Antimicrobial Combination Therapy for Treatment of Enterococcus Faecalis Bacteremia (MicroEFfAECT)

Efficacy of Optimized Antimicrobial Combination Therapy for Treatment of Enterococcus Faecalis Bacteremia and Identification of Intestinal Microbiota Signature

Prospective, multicenter, national, observational pharmacological study on the evaluation of efficacy of appropriate monotherapy vs combination treatment for non-complicated Enterococcus faecalis (EF) bloodstream infection (BSI) and identification of gut microbiota fingerprint of patients with EF-BSI correlated to antimicrobial treatment and clinical outcome

Study Overview

• Status: Recruiting
• Conditions: Blood Stream Infection; Enterococcus Faecalis Infection; Gut Microbiomes

Detailed Description

Enterococcus faecalis (EF) is a common commensal of human gastrointestinal tract that can act as opportunistic pathogen causing mild to severe clinical illness. Severe infections due to EF include bacteremia, endocarditis and catheter-related infections. EF is the fourth causative pathogen of bloodstream infection (BSI) in Europe after E. coli, S. aureus and S. pneumoniae. The incidence of infections caused by E. faecalis has increased over the last decades probably as a consequence of the global aging of the population. EF-BSI is associated to a high mortality rate (11-26% of cases).The main factors that may contribute to short-term mortality are the number of comorbidities, the need of admission in intensive care unit and the prompt administration of appropriate antibiotic treatment.

The optimal treatment of EF-BSI uncomplicated with endocarditis is still a matter of debate. Ampicillin is commonly considered the drug of choice, when active in vitro. However, several studies demonstrated the synergistic effect of the combination treatment with an aminoglycosides or ceftriaxone in case of life-threatening infections. To date the efficacy of the combination treatment in patients with EF-BSI was poorly evaluated in clinical studies and most of the data come from very old uncontrolled clinical observations. One strategy for overcoming this uncertainty is to assess the synergistic interaction of different antimicrobial molecules by in vitro tests and to validate in vitro synergisms with clinical studies. Indeed, in vitro evaluation of the drug combination effect has the potentiality for improving treatment by suggesting the possible synergistic or antagonistic interaction of antimicrobial associations. Although, different studies suggested the potential clinical utility of synergy testing, the real prognostic value of these methods is not defined yet. In this context, synergy testing could be used as strategy for improving antibiotic treatment of EF-BSI by suggesting the optimal antimicrobial combination therapy. Ceftaroline and ceftobiprole are two novel cephalosporins, which exhibit intrinsic activity against methicillin-resistant S. aureus. Both drugs seem to show a good level of affinity to penicillin binding protein (PBP) 5, a class B, commonly expressed by Enterococcus spp. The use of these drugs in association with ampicillin or daptomycin seems promising. However, clinical efficacy of these combinations is not well defined yet. Gut microbiota of healthy individual is composed by a consortium of bacteria balanced by symbiotic or antagonistic relationships. Antimicrobial treatments altered this equilibrium conferring competitive advantage for different species, including host pathogens. Disruption of the balance in the gut microbial composition has been associated to different pathological conditions (metabolic disease, type 2 diabetes, colorectal cancer or inflammatory bowel disease). Also, administration of antimicrobials contributes to increase resistome in the intestinal microbiota and diffusion of antimicrobialresistant pathogens through selective pressure. The central objective of this study is to identify the gut microbiota signature associated to different antimicrobial therapy of EF-BSI and to clinically validate novel diagnostic tools for optimizing antimicrobial therapy in critically ill patients.

The primary aim of the study is to compare efficacy of appropriate monotherapy vs combination treatment for EF-BSI and validate clinically the in vitro synergistic/antagonistic interaction of antimicrobial combinations by synergy tests.

Secondary objectives are:

• To define the prognostic and predictive value of EF genotypic and phenotypic traits on the basis of antimicrobial treatment and clinical outcome
• To compare gut microbiota fingerprint of patients with EF-BSI and correlate to antimicrobial treatment and clinical outcome

• Study Type: Observational
• Enrollment (Estimated): 510

Contacts and Locations

• Study Contact: Name: Maddalena Giannella, MD PhD; Phone Number: +39 0512143199; Email: maddalena.giannella@unibo.it

Study Locations

• Italy
  • Bologna
    • Bologna, Bologna, Italy, 40138
      • Recruiting
      • IRCCS Azienda Ospedaliero-Universitaria di Bologna
      • Contact: Maddalena Giannella, MD PhD; Phone Number: +39 0512143199; Email: maddalena.giannella@unibo.it
    • Bologna, Bologna, Italy, 40133
      • Recruiting
      • Ospedale Maggiore "Carlo Alberto Pizzardi" di Bologna
      • Contact: Luca Guerra, MD; Phone Number: +390515879975; Email: luca.guerra@ausl.bologna.it
  • Catanzaro
    • Catanzaro, Catanzaro, Italy, 88100
      • Recruiting
      • Azienda Ospedaliero Universitaria di Catanzaro "Mater Domini"
      • Contact: Alessandro Russo, MD; Phone Number: +3909613647552; Email: a.russo@unicz.it
  • Milano
    • Milan, Milano, Italy, 20089
      • Recruiting
      • Humanitas Research Hospital
      • Contact: Michele Bartoletti, MD; Phone Number: +390282243568; Email: michele.bartoletti@hunimed.eu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

All adult patients (≥ 18 years) with primary Enterococcus faecalis monomicrobial bloodstream infection

Description

Inclusion Criteria:

• Adult (≥18 years)
• Monomicrobial EF-BSI
• Receipt of ≥ 5 days of at least one in vitro active drug (ampicillin, amoxicillin/clavulanate, ampicillin/sulbactam, piperacillin, vancomycin, teicoplanin, daptomycin and linezolid) with or without a synergistic drug (ceftriaxone, gentamycin, streptomycin), at common suggested dosages for EF-BSI in empirical or definitive therapy
• Written informed consent

Exclusion Criteria:

• Short term (within 3 days from BSI) mortality
• Other concomitant infection

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort
Adult with Enterococcus faecalis monomicrobial bloodstream infection; Adult patients with primary Enterococcus faecalis monomicrobial bloodstream infection

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Evaluation of Clinical Cure and Improvement Rates for EF-BSI	The clinical cure and improvement rates will be evaluated for patients undergoing mono therapy and combination therapy for EF-BSI.	Up to 6 weeks from patient enrollment, with bacterial strains isolated at baseline
Comparison of Clinical Outcomes Between Mono Therapy and Combination Therapy	A comparison of clinical outcomes between mono therapy and combination therapy in terms of clinical cure, improvement, and any adverse events.	Up to 6 weeks from patient enrollment, with bacterial strains isolated at baseline
Validation of In Vitro Synergy Tests	To validate the in vitro synergy or antagonism of antimicrobial combinations tested in the laboratory, correlating these results with clinical outcomes. In vitro synergy tests will be conducted to evaluate the interaction between antimicrobial combinations, and the results of these tests will be correlated with the clinical outcomes of the patients.	Up to 6 weeks from patient enrollment, with bacterial strains isolated at baseline

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Genotypic Analysis of E. faecalis	To explore how the genotypic (e.g., resistance and virulence genes) and phenotypic traits of E. faecalis strains influence infection severity, antimicrobial treatment response, and clinical outcomes. Define the prognostic and predictive value of these genotypic and phenotypic traits based on antimicrobial treatment and clinical outcomes. Genomic analyses will be conducted to identify antimicrobial resistance determinants, clonal relationships through multilocus sequence typing (MLST), and virulence factor genes for To explore how the genotypic traits (e.g., antimicrobial resistance and virulence genes) of E. faecalis strains influence infection severity, antimicrobial treatment response, and clinical outcomes. Weekly genomic analyses will be conducted to identify antimicrobial resistance determinants, clonal relationships through multilocus sequence typing (MLST), and virulence factor genes for each E. faecalis genome.	From enrollment to the end of the follow-up at three months
Phylogenetic Relationship and Clonal Diversity	A phylogenetic tree will be constructed based on the core genome of clinical E. faecalis isolates. This will allow the identification of clonal relationships and shared genetic factors among the strains. A deeper genetic analysis will also be performed to explore genetic factors that may influence infection outcomes.	From enrollment to the end of the follow-up at three months
Correlation Between Genotypic/Phenotypic Traits and Clinical Outcome	The prognostic and predictive value of the genotypic (e.g., resistance and virulence genes) and phenotypic traits of E. faecalis will be defined in relation to antimicrobial treatment and clinical outcomes. A comprehensive E. faecalis genomic database will be created to correlate these traits with infection severity, antimicrobial treatment, and clinical outcomes. The correlation will be explored through weekly genomic analyses and clinical data review.	From enrollment to the end of the follow-up at three months
Gut Microbiota Fingerprint Analysis in EF-BSI Patients	To compare the gut microbiota fingerprint of patients with E. faecalis bloodstream infections (EF-BSI) and correlate it with antimicrobial treatment and clinical outcomes. Faecal samples will be collected during antimicrobial therapy and 90 days after therapy withdrawal. These samples will be analyzed for 16S rRNA and the relative microbial composition. Clinical conditions, diet, infection relapse after therapy withdrawal, and their correlation with antimicrobial treatment and faecal abundance will also be evaluated.	From enrollment to the end of the follow-up at three months
Intestinal Microbiota Composition and Its Correlation with Treatment Outcomes	To evaluate the relationship between antimicrobial treatment, gut microbiota composition, and clinical outcomes (such as infection relapse, health status, or disease progression). Faecal samples will be collected from patients with EF-BSI treated with different antimicrobial therapies. These samples will be analyzed for 16S rRNA and relative microbial abundance. The clinical conditions, diet, infection relapse after therapy withdrawal, and their correlation with antimicrobial treatment and faecal abundance will also be assessed.	From enrollment to the end of the follow-up at three months

Collaborators and Investigators

• Sponsor: IRCCS Azienda Ospedaliero-Universitaria di Bologna
• Investigators: Principal Investigator: Maddalena Giannella, MD PhD, IRCCS Azienda Ospedaliero-Universitaria di Bologna

Study record dates

Study Major Dates

• Study Start (Actual): February 6, 2021
• Primary Completion (Estimated): September 26, 2026
• Study Completion (Estimated): September 26, 2026

Study Registration Dates

• First Submitted: December 30, 2024
• First Submitted That Met QC Criteria: February 11, 2025
• First Posted (Actual): February 19, 2025

Study Record Updates

• Last Update Posted (Estimated): December 3, 2025
• Last Update Submitted That Met QC Criteria: November 26, 2025
• Last Verified: October 1, 2025

More Information

Terms related to this study

• Keywords: Gut microbiota analysis; Enterococcus faecalis bloodstream infection; Human tissue analysis in vitro; Enterococcus faecalis genomic analysis
• Additional Relevant MeSH Terms: Pathologic Processes; Disease Attributes; Systemic Inflammatory Response Syndrome; Inflammation; Bacterial Infections; Bacterial Infections and Mycoses; Bacteremia; Sepsis; Infections; Communicable Diseases
• Other Study ID Numbers: Micro-EFfAECT; "Ricerca Finalizzata 2019" (Other Grant/Funding Number: Italian Ministry of Health)

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No