Contemporary Perspective on the Treatment of Acinetobacter baumannii Infections: Insights from the Society of Infectious Diseases Pharmacists

Development of bacterial resistance in Germany from 2008 to 2022 - major culprit pathogens, antibacterial drugs, and prescribing practices

Rising bacterial resistance is a global threat, causing rising financial burdens on healthcare systems and endangering effective treatment of bacterial infections. To ensure the efficacy of antibacterial drugs, it is essential to identify the most dangerous pathogens and vulnerable antibacterial drugs. Previous research by our group suggested irrational outpatient prescribing practices in Germany, supporting a growing bacterial resistance. This study analyses developments and characteristics for the ten most prescribed antibacterial drugs in Germany from 2008 to 2022. Conclusions are based on the development of bacterial resistance levels and an analysis of correlations between pathogens. We identified cefuroxime axetil, sulfamethoxazole-trimethoprim and nitrofurantoin as the most problematic drugs. Particularly problematic pathogens include E. faecalis, E. faecium, K. pneumoniae, and P. mirabilis. Besides increasing bacterial resistance, they are characterised by a high proportion of significant positive correlations, indicating a high potential for mutually reinforcing resistance development. Alarmingly, most of the antibacterial drugs analysed showed a growing resistance to at least one of the analysed pathogens. In most cases, the best treatment option is threatened by increasing bacterial resistance. We also identified several differences between current bacterial resistance data and therapeutic guidelines. In aggregate, our findings support irrational prescribing behaviour and underscore the urgent need for improved prescribing practices to counter rising bacterial resistance in Germany. Moreover, therapeutic guidelines for bacterial infections, the "holy grail" of pharmacotherapy, must be updated more frequently.

Antimicrobial susceptibility of gram-negative strains isolated from bloodstream infections in China: Results from the study for monitoring antimicrobial resistance trends (SMART) 2018-2020

The study aims were to present in vitro susceptibilities of clinical isolates from Gram-negative bacteria bloodstream infections (GNBSI) collected in China. GNBSI isolates were collected from 18 tertiary hospitals in 7 regions of China from 2018 to 2020. Minimum inhibitory concentrations were assessed using a Trek Diagnostic System. Susceptibility was determined using CLSI broth microdilution, and breakpoints were interpreted using CLSI M100 (2021). A total of 1,815 GNBSI strains were collected, with E. coli (42.4%) and Klebsiella pneumoniae (28.6%) being the most prevalent species, followed by P. aeruginosa (6.7%). Susceptibility analyses revealed low susceptibilities (<40%) of ESBL-producing E. coli and K. pneumonia to third-/fourth-generation cephalosporins, monobactamases, and fluoroquinolones. High susceptibilities to colistin (95.0%) and amikacin (81.3%) were found for K. pneumoniae, while Acinetobacter baumannii exhibited a high susceptibility (99.2%) to colistin but a low susceptibility to other antimicrobials (<27.5%). Isolates from ICUs displayed lower drug susceptibility rates of K. pneumoniae and A. baumannii than isolates from non-ICUs (all P < 0.05). Carbapenem-resistant and ESBL-producing K. pneumoniae detection was different across regions (both P < 0.05). E. coli and K. pneumoniae were major contributors to GNBSI, while A. baumannii exhibited severe drug resistance in isolates obtained from ICU departments.

Society of Critical Care Medicine 2024 Guidelines on Adult ICU Design

RATIONALE

Advances in technology, infection control challenges-as with the COVID-19 pandemic-and evolutions in patient- and family-centered care highlight ideal aspects of ICU design and opportunities for enhancement.

OBJECTIVES

To provide evidence-based recommendations for clinicians, administrators, and healthcare architects to optimize design strategies in new or renovation projects.

PANEL DESIGN

A guidelines panel of 27 members with experience in ICU design met virtually from the panel's inception in 2019 to 2024. The panel represented clinical professionals, architects, engineers, and clinician methodologists with expertise in developing evidence-based clinical practice guidelines. A formal conflict of interest policy was followed throughout the guidelines-development process.

METHODS

Embase, Medline, CINAHL, Central, and Proquest were searched from database inception to September 2023. The Grading of Recommendations Assessment, Development, and Evaluation approach was used to determine certainty in the evidence and to formulate recommendations, suggestions, and practice statements for each Population, Intervention, Control, and Outcomes (PICO) question based on quality of evidence and panel consensus. Recommendations were provided when evidence was actionable; suggestions, when evidence was equivocal; and practice statements when the benefits of the intervention appeared to outweigh the risks, but direct evidence to support the intervention did not exist.

RESULTS

The ICU Guidelines panel issued 17 recommendations based on 15 PICO questions relating to ICU architecture and design. The panel strongly recommends high-visibility ICU layouts, windows and natural lighting in all patient rooms to enhance sleep and recovery. The panel suggests integrated staff break/respite spaces, advanced infection prevention features, and flexible surge capacity. Because of insufficient evidence, the panel could not make a recommendation around in-room supplies, decentralized charting, and advanced heating, ventilation, and air conditioning systems.

CONCLUSIONS

This ICU design guidelines is intended to provide expert guidance for clinicians, administrators, and healthcare architects considering erecting a new ICU or revising an existing structure.

Targeting Acinetobacter baumannii resistance-nodulation-division efflux pump transcriptional regulators to combat antimicrobial resistance

Regulatory elements controlling gene expression fine-tune bacterial responses to environmental cues, including antimicrobials, to optimize survival. Acinetobacter baumannii, a pathogen notorious for antimicrobial resistance, relies on efficient efflux systems. Though the role of efflux systems in antibiotic expulsion are well recognized, the regulatory mechanisms controlling their expression remain understudied. This review explores the current understanding of these regulators, aiming to inspire strategies to combat bacterial resistance and improve therapeutic outcomes.

The Evolution of Antimicrobial Resistance in Acinetobacter baumannii and New Strategies to Fight It

Acinetobacter baumannii is considered one of the prioritized ESKAPE microorganisms for the research and development of novel treatments by the World Health Organization, especially because of its remarkable persistence and drug resistance. In this review, we describe how this can be acquired by the enzymatic degradation of antibiotics, target site modification, altered membrane permeability, multidrug efflux pumps, and their ability to form biofilms. Also, the evolution of drug resistance in A. baumannii, which is mainly driven by mobile genetic elements, is reported, with particular reference to plasmid-associated resistance, resistance islands, and insertion sequences. Finally, an overview of existing, new, and alternative therapies is provided.

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.

Emergence of extensively-drug-resistant hypervirulent Acinetobacter baumannii isolated from patients with bacteraemia: bacterial phenotype and virulence analysis

OBJECTIVES

Individuals infected with extensively-drug-resistant (XDR) Acinetobacter baumannii are difficult to cure and have a high mortality rate. This study compared the genomic and phenotypic differences between XDR and non-multi-drug-resistant (MDR) A. baumannii, and further characterized hypervirulent XDR A. baumannii.

METHODS

In total, 1403 acinetobacter isolates were collected from patients with bacteraemia between 1997 and 2015. Antimicrobial susceptibility tests were performed to categorize isolates into non-MDR, MDR and XDR groups. The presence of selected virulence-associated genes was determined by polymerase chain reaction. Bacterial phenotypes, including iron acquisition, biofilm formation, capsule production, and virulence to larvae and mice, were determined.

RESULTS

Multi-locus sequence typing revealed a high prevalence of sequence type (ST) 2 (81.6%) and ST129 (18.4%) among 49 XDR isolates, and the STs of 18 non-MDR isolates were more diverse. Virulence-associated phenotypic assays showed that XDR isolates had higher iron acquisition ability, greater capsule production, and virulence to Galleria mellonella larvae. However, their ability to form biofilm was lower compared with that of non-MDR isolates. XDR isolates were more likely to have virulence genes (tonB, hemO, abaI and ptk), while non-MDR isolates were more likely to have pld and ompA genes. Twenty-one XDR isolates that had a <20% larvae survival rate after 7 days post-infection were defined as hypervirulent XDR isolates. Among them, isolates 1677 (ST129) and 929-1 (ST2) caused the death of all infected mice within 2 days.

CONCLUSION

Some subpopulations of highly-drug-resistant ST2 isolates exhibit high virulence. As such, it is of utmost importance to continue monitoring the spread of hypervirulent XDR A. baumannii isolates.

Prevalence and molecular characterization of carbapenem-resistant Enterobacterales in patients from a public referral hospital in a non-metropolitan region of Brazil during and post the SARS-CoV-2 pandemic

Antimicrobial resistance (AMR) poses a global threat, with carbapenem-resistant Enterobacterales (CRE) representing a significant concern due to limited therapeutic options. This study investigated the prevalence of carbapenemase genes in CRE strains isolated from tracheal aspirates of patients at a Brazilian university hospital between January 2020 and August 2023. Bacterial identification was conducted using MALDI-TOF, while carbapenemase genes were detected by qPCR. Demographic and clinical data were collected, and univariate analysis was performed using the chi-square test (p < 0.05). Variables with p ≤ 0.10 were further investigated using the chi-square test for linear trend, along with stratified analysis. Out of 1,133 samples, 111 (9.79%) showed CRE growth, with 46 isolates included in the final sample, predominantly comprising Klebsiella pneumoniae (65.21%) and Serratia marcescens (19.57%). The blaKPC gene was prevalent (78.26%), while blaNDM was detected in 21.74% of cases. The identified population was predominantly male (67.39%), elderly (69.57%), white (56.52%), unmarried (63.04%), and had a low level of education (56.52%). Most patients (69.57%) were in the intensive care unit and remained hospitalized for more than 30 days (76.08%). There was a significant inverse trend between Klebsiella pneumoniae and age (p = 0.045), as well as a direct linear trend between blaNDM and the annual increase in COVID-19 cases in Brazil (p = 0.050). A high probability of finding non-Klebsiella pneumoniae bacteria was observed in patients with prolonged hospital stays, independent of COVID-19 (p = 0.006) and the type of resistance genes (p = 0.020). The persistent prevalence of CRE, especially with blaKPC, underscores the urgency of effective control measures.

Recent updates in treating carbapenem-resistant infections in patients with hematological malignancies

INTRODUCTION

Patients with hematological malignancies (PHMs) are at increased risk for infections caused by carbapenem-resistant organisms (CROs) due to frequent exposure to broad-spectrum antibiotics and prolonged hospital stays. These infections result in high mortality and morbidity rates along with delays in chemotherapy, longer hospitalizations, and increased health care costs.

AREAS COVERED

Treatment alternatives for CRO infections in PHMs.

EXPERT OPINION

The best available treatment option for KPC and OXA-48 producers is ceftazidime/avibactam. Imipenem/cilastatin/relebactam and meropenem/vaborbactam remain as the alternative options. They can also be used as salvage therapy in KPC-positive Enterobacterales infections resistant to ceftazidime/avibactam, if in vitro susceptibility is shown. Treatment of metallo-β-lactamase producers is an unmet need. Ceftazidime/avibactam plus aztreonam or aztreonam/avibactam seems to be the most reliable option for metallo-β-lactamase producers. As a first-line option for carbapenem-resistant Pseudomonas aeruginosa infections, ceftolozane/tazobactam is preferable and ceftazidime/avibactam and imipenem/cilastatin/relebactam constitute alternative regimens. Although sulbactam/durlobactam is the most reliable option against carbapenem-resistant Acinetobacter baumannii infections, its utility as monotherapy and in PHMs is not yet known. Cefiderocol can be selected as a 'last-resort' option for CRO infections. New risk score models supported by artificial intelligence algorithms can be used to predict the exact risk of infections in previously colonized patients.

Outcomes of adult patients with multidrug-resistant Acinetobacter baumannii ventilator-associated pneumonia treated with monotherapy versus combination therapy in a tertiary hospital

We compared clinical outcomes of patients who received monotherapy and combination therapy for treatment of MDR A. baumannii VAP. 170 patients were included. Vasopressor use and mortality rate were higher for combination therapy (69.3% versus 28.6%, p=0.024; 67.5% versus 14.3%, p=0.007; respectively). Majority received polymyxin B-based combination therapy, with higher mortality than those without polymyxin B (80.2% versus 19.8%, p=0.043). After adjusting for vasopressor use, monotherapy, dual combination, and triple combination therapy were not associated with mortality (aHR 0.24, 95% CI 0.03 to 1.79, p=0.169; aHR 1.26, 95% CI 0.79 to 2.00, p=0.367; aHR 0.93, 95% CI 0.57 to 1.49, p=0.744; respectively). There was no difference in adverse effects and length of stay between the two groups. Mortality from MDR A. baumannii VAP was high and not associated with monotherapy or combination therapy after adjustment for vasopressor use. Antibiotic regimens other than those containing polymyxin are urgently needed for the treatment of these infections.

Optimizing Treatment Strategies for Carbapenem-Resistant Acinetobacter Baumannii-Associated Pneumonia: A Multicenter Study in Chinese Hospitals

Purpose

To evaluate the clinical outcomes and safety of tigecycline (TGC) plus cefoperazone/sulbactam (CPS) or TGC monotherapy in patients with hospital-acquired pneumonia (HAP) caused by Carbapenem-Resistant Acinetobacter baumannii (CRAB).

Methods

This was a retrospective analysis of multicenter data from 62 Chinese hospitals with CRAB HAP. Risk factors for receiving TGC with CPS therapy and predictors of mortality were assessed using multivariate logistic and Cox regression analyses, respectively. Propensity score matching (PSM) evaluated the efficacy and safety of antimicrobial regimens.

Results

A total of the 180 patients were included, with 95 receiving TGC monotherapy and 85 receiving combination therapy. Multivariate logistic regression analysis revealed that older age (P = 0.011), and intensive care unit (ICU) admission (P = 0.007) were significant risk factors for combination therapy. Multivariate Cox regression demonstrated that combination therapy was associated with a significantly higher risk of 90-day mortality (P = 0.031). Patients in the standard-dose TGC (SDT) plus CPS subgroup had significantly higher rates of SOFA scores ≥ 7 (P = 0.009) and MV used (P = 0.028), as well as higher 30-/90-day mortality compared to high-dose TGC (HDT) plus CPS group. TGC plus CPS significantly reduced CRP levels (P = 0.009), while the variations in ALT, TBIL, Cr, Hb, and PLT levels did not differ between different antimicrobial regimens after PSM.

Conclusion

HDT and CPS combination therapy was more effective in patients with advanced age and more severe condition. Safety profiles of different antimicrobial regimens were similar with liver, kidneys, and coagulation functions.

Understanding the mechanisms of antimicrobial resistance and potential therapeutic approaches against the Gram-negative pathogen Acinetobacter baumannii

Globally, the emergence of anti-microbial resistance in pathogens has become a serious threat to human health and well-being. Infections caused by drug-resistant microorganisms in hospitals are associated with increased morbidity, mortality, and healthcare costs. Acinetobacter baumannii is a Gram-negative bacterium belonging to the ESKAPE group and is widely associated with nosocomial infections. It persists in hospitals and survives antibiotic treatment, prompting acute infections such as urinary tract infections, pneumonia, bacteremia, meningitis, and wound-related infections. An innovation void in drug discovery and the lack of new therapeutic measures against A. baumannii continue to afflict infection control against the rising drug-resistant cases. The emergence of drug-resistant A. baumannii strains has also led to the incessant collapse of newly discovered antibiotics. Therefore exploring novel strategies is requisite to give impetus to A. baumannii drug discovery. The present review discusses the bacterial research community's efforts in the field of A. baumannii, focusing on the strategies adapted to identify potent scaffolds and novel targets to bolster and diversify the chemical space available for drug discovery. Firstly, we have discussed existing chemotherapy and various anti-microbial resistance mechanisms in A. baumannii bacterial strains. Next, we elaborate on multidisciplinary approaches and strategies that may be the way forward to combat the current menace caused by the drug-resistant A. baumannii strains. The review highlights the recent advances in drug discovery, including combinational therapy, high-throughput screening, drug repurposing, nanotechnology, and anti-microbial peptides, which are imperative tools to fight bacterial pathogens in the future.

Survival and virulence of Acinetobacter baumannii in microbial mixtures

Acinetobacter species such as A. venetianus and A. guillouiae have been studied for various biotechnology applications, including bioremediation of recalcitrant and harmful environmental contaminants, as well as bioengineering of enzymes and diagnostic materials. Bacteria used in biotechnology are often combined with other microorganisms in mixtures to formulate efficacious commercial products. However, if the mixture contained a closely related Acinetobacter pathogen such as A. baumannii (Ab), it remains unclear whether the survival and virulence of Ab would be masked or augmented. This uncertainty poses a challenge in ensuring the safety of such biotechnology products, since Ab is one of the most significant pathogens for both hospital and community -acquired infections. This research aimed to investigate the growth and virulence of Ab within a mixture of 11 bacterial species formulated as a mock microbial mixture (MM). Growth challenges with environmental stressors (i.e., temperature, pH, sodium, iron, and antibiotics) revealed that Ab could thrive under diverse conditions except in the presence of ciprofloxacin. When cultured alone, Ab exhibited significantly more growth in the presence of almost all the environmental stressors than when it was co-incubated with the MM. During the exposure of A549 lung epithelial cells to the MM, Ab growth was stimulated compared to that in standard mammalian culture media. Cytotoxicity caused by Ab was suppressed in the presence of the MM. Lymphocytes were significantly reduced in mice exposed to Ab with or without MM via intravenous injection. The levels of the splenic cytokines IL-1α, IL-1β, MCP-1, and MIP-1α were significantly reduced 24 h after exposure to Ab + MM. This study demonstrated that the presence of the MM marginally but significantly reduced the growth and virulence of Ab, which has implications for the safety of mixtures of microorganisms for biotechnological applications. Furthermore, these findings expand our understanding of the virulence of Ab during host-pathogen interactions.

Evaluation of the in vitro activity of ampicillin-sulbactam and cefoperazone-sulbactam against A. Baumannii by the broth disk elution test

To evaluate the in vitro activity of ampicillin-sulbactam and cefoperazone-sulbactam against A. baumannii using the broth disk elution testing, a total of 150 A. baumannii isolates were collected from across China between January 2019 and January 2021, including 51 carbapenem-susceptible and 99 carbapenem-resistant isolates. Broth disk elution (BDE) and the broth microdilution (BMD) method were performed for all strains. The concentration range of the BDE was 10/10 µg/mL, 20/20 µg/mL, and 30/30 µg/mL for ampicillin-sulbactam, and 37.5/15 µg/mL, 75/30 µg/mL, 112.5/45 µg/mL, and 150/60 µg/mL for cefoperazone-sulbactam, respectively. Compared with BMD, the BDE results of ampicillin-sulbactam and cefoperazone-sulbactam showed a categorical agreement of 83.3% (125/150) and 95.3% (143/150), with minor errors of 16.7% (25/150) and 4.7% (7/150), respectively. No major error or very major errors were detected. The sensitivity differences by BDE of carbapenem-resistant A. baumannii (CRAb) to different concentrations of ampicillin-sulbactam showed statistically significant (p < 0.017), while those to cefoperazone-sulbactam at 37.5/15 µg/mL, 75/30 µg/mL, and 112.5/45 µg/mL were significant (p < 0.008). However, no significant difference in sensitivity was observed between 112.5/45 µg/mL and 150/60 µg/mL (p > 0.008). In conclusion, the BDE is a reliable and convenient method to detect the in vitro activity of cefoperazone-sulbactam against A. baumannii, and the results could serve as a clinical reference value when deciding whether or not to use high-dose sulbactam for the treatment of A. baumannii infections.

Molecular typing of reduced susceptibility of Acinetobacter calcoaceticus-baumannii complex to Chlorhexidine in Turkey by pulsed-field gel electrophoresis

Introduction. The global spread of Acinetobacter spp., particularly the Acinetobacter calcoaceticusbaumannii (ACB) complex, has led to its recognition as a significant pathogen by the World Health Organization (WHO). The increasing resistance of the ACB complex to multiple antibiotics presents a challenge for treatment, necessitating accurate antibiotic susceptibility profiling after isolation.Hypothesis or gap statement. There is limited understanding of the antimicrobial resistance and chlorhexidine, a biocide, susceptibility profiles of ACB complex strains, especially in clinical settings in Turkey.Aim. This study aimed to identify ACB complex strains recovered from various clinical specimens at Hacettepe University Hospitals in Ankara, Turkey, in 2019, and to assess identification, their antibiotic and chlorhexidine susceptibility profiles, and genomic relatedness.Methodology. Eighty-two ACB complex strains were identified using MALDI-TOF MS. Susceptibility testing to 12 antibiotics was conducted using the disc diffusion method, and colistin, chlorhexidine susceptibility was assessed using the broth microdilution technique, following the latest EUCAST and CLSI guidelines. ACB complex members with reduced chlorhexidine sensitivity were further analyzed by pulsed-field gel electrophoresis (PFGE) for bacterial typing.Results. Among the isolates, 1.2% were multidrug-resistant (MDR), 73.2% were extensively drug-resistant (XDR), and 12.2% were pandrug-resistant (PDR). Carbapenem resistance was found in 86.7% of MDR, PDR, and XDR strains. Colistin resistance was observed in 15.8% of isolates, and 18.2% exhibited decreased susceptibility to chlorhexidine. PFGE revealed seven different clones among strains with reduced chlorhexidine sensitivity, indicating vertical transmission within the hospital.Conclusion. This study highlights the reduced susceptibility to chlorhexidine in ACB complex members and provides epidemiological insights into their spread. The findings underscore the importance of screening for antimicrobial resistance and biocide susceptibility profiles to effectively manage healthcare-associated infections.

Treatment of infections caused by carbapenem-resistant Acinetobacter baumannii

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

A multiplex RPA coupled with CRISPR-Cas12a system for rapid and cost-effective identification of carbapenem-resistant Acinetobacter baumannii

Background

Carbapenem-resistant Acinetobacter baumannii (CRAB) poses a severe nosocomial threat, prompting a need for efficient detection methods. Traditional approaches, such as bacterial culture and PCR, are time-consuming and cumbersome. The CRISPR-based gene editing system offered a potential approach for point-of-care testing of CRAB.

Methods

We integrated recombinase polymerase amplification (RPA) and CRISPR-Cas12a system to swiftly diagnose CRAB-associated genes, OXA-51 and OXA-23. This multiplex RPA-CRISPR-Cas12a system eliminates bulky instruments, ensuring a simplified UV lamp-based outcome interpretation.

Results

Operating at 37°C to 40°C, the entire process achieves CRAB diagnosis within 90 minutes. Detection limits for OXA-51 and OXA-23 genes are 1.3 × 10-6 ng/μL, exhibiting exclusive CRAB detection without cross-reactivity to common pathogens. Notably, the platform shows 100% concordance with PCR when testing 30 clinical Acinetobacter baumannii strains.

Conclusion

In conclusion, our multiplex RPA coupled with the CRISPR-Cas12a system provides a fast and sensitive CRAB detection method, overcoming limitations of traditional approaches and holding promise for efficient point-of-care testing.

Anti-Acinetobacter Baumannii single-chain variable fragments provide therapeutic efficacy in an immunocompromised mouse pneumonia model

BACKGROUND

The emergence of carbapenem-resistant and extensively drug-resistant (XDR) Acinetobacter baumannii as well as inadequate effective antibiotics calls for an urgent effort to find new antibacterial agents. The therapeutic efficacy of two human scFvs, EB211 and EB279, showing growth inhibitory activity against A. baumannii in vitro, was investigated in immunocompromised mice with A. baumannii pneumonia.

RESULTS

The data revealed that infected mice treated with EB211, EB279, and a combination of the two scFvs showed better survival, reduced bacterial load in the lungs, and no marked pathological abnormalities in the kidneys, liver, and lungs when compared to the control groups receiving normal saline or an irrelevant scFv.

CONCLUSIONS

The results from this study suggest that the scFvs with direct growth inhibitory activity could offer promising results in the treatment of pneumonia caused by XDR A. baumannii.

In vivo efficacy and PK/PD analyses of zifanocycline (KBP-7072), an aminomethylcycline antibiotic, against Acinetobacter baumannii in a neutropenic murine thigh infection model

INTRODUCTION

Zifanocycline (KBP-7072) is a novel aminomethylcycline antibiotic with a broad spectrum of antibacterial activity. This study determined the pharmacokinetic (PK) and pharmacodynamic (PD) characteristics of zifanocycline in mice and the optimal PK/PD index for efficacy against Acinetobacter baumannii in a neutropenic murine thigh infection model.

METHODS

Zifanocycline PK properties were characterized in plasma after single-dose subcutaneous injection in healthy mice at doses of 1, 4, 16, 64, and 256 mg/kg. PK/PD analyses were performed with zifanocycline against 8 clinical A. baumannii isolates in a neutropenic murine thigh infection model.

RESULTS

Plasma total and free drug Cmax, AUC0-inf, and AUC0-24 increased with dose, where Cmax of total drug was 0.12-25.2 mg/L, AUC0-inf was 1.13-234 h*mg/L, AUC0-24 was 1.09-225 h*mg/L, and free drug Cmax was 0.03-5.68 mg/L, AUC0-inf was 0.25-52.6 h*mg/L, and AUC0-24 was 0.25-50.5 h*mg/L. MICs of zifanocycline against A. baumannii ranged from 0.06 to 0.5 mg/L, with significant activity against all 8 strains. Average daily doses of zifanocycline to achieve a static, 1-log10 kill, and 2-log10 kill effect were projected to be 6.92, 9.63, and 13.22 mg/kg, and the mean fAUC/MIC ratios were 6.91, 9.10, and 12.60, respectively. AUC/MIC was the optimal PK/PD index of zifanocycline against A. baumannii.

CONCLUSION

The in vivo efficacy results and PK/PD analyses support the design of optimal dosing regimens in clinical studies and assist with determining clinical breakpoints for zifanocycline.

The efficacy of mesenchymal stem cell treatment and colistin-fosfomycin combination on colistin-resistant Acinetobacter baumannii sepsis model

INTRODUCTION

This study examines the role of mesenchymal stem cells (MSCs) in an experimental sepsis model developed with colistin-resistant Acinetobacter baumannii (CRAB).

MATERIALS AND METHODS

BALB-c mice were divided into treatment groups (MSC, MSC + colistin (C)-fosfomycin (F), and C-F and control groups (positive and negative)). CRAB was administered to mice through intraperitoneal injection. Three hours later, C, F, and MSC were given intraperitoneally to the treatment groups. Colistin administration was repeated every 12 h, F administration was done every 4 h, and the second dose of MSC was administered after 48 h. Mice were sacrificed at 24 and 72 h. The bacterial load was determined as colony-forming units per gram (cfu/g). Histopathological examination was conducted on the left lung, liver, and both kidneys. IL-6 and C-reactive protein (CRP) levels in mouse sera were determined by enzyme-linked immunosorbent assay.

RESULTS

Among the treatment groups, the C-F group had the lowest colony count in the lung (1.24 ± 1.66 cfu/g) and liver (1.03 ± 1.08 cfu/g). The highest bacterial clearance was observed at 72 h compared to 24 h in the MSC-treated groups (p = 0.008). The MSC + C-F group showed the lowest histopathological score in the liver and kidney (p = 0.009). In the negative control group, the IL-6 level at the 24th hour was the lowest (p < 0.001). Among the treatment groups, the CRP level was the lowest in the MSC + C-F group at 24 and 72 h.

CONCLUSION

In a CRAB sepsis model, adding MSCs to a colistin-fosfomycin treatment may be beneficial in terms of reducing bacterial loads and preventing histopathological damage.

Carbapenem-Resistant Acinetobacter baumannii Bloodstream Infection in a Ghanaian Patient with Unilateral Diaphragmatic Eventration and HIV Type 1 Infection

Carbapenem-resistant Acinetobacter baumannii infection is a critically prioritized pathogen by the World Health Organization and a cause for growing concern due to increased mortality among hospitalised patients. Phrenic nerve palsy is a rare complication of herpes zoster infection of the C3, C4, and C5 nerve roots. We present a case of bloodstream carbapenem-resistant A. baumannii infection in a Ghanaian patient with HIV type 1 infection and multiple risk factors, including unilateral diaphragmatic eventration with compression atelectasis likely secondary to phrenic nerve palsy due to herpes zoster infection, consequently leading to recurrent hospital and ICU admission. In this case, we emphasize the need for clinicians in LMICs to be aware of CRAB, in order to advocate for the availability of evidence-based medicines in resource-limited settings for appropriate treatment. In addition, we illustrate the importance of a high index of suspicion for infection with carbapenem-resistant organisms such as A. baumannii and highlight a rare and severe complication of herpes zoster infection in the form of phrenic nerve palsy and consequent diaphragmatic eventration.

Imipenem/funobactam (formerly XNW4107) in vivo pharmacodynamics against serine carbapenemase-producing Gram-negative bacteria: a novel modelling approach for time-dependent killing

BACKGROUND

Imipenem/funobactam (formerly XNW4107) is a novel β-lactam/β-lactamase inhibitor with activity against MDR Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacterales strains. Using a neutropenic murine thigh infection model, we aimed to determine the pharmacokinetic/pharmacodynamic (PK/PD) index, relative to funobactam exposure, that correlated most closely with the in vivo efficacy of imipenem/funobactam combination and the magnitude of index required for efficacy against serine carbapenemase-producing clinical strains.

METHODS

Dose-fractionation was conducted against three strains. Imipenem human-simulated regimen (HSR, 500 mg q6h 1 h infusion) efficacy in combination with escalating funobactam exposures against seven A. baumannii, four P. aeruginosa and four Klebsiella pneumoniae (imipenem/funobactam MICs 0.25-16 mg/L) was assessed as 24 h change in log10cfu/thigh.

RESULTS

Increased funobactam fractionation enhanced efficacy, indicating time-dependent killing. Changes in log10cfu/thigh versus %fT > MIC were poorly predictive of efficacy; bactericidal activity was observed at %fT > MIC = 0%. Across different threshold plasma funobactam concentrations (CTs), %fT > CT(1 mg/L) had the highest correlation with efficacy. Normalizing the %fT > CT = 1 mg/L index to the respective isolate imipenem/funobactam MIC ([%fT > CT]/MIC) allowed integration of the isolate's susceptibility, which further enhanced the correlation. Median (%fT > CT[1 mg/L])/MIC values associated with 1-log reductions were 9.82 and 9.90 for A. baumannii and P. aeruginosa, respectively. Median (%fT > CT[1 mg/L])/MIC associated with stasis was 55.73 for K. pneumoniae. Imipenem/funobactam 500/250 mg q6h 1 h infusion HSR produced >1-log kill against 6/7 A. baumannii, 4/4 P. aeruginosa and stasis against 4/4 K. pneumoniae.

CONCLUSIONS

Imipenem/funobactam showed potent in vivo efficacy against serine carbapenemase-producers. The novel PK/PD index (%fT > CT)/MIC appeared to best describe in vivo activity.

Dissemination of ArmA- and OXA-23-co-producing Acinetobacter baumannii Global Clone 2 in Switzerland, 2020-2021

Following the observation of an increased number of isolation of OXA-23- and ArmA-producing Acinetobacter baumannii at the national level, our aim was to evaluate whether some given clone(s) might actually be spreading and/or emerging in Switzerland. To evaluate this possibility, our study investigated and characterized all A. baumannii isolates harboring both the bla_OXA-23 and armA genes that had been collected at the Swiss National Reference Center for Emerging Antibiotic Resistance (NARA) from 2020 to 2021. Most isolates were obtained from infections rather than colonization with the majority being obtained from respiratory specimens. Pulsed-field gel electrophoresis (PFGE) analysis of 56 isolates identified nine profiles. Then, whole-genome sequencing that was performed on a subset of 11 isolates including at least one representative isolate of each PFGE profile identified three STs; one each of ST25 and ST1902, and nine ST2 (a member of Global Clone 2 (GC-2). The bla_OXA-23 gene was always found embedded within Tn2006 structures, as commonly described with GC-2 (ST2) isolates. Susceptibility testing showed that most of those isolates, despite being highly resistant to all carbapenems and all aminoglycosides, remained susceptible to colistin (94.6%), sulbactam-durlobactam (87.5%), and cefiderocol (83.9% or 91.1% according to EUCAST or CLSI breakpoints, respectively). Overall, this study identified that the A. baumannii co-producing OXA-23 and ArmA are increasing in incidence in Switzerland, largely due to the dissemination of the high-risk GC-2. This highlights the importance of the monitoring of such MDR A. baumannii strains, in order to contribute to reduce their potential further spread.

The Prevalence of Multidrug-Resistant Acinetobacter baumannii and Its Vaccination Status among Healthcare Providers

There is growing concern among healthcare providers worldwide regarding the prevalence of multidrug-resistant Acinetobacter baumannii (A. baumannii). Some of the worst hospital-acquired infections, often in intensive care units (ICUs), are caused by this bacterial pathogen. In recent years, the rise in multidrug-resistant A. baumannii has been linked to the overuse of antimicrobial drugs and the lack of adequate infection control measures. Infections caused by this bacterial pathogen are the result of prolonged hospitalization and ICU stays, and they are associated with increased morbidity and mortality. This review outlines the epidemiology, risk factors, and antimicrobial resistance associated with A. baumannii in various countries, with a special focus on the Kingdom of Saudi Arabia. In response to the growing concern regarding this drug-resistant bacteria, fundamental information about its pathology has been incorporated into the development of vaccines. Although these vaccines have been successful in animal models, their effectiveness in humans remains unproven. The review will discuss the development of A. baumannii vaccines, potential related obstacles, and efforts to find an effective strategy against this pathogen.

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.

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.

Enhanced bacterial killing with a combination of sulbactam/minocycline against dual carbapenemase-producing Acinetobacter baumannii

Carbapenem-resistant Acinetobacter baumannii (CRAB) is often difficult to treat. Considering the current circumstances, there is an unquestionable need for new therapeutic options to treat CRAB infections. In the present study, the synergistic activity of sulbactam-based combination was determined against genetically characterized CRAB isolates. Non-duplicate CRAB isolates (n = 150) recovered from blood culture and endotracheal aspirates were included in this study. The minimum inhibitory concentrations (MICs) of tetracyclines (minocycline, tigecycline, eravacycline) and their comparators (meropenem, sulbactam, cefoperazone/sulbactam, ceftazidime/avibactam, and colistin) were determined using the microbroth dilution method. Six isolates were tested for the synergistic activity of various sulbactam-based combinations using time-kill experiments. Tigecycline and minocycline showed a wide spread of MICs with most isolates in the range of 1 to 16 mg/L. The MIC₉₀ of eravacycline (0.5 mg/L) was four dilutions lower than that of tigecycline (8 mg/L). Minocycline with sulbactam was the most active dual combination against OXA-23 like (n = 2) and NDM with OXA-23 like producers (n = 1), which resulted in ≥ 2 log₁₀ kill. The combination of ceftazidime-avibactam with sulbactam showed ≥ 3 log₁₀ kill against all the three tested OXA-23 like producing CRAB isolates, but showed no activity against dual carbapenemase producers. Sulbactam with meropenem showed ≥ 2 log₁₀ kill against one OXA-23 like producing CRAB isolate. The findings suggest that sulbactam-based combination may confer therapeutic benefits against CRAB infections.

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.

Inhibitor Assessment against the LpxC Enzyme of Antibiotic-resistant Acinetobacter baumannii Using Virtual Screening, Dynamics Simulation, and in vitro Assays

BACKGROUND

Bacterial resistance is currently a significant global public health problem. Acinetobacter baumannii has been ranked in the list of the World Health Organization as the most critical and priority pathogen for which new antibiotics are urgently needed. In this context, computational methods play a central role in the modern drug discovery process. The purpose of the current study was to identify new potential therapeutic molecules to neutralize MDR A. baumannii bacteria.

METHODS

A total of 3686 proteins retrieved from the A. baumannii proteome were subjected to subtractive proteomic analysis to narrow down the spectrum of drug targets. The SWISS-MODEL server was used to perform a 3D homology model of the selected target protein. The SAVES server was used to evaluate the overall quality of the model. A dataset of 74500 analogues retrieved from the PubChem database was docked with LpxC using the AutoDock software.

RESULTS

In this study, we predicted a putative new inhibitor for the Lpxc enzyme of A. baumannii. The LpxC enzyme was selected as the most appropriate drug target for A. baumannii. According to the virtual screening results, N-[(2S)-3-amino-1-(hydroxyamino)-1-oxopropan-2-yl]-4-(4-bromophenyl) benzamide (CS250) could be a promising drug candidate targeting the LpxC enzyme. This molecule shows polar interactions with six amino acids and non-polar interactions with eight other residues. In vitro experimental validation was performed through the inhibition assay.

CONCLUSION

To the best of our knowledge, this is the first study that suggests CS250 as a promising inhibitory molecule that can be exploited to target this gram-negative pathogen.

Acute Kidney Injury Among Patients with Multi-Drug Resistant Infection: A Study from Jordan

Background

Acute kidney injury (AKI) is a well-known complication for hospitalized patients. Sepsis and various infections play a significant role in increasing the incidence of AKI. The present study evaluated the risk for Multidrug-resistant (MDR) infections and its effect on the incidence of AKI, hospitalization, need for dialysis, and mortality.

Methods

In a retrospective study design, data were collected from all adult patients with a positive multi-drug resistant culture who were admitted to King Abdullah University Hospital (KAUH). Records of 436 patients were reviewed between January 2017 - December 2018 with at least one year of follow-up.

Results

The mean age was 57.3 years (SD± 23.1), and 58.5% were males. The most common source of positive cultures was sputum, with 50% positive cultures. The incidence of AKI was 59.2%. The most isolated microorganism was Acinetobacter baumannii (76.8%), followed by Pseudomonas aeruginosa (14.9%).On multivariate analysis, age (OR 1.1, 95% CI 1.1-1.2, P=0.001), HTN (OR 1.8, 95% CI 1.0-3.3, P=0.02), DM (OR 1.1, 95% CI 0.6-1.9, P=0.69) and the use of Foley catheter on chronic bases (OR 4.3, 95% CI 2.6-6.8, P<0.0001) were strong predictors of AKI. Among patients with AKI, 74.4% died compared to 44.4% among non-AKI patients (p<0.001).

Conclusion

In patients with MDR, AKI incidence, hospitalization, and mortality were high. Early detection and addressing the problem may decrease bad outcomes, and health education for reducing antibiotic abuse is needed to lower MDR.

Clinical Outcomes of Eravacycline in Patients Treated Predominately for Carbapenem-Resistant Acinetobacter baumannii

Forty-six patients were treated with eravacycline (ERV) for Acinetobacter baumannii infections, where 69.5% of isolates were carbapenem resistant (CRAB). Infections were primarily pulmonary (58.3%), and most patients received combination therapy (84.4%). The median (IQR) ERV duration was 6.9 days (5.1 to 11.1). Thirty-day mortality was 23.9% in the cohort and 21.9% in CRAB patients. One patient experienced an ERV-possible adverse event. IMPORTANCE Acinetobacter baumannii, particularly when carbapenem resistant (CRAB), is one of the most challenging pathogens in the health care setting. This is complicated by the fact that there is no consensus guideline regarding management of A. baumannii infections. However, the recent Infectious Diseases Society of America guidelines for treatment of resistant Gram-negative infections provided expert recommendations for CRAB management. The panel suggest using minocycline among tetracycline derivatives rather than eravacycline (ERV) until sufficient clinical data are available. Therefore, we present the largest multicenter real-world cohort in patients treated with ERV for A. baumannii, where the majority of isolates were CRAB (69.5%). Our analysis demonstrate that patients treated with ERV-based regimens achieved a 30-day mortality of 23.9% and had a low incidence of ERV-possible adverse events (2.1%). This study is important as it fills the gap in the literature regarding the use of a novel tetracycline (i.e., ERV) in the treatment of this challenging health care infection.

Acinetobacter baumannii: Pathogenesis, virulence factors, novel therapeutic options and mechanisms of resistance to antimicrobial agents with emphasis on tigecycline

WHAT IS KNOWN AND OBJECTIVE

Acinetobacter baumannii is one of the most important nosocomial pathogens with the ability to cause infections such as meningitis, pneumonia, urinary tract, septicaemia and wound infections. A wide range of virulence factors are responsible for pathogenesis and high mortality of A. baumannii including outer membrane proteins, lipopolysaccharide, capsule, phospholipase, nutrient- acquisition systems, efflux pumps, protein secretion systems, quarom sensing and biofilm production. These virulence factors contribute in pathogen survival in stressful conditions and antimicrobial resistance.

COMMENT

According to the World Health Organization (WHO), A. baumannii is one of the most resistant pathogens of ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, A. baumannii, Pseudomonas aeruginosa and Enterobacter spp.). In recent years, resistance to a wide range of antibiotics in A. baumannii has significantly increased and the high emergence of extensively drug resistant (XDR) isolates is challenging. Among therapeutic antibiotics, resistance to tigecycline as a last resort antibiotic has become a global concern. Several mechanisms are involved in tigecycline resistance, the most important of which is RND (Resistance-Nodulation-Division) family efflux pumps overexpression. The development of new therapeutic strategies to confront A. baumannii infections has been very promising in recent years.

WHAT IS NEW AND CONCLUSION

In the present review we highlight microbiological and virulence traits in A. baumannii and peruse the tigecycline resistance mechanisms and novel therapeutic options. Among the novel therapeutic strategies we focus on combination therapy, drug repurposing, novel antibiotics, bacteriophage therapy, antimicrobial peptides (AMPs), human monoclonal antibodies (Hu-mAbs), nanoparticles and gene editing.

Epidemiology, Mechanisms of Resistance and Treatment Algorithm for Infections Due to Carbapenem-Resistant Gram-Negative Bacteria: An Expert Panel Opinion

Antimicrobial resistance represents a serious threat for global health, causing an unacceptable burden in terms of morbidity, mortality and healthcare costs. In particular, in 2017, carbapenem-resistant organisms were listed by the WHO among the group of pathogens for which novel treatment strategies are urgently needed. Fortunately, several drugs and combinations have been introduced in recent years to treat multi-drug-resistant (MDR) bacteria. However, a correct use of these molecules is needed to preserve their efficacy. In the present paper, we will provide an overview on the epidemiology and mechanisms of resistance of the most common MDR Gram-negative bacteria, proposing a treatment algorithm for the management of infections due to carbapenem-resistant bacteria based on the most recent clinical evidence.

Current and Potential Therapeutic Options for Infections Caused by Difficult-to-Treat and Pandrug Resistant Gram-Negative Bacteria in Critically Ill Patients

Carbapenem resistance in Gram-negative bacteria has come into sight as a serious global threat. Carbapenem-resistant Gram-negative pathogens and their main representatives Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa are ranked in the highest priority category for new treatments. The worrisome phenomenon of the recent years is the presence of difficult-to-treat resistance (DTR) and pandrug-resistant (PDR) Gram-negative bacteria, characterized as non-susceptible to all conventional antimicrobial agents. DTR and PDR Gram-negative infections are linked with high mortality and associated with nosocomial infections, mainly in critically ill and ICU patients. Therapeutic options for infections caused by DTR and PDR Gram-negative organisms are extremely limited and are based on case reports and series. Herein, the current available knowledge regarding treatment of DTR and PDR infections is discussed. A focal point of the review focuses on salvage treatment, synergistic combinations (double and triple combinations), as well as increased exposure regimen adapted to the MIC of the pathogen. The most available data regarding novel antimicrobials, including novel β-lactam-β-lactamase inhibitor combinations, cefiderocol, and eravacycline as potential agents against DTR and PDR Gram-negative strains in critically ill patients are thoroughly presented.

Durlobactam in the Treatment of Multidrug-Resistant Acinetobacter baumannii Infections: A Systematic Review

A. baumannii is a frequent cause of difficult-to-treat healthcare-associated infections. The use of a novel beta-lactamase inhibitor, durlobactam, has been proposed against multidrug-resistant A. baumannii. A systematic review of studies assessing the efficacy and safety of durlobactam in the treatment of multidrug-resistant A. baumannii infections was carried out. The study protocol was pre-registered on PROSPERO (CRD42022311723). Published articles on durlobactam were identified through computerized literature searches with the search terms "durlobactam" and "ETX2514" using PubMed. PubMed was searched until 15 February 2022. Articles providing data on the main characteristics of durlobactam and on the efficacy and safety of durlobactam in the treatment of A. baumannii infections were included in this systematic review. Attempt was made to obtain information about unpublished studies. English language restriction was applied. The risk of bias in the included studies was not assessed. Both quantitative and qualitative information were summarized by means of textual descriptions. Thirty studies on durlobactam were identified, published from June 2017 to November 2020. Sixteen studies met the inclusion criteria. Durlobactam is effective against A. baumannii when used in combination with sulbactam. Future clinical trials are needed to confirm the possibility to treat infections caused by multidrug-resistant A. baumannii with this combination.

The Role of Colistin in the Era of New β-Lactam/β-Lactamase Inhibitor Combinations

With the current crisis related to the emergence of carbapenem-resistant Gram-negative bacteria (CR-GNB), classical treatment approaches with so-called “old-fashion antibiotics” are generally unsatisfactory. Newly approved β-lactam/β-lactamase inhibitors (BLBLIs) should be considered as the first-line treatment options for carbapenem-resistant Enterobacterales (CRE) and carbapenem-resistant Pseudomonas aeruginosa (CRPA) infections. However, colistin can be prescribed for uncomplicated lower urinary tract infections caused by CR-GNB by relying on its pharmacokinetic and pharmacodynamic properties. Similarly, colistin can still be regarded as an alternative therapy for infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) until new and effective agents are approved. Using colistin in combination regimens (i.e., including at least two in vitro active agents) can be considered in CRAB infections, and CRE infections with high risk of mortality. In conclusion, new BLBLIs have largely replaced colistin for the treatment of CR-GNB infections. Nevertheless, colistin may be needed for the treatment of CRAB infections and in the setting where the new BLBLIs are currently unavailable. In addition, with the advent of rapid diagnostic methods and novel antimicrobials, the application of personalized medicine has gained significant importance in the treatment of CRE infections.