Multidrug resistance, inappropriate empiric therapy, and hospital mortality in Acinetobacter baumannii pneumonia and sepsis

From Microbial Ecology to Clinical Challenges: The Respiratory Microbiome's Role in Antibiotic Resistance

Antibiotic resistance represents a growing public health threat, with airborne drug-resistant strains being especially alarming due to their ease of transmission and association with severe respiratory infections. The respiratory microbiome plays a pivotal role in maintaining respiratory health, influencing the dynamics of antibiotic resistance among airborne pathogenic microorganisms. In this context, this review proposes the exploration of the complex interplay between the respiratory microbiota and antimicrobial resistance, highlighting the implications of microbiome diversity in health and disease. Moreover, strategies to mitigate antibiotic resistance, including stewardship programs, alternatives to traditional antibiotics, probiotics, microbiota restoration techniques, and nanotechnology-based therapeutic interventions, are critically presented, setting an updated framework of current management options. Therefore, through a better understanding of respiratory microbiome roles in antibiotic resistance, alongside emerging therapeutic strategies, this paper aims to shed light on how the global health challenges posed by multi-drug-resistant pathogens can be addressed.

Using a difficult-to-treat resistance index to gauge imbalance between countries' antibiotic resistance prevalence and access to antibiotics: a scoping review and concept proposal

BACKGROUND

Inferring the impact of antimicrobial resistance on patient outcomes is challenging, given the variability in antibiotic access across countries and over time. By denoting resistance to all highly safe and effective antibiotics, the difficult-to-treat resistance (DTR) definition offers a framework for such assessments globally.

OBJECTIVES

This study aims to conduct a scoping review to understand the international adoption, scalability, and prognostic utility of DTR and enable solutions to incorporate antibiotic access into the DTR framework.

METHODS

Data sources: Data sources included Agricola, Embase, Global Index Medicus, PubMed, Scopus, Web of Science: BIOSIS and Core Collection.

STUDY ELIGIBILITY CRITERIA

Study eligibility criteria included original research publications occurring after January 2018 using the term 'difficult-to-treat resistance' to describe antimicrobial-resistant bacterial isolates demonstrating resistance to all first-line antibiotics (i.e. all β-lactam and fluoroquinolone antibiotics).

ASSESSMENT OF RISK OF BIAS

Assessment of risk of bias included Joanna Briggs Institute critical appraisal tool.

METHODS OF DATA SYNTHESIS

We assessed the overall themes of the included studies and classified them into epidemiological, mortality, or antibiotic effectiveness/efficacy studies. Semiquantitative results among studies evaluating the prevalence of resistant bacterial isolates and mortality were reported. We propose a 'DTR index' (DTRi) that extends beyond gram-negative bacteria and complements DTR by estimating national proportions of bacterial isolates resistant to all first-line antibiotics available specifically in that country.

RESULTS

DTR was utilized in 57 studies spanning 94 countries. The DTR definition was predominantly applied unmodified and retained prognostic utility in 70% of studies. The variability in access to first-line antibiotics and emergence of newer agents across countries and over time influence practical treatment options that cannot be captured by 'fixed' DTR definitions underscoring the value of the proposed DTRi.

CONCLUSIONS

The DTRi could appraise the clinical impact of introducing new agents in a country, identify hot zones of resistance-access imbalance, and optimize resource allocation to improve antibiotic resistance outcomes, especially in under-resourced populations.

Prognostic analysis of elderly patients with pathogenic microorganisms positive for sepsis-associated encephalopathy

Objectives

Sepsis-associated encephalopathy (SAE) has a high incidence and mortality, especially for elderly patients and patients who are positive for pathogenic microbial infection, this study explored the prognostic factors influencing the prognosis of elderly patients with pathogenic microorganisms positive of sepsis-associated encephalopathy.

Methods

Patients with SAE and pathogenic microbiology positive were included in this study from Medical Information Mart for Intensive Care IV (MIMIC IV) database. The main results of this study was analyzed the 28-day mortality rate of patients with pathogenic microorganism positive and SAE by Wilcoxon, Kaplan-Meier curve and other methods.

Results

This study found that older patients with SAE had higher mortality at 28 and 90 days compared with non-older patients with SAE. Klebsiella pneumoniae and Pseudomonas aeruginosa infection, the level of APTT and lactate and SAPS III score were independent risk factors for 28-day mortality in elderly patients with SAE, among them, Klebsiella pneumoniae and Pseudomonas aeruginosa infection had the best sensitivity (0.893; 0.931) in assessing elderly patients with pathogenic microorganisms positive and SAE; the SAPS III score had the highest AUC (0.681) value and specificity (0.761) in assessing elderly patients with pathogenic microorganisms positive and SAE.

Conclusion

The older patients with SAE had a poor prognosis, the elder patients with pathogenic microorganisms positive and SAE with high levels of APTT and lactate and SAPS III score and Klebsiella pneumoniae and Pseudomonas aeruginosa infection should be closely monitored and treated aggressively.

Potentially effective antimicrobial treatment for pneumonia caused by isolates of carbapenem-resistant and extensively drug-resistant Acinetobacter baumannii complex species: what can we expect in the future?

INTRODUCTION

Acinetobacter baumannii complex (Abc) is currently a significant cause of difficult-to-treat pneumonia. Due to the high prevalence rates of carbapenem- and extensively drug-resistant (CR, XDR) phenotypes, limited antibiotic options are available for the effective treatment of pneumonia caused by CR/XDR-Abc.

AREAS COVERED

In vitro susceptibility data, relevant pharmacokinetic profiles (especially the penetration ratios from plasma into epithelial-lining fluid), and pharmacodynamic indices of key antibiotics against CR/XDR-Abc are reviewed.

EXPERT OPINION

Doubling the routine intravenous maintenance dosages of conventional tigecycline (100 mg every 12 h) and minocycline (200 mg every 12 h) might be recommended for the effective treatment of pneumonia caused by CR/XDR-Abc. Nebulized polymyxin E, novel parenteral rifabutin BV100, and new polymyxin derivatives (SPR206, MRX-8, and QPX9003) could be considered supplementary combination options with other antibiotic classes. Regarding other novel antibiotics, the potency of sulbactam-durlobactam (1 g/1 g infused over 3 h every 6 h intravenously) combined with imipenem-cilastatin, and the β-lactamase inhibitor xeruborbactam, is promising. Continuous infusion of full-dose cefiderocol is likely an effective treatment regimen for CR/XDR-Abc pneumonia. Zosurabalpin exhibits potent anti-CR/XDR-Abc activity in vitro, but its practical use in clinical therapy remains to be evaluated. The clinical application of antimicrobial peptides and bacteriophages requires validation.

Challenges of infectious diseases in older adults: From immunosenescence and inflammaging through antibiotic resistance to management strategies

Infectious diseases in older adults present a significant challenge to the healthcare system, marked by increased morbidity, mortality, and rising costs of care. Age-related changes (ARCs) in the immune system, including immunosenescence and inflammaging, contribute to heightened susceptibility to severe infections and reduced vaccine responsiveness. Additionally, alterations in the normal microbial flora due to aging and factors such as antibiotic therapy predispose older individuals to infections and age-related diseases. Changes in body composition also affect the pharmacokinetics and pharmacodynamics of drugs, complicating the management of antibiotics and leading to potential overdoses, adverse drug reactions, or underdoses that foster antibiotic resistance. The inappropriate use of antibiotics has exacerbated the emergence of multidrug-resistant pathogens, posing a critical global concern. This narrative review provides an overview of immunosenescence and inflammaging and focuses on three major infectious diseases affecting older adults: bacterial pneumonia, urinary tract infections, and Clostridium difficile infections. Through this exploration, we aim to highlight the need for targeted approaches in managing infectious diseases in the aging population.

ESKAPE pathogens: antimicrobial resistance, epidemiology, clinical impact and therapeutics

The rise of antibiotic resistance and a dwindling antimicrobial pipeline have been recognized as emerging threats to public health. The ESKAPE pathogens - Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp. - were initially identified as critical multidrug-resistant bacteria for which effective therapies were rapidly needed. Now, entering the third decade of the twenty-first century, and despite the introduction of several new antibiotics and antibiotic adjuvants, such as novel β-lactamase inhibitors, these organisms continue to represent major therapeutic challenges. These bacteria share several key biological features, including adaptations for survival in the modern health-care setting, diverse methods for acquiring resistance determinants and the dissemination of successful high-risk clones around the world. With the advent of next-generation sequencing, novel tools to track and combat the spread of these organisms have rapidly evolved, as well as renewed interest in non-traditional antibiotic approaches. In this Review, we explore the current epidemiology and clinical impact of this important group of bacterial pathogens and discuss relevant mechanisms of resistance to recently introduced antibiotics that affect their use in clinical settings. Furthermore, we discuss emerging therapeutic strategies needed for effective patient care in the era of widespread antimicrobial resistance.

A Streptococcus pneumoniae endolysin mutant protein ΔA146Ply elicits rapid broad-spectrum mucosal protection in mice via upregulation of GPX4 through TLR4/IRG1/NRF2 to alleviate macrophage ferroptosis

Innovative solutions for rapid protection against broad-spectrum infections are very important in dealing with complex infection environments. We utilized a functionally inactive mutated endolysin protein of Streptococcus pneumoniae (ΔA146Ply) to immunize mice against pneumonic infections by multidrug-resistant bacteria, Candida albicans and influenza virus type A. ΔA146Ply protection relied on both immunized tissue-resident and monocyte-derived alveolar macrophages and inhibited infection induced ferroptosis that upregulated expression of GPX4 (glutathione peroxidase) in alveolar macrophages. Ferroptosis resistance endowed macrophages with enhanced phagocytosis by inhibiting lipid peroxidation during infection. Moreover, we demonstrated ΔA146Ply upregulated GPX4 through the TLR4/IRG1/NRF2 pathway. ΔA146Ply also induced ferroptosis inhibition and phagocytosis improvement in human monocytes. This mode of action is a novel and potentially prophylactic and rapid broad-spectrum anti-infection mechanism. Our study provides new insights into protective interventions that act by regulating ferroptosis to improve multiple pathogen resistance via GPX4 targeting.

Clinical characteristics, risk factor analysis and peripheral blood cell changes for early warning of multidrug-resistant bacteria (MDR) infection in elderly patients

OBJECTIVE

To explore peripheral blood indicators that may serve as early indicators for multidrug-resistant bacteria (MDR) infections in this demographic, with the goal of providing reference suggestions for the clinical prevention of MDR infections in elderly inpatients.

METHODS

Clinical data of patients were divided into the MDR-infected group (n = 488) and the MDR-uninfected group (n = 233) according to the results of drug sensitivity experiments, risk factors for MDR infection, and peripheral blood indicators related to MDR infections were analyzed using univariate and multivariate logistic regression in conjunction with the construction of a Chi-squared automatic interaction detector (CHAID) decision tree model, considering statistical significance at p < .05.

RESULTS

Of 721 patients, 488 multidrug-resistant strains were identified. Among them, with Staphylococcus spp. the most prevalent in 148 strains. The most frequent detection of MDR occurred in puncture fluid samples (167 cases). Univariate and multivariate regression analyses revealed that prolonged hospitalization, use of antibiotics preadmission, duration of antibiotics, invasive procedures or recent surgery, and coexisting lung disease were independent risk factors for contracting MDR. Subsequent analysis comparing the aforementioned influences with peripheral blood cells revealed associations between the number of antibiotic treatment days and increased neutrophil-to-lymphocyte ratio (NLR), platelet count-to-lymphocyte ratio (PLR), neutrophils, decreased lymphocytes, and increased eosinophils; preadmission antibiotic use correlated with increased PLR, NLR, neutrophils, and decreased lymphocytes; and invasive manipulation or surgery correlated with increased PLR and NLR.

CONCLUSIONS

Elevated NLR, PLR, neutrophils, lowered lymphocytes, and eosinophils may serve as early indicators of MDR infections in elderly hospitalized patients.

Can flow cytometric measurements of reactive oxygen species levels determine minimal inhibitory concentrations and antibiotic susceptibility testing for Acinetobacter baumannii?

Current antimicrobial susceptibility testing (AST) requires 16-24 hours, delaying initiation of appropriate antibiotics. Hence, there is a need for rapid AST. This study aims to develop and evaluate the feasibility of a rapid flow cytometric AST assay to determine minimum inhibitory concentration (MIC) for carbapenem-resistant Acinetobacter baumannii (CRAB). Antibiotic exposure causes increased intracellular reactive oxygen species (ROS) in bacteria. We hypothesized that ROS can be used as a marker to determine MIC. We assessed three CRAB clinical isolates across fifteen antibiotics at various concentrations in a customized 96-well microtiter plate. The antibiotics assessed include amikacin, beta-lactams (ampicillin/sulbactam, aztreonam, cefepime, ceftolozane/tazobactam, doripenem, imipenem, meropenem, and piperacillin/tazobactam), levofloxacin, polymyxin B, rifampicin, trimethoprim/sulfamethoxazole, and tetracyclines (tigecycline and minocycline). These clinical CRAB isolates were assessed for ROS after antibiotic treatment. Increased ROS levels indicated by increased RedoxSensorTM Green (RSG) fluorescence intensity was assessed using flow cytometry (FCM). MIC was set as the lowest antibiotic concentration that gives a ≥1.5-fold increase in mode RSG fluorescence intensity (MICRSG). Accuracy of MICRSG was determined by comparing against microtiter broth dilution method performed under CLSI guidelines. ROS was deemed accurate in determining the MICs for β-lactams (83.3% accuracy) and trimethoprim/sulfamethoxazole (100% accuracy). In contrast, ROS is less accurate in determining MICs for levofloxacin (33.3% accuracy), rifampicin (0% accuracy), amikacin (33.3% accuracy), and tetracyclines (33.3% accuracy). Collectively, this study described an FCM-AST assay to determine antibiotic susceptibility of CRAB isolates within 5 hours, reducing turnaround time up to 19 hours.

The Molecular Mouse System: A New Useful Tool for Guiding Antimicrobial Therapy in Critically Ill Septic Patients

Bloodstream infections (BSI) caused by multidrug-resistant (MDR) bacteria, pose a major threat for patients, especially for those who are immunosuppressed. Rapid pathogen detection and characterization from positive blood cultures are crucial in the management of patients with BSI to enable an adequate and timely antimicrobial therapy. This study aimed to investigate the potential role of the Molecular Mouse system, a new CE IVD molecular test designed to rapidly detect the causative agents of bacteremia and their resistance determinants, in the management of the therapy in critically ill patients. Agreement between the results of the Molecular Mouse and the conventional routine method was also considered. Overall, 100 positive blood cultures were collected from septic critically ill patients from May 2023 to January 2024 and analyzed with Molecular Mouse and routine protocols. The new instrument consistently agreed with the routine protocols in the case of monomicrobial blood cultures, while some discrepancies were obtained in the polymicrobial samples. Antimicrobial resistance genes were detected in 35 samples, with vanA and CTX-M-1/9 groups being the most frequently detected targets. Therapy was adjusted in 42 critically ill patients confirming the importance of new rapid molecular tests in the management of positive blood cultures, to adjust empirical therapy and use new antibiotics accurately.

Strong Homology Between Colonizing and Bloodstream Carbapenem-Resistant Acinetobacter Spp.: Implications for Empiric Antibiotic Therapy in Hematological Patients

Objective

This study aimed to assess the impact of colonization status on the outcomes of Acinetobacter spp. bloodstream infection (BSI) and investigate the homology and within-host evolution between colonizing and bloodstream carbapenem-resistant Acinetobacter spp. (CRA) to inform antibiotic therapeutic decisions.

Methods

We analyzed clinical outcomes of 46 hematological patients with Acinetobacter spp. BSI and performed whole-genome sequencing on the remaining CRA isolates.

Results

Among the patients, 39.1% (n=18) had prior Acinetobacter spp. colonization. Colonized patients had higher rates of polymicrobial BSI (50.0% vs 21.4%, P=0.044) and CRA BSI (72.2% vs 17.9%, P<0.001), resulting in elevated inflammatory markers and increased 30-day mortality. Each of the eight pairs of the remaining respiratory colonizing and bloodstream CRA strains belonged to the same genomospecies. Each pair exhibited definitive agreement in at least 21 of the 22 most representative antibiotic susceptibility tests. The minimum spanning tree based on multilocus sequence typing (MLST) and phylogenetic trees based on MLST and single nucleotide polymorphism (SNP) all indicated that each pair shared the same minimum branch. Very few non-synonymous SNPs in genic regions were identified during the transition from respiratory colonization to bloodstream infection, with minimal changes in virulence genes. Homology analysis suggested that CRA BSI originated from colonizing isolates in the respiratory tract.

Conclusion

Strict infection control measures are needed to manage Acinetobacter spp. colonisation in hematological patients. Appropriate empirical therapy can be administered for suspected CRA BSI based on the antimicrobial minimum inhibitory concentration of CRA colonising the respiratory tract.

Impact of Gram-Negative Bacilli Resistance Rates on Risk of Death in Septic Shock and Pneumonia

Background

Sepsis is a major cause of morbidity and mortality worldwide. When selecting empiric antibiotics for sepsis, clinicians are encouraged to use local resistance rates, but their impact on individual outcomes is unknown. Improved methods to predict outcomes are needed to optimize treatment selection and improve antibiotic stewardship.

Methods

We expanded on a previously developed theoretical model to estimate the excess risk of death in gram-negative bacilli (GNB) sepsis due to discordant antibiotics using 3 factors: the prevalence of GNB in sepsis, the rate of antibiotic resistance in GNB, and the mortality difference between discordant and concordant antibiotic treatments. We focused on ceftriaxone, cefepime, and meropenem as the anti-GNB treatment backbone in sepsis, pneumonia, and urinary tract infections. We analyzed both publicly available data and data from a large urban hospital.

Results

Publicly available data were weighted toward culture-positive cases. Excess risk of death with discordant antibiotics was highest in septic shock and pneumonia. In septic shock, excess risk of death was 4.53% (95% confidence interval [CI], 4.04%-5.01%), 0.6% (95% CI, .55%-.66%), and 0.19% (95% CI, .16%-.21%) when considering resistance to ceftriaxone, cefepime, and meropenem, respectively. Results were similar in pneumonia. Local data, which included culture-negative cases, showed an excess risk of death in septic shock of 0.75% (95% CI, .57%-.93%) for treatment with discordant antibiotics in ceftriaxone-resistant infections and 0.18% (95% CI, .16%-.21%) for cefepime-resistant infections.

Conclusions

Estimating the excess risk of death for specific sepsis phenotypes in the context of local resistance rates, rather than relying on population resistance data, may be more informative in deciding empiric antibiotics in GNB infections.

Treatment and Management of Acinetobacter Pneumonia: Lessons Learned from Recent World Event

Acinetobacter pneumonia is a significant healthcare-associated infection that poses a considerable challenge to clinicians due to its multidrug-resistant nature. Recent world events, such as the COVID-19 pandemic, have highlighted the need for effective treatment and management strategies for Acinetobacter pneumonia. In this review, we discuss lessons learned from recent world events, particularly the COVID-19 pandemic, in the context of the treatment and management of Acinetobacter pneumonia. We performed an extensive literature review to uncover studies and information pertinent to the topic. The COVID-19 pandemic underscored the importance of infection control measures in healthcare settings, including proper hand hygiene, isolation protocols, and personal protective equipment use, to prevent the spread of multidrug-resistant pathogens like Acinetobacter. Additionally, the pandemic highlighted the crucial role of antimicrobial stewardship programs in optimizing antibiotic use and curbing the emergence of resistance. Advances in diagnostic techniques, such as rapid molecular testing, have also proven valuable in identifying Acinetobacter infections promptly. Furthermore, due to the limited availability of antibiotics for treating infections caused A. baumannii, alternative strategies are needed like the use of antimicrobial peptides, bacteriophages and their enzymes, nanoparticles, photodynamic and chelate therapy. Recent world events, particularly the COVID-19 pandemic, have provided valuable insights into the treatment and management of Acinetobacter pneumonia. These lessons emphasize the significance of infection control, antimicrobial stewardship, and early diagnostics in combating this challenging infection.

n vitro pharmacokinetics/pharmacodynamics of the β-lactamase inhibitor, durlobactam, in combination with sulbactam against Acinetobacter baumannii-calcoaceticus complex

Infections caused by Acinetobacter baumannii are increasingly multidrug resistant and associated with high rates of morbidity and mortality. Sulbactam is a β-lactamase inhibitor with intrinsic antibacterial activity against A. baumannii. Durlobactam is a non-β-lactam β-lactamase inhibitor with an extended spectrum of activity compared to other inhibitors of its class. In vitro pharmacodynamic infection models were undertaken to establish the pharmacokinetic/pharmacodynamic (PK/PD) index and magnitudes associated with sulbactam and durlobactam efficacy and to simulate epithelial lining fluid (ELF) exposures at clinical doses to understand sulbactam-durlobactam activity with and without co-administration of a carbapenem. Hollow fiber infection models (HFIMs) and one-compartment systems were used to identify the PK/PD indices and exposure magnitudes associated of 1-log10 and 2-log10 colony-forming unit (CFU)/mL reductions. Sulbactam and durlobactam demonstrated PK/PD drivers of % time above the minimum inhibition concentration (%T > MIC) and area under the plasma concentration-time curve from time 0 to 24 h (AUC0-24)/MIC, respectively. Against a sulbactam-susceptible strain, sulbactam %T > MIC of 71.5 and 82.0 were associated with 1-log10 and 2-log10 CFU/mL reductions, respectively, in the HFIM. Against a non-susceptible strain, durlobactam restored the activity of sulbactam with an AUC0-24/MICs of 34.0 and 46.8 using a polysulfone cartridge to achieve a 1-log10 and 2-log10 CFU/mL reduction. These magnitudes were reduced to 13.8 and 24.2, respectively, using a polyvinylidene fluoride cartridge with a membrane pore size of 0.1 μm. In the one-compartment model, durlobactam AUC0-24/MIC to achieve 1-log10 and 2-log10 CFU/mL reduction were 7.6 and 33.4, respectively. Simulations of clinical ELF exposures in the HFIM showed cidal activity at MICs ≤4 µg/mL. Penicillin binding protein 3 mutant strains with MICs of 8 μg/mL may benefit from the addition of a carbapenem at clinical exposures.

In vivo dose response and efficacy of the β-lactamase inhibitor, durlobactam, in combination with sulbactam against the Acinetobacter baumannii-calcoaceticus complex

Multi-drug resistant (MDR) Acinetobacter baumannii is emerging as a pathogen of increasing prevalence and concern. Infections associated with this Gram-negative pathogen are often associated with increased morbidity and mortality and few therapeutic options. The β-lactamase inhibitor sulbactam used commonly in combination with ampicillin demonstrates intrinsic antibacterial activity against A. baumannii acting as an inhibitor of PBP1 and PBP3, which participate in cell wall biosynthesis. The production of β-lactamases, particularly class D oxacillinases, however, has limited the utility of sulbactam resorting to increased doses and the need for alternate therapies. Durlobactam is a non-β-lactam β-lactamase inhibitor that demonstrates broad β-lactamase inhibition including class D enzymes produced by A. baumannii and has shown potent in vitro activity against MDR A. baumannii, particularly carbapenem-resistant isolates in susceptibility and pharmacodynamic model systems. The objective of this study is to evaluate the exposure-response relationship of sulbactam and durlobactam in combination using in vivo neutropenic thigh and lung models to establish PK/PD exposure magnitudes to project clinically effective doses. Utilizing established PK/PD determinants of %T>MIC and AUC/MIC for sulbactam and durlobactam, respectively, non-linear regressional analysis of drug exposure was evaluated relative to the 24-hour change in bacterial burden (log10 CFU/g). Co-modeling of the data across multiple strains exhibiting a broad range of MIC susceptibility suggested net 1-log10 CFU/g0 reduction can be achieved when sulbactam T>MIC exceeds 50% of the dosing interval and durlobactam AUC/MIC is 10. These data were ultimately used to support sulbactam-durlobactam dose selection for Phase 3 clinical trials.

Healthcare Resource Utilization and Discharge Readiness in Adult Hospitalized Patients With Candidemia or Invasive Candidiasis Who Received an Echinocandin: An Analysis of United States Hospitals

Background

Scant real-world outcomes data are available among hospitalized patients with candidemia (C) or invasive candidiasis without candidemia (IC) who were treated with an echinocandin and few have assessed if there is an opportunity to accelerate the transition of their care to the outpatient setting. This study described the outcomes associated with echinocandin therapy for C/IC and determined the proportion of patients on an echinocandin at hospital discharge (HD) who were potentially eligible for an earlier HD.

Methods

A retrospective, multicenter observational study was performed using the PINC AI Healthcare Database (January 2016-April 2019) of hospitalized adult patients with C/IC who received ≥3 days of an echinocandin. Outcomes included post-index culture hospital costs and discharge location. Patients were considered potentially dischargeable earlier than actual HD day if they met the following 3 criteria prior to their actual HD day: resided on a non-intensive care unit hospital ward until HD, received any oral medications, and had no diagnostic/therapeutic interventions.

Results

A total of 1865 patients met study criteria. Mean (standard deviation) post-index culture hospital costs for patients with C and IC were 50 196 (64 630) US dollars and 61 551 (73 080) US dollars, respectively. Of the 1008 patients on an echinocandin near HD and discharged alive, 432 (42.9%) were potentially dischargeable prior to their actual hospital day. Most patients (35.8%) were discharged to a long-term care facility.

Conclusions

The findings suggest that a high proportion of hospitalized C/IC patients receiving an echinocandin near the time of HD were potentially dischargeable earlier. Like all studies of this nature, the findings need to be prospectively validated.

Evolutionary trends of carbapenem-resistant and susceptible Acinetobacter baumannii isolates in a major tertiary care setting from North India

Emergence of carbapenem-resistant A. baumannii (CRAB) is a global, ongoing healthcare concern. CRAB is among the topmost priority pathogens, with various studies focusing on its global population structure and resistant allelic profiles. However, carbapenem-susceptible A. baumannii (CSAB) isolates are often overlooked due to their sensitivity to beta-lactams, which can provide important insights into origin of CRAB lineages and isolates. In the present study, we report genomic investigation of CRAB and CSAB coexisting in Indian hospital setting. MLST based population structure and phylogenomics suggest they mainly follow distinct evolutionary routes forming two phylogroups. PG-I exclusively for a successful clone (ST2) of CRAB and PG-II comprises diversified CSAB isolates except PG3373, which is CRAB. Additionally, there are few CRAB isolates not belonging to PG-I and sharing clonal relationship with CSAB isolates indicating role of genome plasticity towards extensive drug resistance in the nosocomial environment. Further, genealogical analysis depicts prominent role of recombination in emergence and evolution of a major CRAB lineage. Further, CRAB isolates are enriched in resistomes as compared to CSAB isolates, which were encoded on the genomic island. Such comparative genomic insights will aid in our understanding and localized management of rapidly evolving pandrug resistant nosocomial pathogens.

Treatment effectiveness of antibiotic therapy in Veterans with multidrug-resistant Acinetobacter spp. bacteremia

Objective

To describe antimicrobial therapy used for multidrug-resistant (MDR) Acinetobacter spp. bacteremia in Veterans and impacts on mortality.

Methods

This was a retrospective cohort study of hospitalized Veterans Affairs patients from 2012 to 2018 with a positive MDR Acinetobacter spp. blood culture who received antimicrobial treatment 2 days prior to through 5 days after the culture date. Only the first culture per patient was used. The association between treatment and patient characteristics was assessed using bivariate analyses. Multivariable logistic regression models examined the relationship between antibiotic regimen and in-hospital, 30-day, and 1-year mortality. Generalized linear models were used to assess cost outcomes.

Results

MDR Acinetobacter spp. was identified in 184 patients. Most cultures identified were Acinetobacter baumannii (90%), 3% were Acinetobacter lwoffii, and 7% were other Acinetobacter species. Penicillins-β-lactamase inhibitor combinations (51.1%) and carbapenems (51.6%)-were the most prescribed antibiotics. In unadjusted analysis, extended spectrum cephalosporins and penicillins-β-lactamase inhibitor combinations-were associated with a decreased odds of 30-day mortality but were insignificant after adjustment (adjusted odds ratio (aOR) = 0.47, 95% CI, 0.21-1.05, aOR = 0.75, 95% CI, 0.37-1.53). There was no association between combination therapy vs monotherapy and 30-day mortality (aOR = 1.55, 95% CI, 0.72-3.32).

Conclusion

In hospitalized Veterans with MDR Acinetobacter spp., none of the treatments were shown to be associated with in-hospital, 30-day, and 1-year mortality. Combination therapy was not associated with decreased mortality for MDR Acinetobacter spp. bacteremia.

Safety and pharmacokinetics of SPR206 in subjects with varying degrees of renal impairment

SPR206 is a novel polymyxin derivative with potent in vitro activity against susceptible and multidrug-resistant strains of Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, and Enterobacter species. SPR206 is eliminated renally. The safety, tolerability, and pharmacokinetics (PK) of SPR206 were evaluated in healthy subjects with normal renal function (Cohort 1) and subjects with varying degrees of renal impairment (RI) (Cohorts 2-4) or end-stage renal disease (ESRD) on hemodialysis (HD) (Cohort 5). Subjects in Cohorts 1-4 received a 100-mg intravenous (IV) dose of SPR206. Subjects in Cohort 5 received a 100-mg IV dose within 2 h after HD on day 1 and 1 h before HD on day 5. Safety and PK analyses included 37 subjects. Mostly mild but no serious treatment-related adverse events were reported. Systemic exposure to SPR206 increased as renal function decreased, with mean area under the concentration-time curve from time 0 to the last quantifiable concentration (AUC0-last) values 39% to 239% greater in subjects with RI vs healthy subjects. Mean plasma clearance (CL) of SPR206 decreased with decreasing renal function (29% to 76% lower vs healthy subjects). In subjects with ESRD, AUC0-last decreased by 51%, and CL increased by 92% for dialyzed vs nondialyzed conditions. SPR206 was excreted in urine within 12 h in healthy subjects and subjects with mild RI (Cohort 2) but was prolonged in those with moderate and severe RI (Cohorts 3 and 4, respectively). In summary, SPR206 was generally safe and well tolerated, and the PK of SPR206 was well characterized in subjects with RI.

Acinetobacter spp. bloodstream infection in hematological patients: a 10-year single-center study

PURPOSE

This study investigated the clinical and antimicrobial characteristics of Acinetobacter spp. bloodstream infection (BSI) in hematological patients. Risk factors for 30-day mortality and carbapenem-resistant Acinetobacter spp. (CRA) BSI acquisition were also identified.

METHODS

We reviewed forty hematological patients with Acinetobacter spp. BSI in a large Chinese blood disease hospital between 2013 and 2022. The remaining CRA isolates were subjected to whole-genome sequencing.

RESULTS

The 30-day mortality rate was high at 35%. Hematological patients with Acinetobacter spp. BSI often presented with severe conditions and co-infections at multiple sites. All strains were colistin-susceptible and 40.0% were CR. Multivariate analysis identified several risk factors associated with CRA BSI acquisition, including previous exposure to carbapenems within 30 days and CRA colonization. Very severe aplastic anaemia, tetracycline-resistant Acinetobacter spp. BSI, and unresolved neutropenia after infection were closely associated with 30-day mortality. Non-survivors often presented with higher median PCT and CRP levels and severe complications, such as intracranial infection, cardiac dysfunction, respiratory failure, and severe sepsis or septic shock. Our study also identified inappropriate empirical antibiotic therapy as an independent predictor of 30-day mortality (OR: 11.234, 95% CI: 1.261-20.086, P = 0.030). This study was the first to report A. oleivorans as a human pathogen, and to identify its unique oxacillinase, OXA-325.

CONCLUSION

An environment-originated non-pathogenic species can become pathogenic when the body's immunity is compromised. Our results also highlighted the importance of improving neutropenia after infection, treating severe organ dysfunction, and administering appropriate empirical antibiotic therapy to reduce mortality in this patient population.

Examining the Burden of Potentially Avoidable Heart Failure Hospitalizations

Background

Two-thirds of the 1 million annual US CHF hospitalizations are for diuresis only; some may be avoidable. We describe a population of low-severity short-stay (

Methods

We conducted a retrospective cohort study within the Premier Healthcare Database, 2016-2021. CHF was defined via an administrative code algorithm. High severity (CHF-H) was marked by cardiogenic shock, the need for respiratory or circulatory support, and/or a Charlson comorbidity index >2. We compared baseline characteristics, processes of care, and outcomes in low-severity (CHF-L) to CHF-H.

Results

Among 301,672 short-stay CHF patients, 135,304 (44.8%) were CHF-L. Compared to CHF-H, CHF-L was younger (70.5 ± 14.1 vs 72.1 ± 13.6 years, p < 0.001), more commonly female (48.6% vs 45.8%, p < 0.001), and more likely to receive IV ACE-I/ARB agents (0.5% vs 0.4%, p = 0.003). Most other IV medications were more common in CHF-H, and anticoagulation was the most prevalent non-diuretic IV therapy in both groups (23.8% vs 33.3%, p < 0.001). Hospital mortality (0.2% vs 1.5%, p < 0.001) and CHF-related 30-day readmissions (8.1% vs 10.5%, p < 0.001) were lower in CHF-L than CHF-H.

Conclusion

Among short-stay CHF patients, nearly ½ meet criteria for CHF-L, and are mainly admitted for fluid management. Avoiding these admissions could result in substantial savings.

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Key Words

• congestive heart failure
• costs
• epidemiology
• hospital
• outcomes

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MESH Headings Collapse

Grants

• scPharmaceuticals, Burlington, MA, USA

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Affiliation(s)

Marya D Zilberberg EviMed Research Group, LLC, Goshen, MA, USA
Brian H Nathanson OptiStatim, LLC, Longmeadow, MA, USA
Kate Sulham scPharmaceuticals, Burlington, MA, USA
John F Mohr scPharmaceuticals, Burlington, MA, USA
Matthew Goodwin scPharmaceuticals, Burlington, MA, USA
Andrew F Shorr Washington Hospital Center, Washington, DC, USA

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Bibliometric Analysis of Global Research Output on Antimicrobial Resistance among Pneumonia Pathogens (2013-2023)

Antimicrobial resistance (AMR) is a pressing global concern, posing significant challenges to the effective treatment of infections, including pneumonia. This bibliometric analysis aims to investigate the research output on AMR among pneumonia pathogens from 2013 to 2023. Data were extracted from the Web of Science Core Collection (WOS-CC) using an inclusive search strategy. The analysis included 152 relevant studies published in 99 different sources, involving 988 authors and yielding an average of 16.33 citations per document over the past decade. The findings reveal a notable increase in research on AMR among pneumonia pathogens, indicating a growing awareness of this critical issue. Collaborative studies were prevalent, with the majority of authors engaging in joint research efforts. Bradford's Law identified twelve core journals that were instrumental in disseminating research in this field, with "Medicine" emerging as the most prolific journal. The USA and China emerged as the leading contributors, while Germany displayed a strong inclination towards collaborative research. Intermountain Medical Center, Saitama Medical University, and Udice-French Research Universities were the most productive institutions, and Yayan J. and Rasche K. were the top authors. Furthermore, the analysis identified commonly encountered microorganisms such as Acinetobacter baumanii and Klebsiella pneumoniae in the context of AMR. Time-based analysis of keywords highlighted the significance of terms like "community-acquired pneumonia" and "ventilator-associated pneumonia". Overall, this comprehensive study sheds light on the global research landscape of AMR among pneumonia pathogens. The insights gained from this analysis are essential for guiding future research priorities and collaborative efforts to combat AMR effectively and improve treatment outcomes for pneumonia and related infections. As the frequency of reports concerning resistance among pneumonia pathogens, notably A. baumannii and K. pneumoniae, continues to rise, there is an immediate requirement for pharmaceutical manufacturers and healthcare providers to respond proactively and ready themselves for the forthcoming implications of this matter. It also underscores the importance of knowledge dissemination and evidence-based interventions to address this growing public health challenge. However, the study acknowledges the limitations associated with using a single publication database and encourages the inclusion of data from other sources in future research.

Pharmacokinetics of SPR206 in Plasma, Pulmonary Epithelial Lining Fluid, and Alveolar Macrophages following Intravenous Administration to Healthy Adult Subjects

SPR206 is a next-generation polymyxin being developed for the treatment of multidrug-resistant (MDR) Gram-negative infections. This Phase 1 bronchoalveolar lavage (BAL) study was conducted to evaluate SPR206's safety and pharmacokinetics in plasma, pulmonary epithelial lining fluid (ELF), and alveolar macrophages (AM) in healthy volunteers. Subjects received a 100 mg intravenous (IV) dose of SPR206 infused over 1 h every 8 h for 3 consecutive doses. Each subject underwent 1 bronchoscopy with BAL at 2, 3, 4, 6, or 8 h after the start of the third IV infusion. SPR206 concentrations in plasma, BAL, and cell pellet were measured with a validated LC-MS/MS assay. Thirty-four subjects completed the study and 30 completed bronchoscopies. Mean SPR206 peak concentrations (Cmax) in plasma, ELF, and AM were 4395.0, 735.5, and 860.6 ng/mL, respectively. Mean area under the concentration-time curve (AUC0-8) for SPR206 in plasma, ELF, and AM was 20120.7, 4859.8, and 6026.4 ng*h/mL, respectively. The mean ELF to unbound plasma concentration ratio was 0.264, and mean AM to unbound plasma concentration ratio was 0.328. Mean SPR206 concentrations in ELF achieved lung exposures above the MIC for target Gram-negative pathogens for the entire 8-h dosing interval. Overall, SPR206 was well tolerated; 22 subjects (64.7%) reported at least 1 treatment-emergent adverse event (TEAE). Of the 40 reported TEAEs, 34 (85.0%) were reported as mild in severity. The most frequent TEAEs were oral paresthesia (10 subjects [29.4%]) and nausea (2 subjects [5.9%]). This study demonstrates pulmonary penetration of SPR206 and supports further development of SPR206 for the treatment of patients with serious infections caused by MDR Gram-negative pathogens.

What’s old is new again: Insights into diabetic foot microbiome

Diabetes is a chronic disease that is considered one of the most stubborn global health problems that continues to defy the efforts of scientists and physicians. The prevalence of diabetes in the global population continues to grow to alarming levels year after year, causing an increase in the incidence of diabetes complications and health care costs all over the world. One major complication of diabetes is the high susceptibility to infections especially in the lower limbs due to the immunocompromised state of diabetic patients, which is considered a definitive factor in all cases. Diabetic foot infections continue to be one of the most common infections in diabetic patients that are associated with a high risk of serious complications such as bone infection, limb amputations, and life-threatening systemic infections. In this review, we discussed the circumstances associated with the high risk of infection in diabetic patients as well as some of the most commonly isolated pathogens from diabetic foot infections and the related virulence behavior. In addition, we shed light on the different treatment strategies that aim at eradicating the infection.

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

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

The Pharmacokinetics/Pharmacodynamic Relationship of Durlobactam in Combination With Sulbactam in In Vitro and In Vivo Infection Model Systems Versus Acinetobacter baumannii-calcoaceticus Complex

Sulbactam-durlobactam is a β-lactam/β-lactamase inhibitor combination currently in development for the treatment of infections caused by Acinetobacter, including multidrug-resistant (MDR) isolates. Although sulbactam is a β-lactamase inhibitor of a subset of Ambler class A enzymes, it also demonstrates intrinsic antibacterial activity against a limited number of bacterial species, including Acinetobacter, and has been used effectively in the treatment of susceptible Acinetobacter-associated infections. Increasing prevalence of β-lactamase-mediated resistance, however, has eroded the effectiveness of sulbactam in the treatment of this pathogen. Durlobactam is a rationally designed β-lactamase inhibitor within the diazabicyclooctane (DBO) class. The compound demonstrates a broad spectrum of inhibition of serine β-lactamase activity with particularly potent activity against class D enzymes, an attribute which differentiates it from other DBO inhibitors. When combined with sulbactam, durlobactam effectively restores the susceptibility of resistant isolates through β-lactamase inhibition. The present review describes the pharmacokinetic/pharmacodynamic (PK/PD) relationship associated with the activity of sulbactam and durlobactam established in nonclinical infection models with MDR Acinetobacter baumannii isolates. This information aids in the determination of PK/PD targets for efficacy, which can be used to forecast efficacious dose regimens of the combination in humans.

Role of nebulized colistin as a substitutive strategy against nosocomial pneumonia caused by CR-GNB in intensive care units: a retrospective cohort study

BACKGROUND

Adverse reactions, especially nephrotoxicity, are great concerns of intravenous colistin treatment. The role of substitutive nebulized colistin in treating nosocomial pneumonia caused by carbapenem-resistant Gram-negative bacterial (CR-GNB) in critically ill patients remains unknown.

METHODS

This retrospective study enrolled patients with nosocomial pneumonia caused by colistin-susceptible CRGNB in the intensive care unit (ICU) without intravenous colistin treatment. Patients were categorized based on whether substitutive nebulized colistin was used alongside other intravenous antibiotics. Clinical responses and mortality rates were compared between the two groups in the original and propensity score (PS)-matched cohorts. This study aimed to investigate the clinical effectiveness of substitutive nebulized colistin in treatment outcomes of nosocomial pneumonia caused by CR-GNB. The impact of dosing strategy of nebulized colistin was also explored.

RESULTS

In total, 343 and 214 patients with and without substitutive nebulized colistin, respectively, were enrolled for analysis. In the PS-matched cohort, clinical failure rates on day 7 (22.6 vs. 42.6%, p = 0.001), day 14 (27.0 vs. 42.6%, p = 0.013), and day 28 (27.8 vs. 41.7%, p = 0.027) were significantly lower in patients with nebulized colistin. In multivariate analysis, nebulized colistin was an independent factor associated with lower day 14 clinical failure (Original cohort: adjusted odds ratio (aOR) 0.45, 95% confidence interval (CI) 0.30-0.67; PS-matched cohort: aOR 0.48, 95% CI 0.27-0.87). There were no differences in clinical failure rate and mortality rate between patients receiving high (> 6 MIU/day) and low (≤ 6 MIU/day) dose nebulized colistin in the PS-matched cohort.

CONCLUSIONS

In ICU-admitted patients with nosocomial pneumonia caused by colistin-susceptible CRGNB, substitutive nebulized colistin was associated with better clinical outcomes.

The threat of multidrug-resistant/extensively drug-resistant Gram-negative respiratory infections: another pandemic

Antibiotic resistance is recognised as a global threat to human health by national healthcare agencies, governments and medical societies, as well as the World Health Organization. Increasing resistance to available antimicrobial agents is of concern for bacterial, fungal, viral and parasitic pathogens. One of the greatest concerns is the continuing escalation of antimicrobial resistance among Gram-negative bacteria resulting in the endemic presence of multidrug-resistant (MDR) and extremely drug-resistant (XDR) pathogens. This concern is heightened by the identification of such MDR/XDR Gram-negative bacteria in water and food sources, as colonisers of the intestine and other locations in both hospitalised patients and individuals in the community, and as agents of all types of infections. Pneumonia and other types of respiratory infections are among the most common infections caused by MDR/XDR Gram-negative bacteria and are associated with high rates of mortality. Future concerns are already heightened due to emergence of resistance to all existing antimicrobial agents developed in the past decade to treat MDR/XDR Gram-negative bacteria and a scarcity of novel agents in the developmental pipeline. This clinical scenario increases the likelihood of a future pandemic caused by MDR/XDR Gram-negative bacteria.

Insights into Acinetobacter baumannii protective immunity

Acinetobacter baumannii is a nosocomic opportunistic Gram-negative bacteria known for its extensive drug-resistant phenotype. A. baumannii hospital-acquired infections are major contributors to increased costs and mortality observed during the COVID-19 pandemic. With few effective antimicrobials available for treatment of this pathogen, immune-based therapy becomes an attractive strategy to combat multi-drug resistant Acinetobacter infection. Immunotherapeutics is a field of growing interest with advances in vaccines and monoclonal antibodies providing insight into the protective immune response required to successfully combat this pathogen. This review focuses on current knowledge describing the adaptive immune response to A. baumannii, the importance of antibody-mediated protection, developments in cell-mediated protection, and their respective therapeutic application going forward. With A. baumannii’s increasing resistance to most current antimicrobials, elucidating an effective host adaptive immune response is paramount in the guidance of future immunotherapeutic development.

Clinical Outcomes, Microbiological Characteristics and Risk Factors for Difficult-to-Treat Resistance to Klebsiella pneumoniae Infection

Purpose

This study aimed to identify the clinical outcomes, microbiological features and risk factors for difficult-to-treat resistance (DTR) Klebsiella pneumoniae (Kp) infection.

Materials and Methods

A retrospective study was conducted at Peking University Third Hospital from January 2020 to March 2021. DTR was defined as resistance to ≥1 carbapenem, ≥1 extended-spectrum cephalosporin, and ≥1 fluoroquinolone. Hypervirulent Kp (HvKp) was defined as peg-344-, iroB-, iucA-, rmpA-, or rmpA2-positive. Clinical data were collected. Antimicrobial susceptibility testing and string tests were performed to determine resistance and hypermucoviscosity phenotype. Whole genome sequencing was performed to analyze the sequence type (ST), capsular serotypes, resistance and virulence genes. Risk factors for 30-day mortality were analyzed.

Results

Fifty DTR-Kp (50.0%) strains were identified among 100 patients. Compared to non-DTR-Kp group, a significant number of patients with DTR-Kp infection experienced ICU admission (44.0% versus 10.0%, P<0.001) and mechanical ventilation after Kp detection (26.0% versus 10.0%, P=0.037). Notably, the percentage of hvKp among the DTR-Kp isolates increased consistently over the 15 months evaluated. Most DTR-Kp strains belonged to ST11 (82.0%), followed by ST15 (12.0%), ST86 (2.0%), ST996 (2.0%), and ST3157 (2.0%). DTR-Kp isolates possessed various resistance genes, such as bla_KPC-2, bla_TEM-1D and fosA3 (90.0%, 80.0% and 72.0%, respectively). Importantly, the yersiniabactin genes were significantly clustered in DTR group (48/50, 96.0%). The 30-day mortality was significantly higher in patients with DTR-Kp infection than non-DTR-Kp group (38.0% versus 8.2%, P=0.001). DTR-Kp infection (odds ratio [OR] = 4.196) was an independent risk factor for the 30-day mortality of Kp-infected patients. Additionally, cerebrovascular disease (OR = 2.780) and Charlson comorbidity index (OR= 1.584) were independent risk factors for DTR-Kp infections.

Conclusion

DTR-hvKp is rapidly emerging. The DTR-Kp strains harbored various resistance genes and high rates of yersiniabactin siderophore genes. DTR-Kp infection was an independent risk factor for mortality, suggesting that enhanced awareness essential.

Early appropriate diagnostics and treatment of MDR Gram-negative infections

The term difficult-to-treat resistance has been recently coined to identify Gram-negative bacteria exhibiting resistance to all fluoroquinolones and all β-lactam categories, including carbapenems. Such bacteria are posing serious challenges to clinicians trying to identify the best therapeutic option for any given patient. Delayed appropriate therapy has been associated with worse outcomes including increase in length of stay, increase in total in-hospital costs and ∼20% increase in the risk of in-hospital mortality. In addition, time to appropriate antibiotic therapy has been shown to be an independent predictor of 30 day mortality in patients with resistant organisms. Improving and anticipating aetiological diagnosis through optimizing not only the identification of phenotypic resistance to antibiotic classes/agents, but also the identification of specific resistance mechanisms, would have a major impact on reducing the frequency and duration of inappropriate early antibiotic therapy. In light of these considerations, the present paper reviews the increasing need for rapid diagnosis of bacterial infections and efficient laboratory workflows to confirm diagnoses and facilitate prompt de-escalation to targeted therapy, in line with antimicrobial stewardship principles. Rapid diagnostic tests currently available and future perspectives for their use are discussed. Early appropriate diagnostics and treatment of MDR Gram-negative infections require a multidisciplinary approach that includes multiple different diagnostic methods and further consensus of algorithms, protocols and guidelines to select the optimal antibiotic therapy.

Molecular Epidemiology of Carbapenem-Resistant Acinetobacter baumannii in the United States, 2013-2017

Healthcare-associated carbapenem-resistant Acinetobacter baumannii (CRAB) infections are a serious threat associated with global epidemic clones and a variety of carbapenemase gene classes. In this study, we describe the molecular epidemiology, including whole-genome sequencing analysis and antimicrobial susceptibility profiles of 92 selected, nonredundant CRAB collected through public health efforts in the United States from 2013 to 2017. Among the 92 isolates, the Oxford (OX) multilocus sequence typing scheme identified 30 sequence types (STs); the majority of isolates (n = 59, 64%) represented STs belonging to the international clonal complex 92 (CC92_OX). Among these, ST208_OX (n = 21) and ST281_OX (n = 20) were the most common. All isolates carried an OXA-type carbapenemase gene, comprising 20 alleles. Ninety isolates (98%) encoded an intrinsic OXA-51-like enzyme; 67 (73%) harbored an additional acquired bla_OXA gene, most commonly bla_OXA-23 (n = 45; 49%). Compared with isolates harboring only intrinsic oxacillinase genes, acquired bla_OXA gene presence was associated with higher prevalence of resistance and a higher median minimum inhibitory concentration to the carbapenem imipenem (64 μg/mL vs. 8 μg/mL), and antibiotics from other drug classes, including penicillin, aminoglycosides, cephalosporins, and polymyxins. These data illustrate the wide distribution of CC92_OX and high prevalence of acquired bla_OXA carbapenemase genes among CRAB in the United States.

Evaluating the Effectiveness of Hospital Antiseptics on Multidrug-Resistant Acinetobacter baumannii: Understanding the Relationship between Microbicide and Antibiotic Resistance

Acinetobacter baumannii hospital infections are difficult to treat due to the rapid emergence of multidrug-resistant (MDR) strains. In addition, A. baumannii can survive in numerous adverse environments, including in the presence of common hospital antiseptics. We hypothesized that in addition to accumulating drug resistance determinants, MDR A. baumannii strains also accumulate mutations that allow for greater microbicide tolerance when compared to pan-susceptible (PS) strains. To test this hypothesis, we compared the survival of five MDR and five PS patient isolates when exposed to bleach, ethanol, quaternary ammonium compounds, chlorhexidine gluconate, and povidone. We evaluated bacteria in a free-living planktonic state and under biofilm conditions. Each disinfectant eliminated 99.9% of planktonic bacteria, but this was not the case for bacterial biofilms. Next, we characterized strains for the presence of the known microbicide-resistance genes cepA, qacEΔ1, qacE, and qacA. MDR strains did not survive more than PS strains in the presence of microbicides, but microbicide-resistant strains had higher survival rates under some conditions. Interestingly, the PS strains were more likely to possess microbicide-resistance genes. Microbicide resistance remains an important topic in healthcare and may be independent of antimicrobial resistance. Hospitals should consider stricter isolation precautions that take pan-susceptible strains into account.

Saving Time in Blood Culture Diagnostics: a Prospective Evaluation of the Qvella FAST-PBC Prep Application on the Fast System

Time to results for identification (ID) and antimicrobial susceptibility testing (AST) from blood cultures is an important factor impacting outcome in sepsis. In this study we evaluated a novel device, the FAST™ system from Qvella that concentrates microbial biomass from positive blood culture flasks with the FAST-PBC Prep™ cartridge thereby producing a liquid colony™ (LC), which can be used immediately in standard laboratory downstream applications. We tested 250 positive blood culture bottles collected from January 2021 to May 2021. Results were obtained either with LC or from bacterial overnight cultures using Bruker's MALDI Biotyper™ and bioMérieux's Vitek 2. We compared ID and AST results obtained by both methods and evaluated turnaround times. Two-hundred and fourteen blood cultures could be included in the analysis. In 94% of the cases (n = 201) identification was obtained directly from the LC with concordant results compared to the standard workflow. No discordant results were observed. AST results could be analyzed for 175 samples. Using categorical analysis, concordant agreement was 97.4% of 1,676 AST results for Gram positive bacteria. Agreement for Gram negative bacteria was 98.5% of 980 AST results. Times-to-result were 36.9 h versus 12.8 h for ID and 52.9 h versus 26.8 h for AST in routine workflow vs FAST^TM system, respectively. The FAST^TM system gives reliable results for ID and AST directly from positive blood cultures and allows for significant time savings in blood culture diagnostics.

How to use new antibiotics in the therapy of ventilator-associated pneumonia

PURPOSE OF REVIEW

Ventilator-associated pneumonia (VAP) is a common nosocomial infection in critically ill patients requiring endotracheal intubation and mechanical ventilation. Recently, the emergence of multidrug-resistant Gram-negative bacteria, including carbapenem-resistant Enterobacterales, multidrug-resistant Pseudomonas aeruginosa and Acinetobacter species, has complicated the selection of appropriate antimicrobials and contributed to treatment failure. Although novel antimicrobials are crucial to treating VAP caused by these multidrug-resistant organisms, knowledge of how to optimize their efficacy while minimizing the development of resistance should be a requirement for their use.

RECENT FINDINGS

Several studies have assessed the efficacy of novel antimicrobials against multidrug-resistant organisms, but high-quality studies focusing on optimal dosing, infusion time and duration of therapy in patients with VAP are still lacking. Antimicrobial and diagnostic stewardship should be combined to optimize the use of these novel agents.

SUMMARY

Improvements in diagnostic tests, stewardship practices and a better understanding of dosing, infusion time, duration of treatment and the effects of combining various antimicrobials should help optimize the use of novel antimicrobials for VAP and maximize clinical outcomes while minimizing the development of resistance.

Derivation and Validation of a Predictive Scoring Model of Infections Due to Acinetobacter baumannii in Patients with Hospital Acquired Pneumonia by Gram-Negative Bacilli

Background

The prognosis of ABA-HAP patients is very poor. This study aimed to develop a scoring model to predict ABA-HAP in patients with GNB-HAP.

Methods

A single center retrospective cohort study was performed among patients with HAP caused by GNB in our hospital during January 2019 to June 2019 (the derivation cohort, DC). The variables were assessed on the day when qualified respiratory specimens were obtained. A prediction score was formulated by using independent risk factors obtained from logistic regression analysis. It was prospectively validated with a subsequent cohort of GNB-HAP patients admitted to our hospital during July 2019 to Dec 2019 (the validation cohort, VC).

Results

The final logistic regression model of DC included the following variables: transferred from other hospitals (3 points); blood purification (3 points); risk for aspiration (4 points); immunocompromised (3 points); pulmonary interstitial fibrosis (3 points); pleural effusion (1 points); heart failure (3 points); encephalitis (5 points); increased monocyte count (2 points); and increased neutrophils count (2 points). The AUROC of the scoring model was 0.845 (95% CI, 0.796 ~ 0.895) in DC and 0.807 (95% CI, 0.759 ~ 0.856) in VC. The scoring model clearly differentiated the low-risk patients (the score < 8 points), moderate-risk patients (8 ≤ the score < 12 points) and high-risk patients (the score ≥ 12 points), both in DC (P < 0.001) and in VC (P < 0.001).

Conclusion

This simple scoring model could predict ABA-HAP with high predictive value and help clinicians to choose appropriate empirical antibiotic therapy.

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

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

Safety and immunogenicity of a new glycoengineered vaccine against Acinetobacter baumannii in mice

Acinetobacter baumannii poses a serious threat to human health, mainly because of its widespread distribution and severe drug resistance. However, no licensed vaccines exist for this pathogen. In this study, we created a conjugate vaccine against A. baumannii by introducing an O-linked glycosylation system into the host strain. After demonstrating the ability of the vaccine to elicit Th1 and Th2 immune responses and observing its good safety in mouse a model, the strong in vitro bactericidal activity and prophylactic effects of the conjugate vaccine against infection were further demonstrated by evaluating post-infection tissue bacterial loads, observing suppressed serum pro-inflammatory cytokine levels. Additionally, the broad protection from the vaccine was further proved via lethal challenge with A. baumannii. Overall, these results indicated that the conjugate vaccine could elicit an efficient immune response and provide good protection against A. baumannii infection in murine sepsis models. Thus, the conjugate vaccine can be considered as a promising candidate vaccine for preventing A. baumannii infection.

Effects of Inactivation of d,d-Transpeptidases of Acinetobacter baumannii on Bacterial Growth and Susceptibility to β-Lactam Antibiotics

Resistance to β-lactams, the most used antibiotics worldwide, constitutes the major problem for the treatment of bacterial infections. In the nosocomial pathogen Acinetobacter baumannii, β-lactamase-mediated resistance to the carbapenem family of β-lactam antibiotics has resulted in the selection and dissemination of multidrug-resistant isolates, which often cause infections characterized by high mortality rates. There is thus an urgent demand for new β-lactamase-resistant antibiotics that also inhibit their targets, penicillin-binding proteins (PBPs). As some PBPs are indispensable for the biosynthesis of the bacterial cell wall and survival, we evaluated their importance for the growth of A. baumannii by performing gene inactivation studies of d,d-transpeptidase domains of high-molecular-mass (HMM) PBPs individually and in combination with one another. We show that PBP3 is essential for A. baumannii survival, as deletion mutants of this d,d-transpeptidase were not viable. The inactivation of PBP1a resulted in partial cell lysis and retardation of bacterial growth, and these effects were further enhanced by the additional inactivation of PBP2 but not PBP1b. Susceptibility to β-lactam antibiotics increased 4- to 8-fold for the A. baumannii PBP1a/PBP1b/PBP2 triple mutant and 2- to 4-fold for all remaining mutants. Analysis of the peptidoglycan structure revealed a significant change in the muropeptide composition of the triple mutant and demonstrated that the lack of d,d-transpeptidase activity of PBP1a, PBP1b, and PBP2 is compensated for by an increase in the l,d-transpeptidase-mediated cross-linking activity of LdtJ. Overall, our data showed that in addition to essential PBP3, the simultaneous inhibition of PBP1a and PBP2 or PBPs in combination with LdtJ could represent potential strategies for the design of novel drugs against A. baumannii.

Treatment, clinical outcomes, and predictors of mortality among a national cohort of admitted patients with Acinetobacter baumannii infection

Objectives: To analyze treatment, clinical outcomes, and predictors of mortality in hospitalized patients with Acinetobacter baumannii infection.

Methods: Retrospective cohort study of inpatients with A. baumannii cultures and treatment from 2010-2019. Patients who died during admission were compared to those who survived to identify predictors of inpatient mortality, using multivariable unconditional logistic regression models.

Results: We identified 4,599 inpatients with A. baumannii infection; 13.6% died during admission. Fluoroquinolones (26.8%), piperacillin/tazobactam (24%) and carbapenems (15.6%) were used for treatment. Tigecycline (3%) and polymyxins (3.7%) were not used often. Predictors of inpatient mortality included current acute respiratory failure (adjusted odds ratio [aOR] 3.94), shock (aOR 3.05), and acute renal failure (aOR 2.01); blood (aOR 1.94) and respiratory (aOR 1.64) infectious source; multidrug-resistant A. baumannii (MDRAB) infection (aOR 1.66); liver disease (aOR 2.15); and inadequate initial treatment (aOR 1.30). Inpatient mortality was higher in those with MDRAB vs. non-MDRAB (aOR 1.61) and in those with CRAB vs. non-CRAB infection (aOR 1.68). Length of stay >10 days was higher among those with MDRAB vs. non-MDRAB (aOR 1.25) and in those with CRAB vs. non-CRAB infection (aOR 1.31).

Conclusions: In our national cohort of inpatients with A. baumannii infection, clinical outcomes were worse among those with MDRAB and/or CRAB infection. Predictors of inpatient mortality included several current conditions associated with severity, infectious source, underlying illness, and inappropriate treatment. Our study may assist healthcare providers in the early identification of admitted patients with A. baumannii infection who are at higher risk of death.

Effect of Delays in Concordant Antibiotic Treatment on Mortality in Patients With Hospital-Acquired Acinetobacter Species Bacteremia: Emulating a Target Randomized Trial With a 13-Year Retrospective Cohort

Delays in treating bacteremias with antibiotics to which the causative organism is susceptible are expected to adversely affect patient outcomes. Quantifying the impact of such delays to concordant treatment is important for decision-making about interventions to reduce the delays and for quantifying the burden of disease due to antimicrobial resistance. There are, however, potentially important biases to be addressed, including immortal time bias. We aimed to estimate the impact of delays in appropriate antibiotic treatment of patients with Acinetobacter species hospital-acquired bacteremia in Thailand on 30-day mortality by emulating a target trial using retrospective cohort data from Sunpasitthiprasong Hospital in 2003–2015. For each day, we defined treatment as concordant if the isolated organism was susceptible to at least 1 antibiotic given. Among 1,203 patients with Acinetobacter species hospital-acquired bacteremia, 682 had 1 or more days of delays to concordant treatment. Surprisingly, crude 30-day mortality was lower in patients with delays of ≥3 days compared with those who had 1–2 days of delays. Accounting for confounders and immortal time bias resolved this paradox. Emulating a target trial, we found that these delays were associated with an absolute increase in expected 30-day mortality of 6.6% (95% confidence interval: 0.2, 13.0), from 33.8% to 40.4%.

The Distribution of Multidrug-resistant Microorganisms and Treatment Status of Hospital-acquired Pneumonia/Ventilator-associated Pneumonia in Adult Intensive Care Units: a Prospective Cohort Observational Study

BACKGROUND

It is essential to determine the distribution of the causative microorganisms in the region and the status of local antibiotic resistance for the proper treatment of hospital-acquired pneumonia/ventilator-associated pneumonia (HAP/VAP). This study aimed to investigate the occurrence and causative strains of HAP/VAP, distribution of resistant bacteria, use of antibiotics, and the ensuing outcomes of patients in Korea.

METHODS

A multicenter prospective observational cohort study was conducted among patients with HAP/VAP admitted to the medical intensive care unit of 5 tertiary referral centers between August 2012 and June 2015. Patients' demographic and clinical data were collected.

RESULTS

A total of 381 patients were diagnosed with HAP/VAP. Their median age was 69 (59-76) years and 71% were males. A majority of the patients (88%) had late-onset (> 5 days) HAP/VAP. One-quarter of the patients (n = 99) had at least one risk factor for multidrug-resistant (MDR) pathogens, such as prior intravenous antibiotic use within the last 90 days. Microbiological specimens were mostly obtained noninvasively (87%) using sputum or endotracheal aspirates. Pathogens were identified in 235 (62%) of the 381 patients. The most common bacterial pathogen was Acinetobacter baumannii (n = 89), followed by Staphylococcus aureus (n = 52), Klebsiella pneumoniae (n = 25) and Pseudomonas aeruginosa (n = 22). Most of isolated A. baumannii (97%) and S. aureus (88%) were multidrug resistant. The most commonly used empirical antibiotic regimens were carbapenem-based antibiotics (38%), followed by extended-spectrum penicillin/β-lactamase inhibitor (34%). Glycopeptide or linezolid were also used in combination in 54% of patients. The 28-day mortality rate of the patients with HAP/VAP was 30% and the 60-day mortality was 46%. Patients who used empirical antibiotics appropriately had significantly lower mortality rates than those who did not (28-day mortality: 25% vs. 40%, P = 0.032; 60-day mortality: 41% vs. 55%, P = 0.032, respectively). Administration of appropriate empirical antibiotics (odds ratio [OR], 0.282; confidence interval [CI], 0.092-0.859; P = 0.026), Day 7 treatment failure (OR, 4.515; CI, 1.545-13.192; P = 0.006), and APACHE II score on day 1 (OR, 1.326; CI, 0.988-1.779; P = 0.012) were the factors that determined the 28-day mortality in patients with HAP who had identified bacteria as pathogens.

CONCLUSION

In HAP/VAP patients, there was a large burden of MDR pathogens, and their associated mortality rate was high. Proper selection of empirical antibiotics was significantly associated with the patient's prognosis; however, there was a discrepancy between major pathogens and empirical antibiotic therapy.

A synergic action of colistin, imipenem, and silver nanoparticles against pandrug-resistant Acinetobacter baumannii isolated from patients

BACKGROUND

The upgrowth and rapid prevalence of pandrug-resistant Acinetobacter baumannii strains that have a pathogenic activity to cause several infections are of considerable influence on the health of communities worldwide. No infections by these bacterial strains were recorded before 1998, and currently, the numbers are on the rise.

METHODS

The A. baumannii strains were isolated from male and female patients in Medical Microbiology Department, King Fahd Medical City (KFMC) in Riyadh, Saudi Arabia between 1/1/2020 to 29/12/2020. The statistical analysis was performed base on sex, age, source of samples, and response to commercially available antibiotics. The A. baumannii strains that resisted all the antibiotics including colistin and imipenem were selected for the synergic test.

RESULTS

The data showed that 62.28%, 77.07% of 342 A. baumannii strains were isolated from males and patients over 35 years of age. A. baumannii strains (pandrug-A. baumannii) that can resist all tested antibiotics were 8.19%. The major source of the A. baumannii isolates was the respiratory system (>50%). Among all isolates (N = 342), azidothymidine-resistant A. baumannii strains were more than 85%. There is a statistically significant difference (P < 0.05) in the number of colistin-resistant A. baumannii strains isolated from males comparing with the female. The combinations of colistin and silver nanoparticles or imipenem and silver nanoparticles resulted in synergistic action led to reduction of MICs of colistin, imipenem, and silver nanoparticles (more than four-fold reduction). Also, the combinations of colistin and imipenem had high synergistic action.

CONCLUSION

The pandrug-resistant A. baumannii strains may represent a current and future threat that must be fought, and the synergy action of antibiotics and nanoparticles may be one of the available, rapid, and easy strategies to confront this global problem.

Vaccination induces rapid protection against bacterial pneumonia via training alveolar macrophage in mice

Vaccination strategies for rapid protection against multidrug-resistant bacterial infection are very important, especially for hospitalized patients who have high risk of exposure to these bacteria. However, few such vaccination strategies exist due to a shortage of knowledge supporting their rapid effect. Here, we demonstrated that a single intranasal immunization of inactivated whole cell of Acinetobacter baumannii elicits rapid protection against broad A. baumannii-infected pneumonia via training of innate immune response in Rag1-/- mice. Immunization-trained alveolar macrophages (AMs) showed enhanced TNF-α production upon restimulation. Adoptive transfer of immunization-trained AMs into naive mice mediated rapid protection against infection. Elevated TLR4 expression on vaccination-trained AMs contributed to rapid protection. Moreover, immunization-induced rapid protection was also seen in Pseudomonas aeruginosa and Klebsiella pneumoniae pneumonia models, but not in Staphylococcus aureus and Streptococcus pneumoniae model. Our data reveal that a single intranasal immunization induces rapid and efficient protection against certain Gram-negative bacterial pneumonia via training AMs response, which highlights the importance and the possibility of harnessing trained immunity of AMs to design rapid-effecting vaccine.

Single- and Multiple-Ascending Dose Study of the Safety, Tolerability, and Pharmacokinetics of the Polymyxin Derivative, SPR206

Carbapenem-resistant Acinetobacter baumannii and Enterobacterales are identified as urgent threats, and multidrug-resistant (MDR) Pseudomonas aeruginosa and extended-spectrum beta-lactamase (ESBL)-producing pathogens are identified as serious threats by the Centers for Disease Control and Prevention (CDC). SPR206 is a novel polymyxin derivative with potent in vitro and in vivo activity against A. baumannii, P. aeruginosa, and multiple clinically important species of Enterobacterales, including multidrug- and extensively drug-resistant strains. This was a first-in-human (FIH) double-blind, placebo-controlled, single-, and multiple-ascending-dose study of the safety, tolerability, and pharmacokinetics (PK) of SPR206 in 94 healthy subjects. Following intravenous (i.v.) administration (1-h infusion) at single doses of 10 mg to 400 mg and multiple doses of 25 mg to 150 mg every 8 h (q8h) for 7 days and 100 mg q8h for 14 days, SPR206 was generally safe and generally well tolerated. While the incidence of adverse events increased with dose, most were of mild severity. Systemic exposure (maximum concentration of drug in serum [C_max] and area under the concentration-time curve [AUC]) to SPR206 was approximately dose proportional, time to peak concentrations ranged from 1.1 to 1.3 h, and half-life ranged from 2.4 to 4.1 h. No appreciable accumulation occurred with repeated dosing of SPR206, and trough concentrations suggest that steady state was achieved by day 2. Urinary excretion of unchanged SPR206 was dose dependent across single- (SAD) and multiple-ascending-dose (MAD) cohorts, and the percentage of dose excreted as SPR206 was up to >50%. Importantly, no evidence of nephrotoxicity was observed over 14 days of 100 mg q8h dosing of SPR206; a dosing regimen anticipated to exceed requirements for clinical efficacy. (This study has been registered at ClinicalTrials.gov under identifier NCT03792308.)

In Vitro Activity of Imipenem/Relebactam and Ceftolozane/Tazobactam Against Clinical Isolates of Gram-negative Bacilli With Difficult-to-Treat Resistance and Multidrug-resistant Phenotypes-Study for Monitoring Antimicrobial Resistance Trends, United States 2015-2017

BACKGROUND

Multidrug-resistant (MDR) bacteria are frequently defined using the criteria established by Magiorakos et al [Clin Microbiol Infect 2012;18:268-81]. Difficult-to-treat resistance (DTR) [Kadri et al, Clin Infect Dis 2018;67:1803-14] is a novel approach to defining resistance in gram-negative bacilli focusing on treatment-limiting resistance to first-line agents (all β-lactams and fluoroquinolones).

METHODS

Clinical and Laboratory Standards Institute-defined broth microdilution minimum inhibitory concentrations (MICs) were determined for imipenem/relebactam, ceftolozane/tazobactam, and comparators against respiratory, intraabdominal, and urinary isolates of Enterobacterales (n = 10 516) and Pseudomonas aeruginosa (n = 2732) collected in 26 US hospitals in 2015-2017.

RESULTS

Among all Enterobacterales, 1.0% of isolates were DTR and 15.6% were MDR; 8.4% of P. aeruginosa isolates were DTR and 32.4% were MDR. MDR rates for Enterobacterales and DTR and MDR rates for P. aeruginosa were significantly higher (P < .05) in isolates collected in intensive care units (ICUs) than in non-ICUs and in respiratory tract isolates than in intraabdominal or urinary tract isolates. In addition, 82.4% of DTR and 92.1% of MDR Enterobacterales and 62.2% of DTR and 82.2% of MDR P. aeruginosa were imipenem/relebactam-susceptible, and 1.5% of DTR and 65.8% of MDR Enterobacterales and 67.5% of DTR and 84.0% of MDR P. aeruginosa were ceftolozane/tazobactam-susceptible.

CONCLUSIONS

MDR phenotypes defined using the Magiorakos criteria may overcall treatment-limiting resistance in gram-negative bacilli. In the US, DTR Enterobacterales were infrequent, while MDR Enterobacterales isolates and DTR and MDR P. aeruginosa were common. Imipenem/relebactam (Enterobacterales, P. aeruginosa) and ceftolozane/tazobactam (P. aeruginosa) retained in vitro activity against most DTR and MDR isolates.

Profiling of bacterial bloodstream infections in hematological and oncological patients based on a comparative survival analysis

Bloodstream infections (BSI) are a frequent complication in patients with hematological and oncological diseases. However, the impact of different bacterial species causing BSI and of multiple BSI remains incompletely understood. We performed a retrospective study profiling 637 bacterial BSI episodes in hematological and oncological patients. Based on the 30-day (30d) overall survival (OS), we analyzed different types of multiple BSI and grouped BSI-associated bacteria into clusters followed by further assessment of clinical and infection-related characteristics. We discovered that polymicrobial BSI (different organisms on the first day of a BSI episode) and sequential BSI (another BSI before the respective BSI episode) were associated with a worse 30d OS. Different bacterial groups could be classified into three BSI outcome clusters based on 30d OS: favorable (FAV) including mainly common skin contaminants, Escherichia spp. and Streptococcus spp.; intermediate (INT) including mainly Enterococcus spp., vancomycin-resistant Enterococcus spp., and multidrug-resistant gram-negative bacteria (MDRGN); and adverse (ADV) including MDRGN with an additional carbapenem-resistance (MDRGN+CR). A polymicrobial or sequential BSI especially influenced the outcome in the combination of two INT cluster BSI. The presence of a polymicrobial BSI and the assignment into the BSI outcome clusters were identified as independent risk factors for 30d mortality in a Cox multivariate regression analysis. The assignment to a BSI outcome cluster and the differentiated perspective of multiple BSI open new insights into the prognosis of patients with BSI and should be further validated in other patient cohorts.

Bacteria Broadly-Resistant to Last Resort Antibiotics Detected in Commercial Chicken Farms

Resistance to last resort antibiotics in bacteria is an emerging threat to human and animal health. It is important to identify the source of these antimicrobial resistant (AMR) bacteria that are resistant to clinically important antibiotics and evaluate their potential transfer among bacteria. The objectives of this study were to (i) detect bacteria resistant to colistin, carbapenems, and β-lactams in commercial poultry farms, (ii) characterize phylogenetic and virulence markers of E. coli isolates to potentiate virulence risk, and (iii) assess potential transfer of AMR from these isolates via conjugation. Ceca contents from laying hens from conventional cage (CC) and cage-free (CF) farms at three maturity stages were randomly sampled and screened for extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae, carbapenem-resistant Acinetobacter (CRA), and colistin resistant Escherichia coli (CRE) using CHROMagar™ selective media. We found a wide-spread abundance of CRE in both CC and CF hens across all three maturity stages. Extraintestinal pathogenic Escherichia coli phylogenetic groups B2 and D, as well as plasmidic virulence markers iss and iutA, were widely associated with AMR E. coli isolates. ESBL-producing Enterobacteriaceae were uniquely detected in the early lay period of both CC and CF, while multidrug resistant (MDR) Acinetobacter were found in peak and late lay periods of both CC and CF. CRA was detected in CF hens only. bla_CMY was detected in ESBL-producing E. coli in CC and CF and MDR Acinetobacter spp. in CC. Finally, the bla_CMY was shown to be transferrable via an IncK/B plasmid in CC. The presence of MDR to the last-resort antibiotics that are transferable between bacteria in food-producing animals is alarming and warrants studies to develop strategies for their mitigation in the environment.

Recent Advances in the Pursuit of an Effective Acinetobacter baumannii Vaccine

Acinetobacter baumannii has been a major cause of nosocomial infections for decades. The absence of an available vaccine coupled with emerging multidrug resistance has prevented the medical community from effectively controlling this human pathogen. Furthermore, the ongoing pandemic caused by SARS-CoV-2 has increased the risk of hospitalized patients developing ventilator-associated pneumonia caused by bacterial opportunists including A. baumannii. The shortage of antibiotics in the development pipeline prompted the World Health Organization to designate A. baumannii a top priority for the development of new medical countermeasures, such as a vaccine. There are a number of important considerations associated with the development of an A. baumannii vaccine, including strain characteristics, diverse disease manifestations, and target population. In the past decade, research efforts have revealed a number of promising new immunization strategies that could culminate in a safe and protective vaccine against A. baumannii. In this review, we highlight the recent progress in the development of A. baumannii vaccines, discuss potential challenges, and propose future directions to achieve an effective intervention against this human pathogen.

Major discrepancy between factual antibiotic resistance and consumption in South of France: analysis of 539,037 bacterial strains

The burden of antibiotic resistance is currently estimated by mathematical modeling, without real count of resistance to key antibiotics. Here we report the real rate of resistance to key antibiotics in bacteria isolated from humans during a 5 years period in a large area in southeast in France. We conducted a retrospective study on antibiotic susceptibility of 539,107 clinical strains isolated from hospital and private laboratories in south of France area from January 2014 to January 2019. The resistance rate to key antibiotics as well as the proportion of bacteria classified as Difficult-to-Treat (DTR) were determined and compared with the Mann–Whitney U test, the χ² test or the Fisher’s exact test. Among 539,037 isolates, we did not observe any significant increase or decrease in resistance to key antibiotics for 5 years, (oxacillin resistance in Staphylococcus aureus, carbapenem resistance in enterobacteria and Pseudomonas aeruginosa and 3rd generation cephalosporin resistance in Escherichia coli and Klebsiella pneumoniae). However, we observed a significant decrease in imipenem resistance for Acinetobacter baumannii from 2014 to 2018 (24.19–12.27%; p = 0.005) and a significant increase of ceftriaxone resistance in Klebsiella pneumoniae (9.9–24.03%; p = 0.001) and Enterobacter cloacae (24.05–42.05%; p = 0.004). Of these 539,037 isolates, 1604 (0.3%) had a DTR phenotype. Over a 5-year period, we did not observe a burden of AR in our region despite a high rate of antibiotic consumption in our country. These results highlight the need for implementation of real-time AR surveillance systems which use factual data.