Cefiderocol treatment for carbapenem-resistant Acinetobacter baumannii infection in the ICU during the COVID-19 pandemic: a multicentre cohort study

Current and novel therapies for management of Acinetobacter baumannii-associated pneumonia

Acinetobacter baumannii is a common pathogen associated with hospital-acquired pneumonia showing increased resistance to carbapenem and colistin antibiotics nowadays. Infections with A. baumannii cause high patient fatalities due to their capability to evade current antimicrobial therapies, emphasizing the urgency of developing viable therapeutics to treat A. baumannii-associated pneumonia. In this review, we explore current and novel therapeutic options for overcoming therapeutic failure when dealing with A. baumannii-associated pneumonia. Among them, antibiotic combination therapy administering several drugs simultaneously or alternately, is one promising approach for optimizing therapeutic success. However, it has been associated with inconsistent and inconclusive therapeutic outcomes across different studies. Therefore, it is critical to undertake additional clinical trials to ascertain the clinical effectiveness of different antibiotic combinations. We also discuss the prospective roles of novel antimicrobial therapies including antimicrobial peptides, bacteriophage-based therapy, repurposed drugs, naturally-occurring compounds, nanoparticle-based therapy, anti-virulence strategies, immunotherapy, photodynamic and sonodynamic therapy, for utilizing them as additional alternative therapy while tackling A. baumannii-associated pneumonia. Importantly, these innovative therapies further require pharmacokinetic and pharmacodynamic evaluation for safety, stability, immunogenicity, toxicity, and tolerability before they can be clinically approved as an alternative rescue therapy for A. baumannii-associated pulmonary infections.

The Multifaceted Landscape of Healthcare-Associated Infections Caused by Carbapenem-Resistant Acinetobacter baumannii

Carbapenem-resistant Acinetobacter baumannii (CRAB) is an emerging and important major cause of nosocomial infections, posing a significant challenge to clinicians worldwide. The intrinsic and acquired resistance mechanisms exhibited by CRAB, associated with its ability to persist in healthcare environments, have transformed it into a critical public health concern. The clinical implications of CRAB infections include severe manifestations, like ventilator-associated pneumonia and bloodstream infections. These infections are often associated with increased morbidity and mortality, particularly in critically ill patients, such as those in intensive care units, immunocompromised, and those undergoing invasive procedures. Considering these characteristics, the therapeutic armamentarium for the treatment of CRAB infections is increasingly limited, as these strains exhibit resistance to a broad range of antibiotics, including carbapenems and the new β-lactam inhibitors, which are considered last-line agents for many bacterial infections. An important role is represented by cefiderocol and data from real-world evidence. The aim of this narrative review is to discuss the main topics of CRAB infection and strategies for prevention, management, and therapy.

Updates on the Activity, Efficacy and Emerging Mechanisms of Resistance to Cefiderocol

In recent years, novel antimicrobials have been developed to counter the emergence of antimicrobial resistance and provide effective therapeutic options against multidrug-resistant (MDR) Gram-negative bacilli (GNB). Cefiderocol, a siderophore cephalosporin, represents a novel valuable antimicrobial drug for the treatment of infections caused by MDR-GNB. The mechanism of cefiderocol to penetrate through the outer membrane of bacterial cells, termed "Trojan horse", makes this antimicrobial drug unique and immune to the various resistance strategies adopted by GNB. Its broad spectrum of action, potent antibacterial activity, pharmacokinetics properties, safety, and tolerability make cefiderocol a key drug for the treatment of infections due to MDR strains. Although this novel antimicrobial molecule contributed to revolutionizing the therapeutic armamentarium against MDR-GNB, the recent emergence of cefiderocol-resistant strains has redefined its role in clinical practice and required new strategies to preserve its antibacterial activity. In this review, we provide an updated discussion regarding the mechanism of action, emerging mechanisms of resistance, pharmacokinetic/pharmacodynamic (PK/PD) properties, and efficacy data of cefiderocol against the major Gram-negative bacteria and future prospects.

Monitoring Immune Dysfunction in Critically Ill Patients with Carbapenem-Resistant Acinetobacter baumannii Sepsis Treated with Regimens Including Cefiderocol: A Pilot Study to Identify Accessible Biomarkers to Stratify Patients' Prognosis

Background: Multidrug-resistant Acinetobacter baumannii (CRAB) infections are a serious problem in critical care. This study aims to develop an early prognostic score for immune paralysis, using practical and cost-effective parameters, to predict ICU mortality in patients with CRAB infections being treated with Cefiderocol. Methods: We carried out an observational pilot study on consecutive patients hospitalized in the ICU with ensuing septic Acinetobacter baumannii infections treated with Cefiderocol monotherapy or Cefiderocol including combinations. We investigated the predictive power of lymphocyte counts, lymphocyte subpopulations, serum cholinesterase levels, and reactivation of herpes viruses. Results: Overall, 36 of 39 patients entered in our analysis: 20 survivors and 16 deceased. A total of 12 patients developed bacteremia, 19 patients had HAP/VAP, and 5 patients had a soft tissue infection. Univariate analyses of factors associated with unfavorable outcome revealed a significant association for age (OR: 1.5, CI: 1.11-2.02), SAPS II (OR: 1.05, CI: 1.01-1.1), SOFA score (OR: 1.37, CI: 1.06-1.76), lymphocytopenia (OR: 32.5, CI: 3.45-306.4), viral reactivation (OR: 9.75, CI: 1.72-55.4), and cholinesterase drop <1600 U/L (OR: 39.7, CI: 5.8-271.6). At variance, monotherapy or associations with Cefiderocol were not associated. In the final multivariable model, the only independent predictors of death were age (OR: 1.42, CI: 0.98-2.05), lymphocytopenia (OR: 18.2, CI: 0.87-371), and cholinesterase drop to below 1600 U/L (OR: 9.7, CI: 0.77-123.7). Conclusions: Age, lymphocytopenia, and serum cholinesterase drops, which were nearly significantly associated with an unfavorable outcome, may help pinpoint patients with acute immune paralysis during sepsis. Knowledge of such an immune state may in turn directly influence patients' care.

Effectiveness and Safety of Cefiderocol in Clinical Practice for Treatment of Patients with Gram-Negative Bacterial Infections: US Interim Results of the PROVE Study

Purpose

The international PROVE retrospective chart-review study aims to assess the real-world effectiveness and safety of cefiderocol for treatment of patients with carbapenem-resistant Gram-negative infections.

Patients and Methods

US centers selected hospitalized patients receiving their first cefiderocol treatment for ≥72 hours for a Gram-negative bacterial infection (November 2020-March 2023). Patient demographics, clinical characteristics, hospitalization, course of infection, antibiotic use, clinical cure (excluding patients with a relapse/reinfection), clinical response at the end of treatment, microbiology, in-hospital all-cause mortality (IH-ACM) at Day 30, and safety were analyzed using descriptive statistics.

Results

This interim analysis included 244 patients. The most frequent infection sites were respiratory tract (55.7%), skin and skin structure (16.8%), and blood (9.8%). The median duration of cefiderocol use was 12 days (interquartile range 8-18.5). Clinical cure was reported for 64.8% (158/244) of patients, clinical response for 74.2% (181/244), and 9.4% (23/244) had relapse/reinfection; 30-day IH-ACM was 18.4% (45/244). Of 82 patients with monomicrobial Pseudomonas aeruginosa infections, 64.6% (n = 53) and 74.4% (n = 61) had clinical cure and clinical response, respectively, and 30-day IH-ACM was 25.6%. Among 43 patients with monomicrobial Acinetobacter baumannii infections, 60.5% (n = 26) and 74.4% (n = 32) had clinical cure and clinical response, respectively, and 30-day IH-ACM was 18.6%. Five patients experienced six adverse drug reactions (one serious event: interstitial nephritis/acute kidney injury), and cefiderocol was discontinued in two cases.

Conclusion

Cefiderocol had similar clinical cure and response rates to previous retrospective studies and lower mortality. Cefiderocol was well tolerated in real-world settings in critically ill US patients with problematic Gram-negative pathogens.

Comparison of cefiderocol and colistin-based regimens for the treatment of severe infections caused by carbapenem-resistant Acinetobacter baumannii: a systematic review with meta-analysis and trial sequential analysis

BACKGROUND

There are multiple antibiotic regimens for the treatment of carbapenem-resistant Acinetobacter baumannii (CRAB) in clinical practice. We conducted this meta-analysis to compare the efficacy and safety of cefiderocol-based regimens and colistin-based regimens in the treatment of CRAB infections.

METHODS

Two authors independently searched the PubMed, Web of Science, Embase, and Cochrane databases from their establishment to April 15, 2024, to search for randomized controlled trials (RCTs) or cohort studies, and compared the clinical efficacy and safety of cefiderocol-based regimens and colistin-based regimens in the treatment of CRAB infections. The Newcastle Ottawa Scale (NOS) checklist was used to evaluate the quality of the included studies. The primary outcome was all-cause mortality, and subgroup analysis was conducted on the basis of the site of infection and the risk of bias in the studies. Trial sequential analysis (TSA) was then conducted.

RESULTS

Six observational studies were included, with 251 cases in the cefiderocol-based group and 372 cases in the colistin-based group. Compared to the colistin-based group, the cefiderocol-based group had lower all-cause mortality (RR = 0.71, 95% CI: 0.54-0.92, P = 0.01) and 30-day mortality (RR = 0.64, 95% CI: 0.43-0.95, P = 0.03). However, for the 14-day and 28-day mortality rates, there was no statistically significant difference between two groups. According to the subgroup analysis, among patients with bloodstream infection (BSI), the cefiderocol-based group had lower all-cause mortality, but it did not reduce the mortality of ventilator-associated pneumonia (VAP) patients. The result of TSA showed that our conclusions are reliable. There was no significant statistical difference in the microbiological cure rate, clinical cure rate, or duration of hospitalization. In addition, the cefiderocol-based group did not have an increased incidence of acute kidney injury (AKI).

CONCLUSIONS

Compared with the colistin-based regimens, the cefiderocol-based regimens were significantly associated with a lower risk of mortality in CRAB-infected patients, especially for patients with BSI. However, they did not show any advantages in terms of the clinical cure rate or microbiological cure rate, nor did they reduce the incidence of AKI.

PROSPERO REGISTRATION NUMBER

CRD42023487213.

Use of Cefiderocol in Adult Patients: Descriptive Analysis from a Prospective, Multicenter, Cohort Study

INTRODUCTION

Cefiderocol is a siderophore cephalosporin showing activity against various carbapenem-resistant Gram-negative bacteria (CR-GNB). No data currently exist about real-world use of cefiderocol in terms of types of therapy (e.g., empirical or targeted, monotherapy or combined regimens), indications, and patient characteristics.

METHODS

In this multicenter, prospective study, we aimed at describing the use of cefiderocol in terms of types of therapy, indications, and patient characteristics.

RESULTS

Cefiderocol was administered as empirical and targeted therapy in 27.5% (55/200) and 72.5% (145/200) of cases, respectively. Overall, it was administered as monotherapy in 101/200 cases (50.5%) and as part of a combined regimen for CR-GNB infections in the remaining 99/200 cases (49.5%). In multivariable analysis, previous isolation of carbapenem-resistant Acinetobacter baumannii odds ratio (OR) 2.56, with 95% confidence interval (95% CI) 1.01-6.46, p = 0.047] and previous hematopoietic stem cell transplantation (OR 8.73, 95% CI 1.05-72.54, p = 0.045) were associated with administration of cefiderocol as part of a combined regimen, whereas chronic kidney disease was associated with cefiderocol monotherapy (OR 0.38 for combined regimen, 95% CI 0.16-0.91, p = 0.029). Cumulative 30-day mortality was 19.8%, 45.0%, 20.7%, and 22.7% in patients receiving targeted cefiderocol for infections by Enterobacterales, A. baumannii, Pseudomonas aeruginosa, and any metallo-β-lactamase producers, respectively.

CONCLUSIONS

Cefiderocol is mainly used for targeted treatment, although empirical therapies account for more than 25% of prescriptions, thus requiring dedicated standardization and guidance. The almost equal distribution of cefiderocol monotherapy and cefiderocol-based combination therapies underlines the need for further study to ascertain possible differences in efficacy between the two approaches.

Should we, and how to, optimize cefiderocol administration during severe nosocomial pneumonia due to carbapenem-resistant Acinetobacter baumanii? A viewpoint

OBJECTIVES

Acinetobacter baumannii is classified by the centre for Disease Control and Prevention (CDC) as an "urgent threat" due to its ability to acquire and develop resistance to multiple classes of antibiotics. As a result, it is one of the most concerning pathogens in healthcare settings, with increasing incidence of infections due to carbapenem-resistant Acinetobacter baumannii (CRAB) associated with high morbidity and mortality rates. Therefore, there are ongoing efforts to find novel treatment options, one of which is cefiderocol. We aim to review available evidence on cefiderocol use for severe nosocomial pneumonia due to carbapenem-resistant Acinetobacter baumannii.

METHODS

A comprehensive review was conducted from 2017 to 2023, covering articles from databases such as Pubmed, Scopus, and Embase, along with conference proceedings from ECCMID 2023. The primary focus was on severe nosocomial pneumonia due A. baumannii and cefiderocol.

DISCUSSION

Cefiderocol, targeting periplasmic space Penicillin-Binding Proteins (PBPs) via siderophore transport pathways, exhibits promise against multi-drug resistant Gram-negative bacilli. Its effectiveness in treating CRAB pneumonia remains debated. The CREDIBLE trial reported higher mortality with cefiderocol compared to the best available treatment, while other cohort studies showed contrasting outcomes. Patient variations and pharmacokinetic factors may underlie these discrepancies. The recommended cefiderocol dosage regimen may fall short of desired pharmacokinetic targets, especially in critically ill patients and lung infections. Pulmonary factors hindering cefiderocol's entry into bacteria through iron transporters are overlooked in clinical breakpoints. Optimized dosing or combination regimens may enhance infection site exposure and outcomes.

CONCLUSIONS

Further research is needed to determine the optimal cefiderocol dosage and administration (mono vs. dual therapy, continuous vs. intermittent infusion), in severe Acinetobacter baumannii nosocomial pneumonia.

Predicting early appropriate therapy for patients infected by carbapenem-resistant Gram-negative pathogens in intensive care units in Italy

BACKGROUND

Antibiotic resistance among Gram-negative bacteria in intensive care units (ICUs) is linked with high morbidity and mortality in patients. In this study, we estimated the therapeutic coverage of various antibiotics, focusing on cefiderocol and comparators, administered empirically against an infection of unknown origin in the ICU.

METHODS

In the ARTEMIS surveillance study, susceptibilities of 624 Italian Gram-negative isolates to amikacin, aztreonam-avibactam, cefiderocol, ceftazidime-avibactam, ceftolozane-tazobactam, colistin, imipenem-relebactam, meropenem, and meropenem-vaborbactam were tested by broth microdilution, and results were interpreted by European Committee on Antimicrobial Susceptibility Testing breakpoints. The susceptibility rates from the ARTEMIS study were extrapolated to Gram-negative isolates obtained from 5,774 patients in Italian ICUs in 2021. The sum of the predicted susceptibilities of individual pathogens represented the overall likelihood of in vitro activity of each antibiotic as early targeted therapy for ICU patients.

RESULTS

A total of 624 Italian Gram-negative isolates included 206 Pseudomonas aeruginosa, 138 Acinetobacter baumannii, 187 Klebsiella pneumoniae, and 93 Escherichia coli. Against A. baumannii, K. pneumoniae, P. aeruginosa, and E. coli, the overall susceptibility rates for cefiderocol were 87.7%, 96.8%, 99%, and 100%, respectively; and for comparator agents, 8.7-96.4%, 25.7-100%, 73.3-100%, and 89.2-100%, respectively. Among the subset of meropenem-resistant isolates, susceptibility rates of A. baumannii, K. pneumoniae, and P. aeruginosa to cefiderocol were 86.4%, 96.2% and 100%, respectively. Corresponding susceptibility rates to comparator agents were 0-96.8%, 0-100%, and 6.4-100%, respectively. There were no meropenem-resistant isolates of E. coli. The extrapolation of data to isolates from Italian ICUs showed that the highest likelihood of therapeutic coverage, both overall and among meropenem-resistant isolates, was reported for colistin (96.8% and 72.2%, respectively) and cefiderocol (95.7% and 71.4%, respectively). All other antibiotics were associated with a likelihood below 73% overall and between 0% and 41.4% for meropenem-resistant isolates.

CONCLUSIONS

Based on confirmed susceptibility rates and reported ICU prevalence of multiple Gram-negative species, cefiderocol showed a higher predicted therapeutic coverage and utility in ICUs compared with comparator beta-lactam-beta-lactamase inhibitor antibiotics. Cefiderocol may be a promising early treatment option for patients at high risk of carbapenem-resistant Gram-negative bacterial infections in the ICU.

Challenges Facing Two Outbreaks of Carbapenem-Resistant Acinetobacter baumannii: From Cefiderocol Susceptibility Testing to the Emergence of Cefiderocol-Resistant Mutants

Carbapenem-resistant Acinetobacter baumannii (CRAB) infections are associated with poor outcomes depending on patient's conditions, clinical severity and type of infection, and treatment is challenging given the limited therapeutic options available. The aim of this study was to describe the clinical and microbiological characteristics of two outbreaks caused by CRAB in an intensive care unit (ICU). In addition, the mechanisms of resistance detected in these strains and the treatment chosen according to the available therapeutic options were analyzed. Overall, 28 patients were included. Ten patients (35.71%) had ventilator-associated pneumonia (VAP), ten (35.71%) had a bloodstream infection (BSI), and eight (28.57%) were only colonized. Recurrent infection occurred in 25% (5/20) of infected patients. Two different strains of A. baumannii were isolated from the index patient of the first outbreak. The first strain belonged to the ST85 and carried the blaNDM-1 carbapenemase gene, while the second belonged to the ST2 and carried blaOXA-23, and blaOXA-66 carbapenemase genes. The phylogenetic analysis revealed that the ST2 strain was the cause of the major outbreak, and mutations in the AmpC gene were related to progressive increasing minimum inhibitory concentration (MIC) and finally, cefiderocol-resistance in one strain. The CRAB isolates from the second outbreak were also identified as ST2. Cefiderocol-resistant strains tests identified by the disc diffusion method were involved in 24% (6/25) of nosocomial infections. Using broth microdilution (BMD) ComASP® only, 33.3% (2/6) of these strains were cefiderocol-resistant. All-cause ICU mortality was 21.4%. Conclusions: Cefiderocol is the first approved siderophore cephalosporin for the treatment of CRAB infections. Cefiderocol-resistant strains were related with blaNDM-1 carbapenemase and mutations in the AmpC gene. Cefiderocol-resistant strains or that cannot be properly interpreted by disk diffusion, should be retested using BMD for definitive categorization.

Cefiderocol-Based Regimen for Acinetobacter NDM-1 Outbreak

Variable outcomes have been reported with cefiderocol in infections due to carbapenem-resistant Acinetobacter baumannii (CRAB). Nonetheless, it may be the only option for metallo-beta-lactamase-producing strains. We describe an outbreak of NDM-CRAB infections treated with cefiderocol. Thirty-eight patients were colonized and/or infected. Thirteen patients developed a systemic infection. A clinical cure was achieved in 10 (83%) patients, one VAP and 9 BSIs, at day 7. In vitro, the activity of cefiderocol does not appear to match in vivo effectiveness using currently available commercial tests. Despite high clinical cures, overall mortality remains high in severely ill patients. Cefiderocol may be considered in this specific setting, though the implementation of susceptibility tests and infection control measures is mandatory.

Treatment of infections caused by carbapenem-resistant Acinetobacter baumannii

Patients with severe carbapenem-resistant Acinetobacter baumannii (CRAB) infections currently face significant treatment challenges. When patients display signs of infection and the clinical suspicion of CRAB infections is high, appropriate treatment should be immediately provided. However, current treatment plans and clinical data for CRAB are limited. Inherent and acquired resistance mechanisms, as well as host factors, significantly restrict options for empirical medication. Moreover, inappropriate drug coverage can have detrimental effects on patients. Most existing studies have limitations, such as a restricted sample size, and are predominantly observational or non-randomized, which report significant variability in patient infection severity and comorbidities. Therefore, a gold-standard therapy remains lacking. Current and future treatment options of infections due to CRAB were described in this review. The dose and considerable side effects restrict treatment options for polymyxins, and high doses of ampicillin-sulbactam or tigecycline appear to be the best option at the time of initial treatment. Moreover, new drugs such as durlobactam and cefiderocol have substantial therapeutic capabilities and may be effective salvage treatments. Bacteriophages and antimicrobial peptides may serve as alternative treatment options in the near future. The advantages of a combination antimicrobial regimen appear to predominate those of a single regimen. Despite its significant nephrotoxicity, colistin is considered a primary treatment and is often used in combination with antimicrobials, such as tigecycline, ampicillin-sulbactam, meropenem, or fosfomycin. The Infectious Diseases Society of America (IDSA) has deemed high-dose ampicillin-sulbactam, which is typically combined with high-dose tigecycline, polymyxin, and other antibacterial agents, the best option for treating serious CRAB infections. A rational combination of drug use and the exploration of new therapeutic drugs can alleviate or prevent the effects of CRAB infections, shorten hospital stays, and reduce patient mortality.

Novel Antibiotics for Gram-Negative Nosocomial Pneumonia

Nosocomial pneumonia, including hospital-acquired pneumonia and ventilator-associated pneumonia, is the leading cause of death related to hospital-acquired infections among critically ill patients. A growing proportion of these cases are attributed to multi-drug-resistant (MDR-) Gram-negative bacteria (GNB). MDR-GNB pneumonia often leads to delayed appropriate treatment, prolonged hospital stays, and increased morbidity and mortality. This issue is compounded by the increased toxicity profiles of the conventional antibiotics required to treat MDR-GNB infections. In recent years, several novel antibiotics have been licensed for the treatment of GNB nosocomial pneumonia. These novel antibiotics are promising therapeutic options for treatment of nosocomial pneumonia by MDR pathogens with certain mechanisms of resistance. Still, antibiotic resistance remains an evolving global crisis, and resistance to novel antibiotics has started emerging, making their judicious use crucial to prolong their shelf-life. This article presents an up-to-date review of these novel antibiotics and their current role in the antimicrobial armamentarium. We critically present data for the pharmacokinetics/pharmacodynamics, the in vitro spectrum of antimicrobial activity and resistance, and in vivo data for their clinical and microbiological efficacy in trials. Where possible, available data are summarized specifically in patients with nosocomial pneumonia, as this cohort may exhibit 'critical illness' physiology that affects drug efficacy.

Management of intra-abdominal infections: recommendations by the Italian council for the optimization of antimicrobial use

Intra-abdominal infections (IAIs) are common surgical emergencies and are an important cause of morbidity and mortality in hospital settings, particularly if poorly managed. The cornerstones of effective IAIs management include early diagnosis, adequate source control, appropriate antimicrobial therapy, and early physiologic stabilization using intravenous fluids and vasopressor agents in critically ill patients. Adequate empiric antimicrobial therapy in patients with IAIs is of paramount importance because inappropriate antimicrobial therapy is associated with poor outcomes. Optimizing antimicrobial prescriptions improves treatment effectiveness, increases patients' safety, and minimizes the risk of opportunistic infections (such as Clostridioides difficile) and antimicrobial resistance selection. The growing emergence of multi-drug resistant organisms has caused an impending crisis with alarming implications, especially regarding Gram-negative bacteria. The Multidisciplinary and Intersociety Italian Council for the Optimization of Antimicrobial Use promoted a consensus conference on the antimicrobial management of IAIs, including emergency medicine specialists, radiologists, surgeons, intensivists, infectious disease specialists, clinical pharmacologists, hospital pharmacists, microbiologists and public health specialists. Relevant clinical questions were constructed by the Organizational Committee in order to investigate the topic. The expert panel produced recommendation statements based on the best scientific evidence from PubMed and EMBASE Library and experts' opinions. The statements were planned and graded according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE) hierarchy of evidence. On November 10, 2023, the experts met in Mestre (Italy) to debate the statements. After the approval of the statements, the expert panel met via email and virtual meetings to prepare and revise the definitive document. This document represents the executive summary of the consensus conference and comprises three sections. The first section focuses on the general principles of diagnosis and treatment of IAIs. The second section provides twenty-three evidence-based recommendations for the antimicrobial therapy of IAIs. The third section presents eight clinical diagnostic-therapeutic pathways for the most common IAIs. The document has been endorsed by the Italian Society of Surgery.

Clinical effectiveness of cefiderocol for the treatment of bloodstream infections due to carbapenem-resistant Acinetobacter baumannii during the COVID-19 era: a single center, observational study

BACKGROUND

We assessed the clinical effectiveness of cefiderocol (CFDC) in comparison with colistin (COL) for the treatment of carbapenem-resistant Acinetobacter baumannii (CRAB) bloodstream infections (BSI).

MATERIALS/METHODS

Retrospective cohort study including adults with CRAB-BSI. Outcomes were mortality, clinical cure and adverse events during therapy. The average treatment effect of CFDC compared to COL was weighted with the inverse-probability treatment weight (IPTW).

RESULTS

Overall, 104 patients were included (50 CFDC, 54 COL), median age 66.5 years, median Charlson Comorbidity Index 5, septic shock in 33.6% of patients. Primary BSI accounted for 43.3% of cases, followed by ventilator-associated pneumonia (VAP) (26%), catheter-related BSI (20.2%) and hospital-acquired pneumonia (HAP) (9.6%). Although not significantly, mortality at all time points was lower for CFDC than COL, while clinical cure was higher in CFDC than COL (66% vs. 44.4%, p = 0.027). Adverse events were more frequent in COL than CFDC-group (38.8% vs. 10%, p < 0.0001), primarily attributed to acute kidney injury (AKI) in the COL group. Patients with bacteremic HAP/VAP treated with CFDC had a significant lower 30-d mortality and higher clinical cure than COL (p = 0.008 and p = 0.0008, respectively). Increment of CCI (p = 0.005), ICU (p = 0.025), SARS-CoV2 (p = 0.006) and ECMO (p < 0.0001) were independently associated with 30-d mortality, while receiving CFDC was not associated with survival.

CONCLUSIONS

CFDC could represent an effective and safe treatment option for CRAB BSI, especially in patients with bacteremic HAP/VAP and frail patients where the risk of acute renal failure during therapy should be avoided.

Optimizing Treatment for Carbapenem-Resistant Acinetobacter baumannii Complex Infections: A Review of Current Evidence

Carbapenem-resistant Acinetobacter baumannii complex (CRAB) poses a significant global health challenge owing to its resistance to multiple antibiotics and limited treatment options. Polymyxin-based therapies have been widely used to treat CRAB infections; however, they are associated with high mortality rates and common adverse events such as nephrotoxicity. Recent developments include numerous observational studies and randomized clinical trials investigating antibiotic combinations, repurposing existing antibiotics, and the development of novel agents. Consequently, recommendations for treating CRAB are undergoing significant changes. The importance of colistin is decreasing, and the role of sulbactam, which exhibits direct antibacterial activity against A. baumannii complex, is being reassessed. High-dose ampicillin-sulbactam-based combination therapies, as well as combinations of sulbactam and durlobactam, which prevent the hydrolysis of sulbactam and binds to penicillin-binding protein 2, have shown promising results. This review introduces recent advancements in CRAB infection treatment based on clinical trial data, highlighting the need for optimized treatment protocols and comprehensive clinical trials to combat the evolving threat of CRAB effectively.

Antibiotic Treatment of Carbapenem-Resistant Acinetobacter baumannii Infections in View of the Newly Developed β-Lactams: A Narrative Review of the Existing Evidence

It is estimated that antimicrobial resistance (AMR) is responsible for nearly 5 million human deaths worldwide each year and will reach 10 million by 2050. Carbapenem-resistant Acinetobacter baumannii (CRAB) infections represent the fourth-leading cause of death attributable to antimicrobial resistance globally, but a standardized therapy is still lacking. Among the antibiotics under consideration, Sulbactam/durlobactam seems to be the best candidate to replace current back-bone agents. Cefiderocol could play a pivotal role within combination therapy regimens. Due to toxicity and the pharmacokinetics/pharmacodynamics (PK/PD) limitations, colistin (or polymyxin B) should be used as an alternative agent (when no other options are available). Tigecycline (or minocycline) and fosfomycin could represent suitable partners for both NBLs. Randomized clinical trials (RCTs) are needed to better evaluate the role of NBLs in CRAB infection treatment and to compare the efficacy of tigecycline and fosfomycin as partner antibiotics. Synergism should be tested between NBLs and "old" drugs (rifampicin and trimethoprim/sulfamethoxazole). Huge efforts should be made to accelerate pre-clinical and clinical studies on safer polymyxin candidates with improved lung activity, as well as on the iv rifabutin formulation. In this narrative review, we focused the antibiotic treatment of CRAB infections in view of newly developed β-lactam agents (NBLs).

Cefiderocol in Difficult-to-Treat Nf-GNB in ICU Settings

BACKGROUND

The efficacy and safety of cefiderocol in ICU patients with difficult-to-treat resistance (DTR) non-fermenting Gram-negative bacteria (Nf-GNB) are not as well-established. Consequently, we conducted a cohort study to compare Cefiderocol with the Best Available Therapy (BAT) in ICU patients.

METHODS

We included adult patients from 9 different ICUs, including a burn ICU unit, from 2019 to 2023 treated with Cefiderocol for DTR Nf-GNB isolated from the blood or lungs. We matched each patient at a 1:2 ratio based on the same DTR Nf-GBN isolated pathogen, and when possible, within the same type of ICU (burn unit or not). The primary endpoint of the study was the clinical cure at 15 days, with secondary endpoints including clinical cure at 30 days, relapse, and in-ICU mortality. For each outcome, adjusted odds ratios were estimated using bidirectional stepwise regression in a final model, which included 13 preselected confounders.

RESULTS

We included 27 patients with cefiderocol, matched with 54 patients receiving the BAT. Four patients were not exactly matched on the type of ICU unit. Characteristics were comparable between groups, mostly male with a Charlson Comorbidity Index of 3 [1-5], and 28% had immunosuppression. Cefiderocol patients were most likely to have higher number of antibiotic lines. The main DTR Nf-GNB identified was Pseudomonas aeruginosa (81.5%), followed by Acinetobater baumanii (14.8%) and Stenotrophomonas maltophilia (3.7%). Pneumonia was the identified infection in 21 (78.8%) patients in the Cefiderocol group and in 51 (94.4%) patients in the BAT group (p = 0.054). Clinical cure at 15 and 30-day and the in-ICU mortality was comparable between groups, however relapse was higher in the cefiderocol group (8-29.6% vs. 4-7.4%;aOR 10.06[1.96;51.53]) CONCLUSION: Cefiderocol did not show an improvement in clinical cure or mortality rates compared to BAT in the treatment of DTR Nf-GNB, but it was associated with a higher relapse rate.

In vitro activity of antibiotics potentially effective against difficult-to-treat strains of Gram-negative rods: retrospective study

Bacterial resistance surveillance is one of the main outputs of microbiological laboratories and its results are important part of antimicrobial stewardship (AMS). In this study, the susceptibility of specific bacteria to selected antimicrobial agents was tested. The susceptibility of 90 unique isolates of pathogens of critical priority obtained from clinically valid samples of ICU patients in 2017-2021 was tested. 50% of these fulfilled difficult-to-treat resistance (DTR) criteria and 50% were susceptible to all antibiotics included in the definition. 10 Enterobacterales strains met DTR criteria, and 2 (20%) were resistant to colistin (COL), 2 (20%) to cefiderocol (FCR), 7 (70%) to imipenem/cilastatin/relebactam (I/R), 3 (30%) to ceftazidime/avibactam (CAT) and 5 (50%) to fosfomycin (FOS). For Enterobacterales we also tested aztreonam/avibactam (AZA) for which there are no breakpoints yet. The highest MIC of AZA observed was 1 mg/l, MIC range in the susceptible cohort was 0.032-0.064 mg/l and in the DTR cohort (incl. class B beta-lactamase producers) it was 0.064-1 mg/l. Two (13.3%) isolates of Pseudomonas aeruginosa (15 DTR strains) were resistant to COL, 1 (6.7%) to FCR, 13 (86.7%) to I/R, 5 (33.3%) to CAT, and 5 (33.3%) to ceftolozane/tazobactam. All isolates of Acinetobacter baumannii with DTR were susceptible to COL and FCR, and at the same time resistant to I/R and ampicillin/sulbactam. New antimicrobial agents are not 100% effective against DTR. Therefore, it is necessary to perform susceptibility testing of these antibiotics, use the data for surveillance (including local surveillance) and conform to AMS standards.

Current Therapeutic Approaches for Multidrug-Resistant and Extensively Drug-Resistant Acinetobacter baumannii Infections

The treatment of Acinetobacter baumannii infections remains a challenge for physicians worldwide in the 21st century. The bacterium possesses a multitude of mechanisms to escape the human immune system. The consequences of A. baumannii infections on morbidity and mortality, as well on financial resources, remain dire. Furthermore, A. baumannii superinfections have also occurred during the COVID-19 pandemic. While prevention is important, the antibiotic armamentarium remains the most essential factor for the treatment of these infections. The main problem is the notorious resistance profile (including resistance to carbapenems and colistin) that this bacterium exhibits. While newer beta lactam/beta-lactamase inhibitors have entered clinical practice, with excellent results against various infections due to Enterobacteriaceae, their contribution against A. baumannii infections is almost absent. Hence, we have to resort to at least one of the following, sulbactam, polymyxins E or B, tigecycline or aminoglycosides, against multidrug-resistant (MDR) and extensively drug-resistant (XDR) A. baumannii infections. Furthermore, the notable addition of cefiderocol in the fight against A. baumannii infections represents a useful addition. We present herein the existing information from the last decade regarding therapeutic advances against MDR/XDR A. baumannii infections.

Cefiderocol either in monotherapy or combination versus best available therapy in the treatment of carbapenem-resistant Acinetobacter baumannii infections: A systematic review and meta-analysis

BACKGROUND

The best treatment for carbapenem-resistant Acinetobacter baumannii (CRAB) infections is still a matter of debate.

OBJECTIVES

To describe the outcomes of patients treated with cefiderocol for CRAB infections, and to compare the efficacy of cefiderocol versus best available therapy (BAT).

DATA SOURCES

We searched MEDLINE, the Cochrane Library and EMBASE to screen original reports published up to September 2023.

STUDY ELIGIBILITY CRITERIA

Randomized controlled trials (RCTs) and observational studies investigating 30-day mortality, clinical failure, microbiological failure or rate of adverse drug reactions of patients treated with cefiderocol or BAT.

PARTICIPANTS

Patients with infections due to CRAB.

INTERVENTIONS

Cefiderocol in monotherapy or in combination with other potentially active agents or BAT.

ASSESSMENT OF RISK OF BIAS

We used the Cochrane Risk of Bias Tool for RCTs, and the Newcastle Ottawa scale for observational studies.

METHODS OF DATA SYNTHESIS

We conducted a meta-analysis pooling risk ratios (RRs) through random effect models.

RESULTS

We screened 801 original reports, and 18 studies (2 RCTs, 13 cohort studies and 3 case-series) were included in the analysis, for a total 733 patients treated with cefiderocol, and 473 receiving the BAT. Among patients receiving cefiderocol, the 30-day mortality rate was 42% (95% CI 38-47%), the rate of microbiological failure 48% (95% CI 31-65%), the clinical failure rate 43% (95% CI 32-55%), and the rate of ADRs was 3% (95% CI 1-6%). A lower mortality rate was observed among patients receiving cefiderocol monotherapy as compared to those treated with combination regimens (RR: 0.64; 95% CI: 0.43-0.94, p = 0.024). We found a significantly lower mortality rate (RR: 0.74; 95% CI: 0.57-0.95, p = 0.02) and a lower rate of ADRs (RR: 0.28; 95% CI: 0.09-0.91, p = 0.03) in the group treated with cefiderocol as compared to BAT. No difference was observed in microbiological and clinical failure rate.

CONCLUSIONS

Our data strengthen the efficacy and safety profile of cefiderocol in CRAB infections.

Clinical efficacy of cefiderocol-based regimens in patients with carbapenem-resistant Acinetobacter baumannii infections: A systematic review with meta-analysis

OBJECTIVES

To perform a systematic review with meta-analysis to assess the clinical efficacy of cefiderocol-based regimens for the treatment of carbapenem-resistant Acinetobacter baumannii (CRAB) infections.

METHODS

Two authors independently searched PubMed-MEDLINE, Scopus, and Cochrane databases, from inception to 02 July 2023, for randomised controlled trials (RCTs) or observational studies comparing clinical efficacy of cefiderocol-based vs. non-cefiderocol-based regimens in patients with CRAB infections. Data were extracted by the two authors independently, and the quality of included studies was independently assessed using ROB 2.0 or ROBINS-I tools. Primary outcome was mortality rate. Meta-analysis was performed by pooling odds ratios (ORs) retrieved from studies providing adjustment for confounders using a random-effects model with the inverse variance method. Multiple subgroups and sensitivity analyses were conducted to investigate the source of heterogeneity.

RESULTS

A total of 530 articles were screened, and 6 studies (1 RCT and 5 observational; N=561; 247 cefiderocol-based vs. 314 non-cefiderocol-based regimens) were included. Cefiderocol did not significantly reduce in-hospital mortality compared to alternative therapies (predominantly colistin-based), but the confidence intervals around the effect estimate included clinically important benefit (N=5; OR 0.64; 95%CI 0.40-1.04; I2=57.5%). When only observational studies providing adjustment for confounders were considered, a lower risk of mortality was found in patients treated with cefiderocol-based regimens (N=4; OR 0.53; 95%CI 0.39-0.71; I2=0.0%).

CONCLUSIONS

Cefiderocol-based regimens were associated with a significantly lower risk of mortality in patients with CRAB infections in observational studies providing proper adjustment for confounders.

Cefiderocol: Clinical application and emergence of resistance

Antibacterial drug resistance of gram-negative bacteria (GNB) results in high morbidity and mortality of GNB infection, seriously threaten human health globally. Developing new antibiotics has become the critical need for dealing with drug-resistant bacterial infections. Cefiderocol is an iron carrier cephalosporin that achieves drug accumulation through a unique "Trojan horse" strategy into the bacterial periplasm. It shows high antibacterial activity against multidrug-resistant (MDR) Enterobacteriaceae and MDR non-fermentative bacteria. The application of cefiderocol offers new hope for treating clinical drug-resistant bacterial infections. However, limited clinical data and uncertainties about its resistance mechanisms constrain the choice of its therapeutic use. This review aimed to summarize the clinical applications, drug resistance mechanisms, and co-administration of cefiderocol.

Cefiderocol and Sulbactam-Durlobactam against Carbapenem-Resistant Acinetobacter baumannii

Infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) remain a clinical challenge due to limited treatment options. Recently, cefiderocol, a novel siderophore cephalosporin, and sulbactam-durlobactam, a bactericidal β-lactam-β-lactamase inhibitor combination, have been approved by the Food and Drug Administration for the treatment of A. baumannii infections. In this review, we discuss the mechanisms of action of and resistance to cefiderocol and sulbactam-durlobactam, the antimicrobial susceptibility of A. baumannii isolates to these drugs, as well as the clinical effectiveness of cefiderocol and sulbactam/durlobactam-based regimens against CRAB. Overall, cefiderocol and sulbactam-durlobactam show an excellent antimicrobial activity against CRAB. The review of clinical studies evaluating the efficacy of cefiderocol therapy against CRAB indicates it is non-inferior to colistin/other treatments for CRAB infections, with a better safety profile. Combination treatment is not associated with improved outcomes compared to monotherapy. Higher mortality rates are often associated with prior patient comorbidities and the severity of the underlying infection. Regarding sulbactam-durlobactam, current data from the pivotal clinical trial and case reports suggest this antibiotic combination could be a valuable option in critically ill patients affected by CRAB infections, in particular where no other antibiotic appears to be effective.

Real-life Data on Cefiderocol Efficacy and Safety to Treat Multidrug-Resistant Acinetobacter baumannii Infections

Background

The objective of this study was to expand real-life data on cefiderocol efficacy to treat multidrug-resistant Acinetobacter baumannii infections.

Methods

This was a retrospective monocentric study including patients hospitalized (>24 hours) at Policlinico Tor Vergata, Rome, Italy, between May 1, 2021, and September 1, 2022, treated with cefiderocol (>48 hours). The primary objective was early clinical improvement at 48-72 hours from cefiderocol start; secondary objectives were clinical success (composite outcome of infection resolution and 14-day survival), breakthrough infection, overall 30-day mortality, and cefiderocol-related adverse events.

Results

Eleven patients were enrolled; 91% males (10/11), with a median age (interquartile range [IQR]) of 69 (59-71) years, 91% had ≥1 comorbidity, and 72.7% (8/11) were hospitalized in internal medicine wards. Six patients with bloodstream infection (54.5%; 4 primary, 2 central line-associated), 2 with pneumonia (18.2%), 2 with urinary tract infections (18.2%), and 1 with intra-abdominal infection (9.1%) were treated. Four patients (36.3%) presented with septic shock at cefiderocol start. Cefiderocol was used as monotherapy in 3/11 patients (27.3%), was combined with colistin in all the other 8 cases, and was used in triple combination with tigecycline in 2 patients. The median duration of treatment (IQR) was 12 (10-14) days. Early clinical improvement was documented in 8/11 patients (72.7%), clinical success in 8/11 patients (72.7%). Overall 30-day mortality was 27.3% (3/11), with death occurring a median (IQR) of 19 (17.5-20.5) days after the start of therapy. No cefiderocol-related adverse events were documented.

Conclusions

Cefiderocol seems to be a safe and effective option for multidrug-resistant Acinetobacter baumannii infections.

Cefiderocol use for the treatment of infections by carbapenem-resistant Gram-negative bacteria: an Italian multicentre real-life experience

BACKGROUND

Cefiderocol is a novel siderophore cephalosporin with promising activity against most carbapenem-resistant Gram-negative bacteria (CRGNB). However, extensive postmarketing experiences are lacking. This study aimed to analyse the early experience on cefiderocol postmarketing use at three tertiary care hospitals in Italy.

METHODS

We retrospectively included patients with infections caused by CRGNB treated with cefiderocol at three Italian tertiary care hospitals from 1 March 2021 to 30 June 2022. A multivariate Cox model was used to identify predictors of 30 day mortality. A propensity score (PS) analysis with inverse probability weighting (IPW) was also performed to compare the treatment effect of cefiderocol monotherapy (CM) versus combination regimens (CCRs).

RESULTS

The cohort included 142 patients (72% male, median age 67 years, with 89 cases of Acinetobacter baumannii infection, 22 cases of Klebsiella pneumoniae, 27 cases of Pseudomonas aeruginosa and 4 of other pathogens). The 30 day all-cause mortality was 37% (52/142). We found no association between bacterial species and mortality. In multivariate analysis, a Charlson Comorbidity Index >3 was an independent predictor of mortality (HR 5.02, 95% CI 2.37-10.66, P < 0.001). In contrast, polymicrobial infection (HR 0.41, 95% CI 0.21-0.82, P < 0.05) was associated with lower mortality. There was no significant difference in mortality between patients receiving CM (n = 70) and those receiving a CCR (n = 72) (33% versus 40%, respectively), even when adjusted for IPW-PS (HR 1.11, 95% CI 0.63-1.96, P = 0.71).

CONCLUSIONS

Real-life data confirm that cefiderocol is a promising option against carbapenem-resistant Gram-negative infections, even as monotherapy.

Severe infections caused by difficult-to-treat Gram-negative bacteria

PURPOSE OF REVIEW

Antimicrobial resistance (AMR) in Gram-negative bacteria (GNB) poses a significant global health concern, contributing to increased infections, mortality rates, and healthcare costs. This review discusses the main clinical manifestations, therapeutic options, and recent findings in managing antibiotic-resistant GNB, with a focus on difficult-to-treat infections.

RECENT FINDINGS

Difficult-to-treat resistance (DTR) is a novel classification that identifies GNB exhibiting intermediate or resistant phenotypes to first-line agents in the carbapenem, beta-lactam, and fluoroquinolone categories. The main pathogens implicated in severe infections include DTR Enterobacterales, DTR Pseudomonas aeruginosa , and DTR Acinetobacter baumannii. Although the clinical implications of DTR strains are still under investigation, certain studies have linked them to prolonged hospital stays and poor patient outcomes.

SUMMARY

Severe infections caused by DTR-GNB pose a formidable challenge for healthcare providers and represent a growing global health issue. The proper administration and optimization of novel antibiotics at our disposal are of paramount importance for combating bacterial resistance and improving patient prognosis.

Outcome of patients with carbapenem-resistant Acinetobacter baumannii infections treated with cefiderocol: A multicenter observational study

BACKGROUND

No clear evidence supports the use of cefiderocol as first line treatment in A. baumannii infections.

METHODS

We conducted an observational retrospective/prospective multicenter study including all patients> 18 years with carbapenem-resistant A. baumannii (CRAB) infections treated with cefiderocol, from June 12021 to October 30 2022. Primary endpoint was 30-day mortality, secondary end-points the clinical and microbiological response at 7 days and at the end of treatment. Furthermore, we compared the clinical and microbiological outcomes among patients who received cefiderocol in monotherapy or in combination.

RESULTS

Thirty-eight patients with forty episodes of infection were included [mean age 65 years (SD+16.3), 75% males, 90% with hospital-acquired infections and 70% showing sepsis or septic shock]. The most common infections included unknown source or catheter-related bacteremia (45%) and pneumonia (40%). We observed at 7 days and at the end of therapy a rate of microbiological failure of 20% and 10%, respectively, and of clinical failure of 47.5% and 32.5%, respectively; the 30-day mortality rate was 47.5%. At multivariate analysis clinical failure at 7 days of treatment was the only independent predictor of 30-day mortality. Comparing monotherapy (used in 72.5%) vs. combination therapy (used in 27.5%), no differences were observed in mortality (51.7 vs 45.5%) and clinical (41.4 vs 63.7%) or microbiological failure (24.1 vs 9.1%).

CONCLUSIONS

The findings of this study reinforce the effectiveness of cefiderocol in CRAB infections, also as monotherapy. However, prospective multicenter studies with larger sample sizes and a control group treated with standard of care are needed to identify the best treatment for CRAB infections.

Cefiderocol-containing regimens for the treatment of carbapenem-resistant A. baumannii ventilator-associated pneumonia: a propensity-weighted cohort study

Background

Cefiderocol is a novel β-lactam with activity against carbapenem-resistant Acinetobacter baumannii (CRAB), but its role in CRAB pulmonary infections is controversial due to limited evidence.

Objectives

To assess the association between cefiderocol-containing regimens treatment and 28-day mortality in carbapenem-resistant A. baumannii ventilator-associated pneumonia (VAP).

Methods

An observational cohort study including critically ill COVID-19 patients with CRAB-VAP admitted to two ICUs of a large academic hospital in Rome between September 2020 and December 2022. The primary outcome was 28-day all-cause mortality. A propensity score was created to balance the cefiderocol- and non-cefiderocol-containing groups. A propensity-weighted multiple logistic regression model was calculated to evaluate risk factors for 28-day mortality. Survival curves were calculated using the Kaplan-Meier method.

Results

121 patients were enrolled, 55 were treated with cefiderocol- and 66 with non-cefiderocol-containing regimens. The 28-day all-cause mortality was 56% (68/121). A statistically significant difference in 28-day mortality was found between cefiderocol- and non-cefiderocol- containing regimens groups (44% versus 67%, P = 0.011). In the propensity-adjusted multiple logistic regression, cefiderocol (OR 0.35 95% CI 0.14, 0.83) was a predictor of 28-day survival, Charlson comorbidity index (OR 1.36 95% CI 1.16, 1.78), SOFA score (OR 1.24 95% CI 1.09, 1.57) and septic shock (OR 3.71 95% CI 1.44, 12.73) were all associated with increased 28-day mortality.

Conclusion

Cefiderocol-containing regimens were associated with reduced 28-day mortality in CRAB-VAP. The sample size and the observational design limit the study's conclusions. Future RCTs are needed to establish cefiderocol's definite role in these infections.

Cefiderocol Versus Colistin for the Treatment of Carbapenem-Resistant Acinetobacter baumannii Complex Bloodstream Infections: A Retrospective, Propensity-Score Adjusted, Monocentric Cohort Study

INTRODUCTION

Bloodstream infections (BSI) caused by carbapenem-resistant Acinetobacter baumannii (CRAB) are associated with high mortality with limited treatment. The aim of this study is to compare effectiveness and safety of colistin-based versus cefiderocol-based therapies for CRAB-BSI.

METHODS

This is a retrospective observational study enrolling patients with monomicrobial CRAB-BSIs treated with colistin or cefiderocol from 1 January 2020, to 31 December 2022. The 30-day all-cause mortality rate was the primary outcome. A Cox regression analysis was performed to identify factors independently associated with mortality. A propensity score analysis using inverse probability of treatment weighting (IPTW) was also performed.

RESULTS

Overall 118 patients were enrolled, 75 (63%) and 43 (37%) treated with colistin- and cefiderocol-based regimens. The median (q1-q3) age was 70 (62-79) years; 70 (59%) patients were men. The 30-day all-cause mortality was 52%, significantly lower in the cefiderocol group (40% vs 59%, p = 0.045). By performing a Cox regression model, age (aHR = 1.03, 95% CI 1.00-1.05), septic shock (aHR = 1.93, 95% CI 1.05-3.53), and delayed targeted therapy (aHR = 2.42, 95% CI 1.11-5.25) were independent predictors of mortality, while cefiderocol-based therapy was protective (aHR = 0.49, 95% CI 0.25-0.93). The IPTW-adjusted Cox analysis confirmed the protective effect of cefiderocol (aHR = 0.53, 95% CI 0.27-0.98).

CONCLUSIONS

Cefiderocol may be a valuable treatment option for CRAB-BSI, especially in the current context of limited treatment options.

Clonal dissemination of Klebsiella pneumoniae resistant to cefiderocol, ceftazidime/avibactam, meropenem/vaborbactam and imipenem/relebactam co-producing KPC and OXA-181 carbapenemase

Objectives

Herein, we describe the epidemiology of carbapenemase-producing Enterobacterales (CPE) before and during the COVID-19 pandemic. Also, we report the emergence of an outbreak of Klebsiella pneumoniae strains co-producing KPC and OXA-181 carbapenemase, resistant to novel β-lactam/β-lactamase inhibitors (βL-βLICs) and cefiderocol.

Methods

CPE were collected during a period of 3 years from 2019 to 2021. Antimicrobial susceptibility testing for novel βL-βLICs and cefiderocol was performed by MIC test strips and microdilution with iron-depleted broth. WGS was performed on 10 selected isolates using the Illumina platform, and resistome analysis was carried out by a web-based pipeline.

Results

Between January 2019 and December 2021, we collected 1430 carbapenemase producers from 957 patients with infections due to CPE. KPC was the most common carbapenemase, followed by VIM, OXA-48 and NDM. During 2021, we identified 78 K. pneumoniae co-producing KPC and OXA-181 carbapenemases in 60 patients, resistant to meropenem/vaborbactam and imipenem/relebactam. Resistance to ceftazidime/avibactam and cefiderocol was observed respectively in 7 and 8 out of the 10 sequenced K. pneumoniae. Genome analysis showed that all isolates were clonally related, shared a common porin and plasmid content, and carried blaOXA-181 and blaKPC carbapenemases. Specifically, 4 out of 10 isolates carried blaKPC-3, while 6 harboured mutated blaKPC. Of note, KPC producers resistant to ceftazidime/avibactam and harbouring mutated blaKPC exhibited higher MICs of cefiderocol (median MIC 16 mg/L, IQR 16-16) than strains harbouring WT blaKPC-3 (cefiderocol 9 mg/L, IQR 1.5-16).

Conclusions

Our results highlight the need for continuous monitoring of CPE to limit widespread MDR pathogens carrying multiple mechanisms conferring resistance to novel antimicrobial molecules.

Carbapenem-Resistant Acinetobacter spp Infection in Critically Ill Patients With Limited Treatment Options: A Descriptive Study of Cefiderocol Therapy During the COVID-19 Pandemic

Background

Carbapenem-resistant Acinetobacter baumannii infections are difficult to treat and are a significant public health threat due to intrinsic/acquired resistance and limited treatment options.

Methods

A retrospective, observational cohort study in patients receiving cefiderocol via Shionogi's early access program for Acinetobacter spp infections (1 April 2020-30 April 2021; 27 sites; Italy, Spain, Germany, France). Primary outcome was clinical success, defined as clinical resolution of infection at day 14 or day 28 survival.

Results

Overall, 147 patients were included. Primary infection sites were respiratory (65.3%) and bloodstream (unknown source [15.6%]; catheter-related [10.9%]); 24.5% of patients had polymicrobial infection. Of 136 patients in intensive care (92.5%), 85.3% (116/136) received mechanical ventilation. Septic shock (55.6% [70/126]) and coronavirus disease 2019 (COVID-19) (81.6%) were prevalent. Prior to cefiderocol, 85.0% of patients received gram-negative treatment, 61.2% received ≥2 antimicrobials, and most received colistin (58.5%; median duration, 11.5 days). Cefiderocol monotherapy was used in 30.6% of patients. Clinical success rate was 53.1% and was higher in patients without septic shock (62.5%), without COVID-19 (77.8%), and with lower Sequential Organ Failure Assessment (SOFA) scores (quartile 1 [median, 3; range, 0-5]: 82.9%). Day 28 survival was 44.9% and was higher in patients without septic shock (60.7%), without COVID-19 (59.3%), with lower SOFA score (quartile 1: 82.9%), and receiving first-line cefiderocol (68.2% [15/22]). Resolution of infection at day 14 occurred in 39.5% of patients.

Conclusions

Despite use in complex patients with limited treatment options and high septic shock/COVID-19 rates, cefiderocol treatment was associated with an overall clinical success rate of 53%.

Acinetobacter baumannii in the critically ill: complex infections get complicated

Acinetobacter baumannii is increasingly associated with various epidemics, representing a serious concern due to the broad level of antimicrobial resistance and clinical manifestations. During the last decades, A. baumannii has emerged as a major pathogen in vulnerable and critically ill patients. Bacteremia, pneumonia, urinary tract, and skin and soft tissue infections are the most common presentations of A. baumannii, with attributable mortality rates approaching 35%. Carbapenems have been considered the first choice to treat A. baumannii infections. However, due to the widespread prevalence of carbapenem-resistant A. baumannii (CRAB), colistin represents the main therapeutic option, while the role of the new siderophore cephalosporin cefiderocol still needs to be ascertained. Furthermore, high clinical failure rates have been reported for colistin monotherapy when used to treat CRAB infections. Thus, the most effective antibiotic combination remains disputed. In addition to its ability to develop antibiotic resistance, A. baumannii is also known to form biofilm on medical devices, including central venous catheters or endotracheal tubes. Thus, the worrisome spread of biofilm-producing strains in multidrug-resistant populations of A. baumannii poses a significant treatment challenge. This review provides an updated account of antimicrobial resistance patterns and biofilm-mediated tolerance in A. baumannii infections with a special focus on fragile and critically ill patients.

Treatment of critically ill patients with cefiderocol for infections caused by multidrug-resistant pathogens: review of the evidence

Appropriate antibiotic treatment for critically ill patients with serious Gram-negative infections in the intensive care unit is crucial to minimize morbidity and mortality. Several new antibiotics have shown in vitro activity against carbapenem-resistant Enterobacterales (CRE) and difficult-to-treat resistant Pseudomonas aeruginosa. Cefiderocol is the first approved siderophore beta-lactam antibiotic with potent activity against multidrug-resistant, carbapenem-resistant, difficult-to-treat or extensively drug-resistant Gram-negative pathogens, which have limited treatment options. The spectrum of activity of cefiderocol includes drug-resistant strains of Acinetobacter baumannii, P. aeruginosa, Stenotrophomonas maltophilia, Achromobacter spp. and Burkholderia spp. and CRE that produce serine- and/or metallo-carbapenemases. Phase 1 studies established that cefiderocol achieves adequate concentration in the epithelial lining fluid in the lung and requires dosing adjustment for renal function, including patients with augmented renal clearance and continuous renal-replacement therapy (CRRT); no clinically significant drug-drug interactions are expected. The non-inferiority of cefiderocol versus high-dose, extended-infusion meropenem in all-cause mortality (ACM) rates at day 14 was demonstrated in the randomized, double-blind APEKS-NP Phase 3 clinical study in patients with nosocomial pneumonia caused by suspected or confirmed Gram-negative bacteria. Furthermore, the efficacy of cefiderocol was investigated in the randomized, open-label, pathogen-focused, descriptive CREDIBLE-CR Phase 3 clinical study in its target patient population with serious carbapenem-resistant Gram-negative infections, including hospitalized patients with nosocomial pneumonia, bloodstream infection/sepsis, or complicated urinary tract infections. However, a numerically greater ACM rate with cefiderocol compared with BAT led to the inclusion of a warning in US and European prescribing information. Cefiderocol susceptibility results obtained with commercial tests should be carefully evaluated due to current issues regarding their accuracy and reliability. Since its approval, real-world evidence in patients with multidrug-resistant and carbapenem-resistant Gram-negative bacterial infections suggests that cefiderocol can be efficacious in certain critically ill patient groups, such as those requiring mechanical ventilation for COVID-19 pneumonia with subsequently acquired Gram-negative bacterial superinfection, and patients with CRRT and/or extracorporeal membrane oxygenation. In this article, we review the microbiological spectrum, pharmacokinetics/pharmacodynamics, efficacy and safety profiles and real-world evidence for cefiderocol, and look at future considerations for its role in the treatment of critically ill patients with challenging Gram-negative bacterial infections.

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

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

Cefiderocol Treatment for Severe Infections due to Difficult-to-Treat-Resistant Non-Fermentative Gram-Negative Bacilli in ICU Patients: A Case Series and Narrative Literature Review

Cefiderocol (FDC) is a siderophore cephalosporin now recognized as a new weapon in the treatment of difficult-to-treat-resistant (DTR) Gram-negative pathogens, including carbapenemase-producing enterobacterales and non-fermentative Gram-negative bacilli (GNB). This article reports our experience with an FDC-based regimen in the treatment of 16 extremely severe patients (invasive mechanical ventilation, 15/16; extracorporeal membrane oxygenation, 9/16; and renal replacement therapy, 8/16) infected with DTR GNB. Our case series provides detailed insight into the pharmacokinetic profile and the microbiological data in real-life conditions. In the narrative review, we discuss the interest of FDC in the treatment of non-fermentative GNB in critically ill patients. We reviewed the microbiological spectrum, resistance mechanisms, pharmacokinetics/pharmacodynamics, efficacy and safety profiles, and real-world evidence for FDC. On the basis of our experience and the available literature, we discuss the optimal FDC-based regimen, FDC dosage, and duration of therapy in critically ill patients with DTR non-fermentative GNB infections.

Salvage therapy with sulbactam/durlobactam against cefiderocol-resistant Acinetobacter baumannii in a critically ill burn patient: clinical challenges and molecular characterization

Background

Carbapenem-resistant Acinetobacter baumannii (CRAB) infections are associated with high mortality rates. The optimal treatment regimen for CRAB has not been defined. Cefiderocol has been recently introduced in the armamentarium against CRAB but there is concern about treatment-emergent resistance. Since mortality rates in CRAB infections remain high, further antibiotic options are needed.

Methods

We report a case of severe infection by CRAB resistant to both colistin and cefiderocol treated with sulbactam/durlobactam and describe the molecular features of the strain. Susceptibility to cefiderocol was detected by disc diffusion according to EUCAST breakpoints. Susceptibility to sulbactam/durlobactam was determined by Etest according to preliminary breakpoints provided by Entasis Therapeutics. Whole Genome Sequencing (WGS) of the CRAB isolate was performed.

Results

A burn patient with ventilator-associated pneumonia by CRAB resistant to colistin and cefiderocol received sulbactam/durlobactam as compassionate use. She was alive after 30 days from the end of therapy. Complete microbiological eradication of CRAB was achieved. The isolate harboured bla_ADC-30, bla_OXA-23 and bla_OXA-66. A missense mutation in PBP3 was detected. The isolate harboured a mutation in the TonB-dependent siderophore receptor gene piuA that showed a frameshift mutation causing a premature stop codon (K384fs). Moreover, the fepA gene, which is orthologous to pirA, was interrupted by a transposon insertion P635-ISAba125 (IS30 family).

Conclusions

Further treatment options for severe infections by CRAB resistant to all available antibiotics are urgently needed. Sulbactam/durlobactam may be a future option against MDR A. baumannii.

Pharmacokinetics/pharmacodynamics of cefiderocol administered by continuous infusion in a case series of critically ill patients with carbapenem-resistant Acinetobacter baumannii infections undergoing continuous venovenous haemodiafiltration (CVVHDF)

OBJECTIVES

To assess the pharmacokinetics/pharmacodynamics (PK/PD) of cefiderocol administered by continuous infusion (CI) in a case series of critically ill patients with carbapenem-resistant Acinetobacter baumannii (CRAB) infections undergoing continuous venovenous haemodiafiltration (CVVHDF).

METHODS

Critically ill patients receiving CI cefiderocol during CVVHDF for documented bloodstream infections (BSIs), ventilator-associated pneumonia (VAP), and/or complicated intrabdominal infections (cIAIs) caused by CRAB and undergoing therapeutic drug monitoring (TDM) from February 2022 to January 2023 were retrospectively assessed. Cefiderocol concentrations were determined at steady-state, and the free fraction (fC_ss) was calculated. Cefiderocol total clearance (CL_tot) was determined at each TDM assessment. fC_ss/MIC ratio was selected as PD determinant of cefiderocol efficacy and defined as optimal if >4, quasi-optimal if between 1 and 4, and suboptimal if <1.

RESULTS

Five patients with documented CRAB infections (two BSI+VAP, two VAP, and one BSI+cIAI) were included. The maintenance dose of cefiderocol was always of 2g q8h over 8h by CI. Median average fC_ss was 26.5 mg/L (21.7-33.6 mg/L). Median CL_tot was 4.84 L/h (2.04-5.22 L/h). Median CVVHDF dose was 41.1 mL/kg/h (35.5-44.9 mL/kg/h), and residual diuresis was reported in 4/5 cases. Optimal PK/PD target was attained in all cases with a median cefiderocol fC_ss/MIC ratio of 14.9 (6.6-33.6).

CONCLUSION

CI administration of full doses could be a useful strategy for attaining aggressive PK/PD targets with cefiderocol for the treatment of severe CRAB infections among critically ill patients undergoing high-intensity CVVHDF and having residual diuresis.

Cefiderocol Efficacy in a Real-Life Setting: Single-Centre Retrospective Study

The current carbapenem-resistant gram-negative bacteria (CR-GN) treatment guidelines lack strong evidence about cefiderocol (CFD) efficacy against CR-GN, especially CRAB. The study's purpose is to evaluate the effectiveness of CFD in a real-life setting. We made a single-center retrospective study of 41 patients who received CFD in our hospital for several CR-GN infections. Bloodstream infections (BSI) affected 43.9% (18/41) of patients, while CRAB affected 75.6% (31/41) of isolated CR-GN patients. Thirty-days (30-D) all-causes mortality affected 36.6% (15/41) of patients, while end-of-treatment (EOT) clinical cure affected 56.1% (23/41). Finally, microbiological eradication at EOT affected 56.1% (23/41) of patients. Univariate and multivariate analysis showed that septic shock is an independent factor associated with mortality. Subgroup analyses showed no difference in CFD effectiveness between monotherapy and combination therapy.

Cefiderocol-Based versus Colistin-Based Regimens for Severe Carbapenem-Resistant Acinetobacter baumannii Infections: A Propensity Score-Weighted, Retrospective Cohort Study during the First Two Years of the COVID-19 Pandemic

BACKGROUND

A large increase in multi-drug-resistant Acinetobacter baumannii, especially carbapenem-resistant strains, occurred during the first two years of the COVID-19 pandemic, posing important challenges in its treatment. Cefiderocol appeared to be a good option for the treatment of Carbapenem-resistant Acinetobacter baumannii (CR-Ab), but to date, the guidelines and evidence available are conflicting.

METHODS

We retrospectively included a group of patients with CR-Ab infections (treated with colistin- or cefiderocol-based regimens) at Padua University Hospital (August 2020-July 2022) and assessed predictors of 30-day mortality, and differences in microbiological and clinical treatment. To evaluate the difference in outcomes, accounting for the imbalance in antibiotic treatment allocation, a propensity score weighting (PSW) approach was adopted.

RESULTS

We included 111 patients, 68% males, with a median age of 69 years (IQR: 59-78). The median duration of antibiotic treatment was 13 days (IQR:11-16). In total, 60 (54.1%) and 51 (45.9%) patients received cefiderocol- and colistin-based therapy, respectively. Notably, 53 (47.7%) patients had bloodstream infections, while 58 (52.3%) had pneumonia. Colistin was combined in 96.1%, 80.4%, and 5.8% of cases with tigecycline, meropenem, and fosfomycin, respectively. Cefiderocol was combined in 13.3%, 30%, and 18.3% of cases with fosfomycin, tigecycline, and meropenem, respectively. At the baseline, the two treatment groups significantly differed in age (patients treated with colistin were significantly older), the prevalence of diabetes and obesity (more frequent in the group treated with colistin), length of stay (longer in the group receiving cefiderocol), and type of infection (BSI were more frequent in the group receiving cefiderocol). The proportion of patients who developed acute kidney injury was significantly higher in the colistin group. By using PSW, no statistically significant differences emerged for mortality or clinical and microbiological cure between the two groups. No independent predictors were detected for hospital mortality or clinical cure, while for the length of stay, the only selected predictor was age, with a non-linear effect (p-value 0.025 for non-linearity) on the prolongation of hospital stay of 0.25 days (95% CI 0.10-0.39) at increasing ages (calculated over the IQR).

CONCLUSIONS

Cefiderocol treatment did not differ in terms of main outcomes and safety profile from colistin-based regimens. More prospective studies with a larger number of patients are required to confirm our results.

What to Do with the New Antibiotics?

Multidrug-resistant Gram-negative bacteria-related infections have become a real public health problem and have exposed the risk of a therapeutic impasse. In recent years, many new antibiotics have been introduced to enrich the therapeutic armamentarium. Among these new molecules, some are mainly of interest for the treatment of the multidrug-resistant infections associated with Pseudomonas aeruginosa (ceftolozane/tazobactam and imipenem/relebactam); others are for carbapenem-resistant infections associated with Enterobacterales (ceftazidime/avibactam, meropenem/vaborbactam); and finally, there are others that are effective on the majority of multidrug-resistant Gram-negative bacilli (cefiderocol). Most international guidelines recommend these new antibiotics in the treatment of microbiologically documented infections. However, given the significant morbidity and mortality of these infections, particularly in the case of inadequate therapy, it is important to consider the place of these antibiotics in probabilistic treatment. Knowledge of the risk factors for multidrug-resistant Gram-negative bacilli (local ecology, prior colonization, failure of prior antibiotic therapy, and source of infection) seems necessary in order to optimize antibiotic prescriptions. In this review, we will assess these different antibiotics according to the epidemiological data.

[Clinical experience using cefiderocol]

BACKGROUND

Infections due to antibiotic-resistant bacteria are threatening modern healthcare, and antibacterial resistance has become one of the greatest threats to public health. In Germany 54,500 patients become infected with antibiotic-resistant bacteria per year, causing about 2400 attributable deaths. Rising resistance in Gram-negative bacteria especially carbapenem-resistant pathogens is of particular concern due to the lack of effective and safe alternative treatment options.

OBJECTIVE

The results from trials and compassionate-use programs with the new antibiotic cefiderocol, which was approved by the European Medicines Agency (EMA) in April 2020 for the treatment of adults with infections caused by aerobic Gram-negative bacteria, are summarized.

RESULTS

The new β‑lactam antibiotic cefiderocol is the first siderophore cephalosporin indicated for the treatment of infections due to aerobic Gram-negative organisms in adults with limited treatment options. Its chemical structure and its unique mechanism of action confer enhanced stability against β‑lactamases including all classes of clinically relevant carbapenemases. In vitro data show high antibacterial activity against multidrug resistant Gram-negative bacteria, Enterobacterales and nonfermenters, including carbapenem-resistant strains. In clinical trials, cefiderocol showed superiority in complicated urinary tract infection in comparison to imipenem and non-inferiority versus meropenem in hospital-acquired/ventilator-associated pneumonia patients and severe infections caused by carbapenem-resistant pathogens.

CONCLUSION

Clinical trial data and case reports identified in the literature search show that cefiderocol is a promising treatment option for severe infections caused by drug-resistant Gram-negative bacteria, particularly carbapenem-resistant bacteria.

Jumping into the future: overcoming pharmacokinetic/pharmacodynamic hurdles to optimize the treatment of severe difficult to treat-Gram-negative infections with novel beta-lactams

INTRODUCTION

The choice of best therapeutic strategy for difficult-to-treat resistance (DTR) Gram-negative infections currently represents an unmet clinical need.

AREAS COVERED

This review provides a critical reappraisal of real-world evidence supporting the role of pharmacokinetic/pharmacodynamic (PK/PD) optimization of novel beta-lactams in the management of DTR Gram-negative infections. The aim was to focus on prolonged and/or continuous infusion administration, penetration rates into deep-seated infections, and maximization of PK/PD targets in special renal patient populations. Retrieved findings were applied to the three most critical clinical scenarios of Gram-negative resistance phenotypes (i.e. carbapenem-resistant Enterobacterales; difficult-to-treat resistant Pseudomonas aeruginosa, and carbapenem-resistant Acinetobacter baumannii).

EXPERT OPINION

Several studies supported the role of PK/PD optimization of beta-lactams in the management of DTR Gram-negative infections for both maximizing clinical efficacy and preventing resistance emergence. Optimizing antimicrobial therapy with novel beta-lactams based on the so called 'antimicrobial therapy puzzle' PK/PD concepts may represent a definitive jump into the future toward a personalized patient management of DTR Gram negative infections. Establishing a dedicated and coordinated multidisciplinary team and implementing a real-time TDM-guided personalized antimicrobial exposure optimization of novel beta-lactams based on expert clinical pharmacological interpretation, could represent crucial cornerstones for the proper management of DTR Gram-negative infections.

Fast and Sensitive Analysis of Cefiderocol in Human Plasma Microsamples by Liquid Chromatography-Isotope Dilution Tandem Mass Spectrometry for Therapeutic Drug Monitoring

Cefiderocol (C) is a parenteral siderophore cephalosporin with relevant inter-individual pharmacokinetic variability among critically ill patients, which may potentially affect effective drug exposure. Therapeutic drug monitoring (TDM) may concur in improving the real-time management of C therapy in clinics. In this study, we developed and validated a fast and sensitive Liquid Chromatography-Isotope Dilution Tandem Mass Spectrometry (LC-ITD-MS/MS) method for measuring C in human plasma microsamples, as small as 3 microliters. Analysis was preceded by a user-friendly pre-analytical single-step and was performed by means of a very fast chromatographic run of 4 min, followed by positive electrospray ionization and detection on a high sensitivity triple quadrupole tandem mass spectrometer operated in multiple reaction monitoring mode. The straightforward analytical procedure was successfully validated, based on the European Medicines Agency (EMA) guidelines, in terms of specificity, sensitivity, linearity, precision, accuracy, matrix effect, extraction recovery, limit of quantification, and stability. The novel method was successfully applied to TDM of C in more than 50 cases of critically carbapenem-resistant Gram-negative bacterial infections and enabled us to optimize antibiotic therapy.

Real-world experience with cefiderocol therapy for Pseudomonas aeruginosa and other multidrug resistant gram-negative infections within the Veterans Health Administration, 2019-2022

Objective

Single-center and regional studies have reported outcomes after treatment with cefiderocol, a novel siderophore cephalosporin. We report on real-world use, clinical outcomes, and microbiological outcomes with cefiderocol therapy within the Veterans' Health Administration (VHA).

Design

Prospective, observational descriptive study.

Setting

Veterans' Health Administration, 132 sites across the United States, during 2019-2022.

Patients

This study included patients admitted to any VHA medical center who received cefiderocol for ≥2 days.

Methods

Data were obtained from the VHA Corporate Data Warehouse and through manual chart review. We extracted clinical and microbiologic characteristics and outcomes.

Results

In total, 8,763,652 patients received 1,142,940,842 prescriptions during the study period. Of these, 48 unique individuals received cefiderocol. The median age of this cohort was 70.5 years (IQR, 60.5-74), and the median Charlson comorbidity score was 6 (IQR, 3-9). The most common infectious syndromes were lower respiratory tract infection in 23 patients (47.9%) and urinary tract infection in 14 patients (29.2%). The most common pathogen cultured was P. aeruginosa in 30 patients (62.5%). The clinical failure rate was 35.4% (17 of 48), and 15 (88.2%) of these 17 patients died within 3 days of clinical failure. The 30-day and 90-day all-cause mortality rates were 27.1% (13 of 48) and 45.8% (22 of 48), respectively. The 30-day and 90-day microbiologic failure rates were 29.2% (14 of 48) and 41.7% (20 of 48), respectively.

Conclusions

In this nationwide VHA cohort clinical and microbiologic failure occurred in >30% of patients treated with cefiderocol, and >40% of these died within 90 days. Cefiderocol is not widely used, and many of the patients who received it had substantial comorbidities.

Intravenous Fosfomycin: A Potential Good Partner for Cefiderocol. Clinical Experience and Considerations

Multidrug resistant Gram-negative bacteremia represents a therapeutic challenge clinicians have to deal with. This concern becomes more difficult when causing germs are represented by carbapenem resistant Acinetobacter baumannii or difficult-to-treat Pseudomonas aeruginosa. Few antibiotics are available against these cumbersome bacteria, although literature data are not conclusive, especially for Acinetobacter. Cefiderocol could represent a valid antibiotic choice, being a molecule with an innovative mechanism of action capable of overcoming common resistance pathways, whereas intravenous fosfomycin may be an appropriate partner either enhancing cefiderocol activity or avoiding resistance development. Here we report two patients with MDR Gram negative bacteremia who were successfully treated with a cefiderocol/fosfomycin combination.

Clinical evidence supporting cefiderol for serious Acinetobacter baumannii infections

PURPOSE OF REVIEW

Nosocomial infections caused by Acinetobacter baumannii currently represent a serious challenge for clinicians because treatment options are limited and frequently associated with significant toxicity. Cefiderocol is a first-in-class siderophore cephalosporin that has a proven efficacy for the treatment of multidrug-resistant Gram-negative infections, including carbapenem-resistant A. baumannii. The aim of this review is to evaluate the current evidence for the role of cefiderocol in the management of A. baumannii infections.

RECENT FINDINGS

In this review, we briefly summarize the available data on the efficacy (from randomized controlled trials) and on effectiveness and cure rates (from observational studies), pertaining to the use of cefiderocol for treatment of serious A. baumannii infections.

SUMMARY

Cefiderocol represents a promising and safe antibiotic option for treating patients with carbapenem-resistant A. baumannii infections. Due to conflicting mortality data from available experience, well-designed future randomized controlled trials and real-life studies are needed.

Secondary Infections in Critically Ill Patients with COVID-19: A Retrospective Study

Patients with severe COVID-19, especially those followed in the ICU, are at risk for developing bacterial and fungal superinfections. In this study, we aimed to describe the burden of hospital-acquired superinfections in a cohort of consecutive, severe COVID-19 patients hospitalized between February and May 2021 in the intensive care unit (ICU) department of San Salvatore Hospital in Pesaro, Italy. Among 89 patients considered, 68 (76.4%) acquired a secondary infection during their ICU stay. A total of 46 cases of ventilator-associated pneumonia (VAP), 31 bloodstream infections (BSIs) and 15 catheter-associated urinary tract infections (CAUTIs) were diagnosed. Overall mortality during ICU stay was 48%. A multivariate analysis showed that factors independently associated with mortality were male gender (OR: 4.875, CI: 1.227-19.366, p = 0.024), higher BMI (OR: 4.938, CI:1.356-17.980, p = 0.015) and the presence of VAP (OR: 6.518, CI: 2.178-19.510, p = 0.001). Gram-negative bacteria accounted for most of the isolates (68.8%), followed by Gram-positive bacteria (25.8%) and fungi (5.3%). Over half of the infections (58%) were caused by MDR opportunistic pathogens. Factors that were independently associated with an increased risk of infections caused by an MDR pathogen were higher BMI (OR: 4.378, CI: 1.467-13.064, p = 0.0008) and a higher Charlson Comorbidity Index (OR: 3.451, 95% CI: 1.113-10.700, p = 0.032). Secondary infections represent a common and life-threatening complication in critically ill patients with COVID-19. Efforts to minimize the likelihood of acquiring such infections, often caused by difficult-to-treat MDR organisms-especially in some subgroups of patients with specific risk factors-must be pursued.