Characterization of the Synergistic Antibacterial Effect of Verapamil on Bacterial Isolates From Cancer Patients

April 2, 2026 updated by: Ahmed Ibrahim Khalaf Mohamed, Assiut University

Characterization of the Synergistic Antibacterial Effect of Verapamil on Bacterial Isolates From Patients in South Egypt Cancer Institute

Multidrug-resistant (MDR) bacteria represent a significant global health challenge, particularly among immunocompromised populations such as cancer patients undergoing chemotherapy. These patients are highly susceptible to severe infections due to weakened immune defenses, often necessitating the use of broad-spectrum or combination antibiotic therapy. Combination regimens may enhance treatment efficacy through synergistic effects, helping to overcome bacterial resistance mechanisms and improve clinical outcomes.

In recent years, there has been growing interest in the use of non-antibiotic drugs as adjunctive agents to enhance antimicrobial activity. These agents, often referred to as antibiotic adjuvants or resistance modifiers, may improve antibiotic effectiveness through mechanisms such as inhibition of bacterial efflux pumps, disruption of biofilm formation, or interference with resistance pathways.

Verapamil, a widely used calcium channel blocker, has demonstrated potential antimicrobial and resistance-modifying properties. Experimental evidence suggests that verapamil can inhibit bacterial efflux pumps, thereby increasing intracellular concentrations of antibiotics and enhancing their activity against resistant organisms.

This study aims to evaluate the in vitro synergistic antibacterial activity of verapamil in combination with selected antibiotics against MDR, extensively drug-resistant (XDR), and pandrug-resistant (PDR) bacterial isolates obtained from cancer patients. Standard microbiological methods will be used to determine antimicrobial susceptibility and minimum inhibitory concentrations, while combination effects will be assessed using established synergy testing approaches.

The findings of this study may contribute to identifying novel, cost-effective strategies to combat antimicrobial resistance through drug repurposing and optimization of existing antibiotic therapies.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

This study evaluates the potential synergistic antibacterial effect of verapamil in combination with selected antibiotics against multidrug-resistant (MDR), extensively drug-resistant (XDR), and pandrug-resistant (PDR) bacterial isolates obtained from cancer patients.

  1. Study Samples Clinical specimens will be collected as part of routine diagnostic care from cancer patients.

    Specimen types may include:

    Blood Urine Respiratory samples Wound swabs Other relevant clinical specimens Only non-duplicate bacterial isolates will be included. Only isolates classified as MDR, XDR, or PDR will be selected for further analysis.

  2. Isolation of Bacterial Isolates Specimens will be cultured using standard microbiological techniques.

    Culture media will include:

    Blood agar MacConkey agar Plates will be incubated under appropriate conditions (temperature and atmosphere) according to standard laboratory protocols.

  3. Identification of Bacteria

    Bacterial isolates will be identified using:

    Colony morphology Gram staining Biochemical tests Where available, automated identification systems will be used. Identification procedures will follow standard microbiological guidelines.

  4. Antimicrobial Susceptibility Testing (AST)

    AST will be performed according to:

    Clinical and Laboratory Standards Institute (CLSI), 2025 guidelines

    Methods include:

    Kirby-Bauer disk diffusion method Automated susceptibility testing systems (if available) Results will be interpreted using CLSI breakpoints. Quality control will be ensured using standard reference strains.

  5. Preparation of Verapamil

    Verapamil stock solution will be prepared:

    Under aseptic conditions Using sterile distilled water or appropriate solvent Serial dilutions will be prepared to achieve required working concentrations.

  6. Determination of Minimum Inhibitory Concentrations (MICs)

    MICs for:

    Selected antibiotics Verapamil

    Will be determined using:

    Broth microdilution method

    Procedures include:

    Preparation of serial twofold dilutions Standardization of bacterial inoculum (e.g., 0.5 McFarland) Incubation under appropriate conditions MIC values will be recorded as the lowest concentration inhibiting visible growth.

  7. Assessment of Synergistic Activity

    Synergy testing will be performed using:

    Checkerboard assay

    Interaction between verapamil and antibiotics will be evaluated by calculating:

    Fractional Inhibitory Concentration Index (FICI)

    Interpretation of FICI:

    ≤ 0.5 → Synergistic > 0.5 - 1 → Additive > 1 - 4 → Indifferent > 4 → Antagonistic

  8. Additional/Confirmatory Testing

    Where applicable, additional methods may be used:

    Disk diffusion-based combination testing These methods will support and validate synergy findings.

  9. Exploratory Analysis

    If significant synergy is observed:

    Further analysis may be conducted to investigate resistance mechanisms

    This may include:

    Evaluation of changes in resistance patterns Analysis of resistance-related gene expression (if feasible)

  10. Quality Control and Laboratory Standards

All procedures will follow:

Standard microbiological protocols Institutional biosafety regulations

Quality assurance measures will be applied to ensure:

Accuracy Reproducibility Reliability of results

Study Type

Observational

Enrollment (Estimated)

100

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

N/A

Sampling Method

Non-Probability Sample

Study Population

The study will be carried out on clinical specimens of cancer patients already withdrawn for routine testing during the study period

Description

Inclusion Criteria:

  1. Bacterial isolates from clinical samples submitted for the SECI laboratory for culture and sensitivity testing that are:
  2. MDR: resistant to one or more agent within three or more of antimicrobial classes
  3. XDR: resistant to one or more agent within all but two antimicrobial classes
  4. PDR: resistant to all agents within all antimicrobial classes.

Exclusion Criteria:

  1. Bacterial isolates from non-cancer patients.
  2. Contaminant or non-pathogenic isolates.
  3. Duplicate isolates from the same patient with identical antibiogram.
  4. Bacterial isolates that are neither MDR, XDR OR PDR.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Characterization of the synergistic antibacterial effect of Verapamil on bacterial isolates from patients in South Egypt Cancer Institute
Time Frame: Baseline
Determination of the antibiotic sensitivity patterns of the bacterial isolates as measured by MIC values
Baseline

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Assiut University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

May 1, 2026

Primary Completion (Estimated)

May 1, 2027

Study Completion (Estimated)

June 1, 2027

Study Registration Dates

First Submitted

March 26, 2026

First Submitted That Met QC Criteria

March 26, 2026

First Posted (Actual)

April 1, 2026

Study Record Updates

Last Update Posted (Actual)

April 8, 2026

Last Update Submitted That Met QC Criteria

April 2, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • Verapamil use in MDR bacteria

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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