolozane-tazobactam and carbapenems, was recovered. It belonged to sequence type 235 and produced the extended-spectrum β-lactamase (ESBL) GES-6 differing from GES-1 by two amino acid substitutions (E104K and G170S). GES-6 possessed an increased hydrolytic activity toward carbapenems and to ceftolozane and a decreased susceptibility to β-lactamase inhibitors compared to GES-1, except for avibactam. We show here that resistance to ceftolozane-tazobactam may occur through acquisition of a specific ESBL in P. aeruginosa but that ceftazidime-avibactam combination remains an effective alternative.

Antimicrobial activity of ceftolozane-tazobactam tested against gram-negative contemporary (2015-2017) isolates from hospitalized patients with pneumonia in US medical centers

Pseudomonas aeruginosa (n = 1531) and Enterobacteriaceae (n = 2373) clinical isolates from hospitalized patients with pneumonia were collected from 31 US medical centers during 2015-2017. Isolates were susceptibility tested against ceftolozane-tazobactam and comparators by broth microdilution. Results from intensive care unit (ICU) patients and patients with ventilator-associated bacterial pneumonia (VABP) were analyzed separately. Ceftolozane-tazobactam was very active against P. aeruginosa (MIC_50/90, 0.5/2 mg/L; 97.5% susceptible), including multidrug-resistant (87.9% susceptible) and extensively drug-resistant (82.9% susceptible). Ceftolozane-tazobactam inhibited 90.3% of Enterobacteriaceae isolates (MIC_50/90, 0.25/2 mg/L), including non-carbapenem-resistant Enterobacteriaceae isolates with an extended-spectrum β-lactamase phenotype (85.7% susceptible). Ceftolozane-tazobactam activity was stable against P. aeruginosa regardless of the US census division or ICU and VABP subsets (>90%); small differences were noted among Enterobacteriaceae isolates from the Middle Atlantic (range 78.3-88.9%) and West South Central (range 86.4-89.2%) divisions. These in vitro results indicate that ceftolozane-tazobactam may represent a valuable option for hospital-acquired bacterial pneumonia and VABP caused by Enterobacteriaceae and P. aeruginosa in the United States.

Antimicrobial Susceptibility of Pseudomonas aeruginosa to Ceftazidime-Avibactam, Ceftolozane-Tazobactam, Piperacillin-Tazobactam, and Meropenem Stratified by U.S. Census Divisions: Results from the 2017 INFORM Program

Pseudomonas aeruginosa isolates (n = 1,909) were collected from 70 U.S. medical centers, and their susceptibilities were tested using the broth microdilution method. Ceftazidime-avibactam (MIC₅₀/MIC₉₀, 2/8 mg/liter) and ceftolozane-tazobactam (MIC₅₀/MIC₉₀, 0.5/2 mg/liter) were the most active (i.e., had the highest susceptibility rates) compounds after colistin, with national susceptibility rates of 96.9% and 97.5%, respectively. Overall, piperacillin-tazobactam (MIC₅₀/MIC₉₀, 4/128 mg/liter) and meropenem (MIC₅₀/MIC₉₀, 0.5/16 mg/liter) were active against 77.5% and 76.0% of the isolates, respectively. Susceptibility variations across census divisions were documented for many antimicrobials.