External Validity of a Randomized Controlled Trial on Duration of Antibiotics for the Treatment of Gram-Negative Bacteremia.

INTRODUCTION: Reports regarding the external validity of randomized controlled trials (RCTs) are scarce. We aimed to assess the population external validity of an investigator-initiated RCT on the duration of antibiotics for the treatment of Gram-negative bacteremia by comparing patients included in the RCT to patients that were not included in the trial. METHODS: Hospitalized patients with Gram-negative bacteremia were recruited into an RCT and randomized to receive 7 or 14 days of covering antibiotic therapy in Israel and Italy from 2013 to 2017. In a concomitant observational study, RCT participants were compared with patients who fulfilled the inclusion criteria but were not included in the trial due to participation in other trials, discharge before approached by researchers, refusal to participate, or unwillingness of the treating physician to allow participants' recruitment. RESULTS: Six hundred and four RCT patients were compared with 613 nonincluded patients. Almost 50% of nonincluded patients (288/613) were dependent on others for activities of daily living at baseline compared to 37.7% of RCT participants (228/604). Dementia was nearly 2-fold more frequent in nonincluded patients than those included (5.9% [36/613] versus 3.6% [22/604], p = 0.07). Patients who were not included in the RCT were more likely to acquire their infection in the hospital (53.3% [327/613] versus 29.1% [176/604], p < 0.001). The primary composite outcome of mortality, clinical failure, readmissions, or extended hospitalization at 90 days occurred in 353 of 613 nonincluded patients (57.6%) compared to 299 of 604 RCT participants (49.6%), p = 0.005. However, on multivariate analysis noninclusion in the RCT was not an independent risk factor for clinical failure and mortality. CONCLUSIONS: RCTs, even with broad eligibility criteria, do not represent the whole spectrum of patients and leave out a population with more severe illness for whom the evidence is lacking.

Duration of antibiotic treatment for Gram-negative bacteremia - Systematic review and individual participant data (IPD) meta-analysis.

Background: We aim to compare the effect of short versus long treatment duration in Gram-negative bacteremia on all-cause mortality in pre-specified sub-groups. Methods: Individual participant data meta-analysis of randomized controlled trials (RCTs) comparing short (≤7) versus longer (>7 days) antibiotic treatment for Gram-negative bacteremia. Participants were adults (≥18 years), with Gram-negative bacteremia during hospital stay. We searched PubMed, Cochrane Central Register of Controlled Trials, and Web of Science to identify trials conducted up to May 2022. Primary outcome was 90-day all-cause mortality. Secondary outcomes were 30-day mortality, relapse of bacteremia, length of hospital stay, readmission, local or distant infection complications, adverse events, and resistance emergence.Outcomes were assessed in pre-specified subgroups: women vs men; non-urinary vs urinary source; presence vs absence of hypotension on initial presentation; immunocompromised patients versus non-immunocompromised patients, and age (above/below 65). Fixed-effect meta-analysis model was used to estimate pooled odds ratio (OR) and 95% confidence interval (CI). All three trials had low risk of bias for allocation generation and concealment. Findings: Three RCTs (1186 patients) were included; 1121 with enterobacterales bacteremia. No significant difference in mortality was demonstrated between 7- and 14-days treatment (90-day mortality: OR 1.08, 95% CI 0.73-1.58; 30-day mortality: 1.08, 0.62-1.91). Relapse (1.00, 0.50-1.97); length of hospital stay (P = 0.78); readmission (0.96, 0.80-1.22); and infection complications (local: 1.62 0.76-3.47; distant: 2.00, 0.18-22.08), were without significant difference, and so were adverse events or resistance emergence.No significant difference in clinical outcomes between 7 and 14 days of antibiotics was demonstrated in the subgroups of gender, age, hemodynamic status, immune status, and source of infection. Interpretation: For patients hemodynamically stable and afebrile at 48 h prior to discontinuation, seven days of antibiotic therapy for enterobacterales bacteremia result in similar outcomes as 14 days, in terms of mortality, relapse, length of hospital stay, complications of infection, resistance emergence, and adverse events. These results apply for any adult age group, gender, source of infection, immune status, and hemodynamic status on presentation. Funding: There was no funding source for this study.

A Desirability of Outcome Ranking Analysis of a Randomized Clinical Trial Comparing Seven Versus Fourteen Days of Antibiotics for Uncomplicated Gram-Negative Bloodstream Infection.

Background: Although a short course (7 days) of antibiotics has been demonstrated to be noninferior to a conventional course (14 days) in terms of mortality and infectious complications for patients with a Gram-negative bacterial bloodstream infection (GNB), it is unknown whether a shorter treatment duration can provide a better overall clinical outcome. Methods: We applied a bloodstream infection-specific desirability of outcome ranking (DOOR) analysis to the results of a previously completed, randomized controlled trial comparing short versus conventional course antibiotic therapy for hospitalized patients with uncomplicated GNB. We determined the probability that a randomly selected participant in the short course group would have a more desirable overall outcome than a participant in the conventional duration group. We performed (1) partial credit analyses allowing for calculated and variable weighting of DOOR ranks and (2) subgroup analyses to elucidate which patients may benefit the most from short durations of therapy. Results: For the 604 patients included in the original study (306 short course, 298 conventional course), the probability of having a more desirable outcome with a short course of antibiotics compared with a conventional course was 51.1% (95% confidence interval, 46.7% to 55.4%), indicating no significant difference. Partial credit analyses indicated that the DOOR results were similar across different patient preferences. Prespecified subgroup analyses using DOOR did not reveal significant differences between short and conventional courses of therapy. Conclusions: Both short and conventional durations of antibiotic therapy provide comparable clinical outcomes when using DOOR to consider benefits and risks of treatment options for GNB.

Risk factors for functional decline among survivors of Gram-negative bloodstream infection: A prospective cohort study.

OBJECTIVE: To identify risk factors for functional decline after hospitalization for Gram-negative bacteremia. PATIENTS AND METHODS: A prospective cohort study based on a randomized controlled trial conducted between January 1, 2013 and August 31, 2017 in Israel and Italy. Hospitalized patients with Gram-negative bacteremia who survived until day 90 and were not bedridden at baseline were included. The primary end point was functional decline at 90 days. RESULTS: Five hundred and nine patients were included. The median age of the cohort was 71 years (interquartile range [IQR], 60-80 years), 46.4% (236/509) were male and 352 of 509 (69%) patients were independent at baseline. Functional decline at 90 days occurred in 24.4% of patients (124/509). In multivariable analysis; older age (odds ratio [OR], 1.03; for an one-year increment, 95% confidence interval [CI] 1.01-1.05), functional dependence in instrumental activities of daily living at baseline (OR, 4.64; 95% CI 2.5-8.6), low Norton score (OR, 0.87; 95% CI 0.79-0.96) and underlying comorbidities: cancer (OR, 2.01; 95% CI 1.14-3.55) and chronic pulmonary disease (OR, 2.23 95% CI 1.12-4.42) and longer length of hospital stay (OR 1.09; for one-day increment, 95% CI 1.04-1.15) were associated with functional decline. Appropriate empirical antibiotic treatment was associated with lower rates of functional decline within 90 days (OR, 0.4; 95% CI 0.21-0.78). CONCLUSIONS: Patients surviving bloodstream infections have poor long term trajectories after clinical recovery and hospital discharge. This has vast implications for patients, their family members and health policy makers.

Excluded versus included patients in a randomized controlled trial of infections caused by carbapenem-resistant Gram-negative bacteria: relevance to external validity.

BACKGROUND: Population external validity is the extent to which an experimental study results can be generalized from a specific sample to a defined population. In order to apply the results of a study, we should be able to assess its population external validity. We performed an investigator-initiated randomized controlled trial (RCT) (AIDA study), which compared colistin-meropenem combination therapy to colistin monotherapy in the treatment of patients infected with carbapenem-resistant Gram-negative bacteria. In order to examine the study's population external validity and to substantiate the use of AIDA study results in clinical practice, we performed a concomitant observational trial. METHODS: The study was conducted between October 1st, 2013 and January 31st, 2017 (during the RCTs recruitment period) in Greece, Israel and Italy. Patients included in the observational arm of the study have fulfilled clinical and microbiological inclusion criteria but were excluded from the RCT due to receipt of colistin for > 96 h, refusal to participate, or prior inclusion in the RCT. Non-randomized cases were compared to randomized patients. The primary outcome was clinical failure at 14 days of infection onset. RESULTS: Analysis included 701 patients. Patients were infected mainly with Acinetobacter baumannii [78.2% (548/701)]. The most common reason for exclusion was refusal to participate [62% (183/295)]. Non-randomized and randomized patients were similar in most of the demographic and background parameters, though randomized patients showed minor differences towards a more severe infection. Combination therapy was less common in non-randomized patients [31.9% (53/166) vs. 51.2% (208/406), p = 0.000]. Randomized patients received longer treatment of colistin [13 days (IQR 10-16) vs. 8.5 days (IQR 0-15), p = 0.000]. Univariate analysis showed that non-randomized patients were more inclined to clinical failure on day 14 from infection onset [82% (242/295) vs. 75.5% (307/406), p = 0.042]. After adjusting for other variables, non-inclusion was not an independent risk factor for clinical failure at day 14. CONCLUSION: The similarity between the observational arm and RCT patients has strengthened our confidence in the population external validity of the AIDA trial. Adding an observational arm to intervention studies can help increase the population external validity and improve implementation of study results in clinical practice. TRIAL REGISTRATION: The trial was registered with ClinicalTrials.gov, number NCT01732250 on November 22, 2012.

Piperacillin-tazobactam versus meropenem for treatment of bloodstream infections caused by third-generation cephalosporin-resistant Enterobacteriaceae: a study protocol for a non-inferiority open-label randomised controlled trial (PeterPen).

INTRODUCTION: The optimal treatment for extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae bloodstream infections has yet to be defined. Retrospective studies have shown conflicting results, with most data suggesting the non-inferiority of beta-lactam-beta-lactamase inhibitor combinations compared with carbapenems. However, the recently published MERINO trial failed to demonstrate the non-inferiority of piperacillin-tazobactam to meropenem. The potential implications of the MERINO trial are profound, as widespread adoption of carbapenem treatment will have detrimental effects on antimicrobial stewardship in areas endemic for ESBL and carbapenem-resistant bacteria. Therefore, we believe that it is justified to re-examine the comparison in a second randomised controlled trial prior to changing clinical practice. METHODS AND ANALYSIS: PeterPen is a multicentre, investigator-initiated, open-label, randomised controlled non-inferiority trial, comparing piperacillin-tazobactam with meropenem for third-generation cephalosporin-resistant Escherichia coli and Klebsiella bloodstream infections. The study is currently being conducted in six centres in Israel and one in Canada with other centres from Israel, Italy and Canada expected to join. The two primary outcomes are all-cause mortality at day 30 from enrolment and treatment failure at day seven (death, fever above 38°C in the last 48 hours, continuous symptoms, increasing Sequential Organ Failure Assessment Score or persistent blood cultures with the index pathogen). A sample size of 1084 patients was calculated for the mortality endpoint assuming a 12.5% mortality rate in the control group with a 5% non-inferiority margin and assuming 100% follow-up for this outcome. ETHICS AND DISSEMINATION: The study is approved by local and national ethics committees as required. Results will be published, and trial data will be made available. TRIAL REGISTRATION NUMBERS: ClinicalTrials.gov Registry (NCT03671967); Israeli Ministry of Health Trials Registry (MOH_2018-12-25_004857).

Seven Versus 14 Days of Antibiotic Therapy for Uncomplicated Gram-negative Bacteremia: A Noninferiority Randomized Controlled Trial.

BACKGROUND: Gram-negative bacteremia is a major cause of morbidity and mortality in hospitalized patients. Data to guide the duration of antibiotic therapy are limited. METHODS: This was a randomized, multicenter, open-label, noninferiority trial. Inpatients with gram-negative bacteremia, who were afebrile and hemodynamically stable for at least 48 hours, were randomized to receive 7 days (intervention) or 14 days (control) of covering antibiotic therapy. Patients with uncontrolled focus of infection were excluded. The primary outcome at 90 days was a composite of all-cause mortality; relapse, suppurative, or distant complications; and readmission or extended hospitalization (>14 days). The noninferiority margin was set at 10%. RESULTS: We included 604 patients (306 intervention, 298 control) between January 2013 and August 2017 in 3 centers in Israel and Italy. The source of the infection was urinary in 411 of 604 patients (68%); causative pathogens were mainly Enterobacteriaceae (543/604 [90%]). A 7-day difference in the median duration of covering antibiotics was achieved. The primary outcome occurred in 140 of 306 patients (45.8%) in the 7-day group vs 144 of 298 (48.3%) in the 14-day group (risk difference, -2.6% [95% confidence interval, -10.5% to 5.3%]). No significant differences were observed in all other outcomes and adverse events, except for a shorter time to return to baseline functional status in the short-course therapy arm. CONCLUSIONS: In patients hospitalized with gram-negative bacteremia achieving clinical stability before day 7, an antibiotic course of 7 days was noninferior to 14 days. Reducing antibiotic treatment for uncomplicated gram-negative bacteremia to 7 days is an important antibiotic stewardship intervention. CLINICAL TRIALS REGISTRATION: NCT01737320.

Colistin alone versus colistin plus meropenem for treatment of severe infections caused by carbapenem-resistant Gram-negative bacteria: an open-label, randomised controlled trial.

BACKGROUND: Colistin-carbapenem combinations are synergistic in vitro against carbapenem-resistant Gram-negative bacteria. We aimed to test whether combination therapy improves clinical outcomes for adults with infections caused by carbapenem-resistant or carbapenemase-producing Gram-negative bacteria. METHODS: A randomised controlled superiority trial was done in six hospitals in Israel, Greece, and Italy. We included adults with bacteraemia, ventilator-associated pneumonia, hospital-acquired pneumonia, or urosepsis caused by carbapenem-non-susceptible Gram-negative bacteria. Patients were randomly assigned (1:1) centrally, by computer-generated permuted blocks stratified by centre, to intravenous colistin (9-million unit loading dose, followed by 4·5 million units twice per day) or colistin with meropenem (2-g prolonged infusion three times per day). The trial was open-label, with blinded outcome assessment. Treatment success was defined as survival, haemodynamic stability, improved or stable Sequential Organ Failure Assessment score, stable or improved ratio of partial pressure of arterial oxygen to fraction of expired oxygen for patients with pneumonia, and microbiological cure for patients with bacteraemia. The primary outcome was clinical failure, defined as not meeting all success criteria by intention-to-treat analysis, at 14 days after randomisation. This trial is registered at ClinicalTrials.gov, number NCT01732250, and is closed to accrual. FINDINGS: Between Oct 1, 2013, and Dec 31, 2016, we randomly assigned 406 patients to the two treatment groups. Most patients had pneumonia or bacteraemia (355/406, 87%), and most infections were caused by Acinetobacter baumannii (312/406, 77%). No significant difference between colistin monotherapy (156/198, 79%) and combination therapy (152/208, 73%) was observed for clinical failure at 14 days after randomisation (risk difference -5·7%, 95% CI -13·9 to 2·4; risk ratio [RR] 0·93, 95% CI 0·83-1·03). Results were similar among patients with A baumannii infections (RR 0·97, 95% CI 0·87-1·09). Combination therapy increased the incidence of diarrhoea (56 [27%] vs 32 [16%] patients) and decreased the incidence of mild renal failure (37 [30%] of 124 vs 25 [20%] of 125 patients at risk of or with kidney injury). INTERPRETATION: Combination therapy was not superior to monotherapy. The addition of meropenem to colistin did not improve clinical failure in severe A baumannii infections. The trial was unpowered to specifically address other bacteria. FUNDING: EU AIDA grant Health-F3-2011-278348.

Polymyxin monotherapy or in combination against carbapenem-resistant bacteria: systematic review and meta-analysis.

OBJECTIVES: The objective of this study was to summarize available data on polymyxin-based combination therapy or monotherapy for carbapenem-resistant Gram-negative bacteria. METHODS: This is a systematic review. We included observational studies and randomized controlled trials (RCTs) comparing polymyxin monotherapy versus polymyxin-based combination therapy in adult patients with infections caused by carbapenem-resistant or carbapenemase-producing Gram-negative bacteria. Only named antibiotic regimens were included. The primary outcome was 30 day mortality. Unadjusted OR (uOR) and adjusted OR where available with 95% CI were pooled in random-effects meta-analyses. RESULTS: Twenty-two studies including 28 comparisons were included. Polymyxin monotherapy was associated with a uOR of 1.58 (95% CI = 1.03-2.42) for mortality compared with polymyxin/carbapenem combination therapy (seven observational studies, 537 patients), without heterogeneity. Subgrouping studies to serious and critical risk of bias resulted in uORs of 0.94 (95% CI = 0.42-2.09) and 1.94 (95% CI = 1.17-3.23), respectively. Mortality was significantly higher with polymyxin monotherapy compared with combination therapy with tigecycline, aminoglycosides or fosfomycin (potentially double-coverage regimens): uOR of 1.57 (95% CI = 1.06-2.32) overall (10 observational studies and 1 RCT, 585 patients, no heterogeneity) and uOR of 2.09 (95% CI = 1.21-3.6) for Klebsiella pneumoniae bacteraemia (7 observational studies, 285 patients, no heterogeneity); very low quality evidence. Two RCTs and one observational study assessing rifampicin/colistin combination therapy for Acinetobacter baumannii infections showed no difference in mortality compared with colistin monotherapy; moderate quality evidence. CONCLUSIONS: The significant association observed in observational studies between polymyxin monotherapy and mortality cannot be taken as proof of combination therapy effects due to the low quality of the evidence. The only three RCTs to date show no effect of rifampicin/colistin or fosfomycin/colistin on mortality for Acinetobacter infections.

Multicentre open-label randomised controlled trial to compare colistin alone with colistin plus meropenem for the treatment of severe infections caused by carbapenem-resistant Gram-negative infections (AIDA): a study protocol.

INTRODUCTION: The emergence of antibiotic-resistant bacteria has driven renewed interest in older antibacterials, including colistin. Previous studies have shown that colistin is less effective and more toxic than modern antibiotics. In vitro synergy studies and clinical observational studies suggest a benefit of combining colistin with a carbapenem. A randomised controlled study is necessary for clarification. METHODS AND ANALYSIS: This is a multicentre, investigator-initiated, open-label, randomised controlled superiority 1:1 study comparing colistin monotherapy with colistin-meropenem combination therapy for infections caused by carbapenem-resistant Gram-negative bacteria. The study is being conducted in 6 centres in 3 countries (Italy, Greece and Israel). We include patients with hospital-associated and ventilator-associated pneumonia, bloodstream infections and urosepsis. The primary outcome is treatment success at day 14, defined as survival, haemodynamic stability, stable or improved respiratory status for patients with pneumonia, microbiological cure for patients with bacteraemia and stability or improvement of the Sequential Organ Failure Assessment (SOFA) score. Secondary outcomes include 14-day and 28-day mortality as well as other clinical end points and safety outcomes. A sample size of 360 patients was calculated on the basis of an absolute improvement in clinical success of 15% with combination therapy. Outcomes will be assessed by intention to treat. Serum colistin samples are obtained from all patients to obtain population pharmacokinetic models. Microbiological sampling includes weekly surveillance samples with analysis of resistance mechanisms and synergy. An observational trial is evaluating patients who met eligibility requirements but were not randomised in order to assess generalisability of findings. ETHICS AND DISSEMINATION: The study was approved by ethics committees at each centre and informed consent will be obtained for all patients. The trial is being performed under the auspices of an independent data and safety monitoring committee and is included in a broad dissemination strategy regarding revival of old antibiotics. TRIAL REGISTRATION NUMBER: NCT01732250 and 2012-004819-31; Pre-results.