Cefiderocol Treatment for Patients with Multidrug- and Carbapenem-Resistant Pseudomonas aeruginosa Infections in the Compassionate Use Program

Effectiveness and safety of cefiderocol treatment in patients with Gram-negative bacterial infections in Spain in the early access programme: results of the PERSEUS study

PURPOSE

We assessed the effectiveness and safety of cefiderocol in patients with Gram-negative bacterial infections, excluding Acinetobacter spp., in the early access programme (EAP) in Spain.

METHODS

The retrospective, multicentre PERSEUS study (2018-2022) enrolled hospitalised patients with serious Gram-negative infections, except Acinetobacter spp., who received first-time cefiderocol for ≥ 72 h following requests through the EAP. Clinical cure at end of treatment, all-cause mortality at Day 28, cefiderocol use, and adverse drug reactions (ADRs) were the key outcomes.

RESULTS

Overall, 261 patients were eligible for analysis. Median (interquartile range) age was 61 (49-68) years, 202 (77.4%) were male and 165 (63.2%) were in the intensive care unit. The most frequent diagnoses were respiratory tract infection (47.9%), intra-abdominal infection (14.6%), and urinary tract infection (14.6%). The median (IQR) duration of cefiderocol treatment was 10 (7-14) days. Overall, the clinical cure rate was 80.5% (210/261) and the 28-day mortality rate was 21.5% (56/261). In patients with Pseudomonas aeruginosa infection (66.7% [n = 174], including 73 [42%] with metallo-β-lactamases), the clinical cure rate was 84.5% (147/174) and the 28-day mortality was 17.2% (30/174). Logistic regression analysis showed that prior antibiotic treatment for > 7 days (OR 0.19, 95% CI 0.05-0.56) and mechanical ventilation (OR 0.32, 95% CI 0.15-0.67) were independent negative predictive factors for clinical cure. ADRs occurred in seven patients, six events resolved, and one was fatal (toxic epidermal necrolysis).

CONCLUSIONS

Cefiderocol is a valuable option in the treatment of serious Gram-negative bacterial infections, particularly for those caused by P. aeruginosa.

CLINICALTRIALS

GOV: NCT05789199 (Registration date: 16 February 2023).

Antipseudomonal cephalosporins versus piperacillin/tazobactam or carbapenems for the definitive antibiotic treatment of Pseudomonas aeruginosa bacteraemia: new kids on the ICU block?

BACKGROUND

Pseudomonas aeruginosa bloodstream infections (Pa-BSIs) are still a major cause of mortality in ICUs, posing many treatment uncertainties.

METHODS

This multicentre, retrospective study analysed data from 14 Italian hospitals, including all consecutive adults developing Pa-BSI in ICU during 2021-22 and treated with antibiotics for at least 48 h. The primary aim was to identify predictors of 30 day mortality using Cox regression. Results were adjusted with inverse probability of treatment weighting (IPTW) and for immortal time bias.

RESULTS

Overall, 170 patients were included. High-risk BSI (source: lung, intra-abdominal, CNS) occurred in 118 (69%) patients, and 54 (32%) had septic shock. In 37 (22%), 73 (43%), 12 (7%) and 48 (28%) the definitive backbone therapy was piperacillin/tazobactam, carbapenems, colistin or new antipseudomonal cephalosporins (ceftolozane/tazobactam, n = 20; ceftazidime/avibactam, n = 22; cefiderocol, n = 6), respectively. Moreover, 58 (34%) received a second drug as combination therapy. The incidence of 30 day all-cause mortality was 27.6% (47 patients). By Cox regression, Charlson comorbidity index, neutropenia, septic shock and high-risk BSI were independent predictors of 30 day mortality, while previous colonization by P. aeruginosa, use of antipseudomonal cephalosporins as definitive treatment, and combination therapy were shown to be protective. However, after IPTW adjustment, only the protective effect of antipseudomonal cephalosporins was confirmed (adjusted HR = 0.27, 95% CI = 0.10-0.69), but not for combination therapy. Hence, the treatment effect was calculated: antipseudomonal cephalosporins significantly reduced mortality risk [-17% (95% CI = -4% to -30%)], while combination therapy was beneficial only in the case of septic shock [-66% (95% CI = -44% to -88%].

CONCLUSIONS

In ICU, antipseudomonal cephalosporins may be the preferred target therapy for the treatment of Pa-BSI; in addition, initial combination therapy may be protective in the case of septic shock.

Difficult-to-Treat Pseudomonas aeruginosa Infections in Critically Ill Patients: A Comprehensive Review and Treatment Proposal

The management of infections caused by difficult-to-treat Pseudomonas aeruginosa in critically ill patients poses a significant challenge. Optimal antibiotic therapy is crucial for patient prognosis, yet the numerous resistance mechanisms of P. aeruginosa, which may even combine, complicate the selection of an appropriate antibiotic. In this review, we examine the epidemiology, resistance mechanisms, risk factors, and available and future therapeutic options, as well as strategies for treatment optimization. Finally, we propose a treatment algorithm to facilitate decision making based on the resistance patterns specific to each Intensive Care Unit.

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.

Genetic characteristics and diversity of PDC variants of Pseudomonas aeruginosa and its clinical relevance

Pseudomonas aeruginosa exhibits significant antibiotic resistance facilitated by both intrinsic and acquired mechanisms, prominently through Pseudomonas-derived cephalosporinase (PDC), serine Ambler class C β-lactamases encoded by the AmpC. AmpC, involved in the peptidoglycan recycling pathway, is regulated by genes such as ampD, ampR, and ampG, leading to increased expression and resistance to various beta-lactams. PDCs are classified into three main types: classical class C β-lactamases, extended-spectrum class C β-lactamases (ESAC β-lactamases), and inhibitor-resistant class C β-lactamases. This study aimed to identify prevalent PDC variants and its genetic characteristics in Indian and global P. aeruginosa isolates, focusing on their role in β-lactam resistance. Analyzing PDC sequences from 111 P. aeruginosa isolates collected at Christian Medical College (CMC), Vellore, we found the ESAC allele PDC-447 to be the most widespread among Indian isolates, present in 18 % of carbapenem-resistant and 11 % of carbapenem-susceptible strains. Global and Indian isolates PDC variants were validated using the NCBI PathogenWatch database, and the sequenced PDC region compared to PDC-1. PDC-398 and PDC-397 followed in prevalence among carbapenem-resistant isolates, while PDC-5 (ESAC) and PDC-1 (classical class C) were common in carbapenem-susceptible strains. A global analysis of 19,478 genomes revealed significant prevalence of ESAC variants such as PDC-3 (17.28 %) and PDC-5 (12.91 %), alongside classical class C beta-lactamases like PDC-8 (10.65 %). Indian isolates exhibited distinct patterns with PDC-3 and PDC-5 prevailing at 19.84 % and 10 %, respectively. Mutations in the omega loop, H-helix, and R2 region of PDCs were linked to enhanced antibiotic resistance, particularly the T105A mutation in the H-helix region. These findings underscore the complexity of antimicrobial resistance mechanisms in P. aeruginosa and highlight the need for novel therapeutic strategies and continuous surveillance to manage infections by this versatile pathogen. Understanding the prevalence and genetic characteristics of PDC variants is crucial for effective treatment strategies against P. aeruginosa and combating antibiotic resistance.

Cefiderocol in the Successful Treatment of Complicated Hospital-Acquired K. pneumoniae NDM, OXA48 Intraabdominal Infection

Background

Klebsiella pneumoniae MDR/XDR constitutes a difficult to treat bacteria in a number of infections as there are few therapeutic options. Promising drugs in such cases can be cefiderocol, aztreonam and ceftazidime/avibactam or meropenem/vaborbactam.

Case Presentation

A 72-year-old female patient with sepsis caused by KP NDM, OXA 48 was admitted to the Intensive Care Unit, immediately after an emergency graftectomy (of a recently transplanted kidney) complicated with bleeding. Because of suspicion of intra-abdominal infection, a broad-spectrum empirical antibiotic therapy was initiated (meropenem, vancomycin, colistin). The patient underwent an abdominal revision 48 hours after admission. On the 3rd day of hospitalization, diagnosis of a septic shock with etiology of KP NDM, OXA 48 was made. The strain had sensitivity to a colistin and a cefiderocol. On 13th day in the ICU a relaparotomy was performed. Again, KP strains with sensitivity to cefiderocol only, were cultured from intra-abdominal fluid. Aztreonam, in combination with meropenem/vaborbactam, were included in the treatment and were used together with colistin and tigecycline. In the following days, the inflammatory markers decreased slightly, but the patient's general condition did not improve. On day 27 ceftazidime/avibactam and aztreonam were added, while colistin, meropenem/vaborbactam and fosfomycin were discontinued. On 37th day of hospitalization, cefiderocol became available in hospital and was included in the treatment. Cefiderocol monotherapy was continued for 8 days. After 4 days of cefiderocol treatment, the inflammatory markers CRP and PCT decreased and a significant improvement in patient's condition were observed. On day 56, the patient was transferred to another department.

Conclusion

A surgical debridement of a source infection, and usage of meropenem/vaborbactam or ceftazidime/avibactam together with aztreonam and colistin allowed survival of the patient but not full recovery. Ultimately, only the cefiderocol monotherapy was effective in treatment of the patient with septic shock of KP NDM OXA 48 etiology.

The Use of Cefiderocol in Gram-Negative Bacterial Infections at International Medical Center, Jeddah, Saudi Arabia

BACKGROUND/OBJECTIVES

The necessity for ground-breaking treatments for Gram-negative infections is evident. The World Health Organization, the Infectious Diseases Society of America, and the European Commission have highlighted the critical insufficiency of efficient antibiotics, urging pharmaceutical businesses to manufacture new antibiotics. Therefore, developing new antibiotics with broad efficacy against Gram-negative pathogens is essential. Thus, this research aimed to evaluate the safety and effectiveness of cefiderocol in treating multidrug-resistant Gram-negative bacterial infections at the International Medical Center (IMC), Jeddah, Saudi Arabia.

METHODS

A retrospective analysis was conducted on patients treated from January 2021 to February 2023. Thirteen case groups treated with cefiderocol were compared to twenty control groups treated with other antibiotics.

RESULTS

The results indicated no statistically significant differences in ICU stay, comorbidity indices, or mortality rates between the two groups. Cefiderocol showed high clinical and microbiological cure rates, despite the severity of the patients' conditions. Carbapenem-resistant Klebsiella pneumoniae and difficult-to-treat resistance Pseudomonas aeruginosa were the most prevalent pathogens in the case and control group, respectively. Two patients treated with cefiderocol developed Clostridioides difficile infection, emphasizing the need for close monitoring of potential adverse effects.

CONCLUSIONS

The results of this study support cefiderocol as a viable alternative for managing serious infections instigated by multidrug-resistant Gram-negative bacteria.

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.

Phage-Based Therapy in Combination with Antibiotics: A Promising Alternative against Multidrug-Resistant Gram-Negative Pathogens

The continued rise in antimicrobial resistance poses a serious threat to public health worldwide. The use of phages that can have bactericidal activity without disrupting the normal flora represents a promising alternative treatment method. This practice has been successfully applied for decades, mainly in Eastern Europe, and has recently been used as an emergency therapy for compassionate care in the United States. Here, we provide a comprehensive review of the pre-clinical and clinical applications of phage therapy concerning three major Gram-negative pathogens: Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. The advantages and the challenges of expanding the usage of phages as an alternative or adjunctive treatment for antimicrobial-resistant bacterial infections are discussed. We emphasize the virologic complexities of using the highly adaptable phage populations as molecular tools, along with antibiotic chemical compounds, to effectively combat rapidly coevolving pathogenic bacteria in the host microenvironment. Pre-clinical studies, isolated clinical reports and a few randomized clinical trials have shown that bacteriophages can be effective in treating multidrug-resistant bacterial infections. The ability of some phages to revert the resistance against antibiotics, and possibly also against the human complement and other phages, appears to be a great advantage of phage therapy despite the inevitable emergence of phage-resistant strains. Bacteriophages (or specific phage-derived products) can enhance antimicrobial efficacy by reducing bacterial virulence via the alteration of basic bacterial structures, primarily of the cellular wall and membrane. Although several issues remain open regarding their effective clinical application, it appears that phage-based therapeutics in combination with antibiotics can provide an effective solution to the spread of antimicrobial resistance.

Structural basis of Pseudomonas aeruginosa penicillin binding protein 3 inhibition by the siderophore-antibiotic cefiderocol

The breakthrough cephalosporin cefiderocol, approved for clinical use in 2019, has activity against many Gram-negative bacteria. The catechol group of cefiderocol enables it to efficiently enter bacterial cells via the iron/siderophore transport system thereby reducing resistance due to porin channel mutations and efflux pump upregulation. Limited information is reported regarding the binding of cefiderocol to its key proposed target, the transpeptidase penicillin binding protein 3 (PBP3). We report studies on the reaction of cefiderocol and the related cephalosporins ceftazidime and cefepime with Pseudomonas aeruginosa PBP3, including inhibition measurements, protein observed mass spectrometry, and X-ray crystallography. The three cephalosporins form analogous 3-exomethylene products with P. aeruginosa PBP3 following elimination of the C3' side chain. pIC50 and k inact/K i measurements with isolated PBP3 imply ceftazidime and cefiderocol react less efficiently than cefepime and, in particular, meropenem with P. aeruginosa PBP3. Crystal structures inform on conserved and different interactions involved in binding of the three cephalosporins and meropenem to P. aeruginosa PBP3. The results will aid development of cephalosporins with improved PBP3 inhibition properties.

Cefiderocol for the Treatment of Infections by VIM-Type-Producing Gram-Negative Bacteria

VIM-type-producing Gram-negative bacteria (GNB) infections are difficult to treat. This is a retrospective single-center study of 34 patients who received cefiderocol for the treatment of VIM-type-producing GNB infections, including 25 Pseudomonas spp., 7 Enterobacterales, and 5 Achromobacter sp. Primary outcomes were clinical failure (defined as death, lack of clinical improvement, or a switch to another drug) at day 14 and 30-day all-cause mortality. The median age was 59 years (IQR 53.7-73.4), and the median Charlson comorbidity index was 3.5 (IQR 2-5). The main infections were respiratory tract infections (n = 9, 27%) and skin and soft tissue infections (n = 9, 27%). Eight patients exhibited bacteremia. In 9/17 patients with a drainable focus, drainage was performed. The median cefiderocol treatment duration was 13 days (IQR 8-24). Five patients (15%) experienced clinical failure on day 14, and the thirty-day mortality rate was 9/34 (27%); two cases occurred because of an uncontrolled infection source, and one was due to a new infection caused by the same bacteria. The other six deaths were unrelated to the index infection. Five patients experienced microbiological recurrence within three months. Susceptibility testing revealed the development of cefiderocol resistance in 1/7 cases with persistent or recurrent positive cultures. Cefiderocol, even in monotherapy, could be considered for the treatment of VIM-type-producing GNB infections.

Genomic Insights into Vietnamese Extended-Spectrum β-Lactamase-9-Producing Extensively Drug-Resistant Pseudomonas aeruginosa Isolates Belonging to the High-Risk Clone ST357 Obtained from Bulgarian Intensive Care Unit Patients

Extensively drug-resistant P. aeruginosa (XDR-PA) has been highlighted as a serious public health threat. The present study aimed to explore the genomic characteristics of two Vietnamese extended-spectrum β-lactamase-9 (VEB-9)-producing XDR-PA isolates from Bulgaria in comparison to all blaVEB-9-positive strains with available genomes. The isolates designated Pae51 and Pae52 were obtained from tracheobronchial aspirates of intensive care unit (ICU) patients. Antimicrobial susceptibility testing, whole-genome sequencing, RT-qPCR, and phylogenomic analysis were performed. Pae51 and Pae52 were resistant to most antipseudomonal β-lactams including carbapenems, aminoglycosides, and fluoroquinolones but remained susceptible to colistin and cefiderocol. Numerous resistance determinants were detected: blaVEB-9, blaPDC-3, blaOXA-10, blaOXA-50, aac(6')-II, ant(2″)-Ia, ant(3″)-IIa, aph(3')-IIb, cprP, catB7, dfrB2, sul1, fosA, and tet(A). Both isolates carried complex integrons with blaVEB-9 and tet(A) embedded next to the conservative 3' end sequences. A variety of virulence factors were also identified, including the type III secretion system exotoxin U. Pae51 and Pae52 differed by only four SNPs and belonged to the high-risk clone ST357. To our knowledge, this is the first report of blaVEB-9-positive XDR-PA isolates in Bulgaria presenting a detailed genomic analysis. The development of novel antimicrobial strategies for such pathogens should be an essential part of infection control stewardship practices in ICU wards.

Cefiderocol heteroresistance associated with mutations in TonB-dependent receptor genes in Pseudomonas aeruginosa of clinical origin

The siderophore-cephalosporin cefiderocol (FDC) presents a promising treatment option for carbapenem-resistant (CR) P. aeruginosa (PA). FDC circumvents traditional porin and efflux-mediated resistance by utilizing TonB-dependent receptors (TBDRs) to access the periplasmic space. Emerging FDC resistance has been associated with loss of function mutations within TBDR genes or the regulatory genes controlling TBDR expression. Further, difficulties with antimicrobial susceptibility testing (AST) and unexpected negative clinical treatment outcomes have prompted concerns for heteroresistance, where a single lineage isolate contains resistant subpopulations not detectable by standard AST. This study aimed to evaluate the prevalence of TBDR mutations among clinical isolates of P. aeruginosa and the phenotypic effect on FDC susceptibility and heteroresistance. We evaluated the sequence of pirR, pirS, pirA, piuA, or piuD from 498 unique isolates collected before the introduction of FDC from four clinical sites in Portland, OR (1), Houston, TX (2), and Santiago, Chile (1). At some clinical sites, TBDR mutations were seen in up to 25% of isolates, and insertion, deletion, or frameshift mutations were predicted to impair protein function were seen in 3% of all isolates (n = 15). Using population analysis profile testing, we found that P. aeruginosa with major TBDR mutations were enriched for a heteroresistant phenotype and undergo a shift in the susceptibility distribution of the population as compared to susceptible strains with wild-type TBDR genes. Our results indicate that mutations in TBDR genes predate the clinical introduction of FDC, and these mutations may predispose to the emergence of FDC resistance.

In vitro activity of cefiderocol in Pseudomonas aeruginosa isolates from people with cystic fibrosis recovered during three multicentre studies in Spain

OBJECTIVES

Despite the introduction of cystic fibrosis transmembrane conductance regulator (CFTR) modulators, Pseudomonas aeruginosa is still a major pathogen in people with cystic fibrosis (pwCF). We determine the activity of cefiderocol and comparators in a collection of 154 P. aeruginosa isolates recovered from pwCF during three multicentre studies performed in 17 Spanish hospitals in 2013, 2017 and 2021.

METHODS

ISO broth microdilution was performed and MICs were interpreted with CLSI and EUCAST criteria. Mutation frequency and WGS were also performed.

RESULTS

Overall, 21.4% were MDR, 20.8% XDR and 1.3% pandrug-resistant (PDR). Up to 17% of the isolates showed a hypermutator phenotype. Cefiderocol demonstrated excellent activity; only 13 isolates (8.4%) were cefiderocol resistant by EUCAST (none using CLSI). A high proportion of the isolates resistant to ceftolozane/tazobactam (71.4%), meropenem/vaborbactam (70.0%), imipenem/relebactam (68.0%) and ceftazidime/avibactam (55.6%) were susceptible to cefiderocol. Nine out of 13 cefiderocol-resistant isolates were hypermutators (P < 0.001). Eighty-three STs were detected, with ST98 being the most frequent. Only one isolate belonging to the ST175 high-risk clone carried blaVIM-2. Exclusive mutations affecting genes involved in membrane permeability, AmpC overexpression (L320P-AmpC) and efflux pump up-regulation were found in cefiderocol-resistant isolates (MIC = 4-8 mg/L). Cefiderocol resistance could also be associated with mutations in genes related to iron uptake (tonB-dependent receptors and pyochelin/pyoverdine biosynthesis).

CONCLUSIONS

Our results position cefiderocol as a therapeutic option in pwCF infected with P. aeruginosa resistant to most recent β-lactam/β-lactamase inhibitor combinations.

Successful Treatment of an AML Patient Infected with Hypervirulent ST463 Pseudomonas Aeruginosa Harboring Rare Carbapenem-Resistant Genes blaAFM-1 and blaKPC-2 Following Allogeneic Hematopoietic Stem Cell Transplantation

Background

Carbapenem-resistant P. aeruginosa (CRPA) is a common hospital-acquired bacterium. It exhibits high resistance to many antibiotics, including ceftazidime/avibactam and cefteolozane/tazobactam. The presence of carbapenem-resistant genes and co-existence Klebsiella pneumoniae carbapenemase (KPC) and metallo-β-lactamases (MBLs) further inactivated all β-lactams. Understanding the resistance genes of CRPA can help in uncovering the resistance mechanism and guiding anti-infective treatment. Herein, we reported a case of perianal infection with hypervirulent ST463 Pseudomonas aeruginosa.

Case Presentation

The case is a 32-year-old acute myeloid leukemia (AML) patient with fever and septic shock during hematopoietic stem cell transplantation (HSCT), and the pathogen was finally identified as a highly virulent sequence type 463 (ST463) P. aeruginosa harboring carbapenem-resistant genes blaAFM-1 and blaKPC-2, which was detected in the bloodstream and originated from a perianal infection. The strain was resistant to ceftazidime/avibactam but successfully treated with polymyxin B, surgical debridement, and granulocyte engraftment after HSCT. The AML was cured during the 19-month follow-up.

Conclusion

This case emphasizes the importance of metagenomic next-generation sequencing (mNGS) and whole-genome sequencing (WGS) in identifying microbes with rare resistant genes, and managing CRPA, especially in immunocompromised patients. Polymyxin B may be the least resistant option.

In vitro activity of cefiderocol against Gram-negative pathogens isolated from people with cystic fibrosis and bronchiectasis

OBJECTIVES

Gram-negative pathogens causing respiratory infection in people with cystic fibrosis and bronchiectasis are becoming progressively more resistant to conventional antibiotics. Although cefiderocol is licenced for the treatment of infections due to Gram-negative organisms, there are limited data on the activity of cefiderocol against pathogens associated with chronic respiratory diseases. The aim of this study was to determine the susceptibility of Gram-negative pathogens from cystic fibrosis and bronchiectasis to cefiderocol and comparator antibiotics.

METHODS

Minimal inhibitory concentrations (MICs) of cefiderocol and 15 comparator antibiotics were determined by broth microdilution against 300 respiratory isolates: Burkholderia spp., Stenotrophomonas spp., Achromobacter spp., Ralstonia spp. and Pandoraea spp., and used to calculate the MIC of each antibiotic required to inhibit 50% (MIC50) and 90% (MIC90) of isolates.

RESULTS

The MIC50 and MIC90 of cefiderocol for all 300 isolates tested was 0.25 and 32 mg/L, with 232 (77.3%) isolates having an MIC value ≤2 mg/L. In addition, cefiderocol demonstrated excellent activity against Stenotrophomonas spp. and Achromobacter spp. isolates, with 86.7% and 87.2%, respectively, exhibiting an MIC of 2 mg/L. Tigecycline also demonstrated good activity against all isolates with an MIC50 of <0.5 mg/L.

CONCLUSIONS

These in vitro data demonstrated that cefiderocol had greater activity than most comparator antibiotics and could be an alternative treatment option for respiratory infection caused by these pathogens that has not responded to first-line therapy.

Cefiderocol: early clinical experience for multi-drug resistant gram-negative infections

Multi-drug resistant gram-negative bacteria present a significant global health threat. Cefiderocol (CFDC), a siderophore cephalosporin, has shown potential in combating this threat, but with the currently available data, its role in therapy remains poorly defined. This multi-center, retrospective cohort study evaluated the real-world application of CFDC across six U.S. medical centers from January 2018 to May 2023. Patients aged ≥18 years and who had received ≥72 hours of CFDC were included. The primary outcome was a composite of clinical success: survival at 30 days, absence of symptomatic microbiologic recurrence at 30 days following CFDC treatment initiation, and resolution of signs and symptoms. Secondary outcomes included time to CFDC therapy and on-treatment non-susceptibility to CFDC. A total of 112 patients were included, with median (interquartile range [IQR]) APACHE II scores of 15 (19-18). Clinical success was observed in 68.8% of patients, with a mortality rate of 16.1% and comparable success rates across patients infected with carbapenem-resistant gram-negative infections. The most common isolated organisms were Pseudomonas aeruginosa (61/112, 54.5%, of which 55/61 were carbapenem-resistant) and carbapenem-resistant Acinetobacter baumannii (32/112, 28.6%). Median (IQR) time to CFDC therapy was 77 (14-141) hours. Two patients experienced a non-anaphylactic rash as an adverse drug reaction. On-treatment non-susceptibility to CFDC was found in six patients, notably due to P. aeruginosa and A. baumannii.IMPORTANCECFDC was safe and clinically effective as a monotherapy or in combination in treating a variety of carbapenem-resistant gram-negative infections. Further prospective studies are warranted to confirm these findings.

Cefiderocol heteroresistance associated with mutations in TonB-dependent receptor genes in Pseudomonas aeruginosa of clinical origin

The siderophore-cephalosporin cefiderocol(FDC) presents a promising treatment option for carbapenem-resistant (CR) P. aeruginosa (PA). FDC circumvents traditional porin and efflux mediated resistance by utilizing TonB-dependent receptors (TBDRs) to access the periplasmic space. Emerging FDC resistance has been associated with loss of function mutations within TBDR genes or the regulatory genes controlling TBDR expression. Further, difficulties with antimicrobial susceptibility testing (AST) and unexpected negative clinical treatment outcomes have prompted concerns for heteroresistance, where a single lineage isolate contains resistant subpopulations not detectable by standard AST. This study aimed to evaluate the prevalence of TBDR mutations among clinical isolates of P. aeruginosa and the phenotypic effect on FDC susceptibility and heteroresistance. We evaluated the sequence of pirR , pirS , pirA , piuA or piuD from 498 unique isolates collected before the introduction of FDC from 4 clinical sites in Portland, OR (1), Houston, TX (2), and Santiago, Chile (1). At some clinical sites, TBDR mutations were seen in up to 25% of isolates, and insertion, deletion, or frameshift mutations were predicted to impair protein function were seen in 3% of all isolates (n=15). Using population analysis profile testing, we found that P. aeruginosa with major TBDR mutations were enriched for a heteroresistant phenotype and undergo a shift in the susceptibility distribution of the population as compared to susceptible strains with wild type TBDR genes. Our results indicate that mutations in TBDR genes predate the clinical introduction of FDC, and these mutations may predispose to the emergence of FDC resistance.

The Use of Cefiderocol as Salvage Therapy in an Infant Receiving ECMO and Continuous Renal Replacement Therapy

BACKGROUND

Infections caused by antimicrobial-resistant (AMR) pathogens are increasing worldwide, representing a serious global public health issue with high morbidity and mortality rates The treatment of Pseudomonas aeruginosa (PA) infections has become a significant challenge due to its ability to develop resistance to many of the currently available antibiotics, especially in intensive care unit (ICU) settings. Among the very few therapeutic lines available against extensively drug-resistant (XDR)-PA and/or with difficult-to-treat resistance (DTR)-PA, cefiderocol is an injectable siderophore cephalosporin not licensed for use in pediatric patients. There are only a few case reports and two ongoing trials describing the administration of this cephalosporin in infants.

CASE PRESENTATION

This report describes the case of a critically ill 8-month-old girl affected by ventilator-associated pneumonia (VAP) infection complicated by bloodstream infection (BSI) sustained by VIM-producing PA. She was treated with cefiderocol as a salvage therapy during ECMO and CRRT support.

CONCLUSIONS

In healthcare settings, treating multidrug-resistant, Gram-negative bacteria poses a serious challenge, especially in pediatric patients. Our findings suggest that cefiderocol can be considered as an off-label rescue therapy in selected pediatric cases.

Management strategies for severe Pseudomonas aeruginosa infections

PURPOSE OF REVIEW

This review focuses on the management of severe Pseudomonas aeruginosa infections in critically ill patients.

RECENT FINDINGS

Pseudomonas aeruginosa is the most common pathogen in intensive care; the main related infections are nosocomial pneumonias, then bloodstream infections. Antimicrobial resistance is common; despite new antibiotics, it is associated with increased mortality, and can lead to a therapeutic deadlock.

SUMMARY

Carbapenem resistance in difficult-to-treat P. aeruginosa (DTR-PA) strains is primarily mediated by loss or reduction of the OprD porin, overexpression of the cephalosporinase AmpC, and/or overexpression of efflux pumps. However, the role of carbapenemases, particularly metallo-β-lactamases, has become more important. Ceftolozane-tazobactam, ceftazidime-avibactam and imipenem-relebactam are useful against DTR phenotypes (noncarbapenemase producers). Other new agents, such as aztreonam-ceftazidime-avibactam or cefiderocol, or colistin, might be effective for carbapenemase producers. Regarding nonantibiotic agents, only phages might be considered, pending further clinical trials. Combination therapy does not reduce mortality, but may be necessary for empirical treatment. Short-term treatment of severe P. aeruginosa infections should be preferred when it is expected that the clinical situation resolves rapidly.

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.