Antimicrobial Stewardship in the Hospital Setting: A Narrative Review.

The increasing global threat of antibiotic resistance, which has resulted in countless fatalities due to untreatable infections, underscores the urgent need for a strategic action plan. The acknowledgment that humanity is perilously approaching the "End of the Miracle Drugs" due to the unjustifiable overuse and misuse of antibiotics has prompted a critical reassessment of their usage. In response, numerous relevant medical societies have initiated a concerted effort to combat resistance by implementing antibiotic stewardship programs within healthcare institutions, grounded in evidence-based guidelines and designed to guide antibiotic utilization. Crucial to this initiative is the establishment of multidisciplinary teams within each hospital, led by a dedicated Infectious Diseases physician. This team includes clinical pharmacists, clinical microbiologists, hospital epidemiologists, infection control experts, and specialized nurses who receive intensive training in the field. These teams have evidence-supported strategies aiming to mitigate resistance, such as conducting prospective audits and providing feedback, including the innovative 'Handshake Stewardship' approach, implementing formulary restrictions and preauthorization protocols, disseminating educational materials, promoting antibiotic de-escalation practices, employing rapid diagnostic techniques, and enhancing infection prevention and control measures. While initial outcomes have demonstrated success in reducing resistance rates, ongoing research is imperative to explore novel stewardship interventions.

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

Resistance of Acinetobacter baumannii to multiple clinically important antimicrobials has increased to very high rates in Greece, rendering most of them obsolete. The aim of this study was to determine the molecular epidemiology and susceptibilities of A. baumannii isolates collected from different hospitals across Greece. Single-patient A. baumannii strains isolated from blood cultures (n = 271), from 19 hospitals, in a 6-month period (November 2020-April 2021) were subjected to minimum inhibitory concentration determination and molecular testing for carbapenemase, 16S rRNA methyltransferase and mcr gene detection and epidemiological evaluation. 98.9% of all isolates produced carbapenemase OXA-23. The vast majority (91.8%) of OXA-23 producers harbored the armA and were assigned mainly (94.3%) to sequence group G1, corresponding to IC II. Apramycin (EBL-1003) was the most active agent inhibiting 100% of the isolates at ≤16 mg/L, followed by cefiderocol which was active against at least 86% of them. Minocycline, colistin and ampicillin-sulbactam exhibited only sparse activity (S <19%), while eravacycline was 8- and 2-fold more active than minocycline and tigecycline respectively, by comparison of their MIC50/90 values. OXA-23-ArmA producing A. baumannii of international clone II appears to be the prevailing epidemiological type of this organism in Greece. Cefiderocol could provide a useful alternative for difficult to treat Gram-negative infections, while apramycin (EBL-1003), the structurally unique aminoglycoside currently in clinical development, may represent a highly promising agent against multi-drug resistant A. baumanni infections, due to its high susceptibility rates and low toxicity.

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

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

Pulmonary and systemic pharmacokinetics of colistin methanesulfonate (CMS) and formed colistin following nebulisation of CMS among patients with ventilator-associated pneumonia.

There has been accumulating interest in nebulised colistin methanesulfonate (CMS) for the treatment of ventilator-associated pneumonia (VAP). In this study, pulmonary and systemic pharmacokinetics following nebulisation of CMS at a dose of 3 MIU and 5 MIU, using a vibrating mesh nebuliser, for VAP caused by extensively drug-resistant Gram-negative pathogens was assessed. Blood samples and mini-bronchoalveolar lavage (mini-BAL) was performed post-dose at 1, 4 and 8 h. Concentrations of CMS and formed colistin in mini-BAL and plasma were determined by liquid chromatography-tandem mass spectrometry, and pharmacokinetic analysis was conducted using a population approach. The study population included three groups (n = 10 per group): (A) intravenous CMS and concomitantly nebulised CMS at a dose of 3 MIU (30 min duration); (B) nebulised CMS at a dose of 3 MIU (30 min duration) as monotherapy; and (C) nebulised CMS 5 MIU (45 min duration) as monotherapy. Mean plasma formed colistin concentrations were <1 mg/L following CMS nebulisation as monotherapy (groups B and C). Predicted trough concentrations of formed colistin in the epithelial lining fluid (ELF) following 24-h dosing of 3 MIU and 5 MIU nebulised CMS were 120.4 mg/L and 200.7 mg/L, respectively. The model predicted that concomitant intravenous CMS (group A) had minimal impact on the formed colistin concentration in ELF. This study demonstrated high ELF formed colistin concentrations following nebulised CMS (constantly above colistin MICs), while plasma concentrations were lower than those associated with nephrotoxicity. Our results provide important information for optimisation of nebulised colistin therapy.

Carbapenemase producing Klebsiella pneumoniae: implication on future therapeutic strategies.

INTRODUCTION: The emergence of carbapenemase resistant Gram-negative is designated as an 'urgent' priority of public health. Carbapenemase producing Klebsiella pneumoniae (CPKP) is linked with significant mortality. Conventionally used antibiotics (polymyxins, tigecycline, aminoglycosides, etc.) are associated with poor efficacy and toxicity profiles are quite worrisome. AREAS COVERED: This article reviews mechanism of resistance and evidence regarding novel treatments of infections caused by CPKP, focusing mainly on currently approved new therapies and implications on future therapeutic strategies. A review of novel ß-lactam/ß-lactamase inhibitors (BLI) recently approved and in clinical development as well as cefiderocol, eravacycline and apramycin are discussed. EXPERT OPINION: Newly approved and forthcoming antimicrobial agents are promising to combat infections caused by CPKP. Ceftazidime-avibactam, meropenem-vaborbactam, and imipenem-cilastatin-relebactam are novel agents with favorable outcome and associated with improved mortality in KPC-producing K. pneumoniae infections. However, are inactive against metallo-ß-lactamases (MBL). Novel BLI in later stage of development, i.e. aztreonam-avibactam, cefepime-zidebactam, cefepime-taniborbactam, and meropenem-nacubactam as well as cefiderocol are active in vitro against both KPC and MBL. Potential expectations of future therapeutic strategies are improved potency against CPKP, more tolerable safety profile, and capability of overcoming current resistance mechanism of multidrug-resistant K. pneumoniae.

Multidrug-resistant Klebsiella pneumoniae: mechanisms of resistance including updated data for novel ß-lactam-ß-lactamase inhibitor combinations.

Introduction: Multi-drug-resistant Klebsiella pneumoniae is currently one of the most pressing emerging issues in bacterial resistance. Treatment of K.pneumoniae infections is often problematic due to the lack of available therapeutic options, with a relevant impact in terms of morbidity, mortality and healthcare-associated costs. Soon after the launch of Ceftazidime-Avibactam, one of the approved new ß-lactam/ß-lactamase inhibitor combinations, reports of ceftazidime-avibactam-resistant strains developing resistance during treatment were published. Being a hospital-associated pathogen, K.pneumoniae is continuously exposed to multiple antibiotics resulting in constant selective pressure, which in turn leads to additional mutations that are positively selected.Areas covered: Herein the authors present the K.pneumoniae mechanisms of resistance to different antimicrobials, including updated data for ceftazidime-avibactam.Expert opinion: K.pneumoniae is a nosocomial pathogen commonly implicated in hospital outbreaks with a propensity for antimicrobial resistance toward mainstay ß-lactam antibiotics and multiple other antibiotic classes. Following the development of drug resistance and understanding the mechanisms involved, we can improve the efficacy of current antimicrobials, by applying careful stewardship and rational use to preserve their potential utility. The knowledge on antibiotic resistance mechanisms should be used to inform the design of novel therapeutic agents that might not be subject to, or can circumvent, mechanisms of resistance.

Evolution of epidemiological characteristics of infective endocarditis in Greece.

OBJECTIVE: The clinical profile, management and outcome of infective endocarditis (IE) may be influenced by socioeconomic issues. METHODS: A nationwide prospective study evaluated IE during the era of deep economic crisis in Greece. Epidemiological data and factors associated with 60-day mortality were analyzed through descriptive statistics, logistic and Cox-regression models. RESULTS: Among 224 patients (male 72.3%, mean age 62.4 years), Staphylococcus aureus (n = 62; methicillin-resistant S. aureus (MRSA) 33.8%) predominated in the young without impact on mortality (p = 0.593), whilst Enterococci (n = 36) predominated in the elderly. Complications of IE were associated with mortality: heart failure [OR 2.415 (95% CI: 1.159-5.029), p = 0.019], stroke [OR 3.206 (95% CI: 1.190-8.632), p = 0.018] and acute kidney injury [OR 2.283 (95% CI: 1.085-4.805), p = 0.029]. A 60-day survival benefit was solely related to cardiac surgery for IE during hospitalization [HR 0.386 (95% CI: 0.165-0.903), p = 0.028] and compliance with antimicrobial treatment guidelines [HR 0.487 (95% CI: 0.259-0.916), p = 0.026]. Compared with a previous country cohort study, history of rheumatic fever and native valve predisposition had declined, whilst underlying renal disease and right-sided IE had increased (p < 0.0001); HIV infection had emerged (p = 0.002). No difference in rates of surgery and outcome was assessed. CONCLUSIONS: A country-wide survey of IE highlighted emergence of HIV, right-sided IE and predominance of MRSA in the youth during a severe socioeconomic crisis. Compliance with treatment guidelines promoted survival.

Emergence of ceftazidime-avibactam resistance through distinct genomic adaptations in KPC-2-producing Klebsiella pneumoniae of sequence type 39 during treatment.

Three ceftazidime-avibactam-resistant KPC-2-producing Klebsiella pneumoniae strains of ST39 were isolated in Greece, from rectal swabs of three patients after 10-15 days of treatment. The patients were treated with ceftazidime-avibactam as monotherapy or in combination with colistin. Two of these strains harbored a D179Y or a D179V substitution in the Ω loop of KPC-2, corresponding to KPC-33, or to the novel KPC-57, respectively. The third strain had a 15 amino acid insertion after position 259 in the KPC-2, corresponding to KPC-44.

De-escalation of antimicrobial therapy in ICU settings with high prevalence of multidrug-resistant bacteria: a multicentre prospective observational cohort study in patients with sepsis or septic shock.

BACKGROUND: De-escalation of empirical antimicrobial therapy, a key component of antibiotic stewardship, is considered difficult in ICUs with high rates of antimicrobial resistance. OBJECTIVES: To assess the feasibility and the impact of antimicrobial de-escalation in ICUs with high rates of antimicrobial resistance. METHODS: Multicentre, prospective, observational study in septic patients with documented infections. Patients in whom de-escalation was applied were compared with patients without de-escalation by the use of a propensity score matching by SOFA score on the day of de-escalation initiation. RESULTS: A total of 262 patients (mean age 62.2 ± 15.1 years) were included. Antibiotic-resistant pathogens comprised 62.9%, classified as MDR (12.5%), extensively drug-resistant (49%) and pandrug-resistant (1.2%). In 97 (37%) patients de-escalation was judged not feasible in view of the antibiotic susceptibility results. Of the remaining 165 patients, judged as patients with de-escalation possibility, de-escalation was applied in 60 (22.9%). These were matched to an equal number of patients without de-escalation. In this subset of 120 patients, de-escalation compared with no de-escalation was associated with lower all-cause 28 day mortality (13.3% versus 36.7%, OR 0.27, 95% CI 0.11-0.66, P = 0.006); ICU and hospital mortality were also lower. De-escalation was associated with a subsequent collateral decrease in the SOFA score. Cox multivariate regression analysis revealed de-escalation as a significant factor for 28 day survival (HR 0.31, 95% CI 0.14-0.70, P = 0.005). CONCLUSIONS: In ICUs with high levels of antimicrobial resistance, feasibility of antimicrobial de-escalation was limited because of the multi-resistant pathogens isolated. However, when de-escalation was feasible and applied, it was associated with lower mortality.

Lipid A profiling and metabolomics analysis of paired polymyxin-susceptible and -resistant MDR Klebsiella pneumoniae clinical isolates from the same patients before and after colistin treatment.

BACKGROUND: The increased incidence of polymyxin-resistant MDR Klebsiella pneumoniae has become a major global health concern. OBJECTIVES: To characterize the lipid A profiles and metabolome differences between paired polymyxin-susceptible and -resistant MDR K. pneumoniae clinical isolates. METHODS: Three pairs of K. pneumoniae clinical isolates from the same patients were examined [ATH 7 (polymyxin B MIC 0.25 mg/L) versus ATH 8 (64 mg/L); ATH 15 (0.5 mg/L) versus ATH 16 (32 mg/L); and ATH 17 (0.5 mg/L) versus ATH 18 (64 mg/L)]. Lipid A and metabolomes were analysed using LC-MS and bioinformatic analysis was conducted. RESULTS: The predominant species of lipid A in all three paired isolates were hexa-acylated and 4-amino-4-deoxy-l-arabinose-modified lipid A species were detected in the three polymyxin-resistant isolates. Significant metabolic differences were evident between the paired isolates. Compared with their corresponding polymyxin-susceptible isolates, the levels of metabolites in amino sugar metabolism (UDP-N-acetyl-α-d-glucosamine and UDP-N-α-acetyl-d-mannosaminuronate) and central carbon metabolism (e.g. pentose phosphate pathway and tricarboxylic acid cycle) were significantly reduced in all polymyxin-resistant isolates [fold change (FC) > 1.5, P < 0.05]. Similarly, nucleotides, amino acids and key metabolites in glycerophospholipid metabolism, namely sn-glycerol-3-phosphate and sn-glycero-3-phosphoethanolamine, were significantly reduced across all polymyxin-resistant isolates (FC > 1.5, P < 0.05) compared with polymyxin-susceptible isolates. However, higher glycerophospholipid levels were evident in polymyxin-resistant ATH 8 and ATH 16 (FC > 1.5, P < 0.05) compared with their corresponding susceptible isolates. CONCLUSIONS: To our knowledge, this study is the first to reveal significant metabolic perturbations associated with polymyxin resistance in K. pneumoniae.

Polymyxin Triple Combinations against Polymyxin-Resistant, Multidrug-Resistant, KPC-Producing Klebsiella pneumoniae.

Resistance to polymyxin antibiotics is increasing. Without new antibiotic classes, combination therapy is often required. We systematically investigated bacterial killing with polymyxin-based combinations against multidrug-resistant (including polymyxin-resistant), carbapenemase-producing Klebsiella pneumoniae Monotherapies and double- and triple-combination therapies were compared to identify the most efficacious treatment using static time-kill studies (24 h, six isolates), an in vitro pharmacokinetic/pharmacodynamic model (IVM; 48 h, two isolates), and the mouse thigh infection model (24 h, six isolates). In static time-kill studies, all monotherapies (polymyxin B, rifampin, amikacin, meropenem, or minocycline) were ineffective. Initial bacterial killing was enhanced with various polymyxin B-containing double combinations; however, substantial regrowth occurred in most cases by 24 h. Most polymyxin B-containing triple combinations provided greater and more sustained killing than double combinations. Standard dosage regimens of polymyxin B (2.5 mg/kg of body weight/day), rifampin (600 mg every 12 h), and amikacin (7.5 mg/kg every 12 h) were simulated in the IVM. Against isolate ATH 16, no viable bacteria were detected across 5 to 25 h with triple therapy, with regrowth to ∼2-log10 CFU/ml occurring at 48 h. Against isolate BD 32, rapid initial killing of ∼3.5-log10 CFU/ml at 5 h was followed by a slow decline to ∼2-log10 CFU/ml at 48 h. In infected mice, polymyxin B monotherapy (60 mg/kg/day) generally was ineffective. With triple therapy (polymyxin B at 60 mg/kg/day, rifampin at 120 mg/kg/day, and amikacin at 300 mg/kg/day), at 24 h there was an ∼1.7-log10 CFU/thigh reduction compared to the starting inoculum for all six isolates. Our results demonstrate that the polymyxin B-rifampin-amikacin combination significantly enhanced in vitro and in vivo bacterial killing, providing important information for the optimization of polymyxin-based combinations in patients.

In vitro activity of ceftolozane/tazobactam alone and in combination with amikacin against MDR/XDR Pseudomonas aeruginosa isolates from Greece.

OBJECTIVES: We evaluated the in vitro activity of ceftolozane/tazobactam and comparator agents against MDR non-MBL Pseudomonas aeruginosa isolates collected from nine Greek hospitals and we assessed the potential synergistic interaction between ceftolozane/tazobactam and amikacin. METHODS: A total of 160 non-MBL P. aeruginosa isolates collected in 2016 were tested for susceptibility to ceftolozane/tazobactam and seven comparator agents including ceftazidime/avibactam. Time-kill assays were performed for synergy testing using ceftolozane/tazobactam 60 or 7.5 mg/L, corresponding to the peak and trough concentrations of a 1.5 g q8h dose, respectively, in combination with 69 mg/L amikacin, corresponding to the free peak plasma concentration. Synergy was defined as a ≥2 log10 cfu/mL reduction compared with the most active agent. RESULTS: Overall, ceftolozane/tazobactam inhibited 64.4% of the P. aeruginosa strains at ≤4 mg/L. Colistin was the most active agent (MIC50/90, 0.5/2 mg/L; 96.3% susceptible) followed by ceftazidime/avibactam (MIC50/90, 4/16 mg/L; 80.6% susceptible). GES-type enzymes were predominantly responsible for ceftolozane/tazobactam resistance; 81.6% of the non-producers were susceptible. MICs for the P. aeruginosa isolates selected for synergy testing were 2-32 mg/L ceftolozane/tazobactam and 2-128 mg/L amikacin. The combination of ceftolozane/tazobactam with amikacin was synergistic against 85.0% of all the isolates tested and against 75.0% of the GES producers. No antagonistic interactions were observed. CONCLUSIONS: Ceftolozane/tazobactam demonstrated good in vitro activity against MDR/XDR P. aeruginosa clinical isolates, including strains with co-resistance to other antipseudomonal drugs. In combination with amikacin, a synergistic interaction at 24 h was observed against 85.0% of P. aeruginosa strains tested, including isolates with ceftolozane/tazobactam MICs of 32 mg/L or GES producers.

The Greek study in the effects of colchicine in COvid-19 complications prevention (GRECCO-19 study): Rationale and study design.

OBJECTIVE: Colchicine has been utilized safely in a variety of cardiovascular clinical conditions. Among its potential mechanisms of action is the non-selective inhibition of NLRP3 inflammasome which is thought to be a major pathophysiologic component in the clinical course of patients with COVID-19. GRECCO-19 will be a prospective, randomized, open-labeled, controlled study to assess the effects of colchicine in COVID-19 complications prevention. METHODS: Patients with laboratory confirmed SARS-CoV-2 infection (under RT PCR) and clinical picture that involves temperature >37.5 oC and at least two out of the: i. sustained coughing, ii. sustained throat pain, iii. Anosmia and/or ageusia, iv. fatigue/tiredness, v. PaO2<95 mmHg will be included. Patients will be randomised (1:1) in colchicine or control group. RESULTS: Trial results will be disseminated through peer-reviewed publications and conference presentations. CONCLUSION: GRECCO-19 trial aims to identify whether colchicine may positively intervene in the clinical course of COVID-19. (ClinicalTrials.gov Identifier: NCT04326790).

Carbapenem-Sparing Strategies for ESBL Producers: When and How.

Extended spectrum ß-lactamase (ESBL)-producing bacteria are prevalent worldwide and correlated with hospital infections, but they have been evolving as an increasing cause of community acquired infections. The spread of ESBL constitutes a major threat for public health, and infections with ESBL-producing organisms have been associated with poor outcomes. Established therapeutic options for severe infections caused by ESBL-producing organisms are considered the carbapenems. However, under the pressure of carbapenem overuse and the emergence of resistance, carbapenem-sparing strategies have been implemented. The administration of carbapenem-sparing antibiotics for the treatment of ESBL infections has yielded conflicting results. Herein, the current available knowledge regarding carbapenem-sparing strategies for ESBL producers is reviewed, and the optimal conditions for the "when and how" of carbapenem-sparing agents is discussed. An important point of the review focuses on piperacillin-tazobactam as the agent arousing the most debate. The most available data regarding non-carbapenem ß-lactams (i.e., ceftolozane-tazobactam, ceftazidime-avibactam, temocillin, cephamycins and cefepime) are also thoroughly presented as well as non ß-lactams (i.e., aminoglycosides, quinolones, tigecycline, eravacycline and fosfomycin).

Outbreak of KPC-2-producing Klebsiella pneumoniae endowed with ceftazidime-avibactam resistance mediated through a VEB-1-mutant (VEB-25), Greece, September to October 2019.

From September to October 2019, seven patients colonised or infected with a ceftazidime-avibactam (CZA)-resistant Klebsiella pneumoniae carbapenemase (KPC)-2-producing K. pneumoniae were detected in two intensive care units of a Greek general hospital. The outbreak strain was sequence type (ST)147 and co-produced KPC-2 and the novel plasmid-borne Vietnamese extended-spectrum ß-lactamase (VEB)-25 harbouring a K234R substitution associated with CZA resistance. Epidemiological investigations revealed that the resistance was probably acquired by horizontal transmission independently from previous CZA exposure.

Evaluation of in vitro methods for testing tigecycline combinations against carbapenemase-producing Klebsiella pneumoniae isolates.

OBJECTIVES: Treatment of infections caused by carbapenemase-producing Klebsiella pneumoniae (CPKP) frequently involves combination therapy with various antimicrobial agents in the hope of achieving synergistic effects. Routine laboratory antimicrobial synergy testing is a service that is currently unavailable owing to the laborious nature of the reference time-kill assay (TKA) as well as the widely used chequerboard method. In this study, we explored whether easier methods, based on the Etest technique, might offer a suitable alternative. METHODS: In vitro interactions of tigecycline combination with colistin, gentamicin, fosfomycin or meropenem against 26 CPKP isolates were evaluated employing the TKA, chequerboard method and three Etest methodologies (the MIC/MIC ratio, the cross formation and the agar/Etest method). Rates of consequent synergy and concordance of the studied methods were determined. RESULTS: All antimicrobial combinations demonstrated some degree of synergy against the CPKP isolates tested. No antagonism was observed for any of the combinations. All methods showed poor synergy concordance with the TKA, producing non-significant kappa (κ) results. Etest methods (MIC/MIC ratio and agar/Etest) exhibited fair agreement (κ=0.29 and 0.38, respectively) with the chequerboard method. CONCLUSION: There is a poor correlation between synergy testing methods of tigecycline combinations, which may be associated with their different endpoints. To elucidate method comparability and reliability, their correlation with clinical outcomes appears important.

Antimicrobial de-escalation in critically ill patients: a position statement from a task force of the European Society of Intensive Care Medicine (ESICM) and European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Critically Ill Patients Study Group (ESGCIP).

BACKGROUND: Antimicrobial de-escalation (ADE) is a strategy of antimicrobial stewardship, aiming at preventing the emergence of antimicrobial resistance (AMR) by decreasing the exposure to broad-spectrum antimicrobials. There is no high-quality research on ADE and its effects on AMR. Its definition varies and there is little evidence-based guidance for clinicians to use ADE in the intensive care unit (ICU). METHODS: A task force of 16 international experts was formed in November 2016 to provide with guidelines for clinical practice to develop questions targeted at defining ADE, its effects on the ICU population and to provide clinical guidance. Groups of 2 experts were assigned 1-2 questions each within their field of expertise to provide draft statements and rationale. A Delphi method, with 3 rounds and an agreement threshold of 70% was required to reach consensus. RESULTS: We present a comprehensive document with 13 statements, reviewing the evidence on the definition of ADE, its effects in the ICU population and providing guidance for clinicians in subsets of clinical scenarios where ADE may be considered. CONCLUSION: ADE remains a topic of controversy due to the complexity of clinical scenarios where it may be applied and the absence of evidence to the effects it may have on antimicrobial resistance.

Multifaceted mechanisms of colistin resistance revealed by genomic analysis of multidrug-resistant Klebsiella pneumoniae isolates from individual patients before and after colistin treatment.

OBJECTIVES: Polymyxins (i.e., polymyxin B and colistin) are used as a last-line therapy to combat multidrug-resistant (MDR) Klebsiella pneumoniae. Worryingly, polymyxin resistance in K. pneumoniae is increasingly reported worldwide. This study identified the genetic variations responsible for high-level colistin resistance in MDR K. pneumoniae clinical isolates. METHODS: Sixteen MDR K. pneumoniae isolates were obtained from stool samples of 8 patients before and after colistin treatment. Their genomes were sequenced on Illumina MiSeq to determine genetic variations. RESULTS: Fifteen of 16 isolates harboured ISKpn26-like element insertion at nucleotide position 75 of mgrB, abolishing its negative regulation on phoPQ; while colistin-susceptible ATH7 contained intact mgrB and phoQ. Interestingly, each of the 7 mgrB-disrupted, colistin-susceptible isolates contained a nonsynonymous substitution in PhoQ (G39S, L239P, N253T or V446G), potentially impairing its function and intergenically suppressing the effect caused by mgrB inactivation. Additionally, three of the 7 corresponding mgrB-disrupted, colistin-resistant isolates harboured a secondary nonsynonymous substitution in PhoQ (N253P, D438H or T439P). CONCLUSIONS: This is the first report of phoQ mutations in mgrB-disrupted, colistin-susceptible K. pneumoniae clinical isolates. We also discovered multiple phoQ mutations in mgrB-disrupted, colistin-resistant strains. Our findings highlight the multifaceted molecular mechanisms of colistin resistance in K. pneumoniae.

Correction to: In vitro activity of imipenem-relebactam against non-MBL carbapenemase-producing Klebsiella pneumoniae isolated in Greek hospitals in 2015-2016.

The publisher regrets that the article has been published online on 01 March 2019 with errors in Table 1. In the originally published Table 1, the percentage of Imipenem-relebactam susceptibility was incorrectly written as 8 0, while correct data is 98.0. Also, in Meropenem row, column MIC50 (mg/L), the incorrect data 4 should be 64.

Correction to: Nationwide epidemiology of carbapenem resistant Klebsiella pneumoniae isolates from Greek hospitals, with regards to plazomicin and aminoglycoside resistance.

Following publication of the original article [1].