Ventilator-associated Bacterial Pneumonia Research Articles

P-282. Cost Effectiveness Analysis of Ceftolozane/Tazobactam for the Treatment of Patients with Ventilated Hospital-Acquired Bacterial Pneumonia and Ventilator-Associated Bacterial Pneumonia in the Philippines

Abstract Background Ceftolozane/tazobactam (C/T) was licensed by Philippine Food and Drug Administration for the treatment of ventilated hospital-acquired bacterial pneumonia (vHABP) and ventilator-associated bacterial pneumonia (VABP) last 2019. Increasing resistance rates to antibiotics available in the Philippine National Formulary (PNF) by Pseudomonas aeruginosa associated vHABP/VABP has concerned clinicians due to its overall morbidity and mortality. This study assessed the cost-effectiveness of C/T treatment compared with existing antimicrobials among adult patients with confirmed susceptibility profile of Pseudomonas aeruginosa associated vHABP/VABP. Methods An economic model was developed to compare the lifetime costs and quality-adjusted life-years (QALYs) associated with C/T and the currently listed antimicrobials (meropenem, aminoglycosides, colistin) in the PNF for the treatment of patients with Pseudomonas aeruginosa associated vHABP/VABP. A short-term decision tree was used for the in-hospital period, followed by a long-term Markov model to depict lifetime costs and outcomes. Pathogen susceptibility was sourced from the Program to Assess Ceftolozane/Tazobactam Susceptibility (PACTS) database; clinical efficacy was obtained from the published literature. The model assumed a public payer perspective, capturing direct costs incurred by the health system, and direct health outcomes for treated patients. Discount rates applied followed local HTA methods guide. Results On treating Pseudomonas aeruginosa associated vHABP/VABP, C/T was associated with a higher absolute cure rate (17%) and lower absolute mortality rate (-3%) than meropenem. The incremental cost-effectiveness ratio (ICER) for C/T compared to meropenem, amikacin, and colistin were ₱267,396, ₱164,570, and ₱47,504 per QALY gained, respectively. C/T generated more QALYs than exiting antimicrobials at an increased cost per patient, but resulting in ICER less than one times the Gross Domestic Product (GDP) of ₱233,902 for amikacin, and colistin, and ∼ 1.2x GDP per capita for meropenem. Conclusion C/T represents a cost-effective treatment for payers and an important option to be listed in the PNF for clinicians treating patients with Pseudomonas aeruginosa vHABP/VABP in the Philippines. Disclosures GEOVIN DEXTER C. UY, RPh, MPH, MSD Philippines: employee|MSD Philippines: Stocks/Bonds (Private Company) Karlo Paredes, RN, MPH, PhD (cand), MSD Philippines: employee|MSD Philippines: Stocks/Bonds (Private Company) Gillian Camille Abello, MD, MSD Philippines: employee Carolyn Cameron, MPH, MSD Australia: employee|MSD Australia: Stocks/Bonds (Private Company) Joe Yang, PhD, Merck & Co., Inc: employee|Merck & Co., Inc: Stocks/Bonds (Private Company)

Sulbactam–Durlobactam: A Novel Antibiotic Combination for the Treatment of Acinetobacter baumannii–Calcoaceticus Complex (ABC) Hospital‐Acquired Bacterial Pneumonia and Ventilator‐Associated Bacterial Pneumonia

Purpose: To evaluate the pharmacology, pharmacokinetics, pharmacodynamics, antimicrobial activity, efficacy, safety, and the regulatory status of sulbactam–durlobactam.Summary: Sulbactam–durlobactam is a recently approved antimicrobial combination of two β‐lactamase inhibitors for the treatment of hospital‐acquired bacterial pneumonia (HABP) and ventilator‐associated bacterial pneumonia (VABP) associated with Acinetobacter baumannii–calcoaceticus complex (ABC) in patients 18 years and older. Sulbactam is a direct antibacterial activity with high susceptibility to A. baumannii species. Durlobactam, diazabicyclooctane β‐lactamase inhibitors possesses a broad‐spectrum activity against Ambler class A, C, and D serine β‐lactamases. This combination has been studied to overcome resistance to ABC species. Data were obtained from in vitro and preclinical studies as well as phase I, II, and III clinical studies published in English between 200t0 and January 2023. A phase II trial showed similar tolerability and pharmacokinetics parameters of sulbactam–durlobactam in patients with urinary tract infections to placebo. However, no ABC infections were included in the trial. ATTACK, a phase III clinical trial of sulbactam–durlobactam, studied the safety and efficacy of sulbactam–durlobactam in patients with ABC HABP/VABP and showed its noninferiority to colistin. Reported adverse events include anemia, elevated liver enzymes, hyperkalemia, headache, diarrhea, nausea, urticaria, and vascular pain. Sulbactam–durlobactam is a new β‐lactamase inhibitors combination active against MDR Gram‐negative bacteria including ABC. It is currently approved for the treatment of HABP/VABP caused by susceptible ABC strains.

Ex vivo assessment of sulbactam-durlobactam clearance during continuous renal replacement therapy to guide dosing recommendations.

Sulbactam-durlobactam is approved for the treatment of hospital-acquired and ventilator-associated bacterial pneumonia caused by susceptible isolates of Acinetobacter baumannii-calcoaceticus complex. Patients with serious Acinetobacter infections may require support with continuous renal replacement therapy (CRRT), which presents challenges for optimal dosing of antibiotics. Sulbactam-durlobactam dosing regimens were derived for this population using an ex vivo CRRT model and Monte Carlo simulation (MCS). Transmembrane clearance (CLTM) was determined in hemofiltration (CVVH) and hemodialysis (CVVHD) modes using the Prismaflex M100 and HF1400 hemofilter sets and with effluent rates of 1, 2, and 3 L/h. Pre-filter, post-filter blood, and effluent samples were collected over 60 min to calculate sieving (SC) and saturation (SA) coefficients for CVVH and CVVHD, respectively. An established population pharmacokinetic model was integrated with the CLTM; then, a 1,000 patient MCS was conducted to determine exposures of potential dosing regimens. Adsorption and degradation in the ex vivo CRRT model were negligible. The overall mean ± standard deviation SC/SA was 1.14 ± 0.12 and 0.93 ± 0.08 for sulbactam and durlobactam, respectively. In multivariable regression analyses, effluent rate was the primary driver of CLTM for both drugs. For effluent rates <3 L/h, sulbactam-durlobactam 1 g-1g q8h as 3 h infusion achieved a high probability of pharmacodynamic target attainment while retaining area under the curve exposures consistent with the standard dose in non-CRRT patients. For effluent rates ≥3 to 5 L/h, the optimal regimen was 1 g-1g q6h 3 h infusion. Sulbactam-durlobactam regimens that provide optimum drug exposures for efficacy and safety were identified for CRRT based on the prescribed effluent rate.

A phase III, randomized, controlled noninferiority trial to study the efficacy and safety of imipenem/cilastatin/relebactam (IMI/REL) vs piperacillin/tazobactam (PIP/TAZ) in patients with hospital-acquired bacterial pneumonia (HABP) or ventilator-associated bacterial pneumonia (VABP).

Imipenem/cilastatin/relebactam (IMI/REL) is a β-lactam/β-lactamase inhibitor combination effective against gram-negative pathogens. Efficacy and safety of IMI/REL were studied in critically ill adults with hospital-acquired bacterial pneumonia (HABP) or ventilator-associated bacterial pneumonia (VABP). In this phase III, double-blind, multinational, randomized trial (NCT03583333), adults with HABP/VABP were randomized 1:1 to receive intravenous IMI/REL (500 mg/250 mg) or piperacillin/tazobactam (PIP/TAZ; 4000 mg/500 mg) every 6 h for 7-14 days. The primary endpoint was 28-day all-cause mortality (ACM). Secondary endpoints were clinical response (CR), microbiological response (MR), and adverse event (AE) incidence. In the modified intention-to-treat population (N = 270 [IMI/REL: n = 134; PIP/TAZ: n = 136]), demographics and baseline characteristics were comparable between treatment groups. Most patients were from China. IMI/REL was noninferior to PIP/TAZ for 28-day ACM (11.2% vs 5.9%; adjusted difference [95% confidence interval]: 5.2% [-1.5 to 12.4]). Secondary outcomes were comparable between treatment groups, including favorable CR and MR. AEs resulting in death were generally consistent with pre-existing or underlying illness. IMI/REL met noninferiority criteria vs PIP/TAZ for 28-day ACM, and safety profiles were comparable. This trial could support the use of IMI/REL to treat adults with HABP/VABP, including regional use in China.

Population pharmacokinetic analyses for sulbactam-durlobactam using Phase 1, 2, and 3 data.

Sulbactam-durlobactam is a β-lactam/β-lactamase inhibitor combination approved in the United States for the treatment of hospital-acquired and ventilator-associated bacterial pneumonia caused by susceptible isolates of Acinetobacter baumannii-calcoaceticus in adults. A population pharmacokinetic (PK) model of sulbactam-durlobactam in plasma was developed using data from eight Phase 1-3 studies. A total of 432 subjects and 8,100 plasma concentrations were available for the population PK data set. The combined model was a four-compartment (two compartments per drug) model with linear kinetics. Both renal clearance and nonrenal clearance were estimated, and total clearance was calculated as the sum of renal and nonrenal clearance. Individual renal clearances were scaled by baseline creatinine clearance. The sampling-importance-resampling analysis indicated that the parameters were estimated reliably with adequate precision. Hemodialysis (HD) and epithelial lining fluid (ELF) sub-models were developed for each analyte separately. Intermittent HD resulted in an approximately 30% decrease in the daily area under the concentration-time curve (AUC0-24) when HD was started 1 hour after the end of the infusion. Assuming protein binding estimates of 10% and 38% for durlobactam and sulbactam, respectively, ELF penetration ratios were found to be 41.3% for durlobactam and 86.0% for sulbactam. Of the statistically significant covariates of PK identified, which included body weight, body mass index, infection type, and region of origin, renal function was the only clinically relevant covariate. Overall, a robust description of the plasma PK of sulbactam and durlobactam was achieved. The resultant population PK model was expected to be appropriate for model-based simulations and assessment of pharmacokinetic-pharmacodynamic relationships.

Flexible Development Programs for Antibacterial Drugs to Address Unmet Medical Needs.

The US Food and Drug Administration recognizes the unmet medical need for antibacterial drugs to treat serious bacterial diseases caused by resistant pathogens for which effective therapies are limited or lacking. The agency also recognizes that designing and conducting clinical trials to assess the safety and efficacy of drugs to treat resistant infections is challenging, especially for drugs only active against a single or a few bacterial species, and that a more flexible development program might be appropriate. In this article, we discuss several regulatory considerations for flexible development programs for antibacterial drugs intended to meet an unmet medical need. As an example, we use the recent approval of sulbactam for injection and durlobactam for injection (XACDURO) for the treatment of hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia caused by susceptible isolates of Acinetobacter baumannii-calcoaceticus complex.

In Vitro Safety Study on the Use of Cold Atmospheric Plasma in the Upper Respiratory Tract.

Cold atmospheric plasma (CAP) devices generate reactive oxygen and nitrogen species, have antimicrobial and antiviral properties, but also affect the molecular and cellular mechanisms of eukaryotic cells. The aim of this study is to investigate CAP treatment in the upper respiratory tract (URT) to reduce the incidence of ventilator-associated bacterial pneumonia (especially superinfections with multi-resistant pathogens) or viral infections (e.g., COVID-19). For this purpose, the surface-microdischarge-based plasma intensive care (PIC) device was developed by terraplasma medical GmbH. This study analyzes the safety aspects using in vitro assays and molecular characterization of human oral keratinocytes (hOK), human bronchial-tracheal epithelial cells (hBTE), and human lung fibroblasts (hLF). A 5 min CAP treatment with the PIC device at the "throat" and "subglottis" positions in the URT model did not show any significant differences from the untreated control (ctrl.) and the corresponding pressurized air (PA) treatment in terms of cell morphology, viability, apoptosis, DNA damage, and migration. However, pro-inflammatory cytokines (MCP-1, IL-6, and TNFα) were induced in hBTE and hOK cells and profibrotic molecules (collagen-I, FKBP10, and αSMA) in hLF at the mRNA level. The use of CAP in the oropharynx may make an important contribution to the recovery of intensive care patients. The results indicate that a 5 min CAP treatment in the URT with the PIC device does not cause any cell damage. The extent to which immune cell activation is induced and whether it has long-term effects on the organism need to be carefully examined in follow-up studies in vivo.

Development of rabbit models of ventilator-associated bacterial pneumonia produced by carbapenem-resistant Pseudomonas aeruginosa.

Ventilator-associated bacterial pneumonia (VABP) is among the most intractable of carbapenem-resistant Gram-negative bacterial infections. New antimicrobial agents are critically needed for the treatment of VABP. However, current conventionally used animal model systems are inadequate to meet this challenge. We, therefore, developed rabbit models of VABP caused by carbapenem-resistant Pseudomonas aeruginosa. Persistently neutropenic New Zealand White rabbits were used throughout the study. The early-phase intubated model (0-24 h) received mechanical ventilation, while the late-phase intubated model (72-96 h) was ambulatory. The following outcome parameters were studied: survival, residual tissue bacterial burden (CFU/g), residual BAL bacterial burden (CFU/mL), lung weights, pulmonary lesion score, histology, O2 saturation, radiographic imaging, and histology. Each anesthetized rabbit received a predetermined endotracheal bacterial inoculum, and ventilators were set to FiO2 = 40% and PEEP = 8 mmHg. Within the first 12 h post-inoculation, mean bacterial burdens in lung tissue and BAL fluid, respectively, were established at approximately 107 CFU/g and 106 CFU/mL, persisted through 24 h in the early-phase model and increased in the late-phase model to approximately 108 CFU/g and 107 CFU/mL. Mean max SpO2 was ≥98 mmHg, and mean nadir SpO2 was ≥68 mmHg. Serial thoracic radiographs demonstrated progressive multilobar pneumonic infiltrates. Lung histology revealed progressive focal bronchopneumonia, coagulative necrosis, intra-alveolar hemorrhage, alveolar epithelial cell necrosis, and bacterial microcolonies. The new rabbit model of VABP produced by carbapenem-resistant Pseudomonas aeruginosa recapitulates the pathophysiological, microbiological, diagnostic imaging, and histological patterns of human disease by which to assess critically needed new antimicrobial agents against this lethal infection.

Cost-effectiveness analysis of CTZ/TAZ for the treatment of ventilated hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia in Japan

BackgroundResistant bacterial infections, particularly those caused by gram-negative pathogens, are associated with high mortality and economic burdens. Ceftolozane/tazobactam demonstrated efficacy comparable to meropenem in patients with ventilated hospital-acquired bacterial pneumonia in the ASPECT-NP study. One cost-effectiveness analysis in the United States revealed that ceftolozane/tazobactam was cost effective, but no Japanese studies have been conducted. Therefore, the objective of this study was to assess the cost-effectiveness of ceftolozane/tazobactam compared to meropenem for patients with ventilated hospital-acquired bacterial pneumonia/ventilator-associated bacterial pneumonia from a health care payer perspective.MethodsA hybrid decision-tree Markov decision-analytic model with a 5-year time horizon were developed to estimate costs and quality-adjusted life-years and to calculate the incremental cost-effectiveness ratio associated with ceftolozane/tazobactam and meropenem in the treatment of patients with ventilated hospital-acquired bacterial pneumonia/ventilator-associated bacterial pneumonia. Clinical outcomes were based on the ASPECT-NP study, costs were based on the national fee schedule of 2022, and utilities were based on published data. One-way sensitivity analysis and probabilistic sensitivity analysis were also conducted to assess the robustness of our modeled estimates.ResultsAccording to our base-case analysis, compared with meropenem, ceftolozane/tazobactam increased the total costs by 424,731.22 yen (£2,626.96) and increased the quality-adjusted life-years by 0.17, resulting in an incremental cost-effectiveness ratio of 2,548,738 yen (£15,763.94) per quality-adjusted life-year gained for ceftolozane/tazobactam compared with meropenem. One-way sensitivity analysis showed that although the incremental cost-effectiveness ratio remained below 5,000,000 yen (£30,925) for most of the parameters, the incremental net monetary benefit may have been less than 0 depending on the treatment efficacy outcome, especially the cure rate and mortality rate for MEPM and mortality rate for CTZ/TAZ. 53.4% of the PSA simulations demonstrated that CTZ/TAZ was more cost-effective than MEPM was.ConclusionAlthough incremental cost-effectiveness ratio was below ￥5,000,000 in base-case analysis, whether ceftolozane/tazobactam is a cost-effective alternative to meropenem for ventilated hospital-acquired bacterial pneumonia/ventilator-associated bacterial pneumonia in Japan remains uncertain. Future research should examine the unobserved heterogeneity across patient subgroups and decision-making settings, to characterise decision uncertainty and its consequences so as to assess whether additional research is required.

Exploration of a Potential DOOR Endpoint for Hospital-acquired Bacterial Pneumonia and Ventilator-associated Bacterial Pneumonia Using Six Registrational Trials for Antibacterial Drugs.

Desirability of outcome ranking (DOOR) is an innovative approach to clinical trial design and analysis that uses an ordinal ranking system to incorporate the overall risks and benefits of a therapeutic intervention into a single measurement. Here we derived and evaluated a disease-specific DOOR endpoint for registrational trials for hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia (HABP/VABP). Through comprehensive examination of data from nearly 4000 participants enrolled in six registrational trials for HABP/VABP submitted to the Food and Drug Administration (FDA) between 2005 and 2022, we derived and applied a HABP/VABP specific endpoint. We estimated the probability that a participant assigned to the study treatment arm would have a more favorable overall DOOR or component outcome than a participant assigned to comparator. DOOR distributions between treatment arms were similar in all trials. DOOR probability estimates ranged from 48.3% to 52.9% and were not statistically different. There were no significant differences between treatment arms in the component analyses. Although infectious complications and serious adverse events occurred more frequently in ventilated participants compared to non-ventilated participants, the types of events were similar. Through a data-driven approach, we constructed and applied a potential DOOR endpoint for HABP/VABP trials. The inclusion of syndrome-specific events may help to better delineate and evaluate participant experiences and outcomes in future HABP/VABP trials and could help inform data collection and trial design.

Optimization of an in vitro Pseudomonas aeruginosa Biofilm Model to Examine Antibiotic Pharmacodynamics at the Air-Liquid Interface

Pseudomonas aeruginosa is an important cause of lower respiratory tract infections, such as ventilator-associated bacterial pneumonia (VABP). Using inhaled antibiotics to treat VABP can achieve high drug concentrations at the infection site while minimizing systemic toxicities. Despite the theoretical advantages, clinical trials have failed to show a benefit for inhaled antibiotic therapy in treating VABP. A potential reason for this discordance is the presence of biofilm-embedded bacteria in lower respiratory tract infections. Drug selection and dosing are often based on data from bacteria grown planktonically. In the present study, an in vitro air-liquid interface pharmacokinetic/pharmacodynamic biofilm model was optimized to evaluate the activity of simulated epithelial lining fluid exposures of inhaled and intravenous doses of polymyxin B and tobramycin against two P. aeruginosa strains. Antibiotic activity was also determined against the P. aeruginosa strains grown planktonically. Our study revealed that inhaled antibiotic exposures were more active than their intravenous counterparts across biofilm and planktonic populations. Inhaled exposures of polymyxin B and tobramycin exhibited comparable activity against planktonic P. aeruginosa. Although inhaled polymyxin B exposures were initially more active against P. aeruginosa biofilms (through 6 h), tobramycin was more active by the end of the experiment (48 h). Together, these data slightly favor the use of inhaled tobramycin for VABP caused by biofilm-forming P. aeruginosa that are not resistant to either antibiotic. The optimized in vitro air-liquid interface pharmacokinetic/pharmacodynamic biofilm model may be beneficial for the development of novel anti-biofilm agents or to optimize antibiotic dosing for infections such as VABP.

Sulbactam-durlobactam: a β-lactam/β-lactamase inhibitor combination targeting Acinetobacter baumannii.

Sulbactam-durlobactam is a pathogen-targeted β-lactam/β-lactamase inhibitor combination that has been approved by the US FDA for the treatment of hospital-acquired and ventilator-associated bacterial pneumonia caused by susceptible isolates of Acinetobacter baumannii-calcoaceticus complex (ABC) in patients 18years of age and older. Sulbactam is a penicillin derivative with antibacterial activity against Acinetobacter but is prone to hydrolysis by β-lactamases encoded by contemporary isolates. Durlobactam is a diazabicyclooctane β-lactamase inhibitor with activity against Ambler classes A, C and D serine β-lactamases that restores sulbactam activity both in vitro and in vivo against multidrug-resistant ABC. Sulbactam-durlobactam is a promising alternative therapy for the treatment of serious Acinetobacter infections, which can have high rates of mortality.

Perspectives on the use of ceftolozane/tazobactam: a review of clinical trial data and real-world evidence.

Hospital-acquired bacterial pneumonia (HABP) and ventilator-associated bacterial pneumonia (VABP) are common healthcare-associated infections linked to high morbidity and mortality. Gram-negative pathogens, such as Pseudomonasaeruginosa, exhibit multidrug resistance and are recognized as major public health concerns, particularly among critically ill patients with HABP/VABP. Ceftolozane/tazobactam is a novel combination antibacterial agent comprising ceftolozane (a potent antipseudomonal cephalosporin) and tazobactam (a β-lactamase inhibitor). Phase III trials have demonstrated non-inferiority of ceftolozane/tazobactam to comparators, leading to the approval of ceftolozane/tazobactam for the treatment of complicated urinary tract infections, complicated intra-abdominal infections, and nosocomial pneumonia. In this article, we review the clinical trial evidence and key real-world effectiveness data of ceftolozane/tazobactam for the treatment of serious healthcare-associated Gram-negative infections, focusing on patients with HABP/VABP.

Animal Models in Regulatory Breakpoint Determination: Review of New Drug Applications of Approved Antibiotics from 2014-2022.

We sought to better understand the utility and role of animal models of infection for Food and Drug Administration (FDA)-approved antibiotics for the indications of community-, hospital-acquired-, and ventilator-associated bacterial pneumonia (CABP, HABP, VABP), complicated urinary tract infection (cUTI), complicated intra-abdominal infection (cIAI), and acute bacterial skin and structural infections (ABSSSIs). We reviewed relevant documents from new drug applications (NDA) of FDA-approved antibiotics from 2014-2019 for the above indications. Murine neutropenic thigh infection models supported the choice of a pharmacokinetic-pharmacodynamic (PKPD) target in 11/12 NDAs reviewed. PKPD targets associated with at least a 1-log bacterial decrease were commonly considered ideal (10/12 NDAs) to support breakpoints. Plasma PK, as opposed to organ specific PK, was generally considered most reliable for PKPD correlation. Breakpoint determination was multi-disciplinary, accounting at minimum for epidemiologic cutoffs, non-clinical PKPD, clinical exposure-response and clinical efficacy. Non-clinical PKPD targets in combination with probability of target attainment (PTA) analyses generated breakpoints that were consistent with epidemiologic cutoffs and clinically derived breakpoints. In 6/12 NDAs, there was limited data to support clinically derived breakpoints, and hence the non-clinical PKPD targets in combination with PTA analyses played a heightened role in the final breakpoint determination. Sponsor and FDA breakpoint decisions were in general agreement. Disagreement may have arisen from differences in the definition of the optimal PKPD index or the ability to extrapolate protein binding from animals to humans. Overall, murine neutropenic thigh infection models supported the reviewed NDAs by providing evidence of pre-clinical efficacy and PKPD target determination, and played, in combination with PTA analysis, a significant role in breakpoint determination for labeling purposes.

P14 Study of Prescribing patterns and Effectiveness of Ceftolozane/Tazobactam Real-world Analysis (SPECTRA): results from a multinational, multicentre observational study

Abstract Background Ceftolozane/tazobactam (C/T) has demonstrated efficacy to treat complicated intra-abdominal infections (cIAI), complicated urinary tract infections (cUTI) and hospital acquired bacterial and ventilator-associated bacterial pneumonia. However, physicians, providers, and other stakeholders including payers want broader real-world evidence to inform clinical decisions and optimize healthcare resource use. Methods SPECTRA is a multinational, multicentre, retrospective, inpatient, observational study of patients treated with C/T in Australia, Austria, Germany, Italy, Mexico, Spain and the UK. Adult inpatients treated with ≥48 h of C/T were included. Demographics, clinical characteristics, treatment management patterns, and outcomes were analysed. Results There were 687 patients from 38 participating hospitals in 7 countries. The average age was 57.6 years (SD ±17.3), and most were male (456, 66.4%). The majority had at least one comorbidity (563, 82.0%), with the most common being heart disease (208, 30.3%), immunocompromised state (207, 30.1%) and chronic pulmonary disease (195, 28.4%). The most common indications were pneumonia (204, 29.7%), sepsis (147, 21.4%) and cIAI (106, 15.4%); 162 (23.6%) had multiple sites of infection and 245 (35.7%) were polymicrobial infections. Median C/T treatment was 12.0 days (IQR 11.0). Half of the patients were admitted to the ICU (343, 49.9%), 43.4% of which was related to the infection. Clinical success was 66.1%. All-cause in-hospital mortality was 22.0% with 8.7% being infection related. The 30 day all-cause readmission was 9.8% and 4.7% were infection related. Conclusions C/T was used to treat infections among critically ill patients and for multi-source, polymicrobial infections. Despite the complexity of the patients in this real-world analysis, most C/T patients had beneficial outcomes that are similar to results of controlled clinical trials.

Ceftazidime-avibactam/aztreonam combination synergy against carbapenem-resistant Gram-negative isolates: In vitro study

ABSTRACT Background: The ceftazidime-avibactam combination is able to inhibit ESBLs, AmpCs and Class A carbapenemases and has been recommended for the treatment of complicated UTIs and ventilator-associated bacterial pneumonia. Aims: The present study was undertaken to evaluate the in vitro activity of ceftazidime-avibactam and to determine the synergistic activity of aztreonam/ceftazidime-avibactam combination against carbapenem-resistant Gram-negative bacilli. Materials and Methods: Gram-negative isolates that exhibited resistance to at least one of the carbapenems (imipenem or meropenem) by the Kirby–Bauer disc diffusion method were subjected to phenotypic characterisation by the Vitek-2 automated method. Phenotypically confirmed isolates were subjected to ceftazidime/avibactam-aztreonam synergy testing by disc diffusion method. Results: Twenty-two carbapenem-resistant isolates showed a minimum inhibitory concentration of 4–64 μg/mL for imipenem and 8–64 μg/mL for meropenem. Out of 22 carbapenem-resistant isolates, 18 (81.82%) isolates showed resistance to ceftazidime-avibactam and aztreonam, and 2 (9.09%) isolates showed intermediate resistance to aztreonam. Nine (40.91%) isolates showed synergy to ceftazidime-avibactam/aztreonam combination by disc diffusion method. An increase in zone diameter of 5–23 mm and 5–16 mm was observed with the ceftazidime-avibactam/aztreonam combination for Klebsiella pneumoniae and Escherichia coli, respectively, when compared to ceftazidime-avibactam and aztreonam disc tested alone. Out of 21 Enterobacterales studied, 21 (100%) isolates showed resistance to amoxicillin-clavulanate (≥32 μg/mL) and piperacillin-tazobactam (128 μg/mL), 12 (57.14%) isolates showed resistance to gentamicin (≥16 μg/mL), 5 (23.81%) isolates were resistant to amikacin (≥64 μg/mL), 21 (100%) isolates were resistant to ciprofloxacin (≥4 μg/mL), 19 (90.48%) isolates were resistant to cotrimoxazole (≥320 μg/mL), 21 (100%) isolates were resistant to cefepime (≥16 μg/mL) and 6 (28.57%) isolates were resistant to tigecycline (2 μg/mL). Conclusion: In the present study, 42.86% of Enterobacterales isolates showed synergism to the ceftazidime-avibactam/aztreonam combination. The optimal dosing strategy and in vivo efficacy of this combination need to be evaluated.

Sulbactam-durlobactam susceptibility test method development and quality control ranges for MIC and disk diffusion tests.

Sulbactam-durlobactam is a β-lactam/β-lactamase inhibitor combination developed to treat hospital-acquired and ventilator-associated bacterial pneumonia caused by Acinetobacter baumannii-calcoaceticus complex (ABC). Durlobactam is a diazabicyclooctane β-lactamase inhibitor with potent activity against Ambler classes A, C, and D serine β-lactamases and restores sulbactam activity against multidrug-resistant ABC. Studies were conducted to establish sulbactam-durlobactam antimicrobial susceptibility testing methods for both broth microdilution minimal inhibitory concentration (MIC) and disk diffusion tests as well as quality control (QC) ranges. To establish the MIC test method, combinations of sulbactam and durlobactam were evaluated using a panel of genetically characterized A. baumannii isolates which were categorized as predicted to be susceptible or resistant based on the spectrum of β-lactamase inhibition by durlobactam. MIC testing with doubling dilutions of sulbactam with a fixed concentration of 4 µg/mL of durlobactam resulted in the greatest discrimination of the pre-defined susceptible and resistant strains. Similarly, the sulbactam/durlobactam 10/10 µg disk concentration showed the best discrimination as well as correlation with the MIC test. A. baumannii NCTC 13304 was selected for QC purposes because it assesses the activity of both sulbactam and durlobactam with clear endpoints. Multi-laboratory QC studies were conducted according to CLSI M23 Tier 2 criteria. A sulbactam-durlobactam broth MIC QC range of 0.5/4-2/4 µg/mL and a zone diameter QC range of 24-30 mm were determined for A. baumannii NCTC 13304 and have been approved by CLSI. These studies will enable clinical laboratories to perform susceptibility tests with accurate and reproducible methods.

Sulbactam/durlobactam (Xacduro) for Acinetobacter pneumonia.

The FDA has approved Xacduro (Innoviva), a combination of the beta-lactam antibacterial sulbactam and the beta-lactamase inhibitor durlobactam, for IV treatment of adults with hospital-acquired or ventilator-associated bacterial pneumonia caused by susceptible isolates of Acinetobacter baumannii-calcoaceticus complex (ABC).

2557. Development of Rabbit Models of Ventilator-Associated Carbapenem-Resistant Acinetobacter baumannii Pneumonia

Abstract Background Carbapenem-resistant (CR) Gram-negative bacteria are emerging worldwide as global public health threats. Mortality rates from these pathogens are especially high in immunocompromised patients. Ventilator-associated bacterial pneumonia (VABP) is among the most intractable of CR Gram-negative bacterial infections. We therefore aimed to develop rabbit animal models of VABP caused by CR strains of Acinetobacter baumannii. Methods Persistently neutropenic NZW rabbits were used throughout the study. A novel endotracheal tracheostomy system was developed for intubation. The early-phase intubated model (0-24h) received mechanical ventilation, while the late-phase intubated model (72-96h) was ambulatory. Ventilators were set to FiO2=40% and PEEP=8mmHg. The following outcome variables were assessed: survival, residual tissue bacterial burden (log CFU/g), residual BAL bacterial burden (log CFU/mL), lung weights, pulmonary lesion score, histology, pulse O2 saturation, radiographic imaging, pro-inflammatory cytokines, quantitative tissue and BAL PCR, and histology. Results Within the first 12h post-inoculation, mean bacterial burdens in lung tissue and BAL fluid, respectively, which were established at approximately 106 CFU/g and 105 CFU/mL, persisted through 24h in the early-phase model and were increased in the late-phase model (72-96h) to approximately 107 CFU/g, and 106 CFU/mL. Mean Max SpO2 was ≥99 mmHg and mean nadir SpO2 was ≥74 mmHg. Serial thoracic radiographs over the course of 12-96h demonstrated progressive multilobar pneumonic infiltrates, while lung histology revealed progressive development of focal bronchopneumonia, intra-alveolar hemorrhage, alveolar epithelial cell necrosis, macrophage activation, monocytic infiltration, alveolar septal disruption, and microcolonies of bacteria. Conclusion The new rabbit model of VABP produced by CR A. baumannii recapitulates the pathophysiological, microbiological, diagnostic imaging, and histological patterns of human disease by which to assess critically needed new antimicrobial agents against this lethal infection. Disclosures All Authors: No reported disclosures

Moving Beyond Mortality: Development and Application of a Desirability of Outcome Ranking (DOOR) Endpoint for Hospital-Acquired Bacterial Pneumonia and Ventilator-Associated Bacterial Pneumonia.

Hospital-acquired and ventilator-associated bacterial pneumonia (HABP/VABP) are frequently caused by multidrug-resistant organisms. Patient-centered endpoints in clinical trials are needed to develop new antibiotics for HABP/VABP. Desirability of outcome ranking (DOOR) is a paradigm for the design, analysis, and interpretation of clinical trials based on a patient-centered, benefit-risk evaluation. A multidisciplinary committee created an infectious diseases DOOR endpoint customized for HABP/VABP, incorporating infectious complications, serious adverse events, and mortality. We applied this to 2 previously completed, large randomized controlled trials for HABP/VABP. ZEPHyR compared vancomycin to linezolid and VITAL compared linezolid to tedizolid. For each trial, we evaluated the DOOR distribution and probability, including DOOR component and partial credit analyses. We also applied DOOR in subgroup analyses. In both trials, the HABP/VABP DOOR demonstrated similar overall clinical outcomes between treatment groups. In ZEPHyR, the probability that a participant treated with linezolid would have a more desirable outcome than a participant treated with vancomycin was 50.2% (95% confidence interval [CI], 45.1%--55.3%). In VITAL, the probability that a participant treated with tedizolid would have a more desirable outcome than a participant treated with linezolid was 48.7% (95% CI, 44.8%-52.6%). The DOOR component analysis revealed that participants treated with tedizolid had a less desirable outcome than those treated with linezolid when considering clinical response alone. However, participants with decreased renal function had improved overall outcomes with tedizolid. The HABP/VABP DOOR provided more granular information about clinical outcomes than is typically presented in clinical trials. HABP/VABP trials would benefit from prospectively using DOOR.