Cefiderocol as Rescue Therapy for Acinetobacter baumannii and Other Carbapenem-resistant Gram-negative Infections in Intensive Care Unit Patients

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.

Carbapenem-resistant Gram-negative bacteria (CR-GNB) in ICUs: resistance genes, therapeutics, and prevention - a comprehensive review

Intensive care units (ICUs) are specialized environments dedicated to the management of critically ill patients, who are particularly susceptible to drug-resistant bacteria. Among these, carbapenem-resistant Gram-negative bacteria (CR-GNB) pose a significant threat endangering the lives of ICU patients. Carbapenemase production is a key resistance mechanism in CR-GNB, with the transfer of resistance genes contributing to the extensive emergence of antimicrobial resistance (AMR). CR-GNB infections are widespread in ICUs, highlighting an urgent need for prevention and control measures to reduce mortality rates associated with CR-GNB transmission or infection. This review provides an overview of key aspects surrounding CR-GNB within ICUs. We examine the mechanisms of bacterial drug resistance, the resistance genes that frequently occur with CR-GNB infections in ICU, and the therapeutic options against carbapenemase genotypes. Additionally, we highlight crucial preventive measures to impede the transmission and spread of CR-GNB within ICUs, along with reviewing the advances made in the field of clinical predictive modeling research, which hold excellent potential for practical application.

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.

What is the clinical significance of 'heteroresistance' in nonfermenting Gram-negative strains?

PURPOSE OF REVIEW

The aim of this study was to discuss the potential clinical significance of heteroresistance in nonfermenting Gram-negative bacilli (GNB).

RECENT FINDINGS

Recently, heteroresistance has been considered potentially responsible for clinical failure in Acinetobacter baumannii infections. This raised a scientific debate, still open, about the potential clinical significance of heteroresistance in nonfermenting GNB.

SUMMARY

We reviewed the literature of last 20 years and found a limited number of studies evaluating the relationship between heteroresistance and clinical outcome in nonfermenting GNB. Unlike Gram-positive bacteria, heteroresistance is reported in a significant proportion of nonfermenting GNB with some studies describing it in all tested strains and for several antibiotics (including tigecycline, carbapenems, levofloxacin, cefiderocol, colistin). One important issue is the need for validated detection method since the population analysis profile test, that is considered the gold standard, requires high costs and time. Studies evaluating the correlation between heteroresistance and clinical outcome are contrasting and have several limitations. Although in-vitro detection of heteroresistance in nonfermenting GNB has not been associated with in-vivo treatment failure, its presence may suggest to prefer combination regimens instead monotherapy when treating infections by nonfermenters. Further studies are needed to clarify the clinical significance of heteroresistance.

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.

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.

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%.

Mortality Attributable to Bloodstream Infections Caused by Different Carbapenem-Resistant Gram-Negative Bacilli: Results From a Nationwide Study in Italy (ALARICO Network)

BACKGROUND

Our aim was to analyze mortality attributable to carbapenem-resistant (CR) gram-negative bacilli (GNB) in patients with bloodstream infections (BSIs).

METHODS

Prospective multicentric study including patients with GNB-BSI from 19 Italian hospitals (June 2018-January 2020). Patients were followed-up to 30 days. Primary outcomes were 30-day mortality and attributable mortality. Attributable mortality was calculated in the following groups: Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacterales, metallo-β-lactamases (MBL)-producing Enterobacterales, CR-Pseudomonas aeruginosa (CRPA), CR-Acinetobacter baumannii (CRAB). A multivariable analysis with hospital fixed-effect was built to identify factors associated with 30-day mortality. Adjusted OR (aORs) were reported. Attributable mortality was calculated according to the DRIVE-AB Consortium.

RESULTS

Overall, 1276 patients with monomicrobial GNB BSI were included: 723/1276 (56.7%) carbapenem-susceptible (CS)-GNB, 304/1276 (23.8%) KPC-, 77/1276 (6%) MBL-producing CRE, 61/1276 (4.8%) CRPA, and 111/1276 (8.7%) CRAB BSI. Thirty-day mortality in patients with CS-GNB BSI was 13.7% compared to 26.6%, 36.4%, 32.8% and 43.2% in patients with BSI by KPC-CRE, MBL-CRE, CRPA and CRAB, respectively (P < .001). On multivariable analysis, age, ward of hospitalization, SOFA score, and Charlson Index were factors associated with 30-day mortality, while urinary source of infection and early appropriate therapy resulted protective factors. Compared to CS-GNB, MBL-producing CRE (aOR 5.86, 95% CI 2.72-12.76), CRPA (aOR 1.99, 95% CI 1.48-5.95) and CRAB (aOR 2.65, 95% CI 1.52-4.61) were significantly associated with 30-day mortality. Attributable mortality rates were 5% for KPC-, 35% for MBL, 19% for CRPA, and 16% for CRAB.

CONCLUSIONS

In patients with BSIs, carbapenem-resistance is associated with an excess of mortality, with MBL-producing CRE carrying the highest risk of death.

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.

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.

Bloodstream Infection and Gram-Negative Resistance: The Role for Newer Antibiotics

Gram-negative resistance remains a major challenge. Rates of in vitro resistance to commonly utilized antibiotics have skyrocketed over the last decade. Clinicians now encounter multidrug-resistant organisms routinely. Fortunately, newer agents, such as ceftazidime-avibactam, ceftolozone-tazobactam, meropenem-vaborbactam, and cefiderocol, have been developed and are now available for use against these pathogens. Clinical trials with these novel therapies have focused on multiple infection types ranging from complicated urinary tract infections to nosocomial pneumonia. Nonetheless, there remains little information about the efficacy of these drugs for bacteremia. To better appreciate the types and limitations of the evidence supporting the role for these unique molecules in bloodstream infection, one requires an appreciation of the initial clinical trials supporting the regulatory approval of these antibiotics. Furthermore, physicians must understand the subsequent case series and reports specifically focusing on outcomes for patients with bacteremia treated with these drugs. Despite the limitations of the data and reports relating to treatment for bacteremia with these antibiotics, each agent appears to be efficacious and can provide good outcomes in bloodstream infections due to resistant pathogens.

Trends in hospital acquired NDM-producing Enterobacterales in Tuscany (Italy) from 2019 to 2021: impact of the COVID-19 pandemic

OBJECTIVES

In Tuscany, Italy, New Delhi metallo-beta-lactamase-producing carbapenem-resistant Enterobacterales (NDM-CRE) in hospitalised patients has increasingly been observed since 2018, leading in 2019 to the implementation of enhanced control measures successfully reducing transmission. We describe the NDM-CRE epidemiology during the COVID-19 pandemic in Tuscany.

METHODS

Data on NDM-CRE patients hospitalised in five Tuscan hospitals were collected from 01/2019 to 12/2021. Weekly rates of NDM-CRE cases on hospital days in medical and critical-care wards were calculated. In March-December 2020, NDM-CRE rates were stratified by COVID-19 diagnosis. Multivariate regression analysis was performed to assess outcomes' differences among two periods analysed and between COVID-19 populations.

RESULTS

Since March 2020 an increase in NDM-CRE cases was observed, associated with COVID-19 admissions. COVID-19 patients differed significantly from non-COVID-19 ones by several variables, including patient features (age, Charlson index) and clinical history and outcomes (NDM-CRE infection/colonisation, ICU stay, length of stay, mortality). During the pandemic, we observed a higher rate of NDM-CRE cases per hospital days in both non-COVID-19 patients (273/100,000) and COVID-19 patients (370/100,00) when compared with pre-pandemic period cases (187/100,00).

CONCLUSIONS

Our data suggest a resurgence in NDM-CRE spread among hospitalised patients in Tuscany during the COVID-19 pandemic, as well as a change in patients' case-mix. The observed increase in hospital transmission of NDM-CRE could be related to changes in infection prevention and control procedures, aimed mainly at COVID-19 management, leading to new challenges in hospital preparedness and crisis management planning.

Navigating Available Treatment Options for Carbapenem-Resistant Acinetobacter baumannii-calcoaceticus Complex Infections

Carbapenem-resistant Acinetobacter baumannii-calcoaceticus complex (CRAB) is one of the top-priority pathogens for new antibiotic development. Unlike other antibiotic-resistant threats, none of the available therapies have been shown to consistently reduce mortality or improve patient outcomes in clinical trials. Antibiotic combination therapy is routinely used in clinical practice; however, the preferred combination has not been defined. This narrative review focuses on evidence-based solutions for the treatment of invasive CRAB infections. We dissect the promise and perils of traditional agents used in combination, such as colistin, sulbactam, and the tetracyclines, and offer clinical pearls based on our interpretation of the available data. Next, we investigate the merits of newly developed β-lactam agents like cefiderocol and sulbactam-durlobactam, which have demonstrated contrasting results in recent randomized clinical trials. The review concludes with the authors' perspective on the evolving treatment landscape for CRAB infections, which is complicated by limited clinical data, imperfect treatment options, and a need for future clinical trials. We propose that effective treatment for CRAB infections requires a personalized approach that incorporates host factors, the site of infection, pharmacokinetic-pharmacodynamic principles, local molecular epidemiology of CRAB isolates, and careful interpretation of antibiotic susceptibility testing results. In most clinical scenarios, a dose-optimized, sulbactam-based regimen is recommended with the addition of at least one other in vitro active agent. Should sulbactam-durlobactam receive regulatory approval, recommendations will need to be re-evaluated with the most recent evidence.

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.

Phenotypic and Molecular Characteristics of Carbapenem-Resistant Acinetobacter baumannii Isolates from Bulgarian Intensive Care Unit Patients

Carbapenem-resistant Acinetobacter baumannii (CRAB) is designated as an urgent public health threat, both due to its remarkable multidrug resistance and propensity for clonal spread. This study aimed to explore the phenotypic and molecular characteristics of antimicrobial resistance in CRAB isolates (n = 73) from intensive care unit (ICU) patients in two university hospitals in Bulgaria (2018–2019). The methodology included antimicrobial susceptibility testing, PCR, whole-genome sequencing (WGS), and phylogenomic analysis. The resistance rates were as follows: imipenem, 100%; meropenem, 100%; amikacin, 98.6%; gentamicin, 89%; tobramycin, 86.3%; levofloxacin, 100%; trimethoprim–sulfamethoxazole, 75.3%; tigecycline, 86.3%; colistin, 0%; and ampicillin–sulbactam, 13.7%. All isolates harbored blaOXA-51-like genes. The frequencies of distribution of other antimicrobial resistance genes (ARGs) were: blaOXA-23-like, 98.6%; blaOXA-24/40-like, 2.7%; armA, 86.3%; and sul1, 75.3%. The WGS of selected extensively drug-resistant A. baumannii (XDR-AB) isolates (n = 3) revealed the presence of OXA-23 and OXA-66 carbapenem-hydrolyzing class D β-lactamases in all isolates, and OXA-72 carbapenemase in one of them. Various insertion sequencies, such as ISAba24, ISAba31, ISAba125, ISVsa3, IS17, and IS6100, were also detected, providing increased ability for horizontal transfer of ARGs. The isolates belonged to the widespread high-risk sequence types ST2 (n = 2) and ST636 (n = 1) (Pasteur scheme). Our results show the presence of XDR-AB isolates, carrying a variety of ARGs, in Bulgarian ICU settings, which highlights the crucial need for nationwide surveillance, especially in the conditions of extensive antibiotic usage during COVID-19.

Real-Life Data on the Effectiveness and Safety of Cefiderocol in Severely Infected Patients: A Case Series

INTRODUCTION

Real-life data about cefiderocol use to treat extensively drug-resistant bacteria are scarce. We aim to report our early experience in patients with difficult-to-treat infections and limited therapeutic options.

METHODS

Patients treated with cefiderocol from March 2018 to April 2022 in a tertiary-care hospital in Spain were included. Demographic, clinical, and microbiological data were collected up to 90 days after the end of treatment or until death. Survival status was recorded at 30 and 90 days.

RESULTS

Ten patients were included, seven of them critically ill. Ventilator-associated pneumonia (40%) and bacteremia (40%) were the main infections. Multidrug-resistant or extensively drug-resistant P. aeruginosa was the most frequently isolated pathogen (70%, of which six patients were infected with bacteria with difficult-to-treat resistance), followed by A. baumannii, E. coli, and A. xylosoxidans (10% each). Seven patients received combination therapy. Clinical and microbiological cures were achieved in 90% and 80% of patients, respectively. Two previously susceptible strains (20%) developed resistance to cefiderocol. Overall, 30-day and 90-day mortality rates were 10% and 50%, respectively, although two out of five patients died due to the infection. No serious adverse events were reported, except for one patient who developed thrombocytopenia.

CONCLUSION

Cefiderocol seems to be an effective and safe rescue therapy for patients infected with difficult-to-treat pathogens, although there is a definite risk of the emergence of resistance.

Clinical Appraisal of Cefiderocol in the Treatment of Non-fermenting Gram-Negative Bacilli

Purpose of Review

Cefiderocol has a potential role in the treatment of infections caused by increasingly resistant non-fermenting Gram-negative organisms.

Recent Findings

Non-fermenting Gram-negative organisms pose a unique threat to public health given their arsenal of inherent resistance mechanisms. High rates of intrinsic resistance to a wide array of agents, inducible adaptive resistance, and the ability to acquire resistance through horizontal transfer of resistance genes limit the utility of conventional antimicrobial treatment options against non-fermenting Gram-negative infections. Beta-lactams, one of the most reliable classes of antimicrobials, are often rendered inactive by the acquisition of beta-lactamases, with activity potentially restored by beta-lactamase inhibitors. Alteration of intrinsic mechanisms of resistance, porin channels, and efflux pumps reduce the ability of beta-lactamase inhibitors to protect the activity of beta-lactams. This multifactorial nature of resistance exhibited by non-fermenting Gram-negative organisms is difficult to overcome and novel agents are needed to combat this growing threat.

Summary

Cefiderocol is a novel siderophore cephalosporin that utilizes the active transport of ferric iron to gain access to the periplasmic space of Gram-negative organisms. Cefiderocol also has additional modifications that confer some stability in the presence of beta-lactamases, which can be particularly beneficial for infections caused by non-fermenters. Herein, we discuss the potential role of cefiderocol therapy in the management of infections caused by non-fermenting Gram-negative bacilli, with an intentional focus on carbapenem-resistant Acinetobacter baumannii (CRAB), Pseudomonas aeruginosa, and Stenotrophomonas spp.

Evolution and Transmission of Cefiderocol-Resistant Acinetobacter baumannii During an Outbreak in the Burn Intensive Care Unit

We report on 11 critically ill burn patients treated with cefiderocol for carbapenem-resistant Acinetobacter baumannii infections. Clinical success was achieved in 36% and complicated by treatment-emergent resistance and interpatient transmission of cefiderocol-resistant A. baumannii. Resistant isolates harbored disrupted pirA and piuA genes that were not disrupted among susceptible isolates.

Clinical efficacy and safety of cefiderocol for resistant Gram-negative infections: a real-life, single-centre experience

OBJECTIVES

Cefiderocol is a 'siderophore' cephalosporin active against Gram-negative bacteria, including carbapenem-resistant strains. Data on the use of cefiderocol in real life are limited. We evaluated the efficacy and safety of cefiderocol in the context of our hospital clinical practice.

METHODS

This was a single-centre, observational, retrospective clinical study. We collected data for all patients who received cefiderocol therapy in our hospital, with a focus on clinical outcomes and adverse events.

RESULTS

The study cohort included 28 patients, with a median age of 73 years (25-83 years) and a high burden of co-morbidities. Up to 45 Gram-negative isolates were cultured from the study patients, the most common pathogen being Acinetobacter baumannii (31.1%). Cefiderocol was mostly prescribed for pneumonia (37.8% of cases), bloodstream infection (24.4%), urinary tract infection (22.2%) and intra-abdominal infection (20%), and largely as salvage therapy (92.8%). Of the 18 patients for whom follow-up cultures were available, 14 (77.8%) achieved eradication of the causative micro-organism. Therapeutic success (improvement/resolution of infection) occurred in 64.3% of cases at 7 days and 50% at 14 days from treatment start. Treatment failed in 9 cases (32.1%). No effects on kidney, liver or bone marrow function were observed.

CONCLUSIONS

Cefiderocol showed fair efficacy and excellent tolerability in highly co-morbid patients with a range of multiresistant infections. It may be an option for infections due to colistin-resistant pathogens, when other regimens fail or in cases at risk of kidney dysfunction.

Carbapenem-Resistant Klebsiella pneumoniae: Virulence Factors, Molecular Epidemiology and Latest Updates in Treatment Options

Klebsiella pneumoniae is a Gram-negative opportunistic pathogen responsible for a variety of community and hospital infections. Infections caused by carbapenem-resistant K. pneumoniae (CRKP) constitute a major threat for public health and are strongly associated with high rates of mortality, especially in immunocompromised and critically ill patients. Adhesive fimbriae, capsule, lipopolysaccharide (LPS), and siderophores or iron carriers constitute the main virulence factors which contribute to the pathogenicity of K. pneumoniae. Colistin and tigecycline constitute some of the last resorts for the treatment of CRKP infections. Carbapenemase production, especially K. pneumoniae carbapenemase (KPC) and metallo-β-lactamase (MBL), constitutes the basic molecular mechanism of CRKP emergence. Knowledge of the mechanism of CRKP appearance is crucial, as it can determine the selection of the most suitable antimicrobial agent among those most recently launched. Plazomicin, eravacycline, cefiderocol, temocillin, ceftolozane-tazobactam, imipenem-cilastatin/relebactam, meropenem-vaborbactam, ceftazidime-avibactam and aztreonam-avibactam constitute potent alternatives for treating CRKP infections. The aim of the current review is to highlight the virulence factors and molecular pathogenesis of CRKP and provide recent updates on the molecular epidemiology and antimicrobial treatment options.

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.

Risk factors for early mortality in patients with carbapenem-resistant Acinetobacter baumannii bacteraemia

OBJECTIVES

Although many deaths due to carbapenem-resistant Acinetobacter baumannii (CRAB) bacteraemia occur within a few days after the onset of bacteraemia, risk factors for early mortality (EM) have not been deeply investigated. We aimed to determine the risk factors for EM and the difference between risk factors associated with EM and late mortality (LM) in CRAB bacteraemia.

METHODS

Clinical information on all patients with CRAB bacteraemia in 10 hospitals during a 1-year period was collected. Among the cases with mortality within 30 days, EM and LM were defined as death within 3 and more than 5 calendar days from the first positive blood culture, respectively.

RESULTS

In total, 212 CRAB bacteraemia cases were included in the analysis. Of 122 (57.5%) patients with 30-day mortality, EM was observed in 75 (61.5%) patients and LM in 39 (32.0%) patients. The proportion of severe sepsis or septic shock, Pitt score, and Sequential Organ Failure Assessment (SOFA) score was significantly higher in patients with EM than those with LM. Although urinary tract infection as the site of infection and the severity of illness were independent predictors of LM, only factors representing the severity of illness were independent risk factors for EM.

CONCLUSION

Our results suggest that a large proportion of CRAB bacteraemia with high severity progresses to a rapidly fatal course, regardless of the underlying diseases or source of infection. Further studies might be needed to investigate the microbiological factors associated with CRAB and pathogen-host interaction in patients with EM.

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.

Empiric treatment of patients with sepsis and septic shock and place in therapy of cefiderocol: a systematic review and expert opinion statement

Carbapenem-resistant Gram-negative bacteria are frequent causes of sepsis and septic shock in intensive care unit (ICU) and thus considered a public health threat. Until now, the best available therapies consist of combinations of preexisting or new antibiotics with β-lactamase inhibitors (either new or preexisting). Several mechanisms of resistance, especially those mediated by metallo-β-lactamases (MBL), are responsible for the inefficacy of these treatments, leaving an unmet medical need. Intravenous cefiderocol has been recently approved by the American Food and Drug Administration (FDA) and European Medicines Agency (EMA) for the treatment of complicated urinary tract infections and nosocomial pneumonia due to Gram-negative, when limited therapeutical options are available. In addition, its ability to hijack bacterial iron uptake mechanisms makes cefiderocol stable against the whole Ambler β-lactamase inhibitors and increases the in vitro efficacy against Gram-negative pathogens (e.g., Enterobacterales spp., Pseudomonas aeruginosa, and Acinetobacter baumannii). Trials have already demonstrated their non-inferiority to comparators. In 2021, ESCMID guidelines released a conditional recommendation supporting the use of cefiderocol against metallo-β-lactamase-producing Enterobacterales and against Acinetobacter baumannii. This review provides the opinion of experts about the general management of empiric treatment of patients with sepsis and septic shock in the intensive care unit and detects the proper place in therapy of cefiderocol considering recent evidence sought through a systematic search.

Efficacy of Cefiderocol in Experimental Stenotrophomonas maltophilia Pneumonia in Persistently Neutropenic Rabbits

Stenotrophomonas maltophilia is an important cause of pneumonia in immunocompromised patients. Cefiderocol is a parenteral siderophore cephalosporin with potent in vitro activity against S. maltophilia. We evaluated the efficacy of cefiderocol in a neutropenic rabbit model of S. maltophilia pneumonia in comparison to trimethoprim-sulfamethoxazole (TMP-SMX). The cefiderocol area under the plasma drug concentration-time curve extrapolated to 8 h (AUC_0–8) was lower (423.0 ± 40.9 μg·h/mL versus 713.6 ± 40.1 μg·h/mL) and clearance higher (252.77 ± 38.9 mL/h/kg versus 142.6 ± 32.9 mL/h/kg) in infected versus noninfected rabbits. We studied a clinical bloodstream S. maltophilia isolate with an MIC of 0.03 μg/mL of cefiderocol. Time spent above the MIC of cefiderocol for the majority of S. maltophilia isolates in rabbits recapitulated the plasma concentration-time profile observed in adult humans at the licensed dose of 2 g given intravenously (i.v.). Experimental groups consisted of 120 mg/kg cefiderocol i.v. every 8 hours (q8h); TMP-SMX, 5 mg/kg i.v. Q12h, and untreated controls (UCs). Treatment was administered for 10 days. Survival in cefiderocol-treated rabbits (87%) was greater than that in TMP-SMX-treated (25%; P < 0.05) and UC (0%; P < 0.05) groups. There was no residual bacterial burden in lung tissue or bronchoalveolar lavage (BAL) fluid in the cefiderocol group. Residual bacterial burden was present in lung tissue and BAL fluid in the TMP-SMX group but was decreased in comparison to UCs (P < 0.001). Lung weights (markers of pulmonary injury) were decreased in cefiderocol-treated versus TMP-SMX (P < 0.001) and UC (P < 0.001) groups. Cefiderocol is highly active in treatment of experimental S. maltophilia pneumonia, laying the foundation for future clinical investigations against this lethal infection in immunocompromised patients.

A review of recent advances in the treatment of adults with complicated urinary tract infection

INTRODUCTION

Complicated urinary tract infections (cUTIs) entail diverse clinical conditions that could be managed differently and not necessarily with premature empiric therapy. Since multidrug-resistant organisms (MDROs) are widely spreading worldwide, the possibility of encountering these resistant bacteria is inevitably part of the daily life of physicians who manage cUTIs.

AREAS COVERED

The advances in the management of cUTIs are explored, illustrating: 1) a proposed therapeutical approach to cUTIs within the antimicrobial stewardship context; 2) evidence regarding novel antibiotics targeting MDROs. Evidence research has been performed through MEDLINE/PubMed using appropriate keywords and terms regarding cUTIs published before June 2022.

EXPERT OPINION

Novel antimicrobial drugs are available in the clinicians' armamentarium. Selecting the optimal therapy for suitable patients may be challenging given the multifaceted group of cUTIs. Carbapenems use is widely increasing, the role of old β-lactam/β-lactamase inhibitors is constantly revised, and novel drugs lack real-life studies. Understanding the different ranges of the complexity of patients affected by cUTIs may help select the most suitable antibiotic for every single case. More multicentric observational studies targeting cUTIs are needed to elucidate the appropriate drug based on patient characteristics and presentations, providing stronger recommendations for cases encountered in everyday clinical practice.

The role of cefiderocol in clinical practice

Cefiderocol is a new antimicrobial with a chemical structure similar to ceftazidime and cefepime. In this review we will focus on the role of cefiderocol in different clinical scenarios produced by resistant Gram-negative microorganisms, especially to carbapenems. In infections caused by Gram-negative microorganisms, inappropriate antibiotic treatment increased the risk of mortality almost fourfold. In patients with hospital-acquired infection and septic shock; with sepsis and poor functional reserve due to fragility; in immunocompromised patients; and in those with local ecology, individual history of colonization or previous infection and risk factors for carbapenem-resistant Enterobacteriaceae (CRE) such as the presence of chronic multi-morbidities, the best option would be to start an active empirical treatment against gram-negative bacteria resistant to carbapenems and later in 24-36 h with the information obtained from the cultures we could decide on a definitive empirical or directed treatment and avoid unnecessary overuse of these antibiotics. Cefiderocol would be in these cases a good candidate due to its excellent in vitro activity against all classes of beta-lactamase-producing Gram-negatives (including carbapenemase class A, B and D producers), as well as against non-fermenting Gram-negatives such as P. aeruginosa, Acinetobacter spp. and S. maltophilia. It is necessary to optimize the use of new antibiotics such as cefiderocol, guaranteeing the best available treatment to patients while delaying the emergence and spread of resistance.

Cefiderocol for Carbapenem-Resistant Bacteria: Handle with Care! A Review of the Real-World Evidence

(1) Background: healthcare-associated infections are one of the most frequent adverse events in healthcare delivery worldwide. Several antibiotic resistance mechanisms have been developed, including those to carbapenemase. Cefiderocol (CFD) is a novel siderophore cephalosporin designed to treat carbapenem-resistant bacteria. (2) Methods: we performed a systematic review of all cases reported in the literature to outline the existing evidence. We evaluated real-world evidence studies of CFD in the treatment of carbapenem-resistant (CR) bacteria. (3) Results: a total of 19 publications treating cases of infection by CR bacteria were included. The three most frequent CR pathogens were Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae. A regimen of 2 g every 8 h was most frequently adopted for CFD with a mean treatment duration of 25.6 days. CFD was generally well tolerated, with fewer side effects. The success rate of CFD therapy was satisfactory and almost 70% of patients showed clinical recovery; of these, nearly half showed negative blood cultures and infection-free status. (4) Conclusions: This review indicates that CFD is active against important GN organisms including Enterobacteriaceae, P. aeruginosa, and A. baumannii. CFD seems to have a safe profile.

Safety and efficacy of cefiderocol for off-label treatment indications: A systematic review

PURPOSE

Cefiderocol is a siderophore cephalosporin recently approved by the United States Food and Drug Administration for the treatment of hospital- and ventilator-acquired bacterial pneumonia and complicated urinary tract infections. However, there is potential for cefiderocol utility for a variety of other infections. The purpose of this systematic review was to identify literature examining the safety and efficacy of cefiderocol for off-label indications.

METHODS

The PRISMA guidelines were utilized for reporting. Databases searched included PubMed, Scopus, and Embase, from inception to September 2021. Manuscripts describing cefiderocol off-label use in clinical settings were included. Exclusion criteria were studies focused on labeled indications, animal studies, pharmacodynamic/pharmacokinetic studies, in vitro or laboratory studies, and manuscripts in languages other than English or Arabic. Each stage of review utilized two independent investigators, with conflicts resolved and critical appraisal performed. Data regarding presentation, clinical course, and infection characteristics were extracted and descriptively analyzed.

RESULTS

The search identified a total of 985 records, narrowed to a final set of 27 studies. Among studies included were 18 (66.7%) case reports, 8 (29.6%) case series, and 1 (3.7%) phase 3 clinical trial. Cefiderocol was most frequently used off-label for bacteremia/sepsis with or without an identified source in 51 (67.1%) out of a total of 76 included patients. Among case series/reports with available data, 43 of 53 patients (81.1%) received combination antibiotic therapy. The most common pathogens identified included multi/extensively drug-resistant Pseudomonas aeruginosa and/or Acinetobacter baumannii. Various clinical end points were reported, while microbiological end points were reported in 18 (66.7%) studies. Cefiderocol-related side effects were uncommon and rarely use-limiting.

CONCLUSIONS

This systematic review depicts relative clinical effectiveness of off-label cefiderocol, most commonly for P. aeruginosa and A. baumannii infections as combination antibiotic therapy. Further study is needed to elucidate the safety and efficacy of cefiderocol across an expanded set of patients and indications.

Diagnosis and management of infections caused by multidrug-resistant bacteria: guideline endorsed by the Italian Society of Infection and Tropical Diseases (SIMIT), the Italian Society of Anti-Infective Therapy (SITA), the Italian Group for Antimicrobial Stewardship (GISA), the Italian Association of Clinical Microbiologists (AMCLI) and the Italian Society of Microbiology (SIM)

Management of patients with infections caused by multidrug-resistant organisms is challenging and requires a multidisciplinary approach to achieve successful clinical outcomes. The aim of this paper is to provide recommendations for the diagnosis and optimal management of these infections, with a focus on targeted antibiotic therapy. The document was produced by a panel of experts nominated by the five endorsing Italian societies, namely the Italian Association of Clinical Microbiologists (AMCLI), the Italian Group for Antimicrobial Stewardship (GISA), the Italian Society of Microbiology (SIM), the Italian Society of Infectious and Tropical Diseases (SIMIT) and the Italian Society of Anti-Infective Therapy (SITA). Population, Intervention, Comparison and Outcomes (PICO) questions about microbiological diagnosis, pharmacological strategies and targeted antibiotic therapy were addressed for the following pathogens: carbapenem-resistant Enterobacterales; carbapenem-resistant Pseudomonas aeruginosa; carbapenem-resistant Acinetobacter baumannii; and methicillin-resistant Staphylococcus aureus. A systematic review of the literature published from January 2011 to November 2020 was guided by the PICO strategy. As data from randomised controlled trials (RCTs) were expected to be limited, observational studies were also reviewed. The certainty of evidence was classified using the GRADE approach. Recommendations were classified as strong or conditional. Detailed recommendations were formulated for each pathogen. The majority of available RCTs have serious risk of bias, and many observational studies have several limitations, including small sample size, retrospective design and presence of confounders. Thus, some recommendations are based on low or very-low certainty of evidence. Importantly, these recommendations should be continually updated to reflect emerging evidence from clinical studies and real-world experience.

Cefiderocol: Systematic Review of Mechanisms of Resistance, Heteroresistance and In Vivo Emergence of Resistance

Cefiderocol appears promising, as it can overcome most β-lactam resistance mechanisms (including β-lactamases, porin mutations, and efflux pumps). Resistance is uncommon according to large multinational cohorts, including against isolates resistant to carbapenems, ceftazidime/avibactam, ceftolozane/tazobactam, and colistin. However, alarming proportions of resistance have been reported in some recent cohorts (up to 50%). A systematic review was conducted in PubMed and Scopus from inception to May 2022 to review mechanisms of resistance, prevalence of heteroresistance, and in vivo emergence of resistance to cefiderocol during treatment. A variety of mechanisms, typically acting in concert, have been reported to confer resistance to cefiderocol: β-lactamases (especially NDM, KPC and AmpC variants conferring resistance to ceftazidime/avibactam, OXA-427, and PER- and SHV-type ESBLs), porin mutations, and mutations affecting siderophore receptors, efflux pumps, and target (PBP-3) modifications. Coexpression of multiple β-lactamases, often in combination with permeability defects, appears to be the main mechanism of resistance. Heteroresistance is highly prevalent (especially in A. baumannii), but its clinical impact is unclear, considering that in vivo emergence of resistance appears to be low in clinical studies. Nevertheless, cases of in vivo emerging cefiderocol resistance are increasingly being reported. Continued surveillance of cefiderocol’s activity is important as this agent is introduced in clinical practice.

Cefiderocol- Compared to Colistin-Based Regimens for the Treatment of Severe Infections Caused by Carbapenem-Resistant Acinetobacter baumannii

Cefiderocol may represent a therapeutic option for carbapenem-resistant Acinetobacter baumannii (CRAB) infections, but clinical data are limited. This is an observational retrospective study conducted in the University Hospital of Pisa including consecutive patients with CRAB infections (January 2020 to August 2021). Patients were divided in two study groups according to the antibiotic treatment received: cefiderocol- and colistin-containing regimens. The primary outcome was the 30-day mortality. A Cox regression analysis was performed to identify factors independently associated with 30-day mortality. A propensity score analysis using inverse probability of treatment weighting (IPTW) was also performed. A total of 124 patients were included: 47 (37.9%) received cefiderocol, while 77 (62.1%) colistin-containing regimens. Overall, 79 (63.7%) patients had a bloodstream infection (BSI), 35 (28.5%) a ventilator-associated pneumonia (VAP) and 10 (8.1%) other infections. Thirty-day mortality was higher in patients receiving colistin- compared to those who received cefiderocol-containing regimens (55.8% versus 34%, P = 0.018). This difference was confirmed in patients with BSI, but not in those with VAP. On multivariable analysis, septic shock, SOFA score, and age were independently associated with 30-day mortality, while cefiderocol therapy was protective in an IPTW analysis (Hazard ratio 0.44, 95% confidence interval 0.22-0.66, P < 0.001). Nephrotoxicity was more common in the colistin group. Microbiological failure occurred in 17.4% of patients receiving cefiderocol versus 6.8% of those receiving colistin (P = 0.079). Among 8 cases in the cefiderocol group who experienced microbiological failure, 4 (50%) developed resistance to cefiderocol. Cefiderocol represents a promising therapeutic option in patients with severe CRAB infections. Randomized clinical trial in this specific patient population should confirm our findings.

Superinfections caused by carbapenem-resistant Enterobacterales in hospitalized patients with COVID-19: a multicentre observational study from Italy (CREVID Study)

Objectives

To describe clinical characteristics and outcomes of COVID-19 patients who developed secondary infections due to carbapenem-resistant Enterobacterales (CRE).

Methods

Retrospective observational study including COVID-19 patients admitted to 12 Italian hospitals from March to December 2020 who developed a superinfection by CRE. Superinfection was defined as the occurrence of documented bacterial infection &gt;48 h from admission. Patients with polymicrobial infections were excluded. Demographic, clinical characteristics and outcome were collected. Isolates were classified as KPC, metallo-β-lactamase (MBL) and OXA-48-producing CRE. A Cox regression analysis was performed to identify factors independently associated with 30 day mortality.

Results

Overall, 123 patients (median age 66 years, IQR 59–75) were included. The majority of infections occurred in the ICU (81, 65.9%), while 42 (34.1%) in medical wards. The most common types of infection were bloodstream infections (BSI) (n = 64, 52%), followed by urinary-tract infections (UTI) (n = 28, 22.8%), hospital-acquired/ventilator-associated pneumonia (HAP/VAP) (n = 28, 22.8%), intra-abdominal infections (n = 2, 1.6%) and skin infections (n = 1, 0.8%). Sixty-three (51.2%) infections were caused by KPC-, 54 (43.9%) by MBL-, and 6 (4.8%) by OXA-48-producing CRE. Thirty-day mortality was 33.3% (41/123). On Cox regression analysis, HAP/VAP compared with UTI (HR 7.23, 95% CI 2.09–24.97, P = 0.004), BSI compared with UTI (HR 3.96, 95% CI, 1.33–11.77, P = 0.004), lymphopenia on admission (HR 3, 95% CI 1.44–6.26, P = 0.003) and age (HR 1.05, 95% CI 1.02–1.08, P = 0.002) were predictors of 30 day mortality.

Conclusions

Superinfections by CRE were associated with high risk of 30 day mortality in patients with COVID-19. HAP/VAP was the strongest predictor of death in these patients.

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

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

Carbapenem-Resistant Acinetobacter baumannii in U.S. Hospitals: Diversification of Circulating Lineages and Antimicrobial Resistance

Carbapenem-resistant Acinetobacter baumannii (CRAb) is a major cause of health care-associated infections. CRAb is typically multidrug resistant, and infection is difficult to treat. Despite the urgent threat that CRAb poses, few systematic studies of CRAb clinical and molecular epidemiology have been conducted. The Study Network of Acinetobacter as a Carbapenem-Resistant Pathogen (SNAP) is designed to investigate the clinical characteristics and contemporary population structure of CRAb circulating in U.S. hospital systems using whole-genome sequencing (WGS). Analysis of the initial 120 SNAP patients from four U.S. centers revealed that CRAb remains a significant threat to hospitalized patients, affecting the most vulnerable patients and resulting in 24% all-cause 30-day mortality. The majority of currently circulating isolates belonged to ST2Pas, a part of clonal complex 2 (CC2), which is the dominant drug-resistant lineage in the United States and Europe. We identified three distinct sublineages within CC2, which differed in their antibiotic resistance phenotypes and geographic distribution. Most concerning, colistin resistance (38%) and cefiderocol resistance (10%) were common within CC2 sublineage C (CC2C), where the majority of isolates belonged to ST2Pas/ST281Ox. Additionally, we identified ST499Pas as the most common non-CC2 lineage in our study. Our findings suggest a shift within the CRAb population in the United States during the past 10 years and emphasize the importance of real-time surveillance and molecular epidemiology in studying CRAb dissemination and clinical impact. IMPORTANCE Carbapenem-resistant Acinetobacter baumannii (CRAb) constitutes a major threat to public health. To elucidate the molecular and clinical epidemiology of CRAb in the United States, clinical CRAb isolates were collected along with data on patient characteristics and outcomes, and bacterial isolates underwent whole-genome sequencing and antibiotic susceptibility phenotyping. Key findings included emergence of new sublineages within the globally predominant clonal complex 2 (CC2), increased colistin and cefiderocol resistance within one of the CC2 sublineages, and emergence of ST499Pas as the dominant non-CC2 CRAb lineage in U.S. hospitals.

Cefiderocol for the Treatment of Multidrug-Resistant Gram-Negative Bacteria: A Systematic Review of Currently Available Evidence

Cefiderocol is a novel synthetic siderophore-conjugated antibiotic that hijacks the bacterial iron transport systems facilitating drug entry into cells, achieving high periplasmic concentrations. This systematic review analyzed the currently available literature on cefiderocol. It summarized in vitro susceptibility data, in vivo antimicrobial activity, pharmacokinetics/pharmacodynamics (PK/PD), clinical efficacy, safety and resistance mechanisms of cefiderocol. Cefiderocol has potent in vitro and in vivo activity against multidrug-resistant (MDR) Gram-negative bacteria, including carbapenem-resistant isolates. But New Delhi Metallo-β-lactamase (NDM)- positive isolates showed significantly higher MICs than other carbapenemase-producing Enterobacterales, with a susceptible rate of 83.4% for cefiderocol. Cefiderocol is well-tolerated, and the PK/PD target values can be achieved using a standard dose regimen or adjusted doses according to renal function. Clinical trials demonstrated that cefiderocol was non-inferiority to the comparator drugs in treating complicated urinary tract infection and nosocomial pneumonia. Case reports and series showed that cefiderocol was a promising therapeutic agent in carbapenem-resistant infections. However, resistant isolates and reduced susceptibility during treatment to cefiderocol have already been reported. In conclusion, cefiderocol is a promising powerful weapon for treating MDR recalcitrant infections.

Treatment of ventilator-associated pneumonia due to carbapenem-resistant Gram-negative bacteria with novel agents: a contemporary, multidisciplinary ESGCIP perspective

INTRODUCTION

: In the past 15 years, treatment of VAP caused by carbapenem-resistant Gram-negative bacteria (CR-GNB) has represented an intricate challenge for clinicians.

AREAS COVERED

In this perspective article, we discuss the available clinical data about novel agents for the treatment of CR-GNB VAP, together with general PK/PD principles for the treatment of VAP, in the attempt to provide some suggestions for optimizing antimicrobial therapy of CR-GNB VAP in the daily clinical practice.

EXPERT OPINION

Recently, novel BL and BL/BLI combinations have become available that have shown potent in vitro activity against CR-GNB and have attracted much interest as novel, less toxic, and possibly more efficacious options for the treatment of CR-GNB VAP compared with previous standard of care. Besides randomized controlled trials, a good solution to enrich our knowledge on how to use these novel agents at best in the near future, while at the same time remaining adherent to current evidence-based guidelines, is to improve our collaboration to conduct larger multinational observational studies to collect sufficiently large populations treated in real life with those novel agents for which guidelines currently do not provide a recommendation (in favor or against) for certain causative organisms.

Pharmacokinetic evaluation of cefiderocol for the treatment of multidrug resistant Gram-negative infections

INTRODUCTION

Cefiderocol is a siderophore cephalosporin antibiotic and first of its kind approved by the Food and Drug Administration for the treatment of complicated urinary tract infections (cUTI) and hospital-acquired and ventilator-associated bacterial pneumonia (HABP/VABP) in patients 18 years or older caused by susceptible organisms. Cefiderocol's unique mechanism of iron chelation improves Gram-negative membrane penetration as the bacteria's iron uptake mechanism recognizes the chelated iron antibiotic and iron for entry. This also allows for the evasion of cefiderocol from cell entry-related resistance mechanisms.

AREAS COVERED

This review covers the mechanism of action, resistance mechanisms, pharmacokinetics in various patient populations, and pharmacodynamics. Relevant literature evaluating efficacy and safety are discussed.

EXPERT OPINION

Limited treatment options are available for the treatment of carbapenem-resistantorganisms. Clinical trials have demonstrated that cefiderocol is no worse than alternative treatment options for cUTIs and HABP/VABP, but more data are currently available to support the use of beta-lactam beta-lactamase inhibitor agents, where susceptible. Mortality differences demonstrated in patients with pneumonia and bloodstream infections must further be explored and logistical and practical considerations regarding susceptibility testing and use as monotherapy vs. combination therapy must be considered prior to confidently recommending cefiderocol for regular use in systemic infections.

Outcomes with Cefiderocol Treatment in Patients with Bacteraemia Enrolled into Prospective Phase 2 and Phase 3 Randomised Clinical Studies

Introduction

A post hoc, descriptive analysis of three prospective, randomised, controlled clinical studies investigating cefiderocol in gram-negative bacterial infections was conducted to assess its efficacy in patients with baseline bacteraemia.

Methods

Data from APEKS-cUTI (NCT02321800), APEKS-NP (NCT03032380) and CREDIBLE-CR (NCT02714595) studies were assessed individually. Patients received cefiderocol 2g, q8h, for 7–14 days or comparators (imipenem/cilastatin [APEKS-cUTI], meropenem [APEKS-NP] or best available therapy [BAT; CREDIBLE-CR]). Bacteraemia and clinical outcomes were assessed at early assessment (EA), end of treatment (EOT) and test of cure (TOC) for patients in the intention-to-treat populations with baseline blood samples positive for aerobic gram-negative species. Eradication, persistence or recurrence of baseline blood pathogen was confirmed from follow-up blood cultures; in the absence of follow-up blood cultures, clinical response, administration of additional antibiotics and vital status were used to assess bacteraemia outcome.

Results

Of 885 patients randomised, 84 had bacteraemia and 89 (cefiderocol: 55, comparators: 34) gram-negative pathogens were isolated, namely Enterobacterales (n = 62) and non-fermenters (n = 27). At EA, on-therapy bacteraemia eradication rates in APEKS-cUTI, APEKS-NP and CREDIBLE-CR were 100% (19/19), 50.0% (4/8) and 72.0% (18/25) with cefiderocol. Corresponding rates for comparators were 77.8% (7/9), 100% (10/10) and 69.2% (9/13), respectively. Persistence in blood at EA was seen in six patients overall (cefiderocol: 3, comparators: 3); indeterminate responses were common (cefiderocol: 8, comparators: 3), usually due to lack of blood cultures. Clinical cure/improvement rates at EA in APEKS-cUTI, APEKS-NP and CREDIBLE-CR were 100% (19/19), 62.5% (5/8) and 64.0% (16/25) with cefiderocol. Corresponding rates for comparators were 77.8% (7/9), 90.0% (9/10) and 30.8% (4/13), respectively. Bacteraemia eradication rates with cefiderocol in APEKS-cUTI, APEKS-NP and CREDIBLE-CR were 89.5%, 37.5% and 60.0% at EOT and 78.9%, 12.5% and 44.0% at TOC.

Conclusion

This descriptive analysis suggests that cefiderocol may be a useful treatment option for gram-negative bacteraemia, including pathogens resistant to other antibiotics.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-022-00598-9.

Infections Due to Acinetobacter baumannii-calcoaceticus Complex: Escalation of Antimicrobial Resistance and Evolving Treatment Options

Bacteria within the genus Acinetobacter (principally A. baumannii-calcoaceticus complex [ABC]) are gram-negative coccobacilli that most often cause infections in nosocomial settings. Community-acquired infections are rare, but may occur in patients with comorbidities, advanced age, diabetes mellitus, chronic lung or renal disease, malignancy, or impaired immunity. Most common sites of infections include blood stream, skin/soft-tissue/surgical wounds, ventilator-associated pneumonia, orthopaedic or neurosurgical procedures, and urinary tract. Acinetobacter species are intrinsically resistant to multiple antimicrobials, and have a remarkable ability to acquire new resistance determinants via plasmids, transposons, integrons, and resistance islands. Since the 1990s, antimicrobial resistance (AMR) has escalated dramatically among ABC. Global spread of multidrug-resistant (MDR)-ABC strains reflects dissemination of a few clones between hospitals, geographic regions, and continents; excessive antibiotic use amplifies this spread. Many isolates are resistant to all antimicrobials except colistimethate sodium and tetracyclines (minocycline or tigecycline); some infections are untreatable with existing antimicrobial agents. AMR poses a serious threat to effectively treat or prevent ABC infections. Strategies to curtail environmental colonization with MDR-ABC require aggressive infection-control efforts and cohorting of infected patients. Thoughtful antibiotic strategies are essential to limit the spread of MDR-ABC. Optimal therapy will likely require combination antimicrobial therapy with existing antibiotics as well as development of novel antibiotic classes.