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ORIGINAL RESEARCH article

Front. Microbiol.
Sec. Phage Biology
Volume 15 - 2024 | doi: 10.3389/fmicb.2024.1386245
This article is part of the Research Topic Bacteriophages and Phage-Engineered Products for Antibacterial and Anticancer Applications View all articles

Comparison of Phage Susceptibility Testing by Two Liquid High-Throughput Methods

Provisionally accepted
Krupa Parmar Krupa Parmar 1Joseph R. Fackler Joseph R. Fackler 2Zuriel Rivas Zuriel Rivas 2Jay Mandrekar Jay Mandrekar 1Kerryl E. Greenwood-Quaintance Kerryl E. Greenwood-Quaintance 1Robin Patel Robin Patel 1*
  • 1 Mayo Clinic, Rochester, Minnesota, United States
  • 2 Adaptive Phage Therapeutics, Gaithersburg, Maryland, United States

The final, formatted version of the article will be published soon.

    Phage therapy is a promising antibacterial strategy especially given that drug resistant bacterial infections are escalating globally. Because phages are not active against all strains of a given species, phages being considered for therapeutic use would ideally be tested against bacterial isolates from individual patient prior to administration. Standardized, clinically validated phage susceptibility testing (PST) methods are needed for assessing in vitro phage activity. This study compared two high-throughput liquid-based PST assays. The first, using the Biolog Omnilog™, assessed changes in microbial respiration leading to color changes based on a tetrazolium dye. The second, Agilent BioTek Cytation 7, assessed changes in optical density. Both used 96 well microtiter plate formats. Fifty-five diverse phages with activity against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii and Enterococcus faecalis were studied against their respective susceptible bacterial hosts and non-susceptible controls, with susceptibility defined based on plaque assay. PST was performed by both assays in replicates, with results compared in terms of hold times (time through which bacterial growth is inhibited by phage compared to controls). Coefficients of variance and interclass correlation coefficients were used to assess inter-and intra-assay reproducibility. Based on a ≤50% coefficient of variance cutpoint, 87% of Biolog and 84% of Agilent assays were considered valid for susceptible bacteria, with 100% considered valid for non-susceptible bacteria by both systems.Using an 8-hour hold time cutpoint, 100% of results matched between the two assays. The interclass correlation coefficient showed 26% excellent agreement, 35% good agreement and 17% moderate agreement between the two assays for susceptible isolates and 100% excellent agreement for non-susceptible isolates. Overall, the assays compared provided good/fair statistical reproducibility for assessment of phage susceptibility.

    Keywords: phage therapy, Phage Susceptibility Testing, assay reproducibility, Staphylococcus aureus, Pseudomonas aeruginosa

    Received: 14 Feb 2024; Accepted: 09 Jul 2024.

    Copyright: © 2024 Parmar, Fackler, Rivas, Mandrekar, Greenwood-Quaintance and Patel. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Robin Patel, Mayo Clinic, Rochester, 55902, Minnesota, United States

    Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.