Penetration of gentamicin into the alveolar lining fluid of critically ill patients with ventilator-associated pneumonia

Sono-Triggered Biomimetically Nanoantibiotics Mediate Precise Sequential Therapy of MRSA-Induced Lung Infection

Bacterial-induced lower respiratory tract infections are a growing global health concern, exacerbated by the inefficacy of conventional antibiotics and delivery methods to effectively target the lower respiratory tract, leading to suboptimal therapeutic outcomes. To address this challenge, this work engineers PBP2a antibody-presenting membrane nanovesicles (AMVs) specifically designed to target the penicillin-binding protein variant on the surface of methicillin-resistant Staphylococcus aureus (MRSA). Concurrently, this work develops pure ciprofloxacin nanoparticles (NanoCip) that, for the first time, exhibits exceptional self-generated sonodynamic properties, attributed to hydrogen-bond-driven self-assembly, while maintaining their inherent pharmacological efficacy. These NanoCip particles are integrated with AMVs to create a novel biomimetic nanomedicine, AMV@NanoCip. This formulation demonstrated remarkable MRSA-targeting affinity in both in vitro and in vivo models, significantly enhancing antibacterial activity. Upon ultrasound stimulation, AMV@NanoCip achieves over 99.99% sterilization of MRSA in vitro, with a reduction exceeding 5.14 Log CFU. Prokaryotic transcriptomic analysis further elucidates the synergistic mechanisms by which AMV@NanoCip, coupled with ultrasound, disrupts the MRSA exoskeleton. In a MRSA-induced pneumonia animal model, AMV@NanoCip+US results in a substantial bacterial load reduction in the lungs (99.99%, 4.02 Log CFU). This sequential treatment strategy (adhesion-membrane disruption-synergistic therapy) offers significant promise as an innovative therapeutic approach for combating bacterial infections.

Aerosolized Antibiotic Therapy in Mechanically Ventilated Patients

Delivering antibiotics directly to the respiratory tract through inhalation to address lung infections has garnered clinical and scientific interest for decades, given the potential favorable pharmacokinetic profile of this administration route. Among critically ill patients, the burden of healthcare-associated pulmonary infections particularly drove continued interest in delivering inhaled antibiotics to intubated patients. We present a concise overview of the existing rationale and evidence and provide guidance for implementing inhaled antibiotics among ventilated critically ill patients, emphasizing insights from recent literature.

Improved characterization of aminoglycoside penetration into human lung epithelial lining fluid via population pharmacokinetics

Aminoglycosides are important treatment options for serious lung infections, but modeling analyses to quantify their human lung epithelial lining fluid (ELF) penetration are lacking. We estimated the extent and rate of penetration for five aminoglycosides via population pharmacokinetics from eight published studies. The area under the curve in ELF vs plasma ranged from 50% to 100% and equilibration half-lives from 0.61 to 5.80 h, indicating extensive system hysteresis. Aminoglycoside ELF peak concentrations were blunted, but overall exposures were moderately high.

Sepsis Stewardship: The Puzzle of Antibiotic Therapy in the Context of Individualization of Decision Making

The main recent change observed in the field of critical patient infection has been universal awareness of the need to make better use of antimicrobials, especially for the most serious cases, beyond the application of simple and effective formulas or rigid protocols. The increase in resistant microorganisms, the quantitative increase in major surgeries and interventional procedures in the highest risk patients, and the appearance of a significant number of new antibiotics in recent years (some very specifically directed against certain mechanisms of resistance and others with a broader spectrum of applications) have led us to shift our questions from "what to deal with" to "how to treat". There has been controversy about how best to approach antibiotic treatment of complex cases of sepsis. The individualized and adjusted dosage, the moment of its administration, the objective, and the selection of the regimen are pointed out as factors of special relevance in a critically ill patient where the frequency of resistant microorganisms, especially among the Enterobacterales group, and the emergence of multiple and diverse antibiotic treatment alternatives have made the appropriate choice of antibiotic treatment more complex, requiring a constant updating of knowledge and the creation of multidisciplinary teams to confront new infections that are difficult to treat. In this article, we have reviewed the phenomenon of the emergence of resistance to antibacterials and we have tried to share some of the ideas, such as stewardship, sparing carbapenems, and organizational, microbiological, pharmacological, and knowledge tools, that we have considered most useful and effective for individualized decision making that takes into account the current context of multidrug resistance. The greatest challenge, therefore, of decision making in this context lies in determining an effective, optimal, and balanced empirical antibiotic treatment.

Treatment and diagnosis of severe KPC-producing Klebsiella pneumoniae infections: a perspective on what has changed over last decades

Antimicrobial resistance is a global health threat. Among Gram-negative bacteria, resistance to carbapenems, a class of β-lactam antibiotics, is usually a proxy for difficult-to-treat resistance, since carbapenem-resistant organisms are often resistant to many classes of antibiotics. Carbapenem resistance in the Gram-negative pathogen Klebsiella pneumoniae is mostly due to the production of carbapenemases, enzymes able to hydrolyze carbapenems, and K. pneumoniae carbapenemase (KPC)-type enzymes are overall the most prevalent carbapenemases in K. pneumoniae. In the last decade, the management of severe infections due to KPC-producing K. pneumoniae (KPC-Kp) in humans has presented many peculiar challenges to clinicians worldwide. In this perspective, we discuss how the treatment of severe KPC-Kp infections has evolved over the last decades, guided by the accumulating evidence from clinical studies, and how recent advances in diagnostics have allowed to anticipate identification of KPC-Kp in infected patients.KEY MESSAGESIn the last decade, the management of severe infections due to KPC-Kp has presented many peculiar challenges to clinicians worldwideFollowing the introduction in clinical practice of novel β-lactam/β-lactamase inhibitor combinations and novel β-lactams active against KPC-producing bacteria, the management of severe KPC-Kp infections has witnessed a remarkable evolutionTreatment of severe KPC-Kp infections is a highly dynamic process, in which the wise use of novel antimicrobials should be accompanied by a continuous refinement based on evolving clinical evidence and laboratory diagnostics.

Aminoglycosides for the Treatment of Severe Infection Due to Resistant Gram-Negative Pathogens

Aminoglycosides are a family of rapidly bactericidal antibiotics that often remain active against resistant Gram-negative bacterial infections. Over the past decade, their use in critically ill patients has been refined; however, due to their renal and cochleovestibular toxicity, their indications in the treatment of sepsis and septic shock have been gradually reduced. This article reviews the spectrum of activity, mode of action, and methods for optimizing the efficacy of aminoglycosides. We discuss the current indications for aminoglycosides, with an emphasis on multidrug-resistant Gram-negative bacteria, such as extended-spectrum β-lactamase-producing Enterobacterales, carbapenemase-producing Enterobacterales, multidrug-resistant Pseudomonas aeruginosa, and carbapenem-resistant Acinetobacter baumannii. Additionally, we review the evidence for the use of nebulized aminoglycosides.

Research Bronchoscopies in Critically Ill Research Participants: An Official American Thoracic Society Workshop Report

Bronchoscopy for research purposes is a valuable tool to understand lung-specific biology in human participants. Despite published reports and active research protocols using this procedure in critically ill patients, no recent document encapsulates the important safety considerations and downstream applications of this procedure in this setting. The objectives were to identify safe practices for patient selection and protection of hospital staff, provide recommendations for sample procurement to standardize studies, and give guidance on sample preparation for novel research technologies. Seventeen international experts in the management of critically ill patients, bronchoscopy in clinical and research settings, and experience in patient-oriented clinical or translational research convened for a workshop. Review of relevant literature, expert presentations, and discussion generated the findings presented herein. The committee concludes that research bronchoscopy with bronchoalveolar lavage in critically ill patients on mechanical ventilation is valuable and safe in appropriately selected patients. This report includes recommendations on standardization of this procedure and prioritizes the reporting of sample management to produce more reproducible results between laboratories. This document serves as a resource to the community of researchers who endeavor to include bronchoscopy as part of their research protocols and highlights key considerations for the inclusion and safety of research participants.

Optimizing antibiotic dosing regimens for nosocomial pneumonia: a window of opportunity for pharmacokinetic and pharmacodynamic modeling

INTRODUCTION

Determining antibiotic exposure in the lung and the threshold(s) needed for effective antibacterial killing is paramount during development of new antibiotics for the treatment of nosocomial pneumonia, as these exposures directly affect clinical outcomes and resistance development. The use of pharmacokinetic and pharmacodynamic modeling is recommended by regulatory agencies to evaluate antibiotic pulmonary exposure and optimize dosage regimen selection. This process has been implemented in newer antibiotic development.

AREAS COVERED

This review will discuss the basis for conducting pharmacokinetic and pharmacodynamic studies to support dosage regimen selection and optimization for the treatment of nosocomial pneumonia. Pharmacokinetic/pharmacodynamic data that supported recent hospital-acquired bacterial pneumonia/ventilator-associated bacterial pneumonia indications for ceftolozane/tazobactam, ceftazidime/avibactam, imipenem/cilastatin/relebactam, and cefiderocol will be reviewed.

EXPERT OPINION

Optimal drug development requires the integration of preclinical pharmacodynamic studies, healthy volunteers and ideally patient bronchoalveolar lavage pharmacokinetic studies, Monte-Carlo simulation, and clinical trials. Currently, plasma exposure has been successfully used as a surrogate for lung exposure threshold. Future studies are needed to identify the value of lung pharmacodynamic thresholds in nosocomial pneumonia antibiotic dosage optimization.

New antibiotics for Gram-negative pneumonia

Pneumonia is frequently encountered in clinical practice, and Gram-negative bacilli constitute a significant proportion of its aetiology, especially when it is acquired in a hospital setting. With the alarming global rise in multidrug resistance in Gram-negative bacilli, antibiotic therapy for treating patients with pneumonia is challenging and must be guided by in vitro susceptibility results. In this review, we provide an overview of antibiotics newly approved for the treatment of pneumonia caused by Gram-negative bacilli. Ceftazidime-avibactam, imipenem-relebactam and meropenem-vaborbactam have potent activity against some of the carbapenem-resistant Enterobacterales, especially Klebsiella pneumoniae carbapenemase producers. Several novel antibiotics have potent activity against multidrug-resistant Pseudomonas aeruginosa, such as ceftazidime-avibactam, ceftolozane-tazobactam, imipenem-relabactam and cefiderocol. Cefiderocol may also play an important role in the management of pneumonia caused by Acinetobacter baumannii, along with plazomicin and eravacycline.

Clinical evidence supporting cefiderol for serious Acinetobacter baumannii infections

PURPOSE OF REVIEW

Nosocomial infections caused by Acinetobacter baumannii currently represent a serious challenge for clinicians because treatment options are limited and frequently associated with significant toxicity. Cefiderocol is a first-in-class siderophore cephalosporin that has a proven efficacy for the treatment of multidrug-resistant Gram-negative infections, including carbapenem-resistant A. baumannii. The aim of this review is to evaluate the current evidence for the role of cefiderocol in the management of A. baumannii infections.

RECENT FINDINGS

In this review, we briefly summarize the available data on the efficacy (from randomized controlled trials) and on effectiveness and cure rates (from observational studies), pertaining to the use of cefiderocol for treatment of serious A. baumannii infections.

SUMMARY

Cefiderocol represents a promising and safe antibiotic option for treating patients with carbapenem-resistant A. baumannii infections. Due to conflicting mortality data from available experience, well-designed future randomized controlled trials and real-life studies are needed.

Ventilator-Associated Pneumonia Prevention in Pediatric Patients: Narrative Review

Ventilator-associated pneumonia (VAP), one of the most common healthcare-associated infections in intensive care settings, is associated with significant morbidity and mortality. VAP is diagnosed in >10% of patients on mechanical ventilation, incidence rising with number of ventilator days. In recent decades, the pathophysiology of VAP, VAP risk factors and treatment have been extensively studied. In critically ill pediatric patients, mechanical issues such as insufficient tightness of the ventilator circuit (mainly due to historically based preference of uncuffed tubes) and excessive humidity in the circuit are both significant risk factors of VAP development. Protocol-based approaches to critically ill patients on mechanical ventilation, closed suctioning, upper body position, enteral feeding and selective gastric acid suppression medication have a beneficial effect on VAP incidence. In recent decades, cuffed tubes applied to the whole spectrum of critically ill pediatric patients (except neonates <2700 g of weight), together with cuff-oriented nursing care including proper cuff-pressure (<20 cm H2O) management and the use of specialized tracheal tubes with subglottic suction ports combined with close infraglottic tracheal suctioning, have been implemented. The aim of this review was to summarize the current evidence-based knowledge about the pathophysiology, risk factors, diagnosis, treatment and prevention of VAP in clinically oriented settings.

Tissue Penetration of Antimicrobials in Intensive Care Unit Patients: A Systematic Review-Part II

In patients that are admitted to intensive care units (ICUs), the clinical outcome of severe infections depends on several factors, as well as the early administration of chemotherapies and comorbidities. Antimicrobials may be used in off-label regimens to maximize the probability of therapeutic concentrations within infected tissues and to prevent the selection of resistant clones. Interestingly, the literature clearly shows that the rate of tissue penetration is variable among antibacterial drugs, and the correlation between plasma and tissue concentrations may be inconstant. The present review harvests data about tissue penetration of antibacterial drugs in ICU patients, limiting the search to those drugs that mainly act as protein synthesis inhibitors and disrupting DNA structure and function. As expected, fluoroquinolones, macrolides, linezolid, and tigecycline have an excellent diffusion into epithelial lining fluid. That high penetration is fundamental for the therapy of ventilator and healthcare-associated pneumonia. Some drugs also display a high penetration rate within cerebrospinal fluid, while other agents diffuse into the skin and soft tissues. Further studies are needed to improve our knowledge about drug tissue penetration, especially in the presence of factors that may affect drug pharmacokinetics.

Treatment of MDR Gram-Negative Bacteria Infections: Ongoing and Prospective

Antimicrobial resistance is a serious public health concern across the world. Gram-negative resistance has propagated over the globe via various methods, the most challenging of which include extended-spectrum β-lactamases, carbapenemases, and AmpC enzymes. Gram-negative bacterial infections are difficult to treat in critically extremely sick persons. Resistance to different antibiotic treatments nearly always lowers the probability of proper empirical coverage, sometimes resulting in severe outcomes. Multidrug resistance can be combated with varying degrees of success using a combination of older drugs with high toxicity levels and novel therapeutics. The current therapies for multidrug-resistant Gram-negative bacteria are discussed in this review, which includes innovative medications, older pharmaceuticals, creative combinations of the two, and therapeutic targets.

The role of cefiderocol in clinical practice

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

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

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

Gram-negative bacteria act as a reservoir for aminoglycoside antibiotics that interact with host factors to enhance bacterial killing in a mouse model of pneumonia

In vitro exposure of multiple Gram-negative bacteria to an aminoglycoside (AG) antibiotic has previously been demonstrated to result in bacterial alterations that interact with host factors to suppress Gram-negative pneumonia. However, the mechanisms resulting in suppression are not known. Here, the hypothesis that Gram-negative bacteria bind and retain AGs, which are introduced into the lung and interact with host defenses to affect bacterial killing, was tested. Following in vitro exposure of one of several, pathogenic Gram-negative bacteria to the AG antibiotics kanamycin or gentamicin, AGs were detected in bacterial cell pellets (up to 208 μg/mL). Using inhibitors of AG binding and internalization, the bacterial outer membrane was implicated as the predominant kanamycin and gentamicin reservoir. Following intranasal administration of gentamicin-bound bacteria or gentamicin solution at the time of infection with live, AG-naïve bacteria, gentamicin was detected in the lungs of infected mice (up to 8 μg/g). Co-inoculation with gentamicin-bound bacteria resulted in killing of AG-naïve bacteria by up to 3-log₁₀, mirroring the effects of intranasal gentamicin treatment. In vitro killing of AG-naïve bacteria mediated by kanamycin-bound bacteria required the presence of detergents or pulmonary surfactant, suggesting that increased bacterial killing inside the murine lung is facilitated by the detergent component of pulmonary surfactant. These findings demonstrate that Gram-negative bacteria bind and retain AGs that can interact with host-derived pulmonary surfactant to enhance bacterial killing in the lung. This may help explain why AGs appear to have unique efficacy in the lung and might expand their clinical utility.

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

Current and future perspectives in the treatment of multidrug-resistant Gram-negative infections

Microbial resistance is a serious threat to human health worldwide. Among the World Health Organisation's list of priority resistant bacteria, three are listed as critical-the highest level of concern-and all three are Gram-negative. Gram-negative resistance has spread worldwide via a variety of mechanisms, the most problematic being via AmpC enzymes, extended-spectrum β-lactamases, and carbapenemases. A combination of older drugs, many with high levels of toxicity, and newer agents are being used to combat multidrug resistance, with varying degrees of success. This review discusses the current treatments for multidrug-resistant Gram-negative bacteria, including new agents, older compounds, and new combinations of both, and some new treatment targets that are currently under investigation.

Management of Infections Caused by Multidrug-resistant Gram-negative Pathogens: Recent Advances and Future Directions

During the last decades, the isolation of multidrug-resistant Gram-negative (MDR-GN) bacteria has dramatically increased worldwide and has been associated with significant delays in the administration of adequate antibiotic treatment, resulting in increased morbidity and mortality rates. Given specific challenges to effective therapy with old antibiotics, there is the need to establish adequate clinical and therapeutic recommendations for antibiotic treatment of MDR-GN pathogens. Herein, we will review risk factors for harbouring infections due to MDR-GN bacteria, proposing an algorithm for the choice of empirical treatment when a MDR-GN pathogen is suspected. In addition, we will report our recommendations regarding the first- and second-line treatment options for hospitalized patients with serious infections caused by extended-spectrum β-lactamases producing Enterobacterales, carbapenem-resistant Enterobacterales, MDR Pseudomonas aeruginosa and MDR Acinetobacter baumannii. Recommendations have been specially focused, for each pathogen, on bloodstream infections, nosocomial pneumonia, and urinary tract infections.

Safety and harms of bronchoalveolar lavage for acute respiratory failure: A systematic review and meta-analysis

BACKGROUND

This review aimed to investigate whether bronchoalveolar lavage (BAL) is safe in patients with severe acute respiratory failure (ARF).

METHODS

We searched the MEDLINE, CENTRAL, and other databases up to June 2, 2021 for studies that examined BAL for severe ARF. We included all cohort studies and randomized or non-randomized trials, while we excluded case-control studies, case reports, and case series. We evaluated the quality of the evidence using the Grading of Recommendations, Assessment, Development, and Evaluation approach.

RESULTS

We included 17 studies (1085 patients) in the meta-analysis. The integrated frequency of death was 0.000% (95% confidence interval [CI]: 0.000-0.045%, I² = 0.0%). The pooled risk of severe complications of respiratory system, cardiovascular system, and major bleeding was 1.32% (95% CI: 0.000-4.41%, I² = 84.8%), 0.040% (95% CI: 0.000-0.71%, I² = 9.3%), and 0.000% (95% CI: 0.000-0.27%, I² = 0.0%), respectively. In the subgroup analysis with mechanical ventilation during BAL, there were few severe complications of the respiratory system (3/717 patients in 13 studies) and almost no heterogeneity (I² = 0.0%).

CONCLUSIONS

Our study suggests that severe complications of BAL for severe ARF are probably rare, particularly in patients receiving mechanical ventilation. After considering the risks and benefits, it would be worthwhile to consider performing BAL in patients with severe ARF of unknown etiology to pursue its cause.

TRIAL REGISTRATION

The protocol was registered with the University Hospital Medical Information Network Clinical Trials Registry (UMIN000040600).

Landscape of Multidrug-Resistant Gram-Negative Infections in Egypt: Survey and Literature Review

Purpose

This article is the first to review published reports on the prevalence of multidrug-resistant (MDR) gram-negative infections in Egypt and gain insights into antimicrobial resistance (AMR) surveillance and susceptibility testing capabilities of Egyptian medical centers.

Materials and Methods

A literature review and online survey were conducted.

Results

The online survey and literature review reported high prevalence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae (19–85.24% of E. coli, and 10–87% of K. pneumoniae), carbapenem-resistant Enterobacteriaceae (35–100% of K. pneumoniae and 13.8–100% of E. coli), carbapenem-resistant Acinetobacter baumannii (10–100%), and carbapenem-resistant Pseudomonas aeruginosa (15–70%) in Egypt. Risk factors for MDR Gram-negative infections were ventilated patients (67.4%), prolonged hospitalization (53.5%) and chronic disease (34.9%). Although antimicrobial surveillance capabilities were deemed at least moderate in most centers, lack of access to rapid AMR diagnostics, lack of use of local epidemiological data in treatment decision-making, lack of antimicrobial stewardship (AMS) programs, and lack of risk prediction tools were commonly reported by respondents.

Conclusion

This survey has highlighted the presence of knowledge gaps as well as limitations in the surveillance and monitoring capabilities of AMR in Egypt, with most laboratories lacking rapid diagnostics and molecular testing. Future efforts in Egypt should focus on tackling these issues via nationwide initiatives, including understanding the AMR trends in the country, capacity building of laboratories and their staff to correctly and timely identify AMR, and introducing newer antimicrobials for targeting emerging resistance mechanisms in Gram-negative species.

Evaluation of a New Culture-Based AtbFinder Test-System Employing a Novel Nutrient Medium for the Selection of Optimal Antibiotics for Critically Ill Patients with Polymicrobial Infections within 4 h

Here, we describe the validation of a new phenotypic culture-based AtbFinder method for rapid selection of antibiotics in vitro using specimens with mono- and polybacterial infections. AtbFinder, which can be applied to any type of non-blood tissue, does not require isolation of pure bacterial cultures. The method uses a novel TGV medium that allows more rapid bacterial growth of Gram-positive and Gram-negative monoisolates compared with that achieved with conventional laboratory media, demonstrating overall sensitivity, specificity, PPV, NPV values of 99.6%, 98.1%, 98.5%, and 99.4%, respectively, after 4 h. For polymicrobial infections, AtbFinder utilized a novel paradigm of the population response to antibiotics, enabling bacterial growth in the form of a mixed microbial community and selecting antibiotics targeting not only the principal pathogen, but also those bacteria that support their growth. TGV medium allowed culturing of a more diverse set of bacteria from polymicrobial biospecimens, compared with that achieved with the standard media, and enabled, within 4 h, accurate selection of the antibiotics that completely eliminated all cultivatable bacteria from clinical samples. In conclusion, the AtbFinder system may be a valuable tool in improving antibiotic selection, and enabling targeted empirical therapy and accurate antibiotic replacement, which is especially important in high-risk patients.

Amikacin nebulization for the adjunctive therapy of gram-negative pneumonia in mechanically ventilated patients: a systematic review and meta-analysis of randomized controlled trials

Treatment of ventilated patients with gram-negative pneumonia (GNP) is often unsuccessful. We aimed to assess the efficacy and safety of nebulized amikacin (NA) as adjunctive therapy to systemic antibiotics in this patient population. PubMed, Embase, China national knowledge infrastructure, Wanfang, and the Cochrane database were searched for randomized controlled trials (RCTs) investigating the effect of NA as adjunctive therapy in ventilated adult patients with GNP. Heterogeneity was explored using subgroup analysis and sensitivity analysis. The Grading of recommendations assessment, development, and evaluation approach was used to assess the certainty of the evidence. Thirteen RCTs with 1733 adults were included. The pooled results showed NA had better microbiologic eradication (RR = 1.51, 95% CI 1.35 to 1.69, P < 0.0001) and improved clinical response (RR = 1.23; 95% CI 1.13 to 1.34; P < 0.0001) when compared with control. Meanwhile, overall mortality, pneumonia associated mortality, duration of mechanical ventilation, length of stay in ICU and change of clinical pneumonia infection scores were similar between NA and control groups. Additionally, NA did not add significant nephrotoxicity while could cause more bronchospasm. The use of NA adjunctive to systemic antibiotics therapy showed better benefits in ventilated patients with GNP. More well-designed RCTs are still needed to confirm our results.

Efficacy of a Fosfomycin-Containing Regimen for Treatment of Severe Pneumonia Caused by Multidrug-Resistant Acinetobacter baumannii: A Prospective, Observational Study

INTRODUCTION

Severe pneumonia caused by multidrug-resistant Acinetobacter baumannii (MDR-AB) remains a difficult-to-treat infection. Considering the poor lung penetration of most antibiotics, the choice of the better antibiotic regimen is debated.

METHODS

We performed a prospective, observational, multicenter study conducted from January 2017 to June 2020. All consecutive hospitalized patients with severe pneumonia due to MDR-AB were included in the study. The primary endpoint of the study was to evaluate risk factors associated with survival or death at 30 days from pneumonia onset. A propensity score for receiving therapy with fosfomycin was added to the model.

RESULTS

During the study period, 180 cases of hospital-acquired pneumonia, including ventilator-associated pneumonia, caused by MDR-AB strains were observed. Cox regression analysis of factors associated with 30-day mortality, after propensity score, showed that septic shock, and secondary bacteremia were associated with death, while a fosfomycin-containing regimen was associated with 30-day survival. Antibiotic combinations with fosfomycin in definitive therapy for 44 patients were: fosfomycin + colistin in 11 (25%) patients followed by fosfomycin + carbapenem + tigecycline in 8 (18.2%), fosfomycin + colistin + tigecycline in 7 (15.9%), fosfomycin + rifampin in 7 (15.9%), fosfomycin + tigecycline in 6 (13.6%), fosfomycin + carbapenem in 3 (6.8%), and fosfomycin + aminoglycoside in 2 (4.5%).

CONCLUSIONS

This real-life clinical experience concerning the therapeutic approach to severe pneumonia caused by MDR-AB provides useful suggestions to clinicians, showing the use of different antibiotic regimens with a predominant role for fosfomycin. Further randomized clinical trials are necessary to confirm or exclude these observations.

Pharmacodynamics of once- versus twice-daily dosing of nebulized amikacin in an in vitro Hollow-Fiber Infection Model against 3 clinical isolates of Pseudomonas aeruginosa

This study aims to compare the bacterial killing of once- versus twice-daily nebulized amikacin against Pseudomonas aeruginosa and to determine the optimal duration of therapy. Three clinical P. aeruginosa isolates (amikacin MICs 2, 8, and 64 mg/L) were exposed to simulated epithelial lining fluid exposures of nebulized amikacin with dosing regimens of 400 mg and 800 mg once- or twice-daily up to 7-days using the in vitro hollow-fiber infection model. Quantitative cultures were performed. Simulated amikacin dosing regimens of 400 mg twice-daily and 800 mg once-daily achieved ≥2-log reduction in the bacterial burden within the first 24-hours of therapy for all isolates tested. No dosing regimen suppressed the emergence of amikacin resistance. No difference in bacterial killing or regrowth was observed between 3- and 7-days of amikacin. Amikacin doses of 800 mg once-daily for up to 3-days may be considered for future clinical trials.

Evaluating Cefiderocol in the Treatment of Multidrug-Resistant Gram-Negative Bacilli: A Review of the Emerging Data

Infections due to multidrug-resistant Gram-negative bacteria (MDR-GNB), especially when carbapenem resistant, have been very difficult to manage in the last fifteen years, owing to the paucity of dependable therapeutic options. Cefiderocol is a siderophore cephalosporin recently approved by the Food and Drug Administration (FDA) and European Medicines Agency (EMA) that may have the potential to fill some of the remaining gaps in the treatment of MDR-GNB infections. Among others, cefiderocol demonstrated in vitro activity against carbapenem-resistant Acinetobacter baumannii and metallo-β-lactamases producers. Clinical data from both registrative studies and post-marketing experiences are essential to confirm whether these promises from in vitro studies could readily translate into clinical practice, as well as to delineate the precise place in therapy for cefiderocol for the treatment of MDR-GNB in the near future. Because of its unique potential, it is essential to provide both randomized controlled trials (RCT) and real-life data to improve the ability of clinicians to exploit its benefit in both empirical and targeted treatment of MDR-GNB infections. In this narrative review, we discuss the emerging data from pivotal RCT and initial real-life experiences on the use of cefiderocol for the treatment of MDR-GNB infections.

The role of new antimicrobials for Gram-negative infections in daily clinical practice

PURPOSE OF REVIEW

To discuss a possible clinical reasoning for treating resistant Gram-negative bacteria (GNB) infections in daily clinical practice, as well as developing a research agenda for the field.

RECENT FINDINGS

Novel agents, both belonging to β-lactams and to other classes of antimicrobials, have recently become available, likely replacing polymyxins or polymyxin-based combination regimens as the preferred choices for the first-line treatment of severe resistant GNB infections in the near future.

SUMMARY

The peculiar characteristics of novel agents for severe resistant GNB infections have abruptly made the structure of previous therapeutic algorithms somewhat obsolete, in view of the differential activity of most of them against different classes of carbapenemases. Furthermore, other agents showing activity against resistant GNB are in late phase of clinical development. Optimizing the use of novel agents in order both to guarantee the best available treatment to patients and to delay the emergence and spread of resistance is an important task that cannot be postponed, especially considering the unavailability of well tolerated and fully efficacious options for treating resistant GNB infections that we faced in the last 15 years.

Treatment of severe infections due to metallo-β-lactamases-producing Gram-negative bacteria

In the last decades, there was an important paucity of agents for adequately treating infections due to metallo-β-lactamases-producing Gram-negative bacteria (MBL-GNB). Cefiderocol, a novel siderophore cephalosporin showing in vitro activity against MBL-GNB, has been recently marketed, and a combination of aztreonam and ceftazidime/avibactam has shown a possible favorable effect on survival of patients with severe MBL-GNB infections in observational studies. Other agents showing in vitro activity against MBL-GNB are currently in clinical development (e.g., cefepime/taniborbactam, LYS228, cefepime/zidebactam) that could be an important addition to our future armamentarium for severe MBL-GNB infections. Nonetheless, we should not discontinue our efforts to optimize the use of non-β-lactams agents, since they could remain an essential last-resort or alternative option in selected cases.

Therapeutic options for difficult-to-treat Acinetobacter baumannii infections: a 2020 perspective

INTRODUCTION

Treatment of severe infections due to Acinetobacter baumannii with difficult-to-treat resistance (DTR-AB), which exhibits resistance to all β-lactams, β-lactam/β-lactamases inhibitor combinations, and fluoroquinolones, remains a challenge for clinicians.

AREAS COVERED

The present perspective provides a personal view on both current and future agents for the treatment of severe DTR-AB infections.

EXPERT OPINION

We currently are in a transition era for the treatment of DTR-AB infections, where in the past 20 years, polymyxin-based regimens have become the most used approach (although possibly suboptimal, there were few or no alternatives) and where in the next 20 years, polymyxins will likely be replaced by less toxic novel agents as first-line choices. Two novel antimicrobial agents have been recently approved that show activity against DTR-AB, cefiderocol and eravacycline, while durlobactam/sulbactam is in phase-3 of clinical development. In the near future, these agents could become important first-line choices for the treatment of DTR-AB within approved indications, or for off-label indications in the absence of dependable alternatives. Good-quality post-marketing experiences remain necessary for arising clinically relevant questions and guiding the design of further dedicated randomized controlled trials to stably optimize the use of novel agents for DTR-AB infections in the next decades.

Pharmacodynamic Evaluation of Plasma and Epithelial Lining Fluid Exposures of Amikacin against Pseudomonas aeruginosa in a Dynamic In Vitro Hollow-Fiber Infection Model

Given that aminoglycosides, such as amikacin, may be used for multidrug-resistant Pseudomonas aeruginosa infections, optimization of therapy is paramount for improved treatment outcomes. This study aims to investigate the pharmacodynamics of different simulated intravenous amikacin doses on susceptible P. aeruginosa to inform ventilator-associated pneumonia (VAP) and sepsis treatment choices. A hollow-fiber infection model with two P. aeruginosa isolates (MICs of 2 and 8 mg/liter) with an initial inoculum of ∼108 CFU/ml was used to test different amikacin dosing regimens. Three regimens (15, 25, and 50 mg/kg) were tested to simulate a blood exposure, while a 30 mg/kg regimen simulated the epithelial lining fluid (ELF) for potential respiratory tract infection. Data were described using a semimechanistic pharmacokinetic/pharmacodynamic (PK/PD) model. Whole-genome sequencing was used to identify mutations associated with resistance emergence. While bacterial density was reduced by >6 logs within the first 12 h in simulated blood exposures following this initial bacterial kill, there was amplification of a resistant subpopulation with ribosomal mutations that were likely mediating amikacin resistance. No appreciable bacterial killing occurred with subsequent doses. There was less (<5 log) bacterial killing in the simulated ELF exposure for either isolate tested. Simulation studies suggested that a dose of 30 and 50 mg/kg may provide maximal bacterial killing for bloodstream and VAP infections, respectively. Our results suggest that amikacin efficacy may be improved with the use of high-dose therapy to rapidly eliminate susceptible bacteria. Subsequent doses may have reduced efficacy given the rapid amplification of less-susceptible bacterial subpopulations with amikacin monotherapy.

Real-World Experience with Ceftolozane-Tazobactam for Multidrug-Resistant Gram-Negative Bacterial Infections

Our objective was to describe the prescribing practices, clinical characteristics, and outcomes of patients treated with ceftolozane-tazobactam (C/T) for multidrug-resistant (MDR) Gram-negative infections. This was a multicenter, retrospective, cohort study at eight U.S. medical centers (2015 to 2019). Inclusion criteria were age ≥18 years and receipt of C/T (≥72 hours) for suspected or confirmed MDR Gram-negative infection. The primary efficacy outcome, evaluated among patients with MDR Pseudomonas aeruginosa infections, was composite clinical failure, namely, 30-day all-cause mortality, 30-day recurrence, and/or failure to resolve or improve infection signs or symptoms after C/T treatment. In total, 259 patients were included, and P. aeruginosa was isolated in 236 (91.1%). The MDR and extremely drug-resistant phenotypes were detected in 95.8% and 37.7% of P. aeruginosa isolates, respectively. The most common infection source was the respiratory tract (62.9%). High-dose C/T was used in 71.2% of patients with a respiratory tract infection (RTI) overall but in only 39.6% of patients with an RTI who required C/T renal dose adjustment. In the primary efficacy population (n = 226), clinical failure and 30-day mortality occurred in 85 (37.6%) and 39 (17.3%) patients, respectively. New C/T MDR P. aeruginosa resistance was detected in 3 of 31 patients (9.7%) with follow-up cultures. Hospital-acquired infection and Acute Physiological and Chronic Health Evaluation II (APACHE II) score were independently associated with clinical failure (adjusted odds ratio [aOR], 2.472 and 95% confidence interval [CI], 1.322 to 4.625; and aOR, 1.068 and 95% CI, 1.031 to 1.106, respectively). Twenty-five (9.7%) patients experienced ≥1 adverse effect (9 acute kidney injury, 13 Clostridioides difficile infection, 1 hepatotoxicity, 2 encephalopathy, and 2 gastrointestinal intolerance). C/T addresses an unmet medical need in patients with MDR Gram-negative infections.

Low penetrance of antibiotics in the epithelial lining fluid. The role of inhaled antibiotics in patients with bronchiectasis

Plasma drug concentrations, spectrum of antibacterial activity and minimum inhibitory concentration (MIC) had been widely considered as markers of the efficacy of antibiotics. Nonetheless, in several cases, antibiotics characterized by all these features were ineffective for the treatment of respiratory tract infections. A typical paradigm represented the case of patients with bronchiectasis who do not always benefit from antibiotics and thus experiencing increased sputum production, worse quality of life, more rapid forced expiratory volume in the first second (FEV1) decline, more frequent exacerbations and increased mortality rates, especially those with Pseudomonas aeruginosa (P. aeruginosa) chronic infection. Subsequently, penetrance of antibiotics in the epithelial lining fluid has gradually emerged as another key factor for the outcome of antibiotic treatment. Given that a plethora of antibiotics presented with poor or intermediate penetrance in the epithelial lining fluid, inhaled antibiotics targeting directly the site of infection emerged as a new option for patients with respiratory disorders including patients with bronchiectasis. This review article intends to summarize the current state of knowledge for the penetrance of antibiotics in the epithelial lining fluid and present results from clinical trials of inhaled antibiotics in patients with bronchiectasis of etiology other than cystic fibrosis.

Real-World Experience With Ceftazidime-Avibactam for Multidrug-Resistant Gram-Negative Bacterial Infections

Background

We conducted this study to describe the clinical characteristics, microbiology, and outcomes of patients treated with ceftazidime-avibactam (CZA) for a range of multidrug-resistant Gram-negative (MDR-GN) infections.

Methods

This is a multicenter, retrospective cohort study conducted at 6 medical centers in the United States between 2015 and 2019. Adult patients who received CZA (≥72 hours) were eligible. The primary outcome was clinical failure defined as a composite of 30-day all-cause mortality, 30-day microbiological failure, and/or failure to resolve or improve signs or symptoms of infection on CZA.

Results

In total, data from 203 patients were evaluated. Carbapenem-resistant Enterobacteriaceae (CRE) and Pseudomonas spp were isolated from 117 (57.6%) and 63 (31.0%) culture specimens, respectively. The most common infection sources were respiratory (37.4%), urinary (19.7%), and intra-abdominal (18.7%). Blood cultures were positive in 22 (10.8%) patients. Clinical failure, 30-day mortality, and 30-day recurrence occurred in 59 (29.1%), 35 (17.2%), and 12 (5.9%) patients, respectively. On therapy, CZA resistance developed in 1 of 62 patients with repeat testing. Primary bacteremia or respiratory tract infection and higher SOFA score were positively associated with clinical failure (adjusted odds ratio [aOR] = 2.270, 95% confidence interval [CI] = 1.115–4.620 and aOR = 1.234, 95% CI = 1.118–1.362, respectively). Receipt of CZA within 48 hours of infection onset was protective (aOR, 0.409; 95% CI, 0.180–0.930). Seventeen (8.4%) patients experienced a potential drug-related adverse effect (10 acute kidney injury, 3 Clostridioides difficile infection, 2 rash, and 1 each gastrointestinal intolerance and neutropenia)

Conclusions

Ceftazidime-avibactam is being used to treat a range of MDR-GN infections including Pseudomonas spp as well as CRE.

Optimizing Antibiotic Administration for Pneumonia

Pneumonia, including community-acquired bacterial pneumonia, hospital-acquired bacterial pneumonia, and ventilator-acquired bacterial pneumonia, carries unacceptably high morbidity and mortality. Despite advances in antimicrobial therapy, emergence of multidrug resistance and high rates of treatment failure have made optimization of antibiotic efficacy a priority. This review focuses on pharmacokinetic and pharmacodynamic approaches to antibacterial optimization within the lung environment and in the setting of critical illness. Strategies for including these approaches in drug development programs as well as clinical practice are described and reviewed.

Aerosol Therapy for Pneumonia in the Intensive Care Unit

Antibiotic aerosolization in patients with ventilator-associated pneumonia (VAP) allows very high concentrations of antimicrobial agents in the respiratory secretions, far more than those achievable using the intravenous route. However, data in critically ill patients with pneumonia are limited. Administration of aerosolized antibiotics might increase the likelihood of clinical resolution, but no significant improvements in important outcomes have been consistently documented. Thus, aerosolized antibiotics should be restricted to the treatment of extensively resistant gram-negative pneumonia. In these cases, the use of a vibrating-mesh nebulizer seems to be more efficient, but specific settings and conditions are required to improve lung delivery.

Bloodstream infections caused by carbapenem-resistant Acinetobacter baumannii: Clinical features, therapy and outcome from a multicenter study

OBJECTIVES

bloodstream infections (BSI) due to multidrug-resistant (MDR) Acinetobacter baumannii (AB) have been increasingly observed among hospitalized patients.

METHODS

prospective, observational study conducted among 12 large tertiary-care hospitals, across 7 Italian regions. From June 2017 to June 2018 all consecutive hospitalized patients with bacteremia due to MDR-AB were included and analyzed in the study.

RESULTS

During the study period 281 episodes of BSI due to MDR-AB were observed: 98 (34.8%) episodes were classified as primary bacteremias, and 183 (65.2%) as secondary bacteremias; 177 (62.9%) of them were associated with septic shock. Overall, 14-day mortality was observed in 172 (61.2%) patients, while 30-day mortality in 207 (73.6%) patients. On multivariate analysis, previous surgery, continuous renal replacement therapy, inadequate source control of infection, and pneumonia were independently associated with higher risk of septic shock. Instead, septic shock and Charlson Comorbidity Index >3 were associated with 14-day mortality, while adequate source control of infection and combination therapy with survival. Finally, septic shock, previous surgery, and aminoglycoside-containing regimen were associated with 30-day mortality, while colistin-containing regimen with survival.

CONCLUSIONS

BSI caused by MDR-AB represents a difficult challenge for physicians, considering the high rates of septic shock and mortality associated with this infection.

Treatment of Infections Due to MDR Gram-Negative Bacteria

The treatment of multidrug-resistant Gram-negative bacteria (MDR-GNB) infections in critically ill patients presents many challenges. Since an effective treatment should be administered as soon as possible, resistance to many antimicrobial classes almost invariably reduces the probability of adequate empirical coverage, with possible unfavorable consequences. In this light, readily available patient's medical history and updated information about the local microbiological epidemiology remain critical for defining the baseline risk of MDR-GNB infections and firmly guiding empirical treatment choices, with the aim of avoiding both undertreatment and overtreatment. Rapid diagnostics and efficient laboratory workflows are also of paramount importance both for anticipating diagnosis and for rapidly narrowing the antimicrobial spectrum, with de-escalation purposes and in line with antimicrobial stewardship principles. Carbapenem-resistant Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter baumannii are being reported with increasing frequencies worldwide, although with important variability across regions, hospitals and even single wards. In the past few years, new treatment options, such as ceftazidime/avibactam, meropenem/vaborbactam, ceftolozane/tazobactam, plazomicin, and eravacycline have become available, and others will become soon, which have provided some much-awaited resources for effectively counteracting severe infections due to these organisms. However, their optimal use should be guaranteed in the long term, for delaying as much as possible the emergence and diffusion of resistance to novel agents. Despite important progresses, pharmacokinetic/pharmacodynamic optimization of dosages and treatment duration in critically ill patients has still some areas of uncertainty requiring further study, that should take into account also resistance selection as a major endpoint. Treatment of severe MDR-GNB infections in critically ill patients in the near future will require an expert and complex clinical reasoning, of course taking into account the peculiar characteristics of the target population, but also the need for adequate empirical coverage and the more and more specific enzyme-level activity of novel antimicrobials with respect to the different resistance mechanisms of MDR-GNB.

Current and emerging pharmacotherapy for the treatment of infections following open-heart surgery

INTRODUCTION

Patients undergoing open-heart surgery may suffer from postoperative complications, including severe infections. Antimicrobials to treat infectious complications in this population should be selected thoughtfully, taking into account three different and fundamental issues: (i) the site of infection; (ii) the suspected or proven causative agent and its susceptibility pattern; and (iii) the risk of suboptimal pharmacokinetic characteristics and potential toxicity of the chosen drug/s.

AREAS COVERED

The present narrative review summarizes the current and future antimicrobial options for the treatment of infections developing after open-heart surgery.

EXPERT OPINION

The pharmacological treatment of infections developing in cardiac surgery patients poses peculiar challenges, including the need for an active empirical therapy for severe events such as bloodstream infections, deep sternal wound infections, or early-onset postoperative prosthetic endocarditis. In addition, the risk for multidrug-resistant pathogens should also be taken into account in endemic areas. A multidisciplinary evaluation on a patient-by-patient basis, deeply involving infectious diseases specialists and cardiothoracic surgeons, remains essential for appropriately balancing both short-term and long-term risks and benefits of any possible surgical reintervention in combination with adequate pharmacotherapy.

Evaluation of Epithelial Lining Fluid Concentration of Amikacin in Critically Ill Patients With Ventilator-Associated Pneumonia

INTRODUCTION

Classically, aminoglycosides are known to have low penetration into the lung tissue. So far, no study has been conducted on human adult patients to evaluate amikacin concentration in epithelial lining fluid (ELF) of the alveoli. Therefore, convincing data are not available from the perspective of pharmacokinetics to support the fact that a dosage of 20 mg/kg of amikacin is sufficient to treat patients with ventilator-associated pneumonia (VAP).

METHOD

This was a pilot study of amikacin concentration measurement in the alveolar site of action in critically ill adult patients with VAP who required aminoglycoside therapy. A dose of 20 mg/kg of amikacin was administered over a 30-minute infusion. The serum concentrations of amikacin were evaluated in the first, second, fourth, and sixth hours. However, the ELF concentration of amikacin was evaluated in the second hour with the help of bronchoalveolar lavage sampling technique.

RESULTS

A total number of 8 patients was included in the study. The mean (SD) administered dose was 20 (0.9) mg/kg. The mean (SD) peak plasma concentration of amikacin was 59.6 (23) mg/L, with the volume of distribution of 0.36 (0.13)L/kg. The amikacin concentration in ELF was successfully measured in 7 patients (6.3) mg/L. The lung tissue penetration of the drug was described as alveolar percentage, proportional to both the first- and second-hour plasma concentrations, with a mean (SD) of 10.1% (8.4%) and 18% (16.7%), respectively.

CONCLUSION

To our knowledge, the current study is the first that investigates whether standard doses of amikacin may lead to sufficient alveolar concentration of the drug. The results show that administration of amikacin in doses of 20 mg/kg in critically ill patients with VAP may not provide sufficient concentrations in ELF.

Application of Antibiotic Pharmacodynamics and Dosing Principles in Patients With Sepsis

Sepsis is associated with marked mortality, which may be reduced by prompt initiation of adequate, appropriate doses of antibiotic. Critically ill patients often have physiological changes that reduce blood and tissue concentrations of antibiotic and high rates of multidrug-resistant pathogens, which may affect patients' outcomes. All critical care professionals, including critical care nurses, should understand antibiotic pharmacokinetics and pharmacodynamics to ensure sound antibiotic dosing and administration strategies for optimal microbial killing and patients' outcomes. Effective pathogen eradication occurs when the dose of antibiotic reaches or maintains optimal concentrations relative to the minimum inhibitory concentration for the pathogen. Time-dependent antibiotics, such as β-lactams, can be given as extended or continuous infusions. Concentration-dependent antibiotics such as aminoglycosides are optimized by using high, once-daily dosing strategies with serum concentration monitoring. Vancomycin and fluoroquinolones are dependent on both time and concentration above the minimum inhibitory concentration.

Antibiotic dosing for multidrug-resistant pathogen pneumonia

PURPOSE OF REVIEW

Nosocomial pneumonia caused by multidrug-resistant pathogens is increasing in the ICU, and these infections are negatively associated with patient outcomes. Optimization of antibiotic dosing has been suggested as a key intervention to improve clinical outcomes in patients with nosocomial pneumonia. This review describes the recent pharmacokinetic/pharmacodynamic data relevant to antibiotic dosing for nosocomial pneumonia caused by multidrug-resistant pathogens.

RECENT FINDINGS

Optimal antibiotic treatment is challenging in critically ill patients with nosocomial pneumonia; most dosing guidelines do not consider the altered physiology and illness severity associated with severe lung infections. Antibiotic dosing can be guided by plasma drug concentrations, which do not reflect the concentrations at the site of infection. The application of aggressive dosing regimens, in accordance to the antibiotic's pharmacokinetic/pharmacodynamic characteristics, may be required to ensure rapid and effective drug exposure in infected lung tissues.

SUMMARY

Conventional antibiotic dosing increases the likelihood of therapeutic failure in critically ill patients with nosocomial pneumonia. Alternative dosing strategies, which exploit the pharmacokinetic/pharmacodynamic properties of an antibiotic, should be strongly considered to ensure optimal antibiotic exposure and better therapeutic outcomes in these patients.

Considerations for effect site pharmacokinetics to estimate drug exposure: concentrations of antibiotics in the lung

Bronchoalveolar lavage (BAL) and microdialysis have become the most reliable and relevant methods for measuring lung concentrations of antibiotics, with the majority of BAL studies involving either healthy adult subjects or patients undergoing diagnostic bronchoscopy. Emphasis on the amount of drug that reaches the site of infection is increasingly recognized as necessary to determine whether a dose selection will translate to good clinical outcomes in the treatment of patients with pneumonia. Observed concentrations and/or parameters of exposure (e.g. area-under-the-curve) need to be incorporated with pharmacokinetic-pharmacodynamic indices so that rational dose selection can be identified for specific pathogens and types of pneumonic infection (community-acquired vs hospital-acquired bacterial pneumonia, including ventilator-associated bacterial pneumonia). Although having measured plasma or lung concentration-time data from critically ill patients to incorporate into pharmacokinetic-pharmacodynamic models is very unlikely during drug development, it is essential that altered distribution, augmented renal clearance, and renal or hepatic dysfunction should be considered. Notably, the number of published studies involving microdialysis and intrapulmonary penetration of antibiotics has been limited and mainly involve beta-lactam agents, levofloxacin, and fosfomycin. Opportunities to measure in high-resolution effect site spatial pharmacokinetics (e.g. with MALDI-MSI or PET imaging) and in vivo continuous drug concentrations (e.g. with aptamer-based probes) now exist. Going forward these studies could be incorporated into antibiotic development programs for pneumonia in order to further increase the probability of candidate success.

Aspiration Pneumonia in the Dog: A Review

OBJECTIVE

To review the human and veterinary literature pertaining to aspiration pneumonitis and pneumonia.

MATERIAL AND METHODS

Data sources included scientific reviews and original research publications from the human and veterinary literature. All reviews and studies that added to the understanding of aspiration pneumonia were included.

RESULTS

Compared to human medicine, aspiration pneumonia can be difficult to diagnose in the canine patient and is often a diagnosis of presumption. Multiple risk factors exist increasing the likelihood of aspiration pneumonia and a thorough understanding of these can aid in prevention. Treatment recommendations center primarily on supportive care, oxygen therapy and antibiotic administration.

CLINCIAL SIGNIFICANCE

Aspiration pneumonia is a common finding in the canine patient and a thorough understanding of the disease will lead to better treatment outcomes. Further studies on treatment and prevention in veterinary medicine are warranted.

Use of nebulized antimicrobials for the treatment of respiratory infections in invasively mechanically ventilated adults: a position paper from the European Society of Clinical Microbiology and Infectious Diseases

With an established role in cystic fibrosis and bronchiectasis, nebulized antibiotics are increasingly being used to treat respiratory infections in critically ill invasively mechanically ventilated adult patients. Although there is limited evidence describing their efficacy and safety, in an era when there is a need for new strategies to enhance antibiotic effectiveness because of a shortage of new agents and increases in antibiotic resistance, the potential of nebulization of antibiotics to optimize therapy is considered of high interest, particularly in patients infected with multidrug-resistant pathogens. This Position Paper of the European Society of Clinical Microbiology and Infectious Diseases provides recommendations based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology regarding the use of nebulized antibiotics in invasively mechanically ventilated adults, based on a systematic review and meta-analysis of the existing literature (last search July 2016). Overall, the panel recommends avoiding the use of nebulized antibiotics in clinical practice, due to a weak level of evidence of their efficacy and the high potential for underestimated risks of adverse events (particularly, respiratory complications). Higher-quality evidence is urgently needed to inform clinical practice. Priorities of future research are detailed in the second part of the Position Paper as guidance for researchers in this field. In particular, the panel identified an urgent need for randomized clinical trials of nebulized antibiotic therapy as part of a substitution approach to treatment of pneumonia due to multidrug-resistant pathogens.

The role of infection models and PK/PD modelling for optimising care of critically ill patients with severe infections

Critically ill patients with severe infections are at high risk of suboptimal antimicrobial dosing. The pharmacokinetics (PK) and pharmacodynamics (PD) of antimicrobials in these patients differ significantly from the patient groups from whose data the conventional dosing regimens were developed. Use of such regimens often results in inadequate antimicrobial concentrations at the site of infection and is associated with poor patient outcomes. In this article, we describe the potential of in vitro and in vivo infection models, clinical pharmacokinetic data and pharmacokinetic/pharmacodynamic models to guide the design of more effective antimicrobial dosing regimens. Individualised dosing, based on population PK models and patient factors (e.g. renal function and weight) known to influence antimicrobial PK, increases the probability of achieving therapeutic drug exposures while at the same time avoiding toxic concentrations. When therapeutic drug monitoring (TDM) is applied, early dose adaptation to the needs of the individual patient is possible. TDM is likely to be of particular importance for infected critically ill patients, where profound PK changes are present and prompt appropriate antibiotic therapy is crucial. In the light of the continued high mortality rates in critically ill patients with severe infections, a paradigm shift to refined dosing strategies for antimicrobials is warranted to enhance the probability of achieving drug concentrations that increase the likelihood of clinical success.

Penetration of Ciprofloxacin and Amikacin into the Alveolar Epithelial Lining Fluid of Rats with Pulmonary Fibrosis

We determined the concentration-time profiles of ciprofloxacin and amikacin in serum and alveolar epithelial lining fluid (ELF) of rats with or without pulmonary fibrosis and investigated the effect of pulmonary fibrosis on the capacity for penetration of antimicrobials into the ELF of rats. Pulmonary fibrosis was induced in rats with a single intratracheal instillation of bleomycin. After intravenous injection of ciprofloxacin or amikacin, blood and bronchoalveolar lavage fluid samples were collected. Urea concentrations in serum and lavage fluid were determined using an enzymatic assay. Ciprofloxacin and amikacin concentrations were determined by high-performance liquid chromatography and liquid chromatography-tandem mass spectrometry, respectively. The mean ratio of ELF to plasma concentrations of ciprofloxacin at each time point in the normal group did not significantly differ from that in the pulmonary fibrosis group. However, the ratio of the ciprofloxacin area under the concentration-time curve from 0 to 24 h (AUC_0-24) in ELF to the AUC_0-24 in plasma was 1.02 in the normal group and 0.76 in the pulmonary fibrosis group. The mean ELF-to-plasma concentration ratios of amikacin at each time point in the normal group were higher than those in the pulmonary fibrosis group, reaching a statistically significant difference at 1, 2, and 4 h. The ratio of the AUC_0-24 in ELF to the AUC_0-24 in plasma was 0.49 in the normal group and 0.27 in the pulmonary fibrosis group. In conclusion, pulmonary fibrosis can influence the penetration of antimicrobials into the ELF of rats and may have a marked effect on the penetration of amikacin than that of ciprofloxacin.