In vitro activities of omadacycline, eravacycline, cefiderocol, apramycin, and comparator antibiotics against Acinetobacter baumannii causing bloodstream infections in Greece, 2020-2021: a multicenter study

The evolving epidemiology of antimicrobial resistance of ESKAPE pathogens isolated in the intensive care unit of a Greek university hospital

BACKGROUND

The ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter) is a major cause of life-threatening infections in Intensive Care Unit (ICU) critically ill patients accounting for significant morbidity and mortality. Management of infections by ESKAPE pathogens is complicated due to the remarkable rise in the rates of multidrug resistance (MDR) to most antimicrobial agents. This study investigated the trends of prevalence and antimicrobial resistance profiles of the ESKAPE pathogens isolated from clinical specimens of adult ICU patients.

METHODS

All ESKAPE isolates collected from clinical specimens of ICU patients during the years 2013-2022 were processed according to routine methods. Identification of the bacterial isolates was performed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry and antimicrobial susceptibility testing by Vitek 2 system.

RESULTS

During the ten-year period, a total of 6,132 ESKAPE strains were isolated from 5,338 samples of 1,792 ICU patients. A. baumannii was the most prevalent microorganism, followed by P. aeruginosa, and K. pneumoniae. High resistance to carbapenems was detected for A. baumannii (96.7 %) and K. pneumoniae (57.4 %). Methicillin-resistant were 39.1 % of S. aureus and vancomycin-resistant 38.7 % of the E. faecium isolates. MDR were characterized 39 % of K. pneumoniae and 13.1 % of P. aeruginosa strains, while 19.7 % of A. baumannii were pandrug resistant.

CONCLUSIONS

An increased antimicrobial resistance among ESKAPE bacteria was found in our ICU setting. Enhanced antimicrobial surveillance, strict implementation of stewardship programmes and infection control practices are crucial to reduce AMR and develop management strategies to optimize outcomes.

Mortality due to carbapenem-resistant Acinetobacter baumannii bacteraemia: a 5-year cohort study in intensive care patients

OBJECTIVES

Carbapenem-resistant Acinetobacter baumannii (CRAB) has emerged as a major and difficult-to-treat nosocomial pathogen. This study estimated the mortality associated with CRAB bacteraemia in patients receiving treatment in the intensive care unit. A susceptible-infection counterfactual framework was applied to reflect the potential benefit of improved antimicrobial therapy.

METHODS

A 5-year (2019-2023) cohort study was conducted in a tertiary-care referral hospital in Greece. Competing risks survival analysis methods were applied to estimate excess in-hospital mortality because of CRAB bacteraemia by comparing patients infected by CRAB with those infected by other more susceptible Gram-negative bacteria (GNB).

RESULTS

The cohort comprised 400 intensive care patients with GNB bacteraemia (median age 70 years, 65% man). CRAB was the most common pathogen (43%), followed by Klebsiella pneumoniae (12%), Escherichia coli (11%), and Pseudomonas aeruginosa (10%). Patients with CRAB bacteraemia experienced significantly higher in-hospital mortality at 14 days (35% vs. 21%), 28 days (53% vs. 30%), and overall (74% vs. 52%) than patients with other GNB bacteraemia. Multivariable competing risks regression confirmed that CRAB bacteraemia was independently associated with an increased risk of 28-day inpatient death (cause-specific hazard ratio: 1.80, 95% CI: 1.28-2.54; sub-distribution hazard ratio: 1.84, 95% CI: 1.28-2.62), simultaneously lowering the probability of discharge alive (cause-specific hazard ratio: 0.68, 95% CI: 0.38-1.21; sub-distribution hazard ratio: 0.52, 95% CI: 0.30-0.91). Estimation of the attributable fraction suggested that effective antimicrobial management may result in a relative decrease in the risk of in-hospital mortality by 44% (95% CI: 22-61%) in patients with CRAB bacteraemia.

DISCUSSION

CRAB's detrimental role as a leading cause of increased inpatient mortality and prolongation of hospitalization in intensive care patients was demonstrated. These outcomes could improve substantially if more effective antimicrobial treatment becomes available. Nevertheless, considering that CRAB is predominantly a hospital-acquired pathogen, efforts should always be directed towards preventing nosocomial transmission.

Outcome of Bloodstream Infections Caused by Antibiotic-Resistant Bacteria: A 7-Year Retrospective Study at the University Hospital of Palermo, Italy

BACKGROUND

Bloodstream infections (BSIs) are both a primary cause and a severe complication of hospitalization. This retrospective study aims to analyze the epidemiology of BSIs at the University Hospital of Palermo from 2018 to 2024.

METHODS

We conducted a single-center, retrospective, observational study at the University Hospital Paolo Giaccone in Palermo, analyzing microbiological data from blood cultures collected between 1 January 2018 and 31 December 2024.

RESULTS

A total of 6345 blood culture isolates from 2967 patients were analyzed. Bacteremia-related mortality per 1000 patients rose from 5.1% in 2018 to 10.5% in 2024. The most isolated pathogens were non-aureus staphylococci (39.7%), followed by Klebsiella pneumoniae (12.1%) and Staphylococcus aureus (7.47%). Acinetobacter baumannii and Pseudomonas aeruginosa were more prevalent in ICUs. The number of K. pneumoniae, A. baumannii, S. aureus, and P. aeruginosa isolates per 1000 admitted patients increased significantly over time. Oxacillin resistance in S. aureus peaked at 49.0% in 2020 before declining, while among non-aureus staphylococci, it remained consistently high (>80%). Carbapenem-resistant K. pneumoniae peaked at 80% in 2022 before decreasing in 2024. Resistance to ceftazidime-avibactam and meropenem-vaborbactam was observed in 11.3% and 11.8% of K. pneumoniae, respectively. Multivariable analysis identified A. baumannii and K. pneumoniae BSIs as independent predictors of in-hospital mortality. Additionally, female sex, pneumonia, and central nervous system infections were significant risk factors for mortality.

CONCLUSIONS

We observed an increasing trend in overall bacteremia-related mortality from 2018 to 2024. Microbiological data highlight the predominance of non-aureus staphylococci, K. pneumoniae, and S. aureus as leading pathogens of BSI, with A. baumannii emerging as a significant threat, particularly in ICUs. Rising antimicrobial resistance, especially among K. pneumoniae, underscores the urgent need for robust antimicrobial stewardship programs. K. pneumoniae and A. baumannii were associated with higher mortality.

From Clinical Trials to Real-World Experiences: Evidence About Cefiderocol Use and Potential Role in Empirical Therapy

Cefiderocol is a novel siderophore cephalosporin that has gained attention for its potent activity against multidrug-resistant (MDR) Gram-negative pathogens, making it a valuable addition to the antimicrobial armamentarium. Its efficacy in treating complicated urinary tract infections (cUTIs) and nosocomial pneumonia has been well-established, although challenges remain regarding its role in Acinetobacter baumannii infections and the possible emergence of resistance. The decision to use cefiderocol as a monotherapy or in combination should be guided by pathogen susceptibility, clinical severity, and local epidemiology. Then, the potential to serve as an effective empirical therapy, careful stewardship, and further research are essential to maximize its therapeutic benefits and ensure its long-term efficacy. This review explores the efficacy of cefiderocol, resistance development, heteroresistance, its use as monotherapy or in combination therapy, and its role in empirical treatment regimens. We discuss data about clinical trials and real-world evidence to assess the future role of cefiderocol in antibiotic regimens.

The future approach for the management of acute bacterial skin and skin structure infections

PURPOSE OF REVIEW

To discuss the new available options for the treatment of acute bacterial skin and skin structure infections (ABSSSIs) and how to implement in the clinical practice innovative approaches for their management.

RECENT FINDINGS

The availability of long-acting antibiotics, including dalbavancin and oritavancin, changed the approach to patients with ABSSSI. Direct discharge from the emergency department and early discharge from the hospital should be considered in patients with ABSSSI. Despite limited data about different bactericidal properties, the choice between dalbavancin and oritavacin is usually based on patients' characteristics and comorbidities. Delafloxacin and omadacycline are other options and have the advantage to be available for both intravenous and oral formulations, allowing a sequential therapy and switch from intravenous to oral treatment in clinically stable patients. Further studies should elucidate the profile of patients who may beneficiate from these drugs.

SUMMARY

Early discharge from the hospital should be considered in patients with ABSSSI at a high risk of methicillin-resistant Staphylococcus aureus and in vulnerable patients for which hospitalization may have detrimental consequences. In elderly individuals, patients with diabetes mellitus, oncological people who need for continuing their healthcare pathway, this approach may reduce complications and costs related to hospitalization.

New Perspectives on Antimicrobial Agents: Omadacycline for community-acquired pneumonia, skin and soft tissue infections, and nontuberculous mycobacteria (focus on M. abscessus)

Omadacycline is a novel antimicrobial belonging to the tetracycline class. It has the ability to evade both efflux and ribosomal methylation types of resistance and therefore has an expanded spectrum compared to other tetracycline agents. Omadacycline is active against a number of multidrug-resistant bacteria, including macrolide and doxycycline-resistant Streptococcus pneumoniae, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus, and several enteric gram-negative bacilli. It also has activity against many nontuberculous mycobacterium (NTM) species. It is available both orally and intravenously, which allows for feasible switch therapy. This review will assess the antimicrobial activity, pharmacology, safety, and clinical efficacy of omadacycline and present the opinions of the authors on where to position omadacycline for clinical practice.

Risk Factors for Development and Mortality of Bloodstream Infections Caused by Carbapenem-Resistant Acinetobacter baumannii

Background

Bloodstream infections (BSIs) caused by Acinetobacter baumannii (AB), especially carbapenem-resistant Acinetobacter baumannii (CRAB), can lead to a high patient mortality rate.

Methods

This study aimed to analyze the clinical data and prognosis of 191 patients with AB-BSI hospitalized in Southern China from January 2017 to December 2023.

Results

CRAB was diagnosed in 128 (67.0%) of the 191 patients with AB-BSI. Endotracheal intubation (OR = 23.957, 95% CI: 5.123-112.022, P < 0.001), carbapenem treatment (OR = 6.422, 95% CI: 1.554-26.542, P = 0.010) and ≥2 antimicrobial drugs therapy (OR = 6.131, 95% CI: 1.763-21.324, P = 0.004) prior to the onset of BSI were independent risk factors for the development of CRAB-BSI, as revealed by the binary logistic regression analysis. The overall mortality rate of patients with AB-BSI was 27.7%, while that of patients with CRAB was significantly higher than that of patients with carbapenem-sensitive Acinetobacter baumannii (CSAB) (39.1% vs 4.8%, P < 0.001). Multivariate Cox regression analysis revealed septic shock (HR = 3.664, 95% CI: 1.537-8.736, P = 0.003) as an independent risk factor for mortality in CRAB-BSI patients. Kaplan-Meier survival analysis showed a significantly lower 28-day survival rate for CRAB-BSI patients who developed septic shock compared to those who did not (58.4% vs 87.1%, P = 0.001).

Conclusion

Clinicians should closely monitor patients at high risk for CRAB-BSI, focusing on invasive procedure management and antimicrobial stewardship. Timely supportive care is crucial for CRAB-BSI patients at risk of septic shock to improve survival outcomes.

Activity and resistance mechanisms of the third generation tetracyclines tigecycline, eravacycline and omadacycline against nationwide Spanish collections of carbapenemase-producing Enterobacterales and Acinetobacter baumannii

INTRODUCTION

The rise in multidrug-resistant bacteria challenges clinical microbiology. Tigecycline, eravacycline, and omadacycline show promise against carbapenem-resistant Enterobacterales and Acinetobacter baumannii. This study evaluates their activity and resistance mechanisms.

METHODS

Two Spanish multicentre collections of WGS-characterized carbapenemase-producing Enterobacterales (n=399) and A. baumannii (n=118) were tested. The MICs of tigecycline, eravacycline, omadacycline and classic tetracyclines were determined. WGS-guided resistome analysis, expression studies, efflux pump inhibition and cloning assays identified potential mechanisms of resistance.

RESULTS

Tigecycline and eravacycline exhibited the highest activity against the whole set of Enterobacterales (MIC50/MIC90 0.5/1 mg/L and 1/2 mg/L, respectively), and A. baumannii (MIC50/MIC90 1/2 mg/L and ≤0.25/1 mg/L, respectively). Omadacycline showed no improvement relative to classic tetracyclines (MIC50/MIC90 values of 8/32 mg/L and 8/16 mg/L for Enterobacterales and A. baumannii, respectively). Resistance mechanisms in Enterobacterales included efflux pumps (AcrAB-TolC, OqxAB) and mutation in their regulatory genes. In A. baumannii, adeS gene mutations and adeABC upregulation decreased tigecycline activity. The prevalent sequence types with reduced susceptibility to eravacycline and tigecycline were ST307 in K. pneumoniae and ST2 in A. baumannii.

CONCLUSION

Eravacycline remains a key agent for the treatment of bacterial infections exhibiting promising efficacy against multidrug-resistant pathogens. As an empirical antibiotic it could be a good alternative for severe infections caused by CPE or CRAB, however, its clinical use is limited by the absence of standardized breakpoints. Resistance mechanisms, including efflux pumps and gene mutations, vary among isolates. High-risk clones like K. pneumoniae ST307 and A. baumannii ST2 underscore the necessity of prudent antibiotic use.

Prevalence and Antimicrobial Resistance Trends among Lower Respiratory Tract Pathogens in Crete, Greece, 2017-2022

BACKGROUND

Lower respiratory tract infections (LRTIs) are the most common infections in humans accounting for significant morbidity and mortality. Management of LRTIs is complicated due to increasing antimicrobial resistance. This study investigated the prevalence and trends of antimicrobial resistance for bacteria isolated from respiratory samples of patients with LRTIs.

MATERIALS AND METHODS

Sputum and bronchial washings were collected from patients of all ages hospitalized with LRTIs and were analyzed by the microbiological laboratory in the University Hospital of Heraklion, Crete, Greece, from January 2017 to December 2022. Identification of the bacterial isolates was performed by matrix-assisted laser desorption ionization-time of flight mass spectrometry and antimicrobial susceptibility testing by Vitek 2 system.

RESULTS

A total of 4,008 strains were isolated from 3,427 respiratory samples. Acinetobacter baumannii was the most frequently isolated pathogen (23.1%), followed by Pseudomonas aeruginosa (20.0%), Staphylococcus aureus (10.6%) and Klebsiella pneumoniae (6.8%). The isolation rate of A. baumannii significantly increased during the study period, while there were lower increases in the isolation rates of P. aeruginosa, K. pneumoniae and S. aureus. A. baumannii and P. aeruginosa were more prevalent during summer, K. pneumoniae was more common during autumn, while for S. aureus higher incidence was noted during winter. A. baumannii exhibited high resistance rates (≥90.0%) to most of the antimicrobial agents tested, and extremely high multidrug-resistance (91.0%). P. aeruginosa showed the lowest rate of resistance for colistin (1.4%). Among β-lactams, resistance rates to piperacillin/tazobactam, ceftazidime, cefepime, imipenem and meropenem were 26.2%, 27%, 25.8%, 29.2% and 29.9%, respectively. A total of 162 (68.1%) meropenem-resistant P. aeruginosa were simultaneously resistant to ceftazidime and piperacillin/tazobactam. Regarding K. pneumoniae, high rates of resistance were observed for the third and fourth generation cephalosporins, namely cefotaxime, ceftriaxone, ceftazidime, and cefepime and the carbapenems, imipenem and meropenem ranging from 46.2% to 53.8%. Carbapenem-resistance was detected among 46.2% of the isolates. Among the 126 carbapenem-resistant K. pneumoniae isolates, 83 (65.9%), 30 (23.8%), 9 (7.2%), and 4 (4.2%) were positive for Klebsiella pneumoniae carbapenemase, New Delhi Metallo-β-lactamase, Verona Integron-Mediated Metallo-β-lactamase and OXA-48 carbapenemase, respectively. Of the total number of S. aureus, 37.2% were methicillin resistant. Low rates of resistance were detected in trimethoprim/sulfamethoxazole (3.3%), gentamicin (2.8%), and rifampicin (0.9%). All isolates were susceptible to linezolid, daptomycin, tigecycline, teicoplanin, and vancomycin.

CONCLUSION

Regularly updated surveillance of local microbial prevalence and monitoring of antimicrobial resistance patterns is of paramount importance to guide the empiric treatment of LRTIs.

Antibacterial Therapy Options for Infections Caused by Carbapenem-Resistant Acinetobacter baumannii

The review presents current treatment regimens for infections associated with carbapenem-resistant Acinetobacter baumannii, which are leading nosocomial pathogens exhibiting multidrug resistance to available antibacterial drugs. To date, widely used beta-lactam antibiotics, including carbapenems, have lost their effectiveness in combating acinetobacter infections, while new antibiotics remain poorly available to patients. Therefore, the only measure to combat the antibiotic resistance of carbapenem-resistant A. baumannii is to evaluate the efficiency of combination therapy in vitro and in vivo, which is of particular interest to Russian and foreign researchers.

Eravacycline: a comprehensive review of in vitro activity, clinical efficacy, and real-world applications

INTRODUCTION

The escalating threat of multidrug-resistant organisms necessitates constant exploration for novel antimicrobial agents. Eravacycline has emerged as a promising solution due to its unique chemical structure, which enhances potency and expands its spectrum of activity.

AREA COVERED

This review provides a thorough examination of eravacycline, encompassing its in vitro activity against Gram-positive and Gram-negative aerobes, carbapenem-non-susceptible organisms, anaerobes, and other bacterial strains. Additionally, it evaluates evidence from clinical studies to establish its clinical effect and safety.

EXPERT OPINION

Eravacycline, a synthetic fluorocycline, belongs to the tetracyclines class. Similar to other tetracycline, eravacycline exerts its antibacterial action by reversibly binding to the bacterial ribosomal 30S subunit. Eravacycline demonstrates potent in vitro activity against many Gram-positive and Gram-negative aerobes, anaerobes, and multidrug-resistant organisms. Randomized controlled trials and its associated meta-analysis affirm eravacycline's efficacy in treating complicated intra-abdominal infections. Moreover, real-world studies showcase eravacycline's adaptability and effectiveness in diverse clinical conditions, emphasizing its utility beyond labeled indications. Despite common gastrointestinal adverse events, eravacycline maintains an overall favorable safety profile, reinforcing its status as a tolerable antibiotic. However, ongoing research is essential for refining eravacycline's role, exploring combination therapy, and assessing its performance against biofilms, in combating challenging bacterial infections.

A Review of Omadacycline for Potential Utility in the Military Health System for the Treatment of Wound Infections

INTRODUCTION

Combat-related wound infections complicate the recovery of wounded military personnel, contributing to overall morbidity and mortality. Wound infections in combat settings present unique challenges because of the size and depth of the wounds, the need to administer emergency care in the field, and the need for subsequent treatment in military facilities. Given the increase in multidrug-resistant pathogens, a novel, broad-spectrum antibiotic is desired across this continuum of care when the standard of care fails. Omadacycline was FDA-approved in 2018 for treatment of adults with acute bacterial skin and skin structure infections (ABSSSI), as well as community-acquired bacterial pneumonia (CABP). It is a broad-spectrum antibiotic with activity against gram-positive, gram-negative, and atypical bacterial pathogens, including multidrug-resistant species. Omadacycline can overcome commonly reported tetracycline resistance mechanisms, ribosomal protection proteins, and efflux pumps, and is available in once-daily intravenous or oral formulations. In this review, we discuss the potential role of omadacycline, which is included in the Department of Defense Formulary, in the context of combat wound infections.

MATERIALS AND METHODS

A literature review was undertaken for manuscripts published before July 21, 2023. This included a series of publications found via PubMed and a bibliography made publicly available on the Paratek Pharmaceuticals, Inc. website. Publications presenting primary data published in English on omadacycline in relation to ESKAPEE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Escherichia coli, and Enterobacter species) pathogens and Clostridioides difficile, including in vitro, in vivo, and clinical data were included.

RESULTS

Of 260 identified records, 66 were included for evidence review. Omadacycline has in vitro activity against almost all the ESKAPEE pathogens, apart from P. aeruginosa. Importantly, it has activity against the four most prevalent bacterial pathogens that cause wound infections in the military healthcare system: S. aureus, including methicillin-resistant S. aureus, A. baumannii, K. pneumoniae, and E. coli. In vivo studies in rats have shown that omadacycline is rapidly distributed in most tissues, with the highest tissue-to-blood concentration ratios in bone mineral. The clinical efficacy of omadacycline has been assessed in three separate Phase 3 studies in patients with ABSSSI (OASIS-1 and OASIS-2) and with CABP (OPTIC). Overall, omadacycline has an established safety profile in the treatment of both ABSSSI and CABP.

CONCLUSIONS

Omadacycline has broad-spectrum activity, the option to be orally administered and an established safety profile, making it a potentially attractive replacement for moxifloxacin in the military individual first aid kit, especially when accounting for the increasing resistance to fluoroquinolones. Further studies and clinical evaluation are warranted to support broader use of omadacycline to treat combat wound infections in the military healthcare system.

In vitro activity of apramycin (EBL-1003) in combination with colistin, meropenem, minocycline or sulbactam against XDR/PDR Acinetobacter baumannii isolates from Greece

OBJECTIVES

To evaluate the in vitro activity of the combination of apramycin with colistin, meropenem, minocycline or sulbactam, against some well-characterized XDR Acinetobacter baumannii clinical isolates from Greece, to understand how apramycin can be best incorporated into clinical practice and optimize effectiveness.

METHODS

In vitro interactions of apramycin (0.5×, 1× and 2× the MIC value) with colistin (2 mg/L), meropenem (30 mg/L), minocycline (3.5 mg/L) or sulbactam (24 mg/L) were tested using time-kill methodology. Twenty-one clinical A. baumannii isolates were chosen, exhibiting apramycin MICs of 4-16 mg/L, which were at or below the apramycin preliminary epidemiological cut-off value of 16 mg/L. These isolates were selected for a range of colistin (4-32 mg/L), meropenem (16-256 mg/L), minocycline (8-32 mg/L) and sulbactam (8-32 mg/L) MICs across the resistant range. Synergy was defined as a ≥2 log10 cfu/mL reduction compared with the most active agent.

RESULTS

The combination of apramycin with colistin, meropenem, minocycline or sulbactam was synergistic, at least at one of the concentrations of apramycin (0.5×, 1× or 2× MIC), against 83.3%, 90.5%, 90.9% or 92.3% of the tested isolates, respectively. Apramycin alone was bactericidal at 24 h against 9.5% and 33.3% of the tested isolates at concentrations equal to 1× and 2× MIC, while the combination of apramycin at 2× MIC with colistin, meropenem or sulbactam was bactericidal against all isolates tested (100%). The apramycin 2× MIC/minocycline combination had bactericidal activity against 90.9% of the tested isolates.

CONCLUSIONS

Apramycin combinations may have potential as a treatment option for XDR/pandrug-resistant (PDR) A. baumannii infections and warrant validation in the clinical setting, when this new aminoglycoside is available for clinical use.

Characteristics of the Genetic Spread of Carbapenem-Resistant Acinetobacter baumannii in a Tertiary Greek Hospital

Acinetobacter baumannii (Ab) has increasingly been identified as a cause of hospital-acquired infections and epidemics. The rise of carbapenem-resistant Acinetobacter baumannii (CRAB) poses significant challenges in treatment. Nosocomial outbreaks linked to CRAΒ A. baumannii strains have been reported worldwide, including in Greece. This study aimed to analyze the molecular epidemiology trends of multidrug-resistant A. baumannii isolates in a tertiary hospital in Athens, Greece. A total of 43 clinical isolates of extensively drug-resistant (XDRAB), pan-drug-resistant (PDRAB), and CRAB were collected from patients suffering from blood infection, hospitalized between 2016 and 2020 at the internal medicine clinics and the ICU. A.baumannii isolates underwent testing for Ambler class B and D carbapenemases and the detection of ISAba1, and were typed, initially, using pulsed-field gel electrophoresis, and, subsequently, using sequence-based typing and multiplex PCR to determine European Clone lineages. The blaOXA-23 gene accompanied by ISAba1 was prevalent in nearly all A. baumannii isolates, except for one carrying blaOXA-58. The intrinsic blaOXA-51-like gene was found in all isolates. No Ambler class B carbapenemases (VIM, NDM) were detected. Isolates were grouped into four PF-clusters and no one-cluster spread was documented, consistent with the absence of outbreak. The study indicated that XDR/PDR-CRAB isolates predominantly produce OXA-23 carbapenemase and belong to European Clone II. Further research is needed to understand the distribution of resistant bacteria and develop effective prevention and control strategies.

Antibacterial agents active against Gram Negative Bacilli in phase I, II, or III clinical trials

INTRODUCTION

Antimicrobial resistance is a major threat to modern healthcare, and it is often regarded that the antibiotic pipeline is 'dry.'

AREAS COVERED

Antimicrobial agents active against Gram negative bacilli in Phase I, II, or III clinical trials were reviewed.

EXPERT OPINION

Nearly 50 antimicrobial agents (28 small molecules and 21 non-traditional antimicrobial agents) active against Gram-negative bacilli are currently in clinical trials. These have the potential to provide substantial improvements to the antimicrobial armamentarium, although it is known that 'leakage' from the pipeline occurs due to findings of toxicity during clinical trials. Significantly, a lack of funding for large phase III clinical trials is likely to prevent trials occurring for the indications most relevant to loss of life attributed to antimicrobial resistance such as ventilator-associated pneumonia. Non-traditional antimicrobial agents face issues in clinical development such as a lack of readily available and reliable susceptibility tests, and the potential need for superiority trials rather than non-inferiority trials. Most importantly, concrete plans must be made during clinical development for access of new antimicrobial agents to areas of the world where resistance to Gram negative bacilli is most frequent.

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

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

Global prevalence of cefiderocol non-susceptibility in Enterobacterales, Pseudomonas aeruginosa, Acinetobacter baumannii, and Stenotrophomonas maltophilia: a systematic review and meta-analysis

BACKGROUND

Cefiderocol is a last resort option for carbapenem-resistant (CR) Gram-negative bacteria, especially metallo-β-lactamase-producing Pseudomonas aeruginosa and CR Acinetobacter baumannii. Monitoring global levels of cefiderocol non-susceptibility (CFDC-NS) is important.

OBJECTIVES

To systematically collate and examine studies investigating in vitro CFDC-NS and estimate the global prevalence of CFDC-NS against major Gram-negative pathogens.

DATA SOURCES

PubMed and Scopus, up to May 2023.

STUDY ELIGIBILITY CRITERIA

Eligible were studies reporting CFDC-NS in Enterobacterales, P. aeruginosa, A. baumannii, or Stenotrophomonas maltophilia clinical isolates.

RISK-OF-BIAS ASSESSMENT

Two independent reviewers extracted study data and assessed the risk of bias on the population, setting, and measurement (susceptibility testing) domains.

DATA SYNTHESIS

Binomial-Normal mixed-effects models were applied to estimate CFDC-NS prevalence by species, coresistance phenotype, and breakpoint definition (EUCAST, CLSI, and FDA). Sources of heterogeneity were investigated by subgroup and meta-regression analyses.

RESULTS

In all, 78 studies reporting 82 035 clinical isolates were analysed (87% published between 2020 and 2023). CFDC-NS prevalence (EUCAST breakpoints) was low overall but varied by species (S. maltophilia 0.4% [95% CI 0.2-0.7%], Enterobacterales 3.0% [95% CI 1.5-6.0%], P. aeruginosa 1.4% [95% CI 0.5-4.0%]) and was highest for A. baumannii (8.8%, 95% CI 4.9-15.2%). CFDC-NS was much higher in CR Enterobacterales (12.4%, 95% CI 7.3-20.0%) and CR A. baumannii (13.2%, 95% CI 7.8-21.5%), but relatively low for CR P. aeruginosa (3.5%, 95% CI 1.6-7.8%). CFDC-NS was exceedingly high in New Delhi metallo-β-lactamase-producing Enterobacterales (38.8%, 95% CI 22.6-58.0%), New Delhi metallo-β-lactamase-producing A. baumannii (44.7%, 95% CI 34.5-55.4%), and ceftazidime/avibactam-resistant Enterobacterales (36.6%, 95% CI 22.7-53.1%). CFDC-NS varied considerably with breakpoint definition, predominantly among CR bacteria. Additional sources of heterogeneity were single-centre investigations and geographical regions.

CONCLUSIONS

CFDC-NS prevalence is low overall, but alarmingly high for specific CR phenotypes circulating in some institutions or regions. Continuous surveillance and updating of global CFDC-NS estimates are imperative while cefiderocol is increasingly introduced into clinical practice. The need to harmonize EUCAST and CLSI breakpoints was evident.

In vitro activity of novel apramycin-dextran nanoparticles and free apramycin against selected Dutch and Pakistani Klebsiella pneumonia isolates

Klebsiella pneumoniae are bacteria associated with respiratory tract infections and are increasingly becoming resistant to antibiotics, including carbapenems. Apramycin is a veterinary antibiotic that may have the potential to be re-purposed for use in human health, for example, for the treatment of respiratory tract infections after coupling to inhalable nanoparticles. In the present study, the antibiotic apramycin was formulated with single chain polymeric nanoparticles and tested in free and formulated forms against a set of 13 Klebsiella pneumoniae isolates (from the Netherlands and Pakistan) expressing different aminoglycoside resistance phenotypes. Minimum Inhibitory Concentration, Time Kill Kinetics and biofilm experiments were performed providing evidence for the potential efficacy of apramycin and apramycin-based nanomedicines for the treatment of human Klebsiella pneumonia infections.

How to treat severe Acinetobacter baumannii infections

PURPOSE OF REVIEW

To update the management of severe Acinetobacter baumannii infections (ABI), particularly those caused by multi-resistant isolates.

RECENT FINDINGS

The in vitro activity of the various antimicrobial agents potentially helpful in treating ABI is highly variable and has progressively decreased for many of them, limiting current therapeutic options. The combination of more than one drug is still advisable in most circumstances. Ideally, two active first-line drugs should be used. Alternatively, a first-line and a second-line drug and, if this is not possible, two or more second-line drugs in combination. The emergence of new agents such as Cefiderocol, the combination of Sulbactam and Durlobactam, and the new Tetracyclines offer therapeutic options that need to be supported by clinical evidence.

SUMMARY

The apparent limitations in treating infections caused by this bacterium, the rapid development of resistance, and the serious underlying situation in most cases invite the search for alternatives to antibiotic treatment, the most promising of which seems to be bacteriophage therapy.

Laboratory Surveillance of Acinetobacter spp. Bloodstream Infections in a Tertiary University Hospital during a 9-Year Period

Multidrug-resistant Acinetobacter baumannii infections have become a threat for public health worldwide. The aim of the present study was to follow-up resistance patterns of Acinetobacter spp. bloodstream isolates in a Tertiary University Hospital over the last nine years, from 2014 to 2022. Susceptibility patterns were followed for the following antimicrobial agents: amikacin, gentamicin, tobramycin, ciprofloxacin, levofloxacin, imipenem, meropenem, tigecycline, trimethoprim/sulfamethoxazole, and colistin. Minimal inhibitory concentration (MIC) values to ampicillin/sulbactam, cefepime, ceftazidime, minocycline, piperacillin/tazobactam were evaluated from 2020 to 2023. During the study period, 853 Acinetobacter spp. bloodstream infections (BSIs) were recorded, accounting for 5.36% of all BSIs. A. baumannii was isolated in 795 cases (93.2%), during the study period. Most BSIs were recorded in adult intensive care units (ICU) (46.2%) and medical wards (42%). Among A. baumannii isolates, 4.5% were multidrug-resistant, 84.7% were extensively drug-resistant, and 8.5% were pandrug-resistant. Resistance to carbapenems was over 95%. Resistance to tigecycline increased significantly during the last years of the study (2020-2022); A. baumannii isolates with MIC ≤ 2 μg/mL accounted for 28.5% of all isolates. Resistance to colistin exhibited an increasing pattern up to 42.2% in 2022. Increasing resistance rates and the evolution of pandrug-resistant isolates call for the urgent application of preventive and response actions.