Ceftazidime/avibactam tested against Gram-negative bacteria from intensive care unit (ICU) and non-ICU patients, including those with ventilator-associated pneumonia

Development of an effective meropenem/KPC-2 inhibitor combination to combat infections caused by carbapenem-resistant Klebsiella pneumoniae

The global public health threat of antibiotic resistance continues to escalate, and necessitates the implementation of urgent measures to expand the arsenal of antimicrobial drugs. This study identified a benzoxaborane compound, namely 5-chloro-1,3-dihydro-1-hydroxy-2,1-benzoxaborole (AN2178), which can inhibit the catalytic activity of the Klebsiella pneumoniae carbapenemase (KPC-2) enzyme effectively. The efficacy of AN2718 as an inhibitor for the KPC-2 enzyme was verified through various assays, including enzyme activity assays and isothermal titration calorimetry. Results of multiple biochemical assays, minimum inhibitory concentration assays and time-killing assays also showed that binding of AN2718 to KPC-2 enabled restoration of the bactericidal effect of meropenem. The survival rate of mice infected with carbapenem-resistant, high-virulence strains increased significantly upon treatment with AN2718. Most importantly, the meropenem and AN2718 combination was effective on KPC-2 mutations such as KPC-33, which evolved clinically and exhibited resistance to ceftazidime-avibactam after clinical use for a couple of years. Comprehensive safety tests both in vitro and in vivo, such as cytotoxicity, haemolytic activity and cytochrome P450 inhibition assays, demonstrated that AN2718 was safe for clinical use. These promising data indicate that AN2718 has high potential for approval for the treatment of drug resistant-bacterial infections, including those caused by ceftazidime-avibactam-resistant strains. AN2718 can be regarded as a valuable addition to the current antimicrobial armamentarium, and a promising tool to combat antimicrobial resistance.

Novel Siderophore Cephalosporin and Combinations of Cephalosporins with β-Lactamase Inhibitors as an Advancement in Treatment of Ventilator-Associated Pneumonia

In an era of increasing antibiotic resistance among pathogens, the treatment options for infectious diseases are diminishing. One of the clinical groups especially vulnerable to this threat are patients who are hospitalized in intensive care units due to ventilator-associated pneumonia caused by multidrug-resistant/extensively drug-resistant Gram-negative bacteria. In order to prevent the exhaustion of therapeutic options for this life-threatening condition, there is an urgent need for new pharmaceuticals. Novel β-lactam antibiotics, including combinations of cephalosporins with β-lactamase inhibitors, are proposed as a solution to this escalating problem. The unique mechanism of action, distinctive to this new group of siderophore cephalosporins, can overcome multidrug resistance, which is raising high expectations. In this review, we present the summarized results of clinical trials, in vitro studies, and case studies on the therapeutic efficacy of cefoperazone-sulbactam, ceftolozane-tazobactam, ceftazidime-avibactam, and cefiderocol in the treatment of ventilator-associated pneumonia. We demonstrate that treatment strategies based on siderophore cephalosporins and combinations of β-lactams with β-lactamases inhibitors show comparable or higher clinical efficacy than those used with classic pharmaceuticals, like carbapenems, colistin, or tigecycline, and are often associated with a lower risk of adverse events.

Clinical distribution of carbapenem genotypes and resistance to ceftazidime-avibactam in Enterobacteriaceae bacteria

Introduction

Bacterial resistance is a major threat to public health worldwide. To gain an understanding of the clinical infection distribution, drug resistance information, and genotype of CRE in Dongguan, China, as well as the resistance of relevant genotypes to CAZ-AVI, this research aims to improve drug resistance monitoring information in Dongguan and provide a reliable basis for the clinical control and treatment of CRE infection.

Methods

VITEK-2 Compact automatic analyzer was utilized to identify 516 strains of CRE collected from January 2017 to June 2023. To determine drug sensitivity, the K-B method, E-test, and MIC methods were used. From June 2022 to June 2023, 80 CRE strains were selected, and GeneXpert Carba-R was used to detect and identify the genotype of the carbapenemase present in the collected CRE strains. An in-depth analysis was conducted on the CAZ-AVI in vitro drug sensitivity activity of various genotypes of CRE, and the results were statistically evaluated using SPSS 23.0 and WHONET 5.6 software.

Results

This study identified 516 CRE strains, with the majority (70.16%) being K.pneumoniae, followed by E.coli (18.99%). Respiratory specimens had highest detection rate with 53.77% identified, whereas urine specimens had the second highest detection rate with 17.99%. From June 2022 to June 2023, 95% of the strains tested using the CRE GeneXpert Carba-R assay possessed carbapenemase genes, of which 32.5% were blaNDM strains and 61.25% blaKPC strains. The results showed that CRE strains containing blaKPC had a significantly higher rate of resistance to amikacin, cefepime, and aztreonam than those harboring blaNDM.

Conclusions

The CRE strains isolated from Dongguan region demonstrated a high resistance rate to various antibiotics used in clinical practice but a low resistance rate to tigecycline. These strains produce Class A serine carbapenemases and Class B metals β-lactamases, with the majority of them carrying blaNDM and blaKPC. Notably, CRE strains with blaKPC and blaNDM had significantly lower resistance rates to tigecycline. CAZ-AVI showed a good sensitivity rate with no resistance to CRE strains carrying blaKPC. Therefore, CAZ-AVI and tigecycline should be used as a guide for rational use of antibiotics in clinical practice to effectively treat CRE.

Worldwide trend discovery of structural and functional relationship of metallo-β-lactamase for structure-based drug design: A bibliometric evaluation and patent analysis

Metallo-β-lactamase (MBL) is an enzyme produced by clinically important bacteria that can inactivate many commonly used antibiotics, making them a significant concern in treating bacterial infections and the risk of having high antibiotic resistance issues among the community. This review presents a bibliometric and patent analysis of MBL worldwide research trend based on the Scopus and World Intellectual Property Organization databases in 2013-2022. Based on the keywords related to MBL in the article title, abstract, and keywords, 592 research articles were retrieved for further analysis using various tools such as Microsoft Excel to determine the frequency analysis, VOSviewer for bibliometric networks visualization, and Harzing's Publish or Perish for citation metrics analysis. Standard bibliometric parameters were analysed to evaluate the field's research trend, such as the growth of publications, topographical distribution, top subject area, most relevant journal, top cited documents, most relevant authors, and keyword trend analysis. Within 10 years, MBL discovery has shown a steady and continuous growth of interest among the community of researchers. United States of America, China, and the United Kingdom are the top 3 countries contribute high productivity to the field. The patent analysis also shows several impactful filed patents, indicating the significance of development research on the structural and functional relationship of MBL for an effective structure-based drug design (SBDD). Developing new MBL inhibitors using SBDD could help address the research gap and provide new successful therapeutic options for treating MBL-producing bacterial infections.

Clinical efficacy and drug resistance of ceftazidime-avibactam in the treatment of Carbapenem-resistant gram-negative bacilli infection

Objective

To examine the clinical efficacy, safety, and resistance of Ceftazidime-Avibactam (CAZ-AVI) in patients with Carbapenem-resistant Gram-negative bacilli (CR-GNB) infections.

Methods

We retrospectively analyzed relevant data of CR-GNB infected patients receiving CAZ-AVI treatment, analyzed relevant factors affecting drug efficacy, and compared the efficacy and safety with patients receiving Polymyxin B treatment.

Results

A total of 139 patients were included. Agranulocytosis, septic shock, SOFA score, and CAZ-AVI treatment course were independent risk factors affecting the prognosis of patients with CR-GNB infection treated with CAZ-AVI while prolonging the treatment course of CAZ-AVI was the only protective factor for bacterial clearance. The fundamental indicators showed no statistically significant differences between CAZ-AVI and Polymyxin B treatment groups. At the same time, the proportion of patients treated with monotherapy was significantly higher in the CAZ-AVI group than in the Polymyxin B group (37.2% vs. 8.9%, p < 0.05), the 30-day mortality rate of the CAZ-AVI treatment group (27.7% vs. 46.7%, p = 0.027) was lower than that of the Polymyxin B treatment group. The 30-day clinical cure rate (59.6% vs. 40% p = 0.030) and 14-day microbiological clearance rate (42.6% vs. 24.4%, p = 0.038) were significantly higher in the CAZ-AVI than in the Polymyxin B treatment group. Eighty nine patients were monitored for CAZ-AVI resistance, and the total resistance rate was 14.6% (13/89). The resistance rates of Carbapenem-resistant Klebsiella pneumoniae (CRKP) and Carbapenem-resistant Pseudomonas aeruginosa (CRPA) to CAZ-AVI were 13.5 and 15.4%, respectively.

Conclusion

CAZ-AVI has shown high clinical efficacy and bacterial clearance in treating CR-GNB infections. Compared with Polymyxin B, CAZ-AVI significantly improved the outcome of mechanical ventilation in patients with septic shock, agranulocytosis, Intensive Care Unit (ICU) patients, bloodstream infection, and patients with SOFA score > 6, and had a lower incidence of adverse events. We monitored the emergence of CAZ-AVI resistance and should strengthen the monitoring of drug susceptibility in clinical practice and the rational selection of antibiotic regimens to delay the onset of resistance.

Evaluation of the Efficacy of Optimized Two-Step-Administration Therapy with Ceftazidime/Avibactam for Treating Extensively Drug-Resistant Pseudomonas aeruginosa Pulmonary Infections: a Pharmacokinetic/Pharmacodynamic Analysis

The objective of this pharmacokinetic (PK)/pharmacodynamic (PD) analysis was to evaluate the efficacy of different dosing regimens of ceftazidime/avibactam (CZA) for the treatment of pulmonary infections by extensively drug-resistant (XDR) Pseudomonas aeruginosa using optimized two-step administration therapy (OTAT) and traditional infusion (TI). We used Monte Carlo simulations (MCS) to integrate PK parameters with PD parameters to assess the adequacy of CZA dosing in critically ill patients with XDR P. aeruginosa pulmonary infections. Dosing models were as follows: 2.5 g q8h, 2.5 g q6h, 4 g q8h, 4 g q6h, 1.25 g q8h, 1.25 g q6h, and 0.94 g q12h. MCS showed that the cumulative fraction of response of all dosing regimens of OTAT was higher than 90%. The probability of target attainment of all dosing regimens of OTAT at MICs (minimal inhibitory concentrations) between 16 mg/L and 32 mg/L was higher than that of TI. Based on these models, PK/PD goals were met with OTAT regimens, even with high MICs (>16 mg/L) compared to traditional infusion (TI) intervals. Thus, this study indicates that OTAT with sufficient PK exposure could improve the efficacy of CZA in critically ill patients with XDR P. aeruginosa pulmonary infections.

Carbapenem-Resistant Klebsiella pneumoniae: Virulence Factors, Molecular Epidemiology and Latest Updates in Treatment Options

Klebsiella pneumoniae is a Gram-negative opportunistic pathogen responsible for a variety of community and hospital infections. Infections caused by carbapenem-resistant K. pneumoniae (CRKP) constitute a major threat for public health and are strongly associated with high rates of mortality, especially in immunocompromised and critically ill patients. Adhesive fimbriae, capsule, lipopolysaccharide (LPS), and siderophores or iron carriers constitute the main virulence factors which contribute to the pathogenicity of K. pneumoniae. Colistin and tigecycline constitute some of the last resorts for the treatment of CRKP infections. Carbapenemase production, especially K. pneumoniae carbapenemase (KPC) and metallo-β-lactamase (MBL), constitutes the basic molecular mechanism of CRKP emergence. Knowledge of the mechanism of CRKP appearance is crucial, as it can determine the selection of the most suitable antimicrobial agent among those most recently launched. Plazomicin, eravacycline, cefiderocol, temocillin, ceftolozane-tazobactam, imipenem-cilastatin/relebactam, meropenem-vaborbactam, ceftazidime-avibactam and aztreonam-avibactam constitute potent alternatives for treating CRKP infections. The aim of the current review is to highlight the virulence factors and molecular pathogenesis of CRKP and provide recent updates on the molecular epidemiology and antimicrobial treatment options.

Antibiotics in development for multiresistant gram-negative bacilli

The rapid increase in antibiotic(ATB) resistance among Gram-negative bacilli(BGN), especially in strains of Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter baumannii, with high resistance patterns (XDR), poses a huge threat to health systems worldwide. In the last decade, different ATBs have been developed against XDR, some of which combine a lactam β along with a β-lactamase inhibitor, while others use non-β-lactam inhibitors. Most of them have adequate "in vitro" activity on several β-lactamases of class A, C and D of Ambler. However, combinations such as Ceftazidime/avibactam, Ceftolozane/Tazobactam and Meropenem/vaborbactam have no activity against metallo-β-lactamases(MβL). New combinations such as Aztreonan/AVI, Cefepime/Zidebactam, or new cephalosporins such as Cefiderocol, have efficacy against MβL enzymes. Although some of these combinations are already approved and in the commercialization phase, many of them have yet to define their place within the treatment of microorganisms with high resistance through clinical studies.

Surgical Site Infection in the Intensive Care Setting After Posterior Spinal Fusion: A Case Series Highlighting the Microbial Profile, Risk Factors, and the Importance of Comorbid Disease Burden

BACKGROUND

Most posterior spinal fusion (PSF) patients do not require admission to an intensive care unit (ICU), and those who do may represent an underinvestigated, high-risk subpopulation.

OBJECTIVE

To identify the microbial profile of and risk factors for surgical site infection (SSI) in PSF patients admitted to the ICU postoperatively.

METHODS

We examined 3965 consecutive PSF patients treated at our institution between 2000 and 2015 and collected demographic, clinical, and procedural data. Comorbid disease burden was quantified using the Charlson Comorbidity Index (CCI). We performed multivariable logistic regression to identify risk factors for SSI, readmission, and reoperation.

RESULTS

Anemia, more levels fused, cervical surgery, and cerebrospinal fluid leak were positively associated with ICU admission, and minimally invasive surgery was negatively associated. The median time to infection was equivalent for ICU patients and non-ICU patients, and microbial culture results were similar between groups. Higher CCI and undergoing a staged procedure were associated with readmission, reoperation, and SSI. When stratified by CCI into quintiles, SSI rates show a strong linear correlation with CCI ( P = .0171, R = 0.941), with a 3-fold higher odds of SSI in the highest risk group than the lowest (odds ratio = 3.15 [1.19, 8.07], P = .032).

CONCLUSION

Procedural characteristics drive the decision to admit to the ICU postoperatively. Patients admitted to the ICU have higher rates of SSI but no difference in the timing of or microorganisms that lead to those infections. Comorbid disease burden drives SSI in this population, with a 3-fold greater odds of SSI for high-risk patients than low-risk patients.

Virulence Characteristics and Emerging Therapies for Biofilm-Forming Acinetobacter baumannii: A Review

Simple Summary

Acinetobacter baumannii (A. baumannii) is one of the ESKAPE organisms and has the competency to build biofilms. These biofilms account for the most nosocomial infections all over the world. This review reflects on the various physicochemical and environmental factors such as adhesion, pili expression, growth surfaces, drug-resistant genes, and virulence factors that profoundly affect its resistant forte. Emerging drug-resistant issues and limitations to newer drugs are other factors affecting the hospital environment. Here, we discuss newer and alternative methods that can significantly enhance the susceptibility to Acinetobacter spp. Many new antibiotics are under trials, such as GSK-3342830, The Cefiderocol (S-649266), Fimsbactin, and similar. On the other hand, we can also see the impact of traditional medicine and the secondary metabolites of these natural products’ application in searching for new treatments. The field of nanoparticles has demonstrated effective antimicrobial actions and has exhibited encouraging results in the field of nanomedicine. The use of various phages such as vWUPSU and phage ISTD as an alternative treatment for its specificity and effectiveness is being investigated. Cathelicidins obtained synthetically or from natural sources can effectively produce antimicrobial activity in the micromolar range. Radioimmunotherapy and photodynamic therapy have boundless prospects if explored as a therapeutic antimicrobial strategy.

Abstract

Acinetobacter species is one of the most prevailing nosocomial pathogens with a potent ability to develop antimicrobial resistance. It commonly causes infections where there is a prolonged utilization of medical devices such as CSF shunts, catheters, endotracheal tubes, and similar. There are several strains of Acinetobacter (A) species (spp), among which the majority are pathogenic to humans, but A. baumannii are entirely resistant to several clinically available antibiotics. The crucial mechanism that renders them a multidrug-resistant strain is their potent ability to synthesize biofilms. Biofilms provide ample opportunity for the microorganisms to withstand the harsh environment and further cause chronic infections. Several studies have enumerated multiple physiological and virulence factors responsible for the production and maintenance of biofilms. To further enhance our understanding of this pathogen, in this review, we discuss its taxonomy, pathogenesis, current treatment options, global resistance rates, mechanisms of its resistance against various groups of antimicrobials, and future therapeutics.

Fluoroquinolones Hybrid Molecules as Promising Antibacterial Agents in the Fight against Antibacterial Resistance

The emergence of bacterial resistance has motivated researchers to discover new antibacterial agents. Nowadays, fluoroquinolones keep their status as one of the essential classes of antibacterial agents. The new generations of fluoroquinolones are valuable therapeutic tools with a spectrum of activity, including Gram-positive, Gram-negative, and atypical bacteria. This review article surveys the design of fluoroquinolone hybrids with other antibacterial agents or active compounds and underlines the new hybrids' antibacterial properties. Antibiotic fluoroquinolone hybrids have several advantages over combined antibiotic therapy. Thus, some challenges related to joining two different molecules are under study. Structurally, the obtained hybrids may contain a cleavable or non-cleavable linker, an essential element for their pharmacokinetic properties and mechanism of action. The design of hybrids seems to provide promising antibacterial agents helpful in the fight against more virulent and resistant strains. These hybrid structures have proven superior antibacterial activity and less susceptibility to bacterial resistance than the component molecules. In addition, fluoroquinolone hybrids have demonstrated other biological effects such as anti-HIV, antifungal, antiplasmodic/antimalarial, and antitumor activity. Many fluoroquinolone hybrids are in various phases of clinical trials, raising hopes that new antibacterial agents will be approved shortly.

Ceftazidime/Avibactam in Ventilator-Associated Pneumonia Due to Difficult-to-Treat Non-Fermenter Gram-Negative Bacteria in COVID-19 Patients: A Case Series and Review of the Literature

Ventilator-associated pneumonia (VAP) in critically ill patients with COVID-19 represents a very huge global threat due to a higher incidence rate compared to non-COVID-19 patients and almost 50% of the 30-day mortality rate. Pseudomonas aeruginosa was the first pathogen involved but uncommon non-fermenter gram-negative organisms such as Burkholderia cepacea and Stenotrophomonas maltophilia have emerged as other potential etiological causes. Against carbapenem-resistant gram-negative microorganisms, Ceftazidime/avibactam (CZA) is considered a first-line option, even more so in case of a ceftolozane/tazobactam resistance or shortage. The aim of this report was to describe our experience with CZA in a case series of COVID-19 patients hospitalized in the ICU with VAP due to difficult-to-treat (DTT) P. aeruginosa, Burkholderia cepacea, and Stenotrophomonas maltophilia and to compare it with data published in the literature. A total of 23 patients were treated from February 2020 to March 2022: 19/23 (82%) VAPs were caused by Pseudomonas spp. (16/19 DTT), 2 by Burkholderia cepacea, and 6 by Stenotrophomonas maltophilia; 12/23 (52.1%) were polymicrobial. Septic shock was diagnosed in 65.2% of the patients and VAP occurred after a median of 29 days from ICU admission. CZA was prescribed as a combination regimen in 86% of the cases, with either fosfomycin or inhaled amikacin or cotrimoxazole. Microbiological eradication was achieved in 52.3% of the cases and the 30-day overall mortality rate was 14/23 (60.8%). Despite the high mortality of critically ill COVID-19 patients, CZA, especially in combination therapy, could represent a valid treatment option for VAP due to DTT non-fermenter gram-negative bacteria, including uncommon pathogens such as Burkholderia cepacea and Stenotrophomonas maltophilia.

Genomic Analysis of Ceftazidime/Avibactam-Resistant GES-Producing Sequence Type 235 Pseudomonas aeruginosa Isolates

The emergence of ceftazidime/avibactam (CZA) resistance among Guiana extended-spectrum β-lactamase (GES)-producing Pseudomonas aeruginosa isolates has rarely been described. Herein, we analyze the phenotypic and genomic characterization of CZA resistance in different GES-producing P. aeruginosa isolates that emerged in our institution. A subset of nine CZA-resistant P. aeruginosa isolates was analyzed and compared with thirteen CZA-susceptible isolates by whole-genome sequencing (WGS). All CZA-resistant isolates belonged to the ST235 clone and O11 serotype. A variety of GES enzymes were detected: GES-20 (55.6%, 5/9), GES-5 (22.2%, 2/9), GES-1 (11.1%, 1/9), and GES-7 (11.1%, 1/9). WGS revealed the presence of two mutations within the bla_GES-20 gene comprising two single-nucleotide substitutions, which caused aspartic acid/serine and leucine/premature stop codon amino acid changes at positions 165 (D165S) and 237 (L237X), respectively. No major differences in the mutational resistome (AmpC, OprD porin, and MexAB-OprM efflux pump-encoding genes) were found among CZA-resistant and CZA-susceptible isolates. None of the mutations that have been previously demonstrated to cause CZA resistance were observed. Different mutations within the bla_GES-20 gene were documented in CZA-resistant GES-producing P. aeruginosa isolates belonging to the ST235 clone in our institution. Although further analysis should be performed, according to our results, other resistance mechanisms might be involved in CZA resistance.

Resistance to Ceftazidime/Avibactam, Meropenem/Vaborbactam and Imipenem/Relebactam in Gram-Negative MDR Bacilli: Molecular Mechanisms and Susceptibility Testing

Multidrug resistance (MDR) represents a serious global threat due to the rapid global spread and limited antimicrobial options for treatment of difficult-to-treat (DTR) infections sustained by MDR pathogens. Recently, novel β-lactams/β-lactamase inhibitor combinations (βL-βLICs) have been developed for the treatment of DTR infections due to MDR Gram-negative pathogens. Although novel βL-βLICs exhibited promising in vitro and in vivo activities against MDR pathogens, emerging resistances to these novel molecules have recently been reported. Resistance to novel βL-βLICs is due to several mechanisms including porin deficiencies, increasing carbapenemase expression and/or enzyme mutations. In this review, we summarized the main mechanisms related to the resistance to ceftazidime/avibactam, meropenem/vaborbactam and imipenem/relebactam in MDR Gram-negative micro-organisms. We focused on antimicrobial activities and resistance traits with particular regard to molecular mechanisms related to resistance to novel βL-βLICs. Lastly, we described and discussed the main detection methods for antimicrobial susceptibility testing of such molecules. With increasing reports of resistance to novel βL-βLICs, continuous attention should be maintained on the monitoring of the phenotypic traits of MDR pathogens, into the characterization of related mechanisms, and on the emergence of cross-resistance to these novel antimicrobials.

Infectious Diseases Society of America 2022 Guidance on the Treatment of Extended-Spectrum β-lactamase Producing Enterobacterales (ESBL-E), Carbapenem-Resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with Difficult-to-Treat Resistance (DTR-P. aeruginosa)

BACKGROUND

The Infectious Diseases Society of America (IDSA) is committed to providing up-to-date guidance on the treatment of antimicrobial-resistant infections. The initial guidance document on infections caused by extended-spectrum β-lactamase producing Enterobacterales (ESBL-E), carbapenem-resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with difficult-to-treat resistance (DTR-P. aeruginosa) was published on 17 September 2020. Over the past year, there have been a number of important publications furthering our understanding of the management of ESBL-E, CRE, and DTR-P. aeruginosa infections, prompting a rereview of the literature and this updated guidance document.

METHODS

A panel of 6 infectious diseases specialists with expertise in managing antimicrobial-resistant infections reviewed, updated, and expanded previously developed questions and recommendations about the treatment of ESBL-E, CRE, and DTR-P. aeruginosa infections. Because of differences in the epidemiology of resistance and availability of specific anti-infectives internationally, this document focuses on the treatment of infections in the United States.

RESULTS

Preferred and alternative treatment recommendations are provided with accompanying rationales, assuming the causative organism has been identified and antibiotic susceptibility results are known. Approaches to empiric treatment, duration of therapy, and other management considerations are also discussed briefly. Recommendations apply for both adult and pediatric populations.

CONCLUSIONS

The field of antimicrobial resistance is highly dynamic. Consultation with an infectious diseases specialist is recommended for the treatment of antimicrobial-resistant infections. This document is current as of 24 October 2021. The most current versions of IDSA documents, including dates of publication, are available at www.idsociety.org/practice-guideline/amr-guidance/.

Use of Antimicrobials for Bloodstream Infections in the Intensive Care Unit, a Clinically Oriented Review

Bloodstream infections (BSIs) in critically ill patients are associated with significant mortality. For patients with septic shock, antibiotics should be administered within the hour. Probabilistic treatment should be targeted to the most likely pathogens, considering the source and risk factors for bacterial resistance including local epidemiology. Source control is a critical component of the management. Sending blood cultures (BCs) and other specimens before antibiotic administration, without delaying them, is key to microbiological diagnosis and subsequent opportunities for antimicrobial stewardship. Molecular rapid diagnostic testing may provide faster identification of pathogens and specific resistance patterns from the initial positive BC. Results allow for antibiotic optimisation, targeting the causative pathogen with escalation or de-escalation as required. Through this clinically oriented narrative review, we provide expert commentary for empirical and targeted antibiotic choice, including a review of the evidence and recommendations for the treatments of extended-spectrum β-lactamase-producing, AmpC-hyperproducing and carbapenem-resistant Enterobacterales; carbapenem-resistant Acinetobacter baumannii; and Staphylococcus aureus. In order to improve clinical outcomes, dosing recommendations and pharmacokinetics/pharmacodynamics specific to ICU patients must be followed, alongside therapeutic drug monitoring.

Novel investigational treatments for ventilator-associated pneumonia and critically ill patients in the intensive care unit

INTRODUCTION

Ventilator-associated pneumonia (VAP) is common; its prevalence has been highlighted by the Covid-19 pandemic. Even young patients can suffer severe nosocomial infection and prolonged mechanical ventilation. Multidrug-resistant bacteria can spread alarmingly fast around the globe and new antimicrobials are struggling to keep pace; hence physicians must stay abreast of new developments in the treatment of nosocomial pneumonia and VAP.

AREAS COVERED

This narrative review examines novel antimicrobial investigational drugs and their implementation in the ICU setting for VAP. The paper highlights novel approaches such as monoclonal antibody treatments for P. aeruginosa and S. aureus, and phage antibiotic synthesis. The paper also examines mechanisms of resistance in gram-negative bacteria, virulence factors and inhaled antibiotics and questions what may be on the horizon in terms of emerging treatment strategies.

EXPERT OPINION

The post-antibiotic era is rapidly approaching and the need for personalised medicine, point-of-care microbial sensitivity testing and development of biomarkers for severe infections is clear. Results from emerging and new antibiotics are encouraging, but infection control measures and de-escalation protocols must be employed to prolong their usefulness in critical illness.

Effectiveness of ceftazidime-avibactam for the treatment of infections due to Pseudomonas aeruginosa

BACKGROUND

Clinical experience with ceftazidime-avibactam (CAZ-AVI) for the treatment due to multidrug or extremely resistant (MDR/XDR) Pseudomonas aeruginosa is limited.

METHODS

We conducted a retrospective cohort study of patients with MDR/XDR P. aeruginosa infections treated with CAZ-AVI Primary outcome was clinical cure by day 14, evaluated by logistic regression adjusted for the propensity score to receive CAZ-AVI as combination therapy. 30-day all-cause mortality, 90-day recurrence, emerging CAZ-AVI resistance, and safety of therapy were secondary outcomes.

RESULTS

Sixty-one first episodes of MDR/XDR P. aeruginosa infection were included. The most common source was lower respiratory tract (34.4%), 14.8% episodes developed bloodstream infection and 50.8% sepsis at presentation. Ceftazidime-avibactam therapy was initiated at a median of 7.0 (interquartile range [IQR]: 3.5-12.0) days from symptoms onset. It was used as combined therapy in 29 (47.5%) episodes. Clinical cure rate by day 14 was 54.1% and predictors of response were days to source control (adjusted odds ratio [aOR]: 0.84; 95% confidence interval [CI]: 0.72-0.98; P-value = 0.024), days until the initiation of CAZ-AVI therapy (aOR: 0.65; 95% CI: 0.49-0.86; P-value = 0.003), age (aOR: 1.07; 95% CI: 0.99-1.15; P-value = 0.066) and CAZ-AVI combination therapy (aOR: 0.02; 95% CI: 0.01-0.38; P-value = 0.009). Rates of 30-day all-cause mortality and 90-day recurrence were 13.1% and 12.5%, respectively. Emergence of drug resistance to CAZ-AVI was not detected. Treatment-related adverse events occurred in 3 episodes (4.9%).

CONCLUSIONS

CAZ-AVI constitutes a valid alternative for the treatment of infections due to MDR/XDR P. aeruginosa.

Efficacy and appropriateness of novel antibiotics in response to antimicrobial-resistant Gram-negative bacteria in patients with sepsis in the ICU

INTRODUCTION

There is an ever-increasing range of antibiotic-resistant pathogens that have led to higher community-acquired infections, and substantial mortality rates in critically ill patients.

AREAS COVERED

We have critically appraised available evidence through a structured literature review, investigating effective empiric antibiotic administration and appropriateness on outcomes of critically ill patients with an increased risk of developing resistant pathogens. The use of new antibiotics should be determined based on relevant knowledge of their spectrum and properties to provide effective mode of action for critically ill patients.

EXPERT OPINION

Restricting severely ill patients access to new broad-spectrum empirical drugs is not the answer. Rather there should be a focus on identifying host response to infection to differentiate between colonization or contamination and true infection, and the sensitivity to antibiotics used in the intensive care unit (ICU).

Management relies on adequate antibiotic administration, the ability to monitor response, and facilitate the cessation of antibiotic treatment. The major determinant of patient success in a patient with a severe infection is the 'right' antibiotic or complementary course of treatment. As an overarching criterion, the following 3 appropriate "Ds" should be considered: Dosing, Duration and De-escalation to empirically assess the right antibiotic optimal antimicrobial selection.

Antimicrobial susceptibility of Gram-negative bacteria from intensive care unit and non-intensive care unit patients from United States hospitals (2018-2020)

We evaluated the antimicrobial susceptibility of Gram-negative bacteria recovered from ICU patients in US hospitals and compared them to those from non-ICU patients from the same hospitals during the same period. Overall, 4,680 isolates from ICU patients and 16,263 isolates from non-ICU patients were collected from 70 US medical centers in 2018-2020 and susceptibility tested by the broth microdilution method. Ceftazidime-avibactam and ceftolozane-tazobactam were the most active agents against P. aeruginosa and retained activity against multidrug-resistant (MDR) and extensively drug-resistant (XDR) isolates. Minocycline and trimethoprim-sulfamethoxazole were very active against S. maltophilia, whereas most antimicrobial agents exhibited low susceptibility to A. baumannii. Ceftazidime-avibactam and meropenem-vaborbactam were the most active agents against Enterobacterales, and retained potent activity against ESBL producers, carbapenem-resistant Enterobacterales (CRE), MDR, and XDR isolates. In summary, antimicrobial susceptibility was generally lower and the occurrence of ESBL, CRE, MDR, and XDR phenotypes were clearly higher among ICU compared to non-ICU isolates.

Ceftazidime-avibactam: are we safe from class A carbapenemase producers' infections?

Recently, new combinations of β-lactams and β-lactamase inhibitors became available, including ceftazidime-avibactam, and increased the ability to treat infections caused by carbapenem-resistant Enterobacterales (CRE). Despite the reduced time of clinical use, isolates expressing resistance to ceftazidime-avibactam have been reported, even during treatment or in patients with no previous contact with this drug. Here, we detailed review data on global ceftazidime-avibactam susceptibility, the mechanisms involved in resistance, and the molecular epidemiology of resistant isolates. Ceftazidime-avibactam susceptibility remains high (≥ 98.4%) among Enterobacterales worldwide, being lower among extended-spectrum β-lactamase (ESBL) producers and CRE. Alterations in class A β-lactamases are the major mechanism involved in ceftazidime-avibactam resistance, and mutations are mainly, but not exclusively, located in the Ω loop of these enzymes. Modifications in Klebsiella pneumoniae carbapenemase (KPC) 3 and KPC-2 have been observed by many authors, generating variants with different mutations, insertions, and/or deletions. Among these, the most commonly described is Asp179Tyr, both in KPC-3 (KPC-31 variant) and in KPC-2 (KPC-33 variant). Changes in membrane permeability and overexpression of efflux systems may also be associated with ceftazidime-avibactam resistance. Although several clones have been reported, ST258 with Asp179Tyr deserves special attention. Surveillance studies and rationale use are essential to retaining the activity of this and other antimicrobials against class A CRE.

Ceftolozane/Tazobactam and Imipenem/Relebactam Cross-Susceptibility Among Clinical Isolates of Pseudomonas aeruginosa From Patients With Respiratory Tract Infections in ICU and Non-ICU Wards-SMART United States 2017-2019

BACKGROUND

Carbapenem-nonsusceptible and multidrug-resistant (MDR) P. aeruginosa, which are more common in patients with lower respiratory tract infections (LRTIs) and in patients in intensive care units (ICUs), pose difficult treatment challenges and may require new therapeutic options. Two β-lactam/β-lactamase inhibitor combinations, ceftolozane/tazobactam (C/T) and imipenem/relebactam (IMI/REL), are approved for treatment of hospital-acquired/ventilator-associated bacterial pneumonia.

METHODS

The Clinical and Laboratory Standards Institute-defined broth microdilution methodology was used to determine minimum inhibitory concentrations (MICs) against P. aeruginosa isolates collected from patients with LRTIs in ICUs (n = 720) and non-ICU wards (n = 914) at 26 US hospitals in 2017-2019 as part of the Study for Monitoring Antimicrobial Resistance Trends (SMART) surveillance program.

RESULTS

Susceptibility to commonly used β-lactams including carbapenems was 5-9 percentage points lower and MDR rates 7 percentage points higher among isolates from patients in ICUs than those in non-ICU wards (P < .05). C/T and IMI/REL maintained activity against 94.0% and 90.8% of ICU isolates, respectively, while susceptibility to all comparators except amikacin (96.0%) was 63%-76%. C/T and IMI/REL inhibited 83.1% and 68.1% of meropenem-nonsusceptible (n = 207) and 71.4% and 65.7% of MDR ICU isolates (n = 140), respectively. Among all ICU isolates, only 2.5% were nonsusceptible to both C/T and IMI/REL, while 6.7% were susceptible to C/T but not to IMI/REL and 3.5% were susceptible to IMI/REL but not to C/T.

CONCLUSIONS

These data suggest that susceptibility to both C/T and IMI/REL should be considered for testing at hospitals, as both agents could provide important new options for treating patients with LRTIs, especially in ICUs where collected isolates show substantially reduced susceptibility to commonly used β-lactams.

In-vitro activity of imipenem/relebactam and key β-lactam agents against Gram-negative bacilli isolated from lower respiratory tract infection samples of intensive care unit patients - SMART Surveillance United States 2015-2017

β-lactam- and multi-drug-resistant (MDR) Gram-negative bacilli frequently cause lower respiratory tract infections (LRTIs) in patients housed in intensive care units (ICUs). Relebactam, a novel diazabicyclooctane inhibitor of Ambler class A and C β-lactamases, in combination with imipenem-cilastatin was approved by the US Food and Drug Administration in July 2019 for the treatment of adults with complicated intra-abdominal infections and complicated urinary tract infections. A phase III study of imipenem/relebactam for the treatment of patients with respiratory tract infections, including antimicrobial-resistant Gram-negative infections, has also been completed. The Clinical and Laboratory Standards Institute's broth microdilution methodology was used to determine minimum inhibitory concentrations against non-Proteeae Enterobacteriaceae (NPE) and Pseudomonas aeruginosa collected from ICU patients with LRTIs at 26 US hospitals in 2015-2017. Percent susceptibilities to imipenem/relebactam were 97.0%, 66.4% and 98.1%, respectively, for all NPE (n=1298), imipenem-non-susceptible NPE (n=113, of which 71% were Serratia marcescens) and MDR NPE (n=206), and 92.2%, 77.2% and 79.6%, respectively, for all P. aeruginosa (n=638), imipenem-non-susceptible P. aeruginosa (n=219) and MDR P. aeruginosa (n=225). Percent susceptibilities to imipenem/relebactam were 98.0-98.6% for cefepime-, ceftazidime- and piperacillin-tazobactam-non-susceptible NPE and 77.8-82.5% for cefepime-, ceftazidime- and piperacillin-tazobactam-non-susceptible P. aeruginosa. Generally, only slight variations in susceptibility were observed across US census regions. Imipenem/relebactam may provide a valuable therapeutic option for the treatment of ICU patients with LRTI caused by Gram-negative bacilli resistant to commonly used β-lactams, as it demonstrated potent in-vitro activity against the majority of tested β-lactam-non-susceptible and MDR Gram-negative bacilli from ICU patients with LRTIs in US hospitals.

Antimicrobial susceptibility testing of Enterobacteriaceae: determination of disk content and Kirby-Bauer breakpoint for ceftazidime/avibactam

BACKGROUND

Detection of ceftazidime/avibactam (CAZ/AVI) antibacterial activity is absolutely vital with the rapid growth of carbapenem resistant Enterobacteriaceae (CRE). But now, there is no available automated antimicrobial susceptibility testing card for CAZ/AVI, so Kirby-Bauer has become an economical and practical method for detecting CAZ/AVI antibacterial activity against Enterobacteriaceae.

RESULT

In this study, antimicrobial susceptibility testing of CAZ/AVI against 386 Enterobacteriaceae (188 Klebsiella pneumoniae, 122 Escherichia coli, 76 Enterobacter cloacae) isolated from clinical patients was performed by broth microdilution. Of the 386 strains, 54 extended spectrum β lactamases negative (ESBL(-)), 104 extended spectrum β lactamases positive (ESBL(+)), 228 CRE. 287 isolates were susceptible to CAZ/AVI and 99 isolates were resistant to CAZ/AVI. At the same time, to obtain optimal content avibactam (AVI) disk containing ceftazidime (30 μg), inhibition zone diameter of four kinds of ceftazidime (30 μg) disk containing different AVI content (0 μg, 10 μg, 25 μg, 50 μg) were tested by Kirby-Bauer method. The microdilution broth method interpretation was used as the standard to estimate susceptible or resistance and then coherence analysis was carried out between Kirby-Bauer and broth microdilution. The result shows the inhibition zone diameter of 30 μg/50 μg disk, susceptible isolates: 20.5 mm-31.5 mm, resistance isolates: 8.25 mm-21.5 mm. The inhibition zone diameter of 30 μg/25 μg disk, susceptible isolates: 19.7 mm-31.3 mm, resistance isolates: 6.5 mm-19.2 mm. The inhibition zone diameter of 30 μg/10 μg disk, susceptible isolates: 19.5 mm-31 mm, resistance isolates: 6.5 mm-11 mm. The inhibition zone diameter of ceftazidime (30 μg), susceptible isolates: 6.5 mm-27.5 mm, resistance isolates 6.5 mm.

CONCLUSION

Our results show that 30 μg/50 μg, 30 μg/25 μg, 30 μg/10 μg CAZ/AVI disk have significant statistical differences to determinate CAZ/AVI antibacterial activity, but for 30 μg/50 μg disk, there has a cross section between susceptible isolates (minimum 20.5 mm) and resistance isolates (maximum 21.5 mm). For 30 μg/25 μg disk, it is hard to distinguish the difference between susceptible isolates (minimum 19.7 mm) and resistance isolates (maximum 19.2 mm), so 30 μg/10 μg CAZ/AVI disk is more conducive to determinate antibacterial activity.

Epidemiology and Treatment of Multidrug-Resistant and Extensively Drug-Resistant Pseudomonas aeruginosa Infections

In recent years, the worldwide spread of the so-called high-risk clones of multidrug-resistant or extensively drug-resistant (MDR/XDR) Pseudomonas aeruginosa has become a public health threat. This article reviews their mechanisms of resistance, epidemiology, and clinical impact and current and upcoming therapeutic options. In vitro and in vivo treatment studies and pharmacokinetic and pharmacodynamic (PK/PD) models are discussed. Polymyxins are reviewed as an important therapeutic option, outlining dosage, pharmacokinetics and pharmacodynamics, and their clinical efficacy against MDR/XDR P. aeruginosa infections. Their narrow therapeutic window and potential for combination therapy are also discussed. Other "old" antimicrobials, such as certain β-lactams, aminoglycosides, and fosfomycin, are reviewed here. New antipseudomonals, as well as those in the pipeline, are also reviewed. Ceftolozane-tazobactam has clinical activity against a significant percentage of MDR/XDR P. aeruginosa strains, and its microbiological and clinical data, as well as recommendations for improving its use against these bacteria, are described, as are those for ceftazidime-avibactam, which has better activity against MDR/XDR P. aeruginosa, especially strains with certain specific mechanisms of resistance. A section is devoted to reviewing upcoming active drugs such as imipenem-relebactam, cefepime-zidebactam, cefiderocol, and murepavadin. Finally, other therapeutic strategies, such as use of vaccines, antibodies, bacteriocins, anti-quorum sensing, and bacteriophages, are described as future options.

Activity of ceftolozane-tazobactam and comparators against Pseudomonas aeruginosa from patients in different risk strata - SMART United States 2016-2017

OBJECTIVES

Infections caused by Pseudomonas aeruginosa are often difficult to treat. Knowledge of the risk of infection with resistant P. aeruginosa would allow more discriminatory prescribing of broad-spectrum antimicrobials. Using clinical isolates collected as part of the Study for Monitoring Antimicrobial Resistance Trends (SMART), we examined the activity of commonly used β-lactams, levofloxacin, and ceftolozane-tazobactam (C/T), an antipseudomonal cephalosporin/β-lactamase inhibitor approved in the United States and over 60 countries worldwide, against P. aeruginosa isolates from patients in different risk strata.

METHODS

In 2016-2017, 25 hospitals in the US each collected up to 250 consecutive gram-negative bacilli per year from respiratory tract (RTI), intraabdominal (IAI), and urinary tract (UTI) infections. MICs of 9,964 isolates (including 1,887 P. aeruginosa) were determined using CLSI broth microdilution and interpreted with CLSI breakpoints.

RESULTS

Susceptibility of all P. aeruginosa isolates combined was 94.7% to C/T and 76.8%, 77.0%, 70.2%, and 69.0% to ceftazidime, meropenem, piperacillin-tazobactam, and levofloxacin, respectively. Susceptibility to the β-lactam comparators was 8-11 percentage points lower among ICU than non-ICU isolates, 7-11 points lower in isolates collected ≥48h than <48h post-admission, 1-5 points lower in patients <65 years of age than older patients, and 3-12 points lower in RTI than IAI and UTI isolates. C/T maintained activity against >90% of P. aeruginosa isolates in all risk strata and against 75-88% of isolates nonsusceptible to ceftazidime, meropenem, or piperacillin-tazobactam.

CONCLUSIONS

C/T represents a promising new treatment option even in strata in which the risk of infection with β-lactam-nonsusceptible P. aeruginosa appeared higher.

Evaluating the Efficacies of Carbapenem/β-Lactamase Inhibitors Against Carbapenem-Resistant Gram-Negative Bacteria in vitro and in vivo

Background

Carbapenem-resistant Gram-negative bacteria are a major clinical concern as they cause virtually untreatable infections since carbapenems are among the last-resort antimicrobial agents. β-Lactamases implicated in carbapenem resistance include KPC, NDM, and OXA-type carbapenemases. Antimicrobial combination therapy is the current treatment approach against carbapenem resistance in order to limit the excessive use of colistin; however, its advantages over monotherapy remain debatable. An alternative treatment strategy would be the use of carbapenem/β-lactamase inhibitor (βLI) combinations. In this study, we assessed the in vitro and in vivo phenotypic and molecular efficacies of three βLIs when combined with different carbapenems against carbapenem-resistant Gram-negative clinical isolates. The chosen βLIs were (1) Avibactam, against OXA-type carbapenemases, (2) calcium-EDTA, against NDM-1, and (3) Relebactam, against KPC-2.

Methods

Six Acinetobacter baumannii clinical isolates were screened for bla _OXA-23-like, bla _OXA-24/40, bla _OXA-51-like, bla _OXA-58, and bla _OXA-143-like, and eight Enterobacteriaceae clinical isolates were screened for bla _OXA-48, bla _NDM-1, and bla _KPC-2. The minimal inhibitory concentrations of Imipenem (IPM), Ertapenem (ETP), and Meropenem (MEM) with corresponding βLIs for each isolate were determined. The efficacy of the most suitable in vitro treatment option against each of bla _OXA-48, bla _NDM-1, and bla _KPC-2 was assessed via survival studies in a BALB/c murine infection model. Finally, RT-qPCR was performed to assess the molecular response of the genes of resistance to the carbapenem/βLI combinations used under both in vitro and in vivo settings.

Results

Combining MEM, IPM, and ETP with the corresponding βLIs restored the isolates' susceptibilities to those antimicrobial agents in 66.7%, 57.1%, and 30.8% of the samples, respectively. Survival studies in mice revealed 100% survival rates when MEM was combined with either Avibactam or Relebactam against bla _OXA-48 and bla _KPC-2, respectively. RT-qPCR demonstrated the consistent overexpression of bla _OXA-48 upon treatment, without hindering Avibactam's activity, while bla _NDM-1 and bla _KPC-2 experienced variable expression levels upon treatment under in vitro and in vivo settings despite their effective phenotypic results.

Conclusion

New carbapenem/βLI combinations may be viable alternatives to antimicrobial combination therapy as they displayed high efficacy in vitro and in vivo. Meropenem/Avibactam and Meropenem/Relebactam should be tested on larger sample sizes with different carbapenemases before progressing further in its preclinical development.

Rapid genetic and phenotypic changes in Pseudomonas aeruginosa clinical strains during ventilator-associated pneumonia

Treatment with antibiotics leads to the selection of isolates with increased resistance. We investigated if evolution towards resistance was associated with virulence changes, in the context of P. aeruginosa ventilator-associated pneumonia (VAP). Four patients were selected because they had multiple VAP episodes during short periods (12 days to 5 weeks), with emergence of resistance. We performed whole-genome sequencing of 12 P. aeruginosa from bronchoalveolar lavages or blood culture (3 isolates per patient). Production of quorum sensing-dependent virulence factors, serum resistance, cytotoxicity against A549 cells, biofilm production, and twitching motility were studied. Each patient was infected with a unique strain. For all patients, resistance development was explained by genetic events in ampD, mexR or oprD. Additional variations were detected in virulence- and/or fitness-associated genes (algB, gacA, groEL, lasR, mpl, pilE, pilM, rhlR) depending on the strain. We noticed a convergence towards quorum sensing deficiency, correlated with a decrease of pyocyanin and protease production, survival in serum, twitching motility and cytotoxicity. In one patient, changes in pilM and pilE were related to enhanced twitching. We show that the emergence of resistance in P. aeruginosa is associated with virulence modification, even in acute infections. The consequences of this short-term pathoadaptation need to be explored.

Acinetobacter baumannii biofilms: effects of physicochemical factors, virulence, antibiotic resistance determinants, gene regulation, and future antimicrobial treatments

Acinetobacter baumannii is a leading cause of nosocomial infections due to its increased antibiotic resistance and virulence. The ability of A. baumannii to form biofilms contributes to its survival in adverse environmental conditions including hospital environments and medical devices. A. baumannii has undoubtedly propelled the interest of biomedical researchers due to its broad range of associated infections especially in hospital intensive care units. The interplay among microbial physicochemistry, alterations in the phenotype and genotypic determinants, and the impact of existing ecological niche and the chemistry of antimicrobial agents has led to enhanced biofilm formation resulting in limited access of drugs to their specific targets. Understanding the triggers to biofilm formation is a step towards limiting and containing biofilm-associated infections and development of biofilm-specific countermeasures. The present review therefore focused on explaining the impact of environmental factors, antimicrobial resistance, gene alteration and regulation, and the prevailing microbial ecology in A. baumannii biofilm formation and gives insights into prospective anti-infective treatments.

Carbapenem-Nonsusceptible Gram-Negative Pathogens in ICU and Non-ICU Settings in US Hospitals in 2017: A Multicenter Study

Background

Infections caused by Gram-negative pathogens resistant to carbapenems have limited treatment options and are associated with increased morbidity and mortality. We evaluated the rates, infection sources, and pathogen types associated with carbapenem-nonsusceptible (Carb-NS) Gram-negative isolates in intensive care unit (ICU) and non-ICU settings in a large US hospital database.

Methods

We conducted a retrospective cross-sectional analysis of carbapenem susceptibility of all nonduplicate isolates of Gram-negative pathogens collected from January 1, 2017, to December 31, 2017, at 358 US hospitals in the BD Insights Research Database. Carb-NS isolates included all pathogens reported at the institutional level as intermediate or resistant.

Results

Of 312 075 nonduplicate Gram-negative isolates, 10 698 (3.4%) were Carb-NS. Respiratory samples were the most frequent source of Carb-NS isolates (35.2%); skin/wound accounted for 23.6%. Pseudomonas aeruginosa was the most common Carb-NS pathogen (58.5% of isolates), and about 30% were Enterobacteriaceae. The highest rates of Carb-NS were found in Acinetobacter spp. (35.6%) and P. aeruginosa (14.6%). The rate of Carb-NS was significantly higher in ICU (5.4%) vs non-ICU settings (2.7%; P < .0001 in univariate analysis). This difference remained significant in multivariable analysis after adjusting for infection and hospital characteristics (odds ratio, 1.35; 95% confidence interval, 1.17–1.56; P < .0001).

Conclusions

Infections caused by Carb-NS isolates pose a significant clinical problem across different sources of infection, species of pathogen, and hospital settings. Widespread infection prevention and antimicrobial stewardship initiatives, in combination with new treatment options, may be required to reduce the burden of carbapenem resistance in health care settings.

Multidrug-resistant Pseudomonas aeruginosa from sputum of patients with cystic fibrosis demonstrates a high rate of susceptibility to ceftazidime-avibactam

Purpose

Ceftazidime–avibactam is a novel antimicrobial combining a third-generation cephalosporin with a non-β-lactam β-lactamase inhibitor that was recently approved to treat Gram-negative hospital- and ventilator-acquired pneumonia. The use of ceftazidime–avibactam to treat Pseudomonas aeruginosa respiratory infections in patients with cystic fibrosis (CF) has not been evaluated. In this study, we assessed the ceftazidime–avibactam susceptibility of multidrug-resistant (MDR) P. aeruginosa sputum isolates from adults with CF.

Methods

Sputum was collected from individuals with CF, aged ≥18 years, known to be colonized with MDR P. aeruginosa, and tested for susceptibility to 11 different antipseudomonal antimicrobial agents. Isolates were included in the analysis if they were resistant to both ceftazidime and at least one agent in ≥3 different antimicrobial categories routinely used to treat P. aeruginosa. Subject demographics and clinical characteristics were collected. Ceftazidime–avibactam-resistant isolates were screened for the presence of β-lactam-resistant mechanisms.

Results

Thirty-two P. aeruginosa isolates were analyzed, of which 23 isolates were sensitive to ceftazidime–avibactam (71.9%). Ten of the isolates were mucoid and 22 isolates were nonmucoid, both demonstrating >70% susceptibility to ceftazidime–avibactam. The most notable difference in the subjects with resistant strains was an older age and lower body mass index (BMI). Ceftazidime–avibactam-resistant strains showed elevated AmpC expression in >60% of the strains and loss of OprD detection in >70% of the strains.

Conclusion

Ceftazidime–avibactam demonstrated a significant in vitro activity against highly resistant P. aeruginosa sputum isolates from individuals with CF. Further evaluation of the cause of resistance and clinical impact of ceftazidime–avibactam in CF patients with MDR P. aeruginosa is warranted.

What's new in the treatment of multidrug-resistant gram-negative infections?

Eradicating multi-drug resistant (MDR) organisms has been a major challenge in healthcare settings worldwide. Newly approved drugs and those currently in the pipeline may have a promising solution to this issue. The purposes of this review are to describe the various resistance mechanisms of Gram-negative bacteria and to provide a summary of the current literature available on the newer agents, such as ceftazidime/avibactam, ceftolozane/tazobactam, meropenem/vaborbactam, and other emerging agents used for the treatment of MDR Gram-negative infections. Given that MDR organisms confer resistance to treatment by various methods, including enzymatic degradation, efflux pumps, and porin mutation, an understanding of mechanisms of bacterial resistance combined with information on newer antimicrobial agents against MDR Gram-negative bacteria will further assist clinicians in determining the best suitable therapy for the treatment of various complicated infections.

Production of β-Lactamase Inhibitors by Streptomyces Species

β-Lactamase inhibitors have emerged as an effective alternative to reduce the effects of resistance against β-lactam antibiotics. The Streptomyces genus is known for being an exceptional natural source of antimicrobials and β-lactamase inhibitors such as clavulanic acid, which is largely applied in clinical practice. To protect against the increasing prevalence of multidrug-resistant bacterial strains, new antibiotics and β-lactamase inhibitors need to be discovered and developed. This review will cover an update about the main β-lactamase inhibitors producers belonging to the Streptomyces genus; advanced methods, such as genetic and metabolic engineering, to enhance inhibitor production compared with wild-type strains; and fermentation and purification processes. Moreover, clinical practice and commercial issues are discussed. The commitment of companies and governments to develop innovative strategies and methods to improve the access to new, efficient, and potentially cost-effective microbial products to combat the antimicrobial resistance is also highlighted.

Activity of imipenem/relebactam against Gram-negative bacilli from global ICU and non-ICU wards: SMART 2015-2016

OBJECTIVES

Antimicrobial resistance is increasing worldwide and is especially problematic in ICUs. Relebactam is a new bicyclic diazabicyclooctane β-lactamase inhibitor of class A and C β-lactamases that is in development in combination with imipenem. This study describes geographical resistance patterns among isolates from ICU and non-ICU wards in seven global regions and examines the activity of imipenem/relebactam in these settings.

METHODS

In 2015-2016, 194 hospitals from 55 countries each collected up to 100 consecutive Gram-negative pathogens from intra-abdominal, 100 from lower respiratory and 50 from urinary tract infections per year. Susceptibility was determined for 45699 non-Proteeae Enterobacteriaceae (NPE) and 10834 Pseudomonas aeruginosa using CLSI broth microdilution and breakpoints, with imipenem breakpoints applied to imipenem/relebactam.

RESULTS

Isolates from ICUs were more resistant to almost all tested agents across regions and infection sources. The size of the ICU/non-ICU difference varied, with a smaller gap in USA/Canada and South Pacific (regions with highest susceptibility) and for imipenem/relebactam, amikacin and colistin (drugs with highest activity). Susceptibility of NPE to imipenem/relebactam was >90% in ICUs in all regions except Africa (88.2%). Only amikacin exceeded these rates in most regions. Against cefepime-non-susceptible and multidrug-resistant (MDR) NPE from ICUs, imipenem/relebactam maintained activity >90% in three regions and >80% in the remaining regions except Africa (75%). Susceptibility of P. aeruginosa was >90% in ICUs in USA/Canada, South Pacific and Europe and >82% elsewhere.

CONCLUSIONS

Imipenem/relebactam could provide a valuable therapeutic option in ICUs, especially against MDR isolates and those non-susceptible to other β-lactam antibiotics.

New Bugs and New Drugs: Updates in Clinical Microbiology

BACKGROUND

The landscape of clinical microbiology laboratories is changing. As new technologies are introduced, we are better able to detect and identify pathogens and to recognize and characterize emerging antimicrobial resistance mechanisms.

CONTENT

In this review, a selected cross-section of current hot topics in clinical microbiology is discussed. These topics include (a) diagnostics for urinary tract and sexually transmitted infections; (b) phenotypic and genotypic methods of detecting carbapenem resistance and discussion of newly approved anti-infective agents for these multi-drug resistant organisms; and (c) the significance, epidemiology, and identification of the emerging pathogens Mycobacterium chimaera and Candida auris.

SUMMARY

Communication between clinical microbiologists and their clinical colleagues is imperative to convey the significance of emerging pathogens and resistance determinants, as well as the performance characteristics of new diagnostic methods. Additionally, as antimicrobial resistance is surging, it is important to comprehensively evaluate the resistance profiles of clinical isolates to facilitate antimicrobial stewardship and inform infection prevention measures. Although antimicrobial resistance is a global public health crisis, it is encouraging that new anti-infective agents are in the pipeline and being approved for use in patients.

Pharmacokinetic drug evaluation of avibactam + ceftazidime for the treatment of hospital-acquired pneumonia

INTRODUCTION

Ceftazidime-avibactam (CAZ-AVI) is a combination of a third-generation cephalosporin and a non-β-lactam, β-lactamase inhibitor, recently approved for urinary tract infections and complicated abdominal infections. Moreover, it represents a treatment option for patients with hospital acquired pneumonia (HAP), especially when caused by multidrug-resistant (MDR) bacteria. Areas covered: The review focuses on the pharmacokinetics (PK) of CAZ-AVI in HAP and on preclinical and clinical studies evaluating PK/pharmacodynamics (PD) in this field. Expert opinion: In vitro and in vivo data about PK/PD of CAZ-AVI confirm that penetration of CAZ-AVI in the epithelial lining fluid (ELF) represents approximately 30% of the plasma concentrations. Clinical studies documented that CAZ-AVI 2000 mg/500 mg every 8 h is the optimal dose regimen to achieve the PK/PD target attainment in patients with HAP. Thus, CAZ-AVI could represent an option both to treat HAP caused by Gram-negative bacilli (GNB) displaying resistance to most of the antibiotics and to reduce the use of carbapenems, limiting the onset of resistance profiles among GNB. Additional information about specific patients populations, such as critically-ill subjects or pediatric patients, are needed for a more individualized use of CAZ-AVI.

Triple combination antibiotic therapy for carbapenemase-producing Klebsiella pneumoniae: a systematic review

Background

The spread of carbapenemase-producing K. pneumoniae (CPKP) has become a significant problem worldwide. Combination therapy for CPKP is encouraging, but polymyxin resistance to many antibiotics is hampering effective treatment. Combination therapy with three or more antibiotics is being increasingly reported, therefore we performed a systematic review of triple combination cases in an effort to evaluate their clinical effectiveness for CPKP infections.

Methods

The PubMed database was searched to identify all published clinical outcomes of CPKP infections treated with triple combination therapy. Articles were stratified into two tiers depending on the level of clinical detail provided. A tier 1 study included: antibiotic regimen, regimen-specific outcome, patient status at onset of infection, and source of infection. Articles not reaching these criteria were considered tier 2.

Results

Thirty-three studies were eligible, 23 tier 1 and ten tier 2. Among tier 1 studies, 53 cases were included in this analysis. The most common infection was pneumonia (31%) followed by primary or catheter-related bacteremia (21%) and urinary tract infection (17%). Different combinations of antibiotic classes were utilized in triple combinations, the most common being a polymyxin (colistin or polymyxin B, 86.8%), tigecycline (73.6%), aminoglycoside (43.4%), or carbapenem (43.4%). Clinical and microbiological failure occurred in 14/39 patients (35.9%) and 22/42 patients (52.4%), respectively. Overall mortality for patients treated with triple combination therapy was 35.8% (19/53 patients).

Conclusions

Triple combination therapy is being considered as a treatment option for CPKP. Polymyxin-based therapy is the backbone antibiotic in these regimens, but its effectiveness needs establishing in prospective clinical trials.

Pharmacological aspects and spectrum of action of ceftazidime-avibactam: a systematic review

PURPOSE

Ceftazidime-avibactam is an antimicrobial association active against several Enterobacteriaceae species, including those resistant to carbapenem. Considering the importance of this drug in the current panorama of multidrug-resistant bacteria, we performed a systematic review about ceftazidime-avibactam with emphasis on clinical and pharmacological published data.

METHODS

A systematic search of the medical literature was performed. The databases searched included MEDLINE, EMBASE and Web of Science (until September 2017). The search terms used were 'avibactam', 'NXL104' and 'AVE1330A'. Bibliographies from those studies were also reviewed. Ceftazidime was not included as a search term, once relevant studies about avibactam in association with other drugs could be excluded. Only articles in English were selected. No statistical analysis or quality validation was included in this review.

RESULTS

A total of 151 manuscripts were included. Ceftazidime-avibactam has limited action against anaerobic bacteria. Avibactam is a potent inhibitor of class A, class C, and some class D enzymes, which includes KPC-2. The best pharmacodynamic profile of ceftazidime-avibactam is ƒT > MIC, validated in an animal model of soft tissue infection. Three clinical trials showed the efficacy of ceftazidime-avibactam in patients with intra-abdominal and urinary infections. Ceftazidime-avibactam has been evaluated versus meropenem/doripenem in hospitalized adults with nosocomial pneumonia, neutropenic patients and pediatric patients.

CONCLUSION

Ceftazidime-avibactam has a favorable pharmacokinetic profile for severe infections and highly active against carbapenemases of KPC-2 type.

Controversies and advances in the management of ventilator associated pneumonia

INTRODUCTION

Although national surveillance data suggests that the incidence of ventilator associated pneumonia (VAP) is down-trending, it remains one of the most commonly encountered hospital acquired infections in the United States and worldwide. Its association with increased healthcare costs and worsened patient outcomes warrants continued effort to improve the care of patients with VAP. Areas covered: The increasing prevalence of multi-drug resistant bacteria further drives the need to explore advances in diagnostic and treatment options. In this review, controversies pertaining to the definition and diagnosis of VAP as well as empiric treatment strategies will be discussed along with several developments related to rapid microbiologic testing methods and the use of non-traditional antimicrobial agents. Expert commentary: The application of rapid diagnostic techniques to identify microbial pathogens is perhaps one of the most impactful advancements in the treatment of serious nosocomial infections. This technology has the potential to reduce inappropriate initial antimicrobial therapy, unnecessary antimicrobial exposure, and mortality in patients with VAP. In addition, the anticipated approval of new antimicrobial agents within the next several years will provide a much-needed expansion of available treatment options in an era of growing antimicrobial resistance.

New agents for the treatment of infections with Gram-negative bacteria: restoring the miracle or false dawn?

BACKGROUND

Antibiotic resistance in Gram-negative resistance has developed without a commensurate response in the successful development of antibiotic agents, though recent progress has been made.

AIMS

This review aims to provide a summary of the existing evidence on efficacy, spectrum of activity and the development of resistance of new agents that have been licensed or have completed advanced clinical trials and that possess activity against resistant Gram-negative organisms.

SOURCES

A review of the published literature via MEDLINE database was performed. Relevant clinical trials were identified with the aid of the clinicaltrials.gov registry. Further data were ascertained from review of abstracts from recent international meetings and pharmaceutical companies.

CONTENT

Data on the mechanism of action, microbiological spectrum, clinical efficacy and development of resistance are reported for new agents that have activity against Gram-negative organisms. This includes the β-lactam/β-lactamase inhibitor combinations ceftazidime/avibactam, ceftolozane/tazobactam, imipenem/cilastatin/relebactam, meropenem/vaborbactam and aztreonam/avibactam; cefiderocol, a siderophore cephalosporin; plazomicin and eravacycline.

IMPLICATIONS

The development of new agents with activity against multidrug-resistant Gram-negative pathogens has provided important therapeutic options for clinicians. Polymyxins appear to have been supplanted by new agents as first-line therapy for Klebsiella pneumoniae carbapenemase producers. Cefiderocol and ceftazidime/avibactam/aztreonam are promising options for metallo-β-lactamase producers, and cefiderocol and ceftolozane/tazobactam for multiply resistant Pseudomonas aeruginosa, but definitive data showing clinical efficacy is as yet lacking. Reports of the development of resistance early after the release and use of new agents is of concern. Orally administered options and agents active effective against Acinetobacter baumannii are under-represented in clinical development.

The Effect of a Piperacillin/Tazobactam Shortage on Antimicrobial Prescribing and Clostridium difficile Risk in 88 US Medical Centers

BACKGROUND

Anti-infective shortages are a pervasive problem in the United States. The objective of this study was to identify any associations between changes in prescribing of antibiotics that have a high risk for CDI during a piperacillin/tazobactam (PIP/TAZO) shortage and hospital-onset Clostridium difficile infection (HO-CDI) risk in 88 US medical centers.

METHODS

We analyzed electronically captured microbiology and antibiotic use data from a network of US hospitals from July 2014 through June 2016. The primary outcome was HO-CDI rate and the secondary outcome was changes in antibiotic usage. We fit a Poisson model to estimate the risk of HO-CDI associated with PIP/TAZO shortage that were associated with increased high-risk antibiotic use while controlling for hospital characteristics.

RESULTS

A total of 88 hospitals experienced PIP/TAZO shortage and 72 of them experienced a shift toward increased use of high-risk antibiotics during the shortage period. The adjusted relative risk (RR) of HO-CDI for hospitals experiencing a PIP/TAZO shortage was 1.03 (95% confidence interval [CI], .85-1.26; P = .73). The adjusted RR of HO-CDI for hospitals that both experienced a shortage and also showed a shift toward increased use of high-risk antibiotics was 1.30 (95% CI, 1.03-1.64; P < .05).

CONCLUSIONS

Hospitals that experienced a PIP/TAZO shortage and responded to that shortage by shifting antibiotic usage toward antibiotics traditionally known to place patients at greater risk for CDI experienced greater HO-CDI rates; this highlights an important adverse effect of the PIP/TAZO shortage and the importance of antibiotic stewardship when mitigating drug shortages.

The Surgical Infection Society Revised Guidelines on the Management of Intra-Abdominal Infection

BACKGROUND

Previous evidence-based guidelines on the management of intra-abdominal infection (IAI) were published by the Surgical Infection Society (SIS) in 1992, 2002, and 2010. At the time the most recent guideline was released, the plan was to update the guideline every five years to ensure the timeliness and appropriateness of the recommendations.

METHODS

Based on the previous guidelines, the task force outlined a number of topics related to the treatment of patients with IAI and then developed key questions on these various topics. All questions were approached using general and specific literature searches, focusing on articles and other information published since 2008. These publications and additional materials published before 2008 were reviewed by the task force as a whole or by individual subgroups as to relevance to individual questions. Recommendations were developed by a process of iterative consensus, with all task force members voting to accept or reject each recommendation. Grading was based on the GRADE (Grades of Recommendation Assessment, Development, and Evaluation) system; the quality of the evidence was graded as high, moderate, or weak, and the strength of the recommendation was graded as strong or weak. Review of the document was performed by members of the SIS who were not on the task force. After responses were made to all critiques, the document was approved as an official guideline of the SIS by the Executive Council.

RESULTS

This guideline summarizes the current recommendations developed by the task force on the treatment of patients who have IAI. Evidence-based recommendations have been made regarding risk assessment in individual patients; source control; the timing, selection, and duration of antimicrobial therapy; and suggested approaches to patients who fail initial therapy. Additional recommendations related to the treatment of pediatric patients with IAI have been included.

SUMMARY

The current recommendations of the SIS regarding the treatment of patients with IAI are provided in this guideline.