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Khong E, Oh JJ, Jimenez JM, Liu R, Dunham S, Monsibais A, Rhoads A, Ghatbale P, Garcia A, Cobián Güemes AG, Blanc AN, Chiu M, Kuo P, Proost M, Kline A, Aslam S, Schooley RT, Whiteson K, Fraley SI, Pride DT. A simple solid media assay for detection of synergy between bacteriophages and antibiotics. Microbiol Spectr 2024:e0322123. [PMID: 38526142 DOI: 10.1128/spectrum.03221-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Accepted: 02/24/2024] [Indexed: 03/26/2024] Open
Abstract
The emergence of antibiotic-resistant bacteria (ARB) has necessitated the development of alternative therapies to deal with this global threat. Bacteriophages (viruses that target bacteria) that kill ARB are one such alternative. Although phages have been used clinically for decades with inconsistent results, a number of recent advances in phage selection, propagation, and purification have enabled a reevaluation of their utility in contemporary clinical medicine. In most phage therapy cases, phages are administered in combination with antibiotics to ensure that patients receive the standard-of-care treatment. Some phages may work cooperatively with antibiotics to eradicate ARB, as often determined using non-standardized broth assays. We sought to develop a solid media-based assay to assess cooperativity between antibiotics and phages to offer a standardized platform for such testing. We modeled the interactions that occur between antibiotics and phages on solid medium to measure additive, antagonistic, and synergistic interactions. We then tested the method using different bacterial isolates and identified a number of isolates where synergistic interactions were identified. These interactions were not dependent on the specific organism, phage family, or antibiotic used. A priori susceptibility to the antibiotic or the specific phage were not requirements to observe synergistic interactions. Our data also confirm the potential for the restoration of vancomycin to treat vancomycin-resistant Enterococcus (VRE) when used in combination with phages. Solid media assays for the detection of cooperative interactions between antibiotics and phages can be an accessible technique adopted by clinical laboratories to evaluate antibiotic and phage choices in phage therapy.IMPORTANCEBacteriophages have become an important alternative treatment for individuals with life-threatening antibiotic-resistant bacteria (ARB) infections. Because antibiotics represent the standard-of-care for treatment of ARB, antibiotics and phages often are delivered together without evidence that they work cooperatively. Testing for cooperativity can be difficult due to the equipment necessary and a lack of standardized means for performing the testing in liquid medium. We developed an assay using solid medium to identify interactions between antibiotics and phages for gram-positive and gram-negative bacteria. We modeled the interactions between antibiotics and phages on solid medium, and then tested multiple replicates of vancomycin-resistant Enterococcus (VRE) and Stenotrophomonas in the assay. For each organism, we identified synergy between different phage and antibiotic combinations. The development of this solid media assay for assessing synergy between phages and antibiotics will better inform the use of these combinations in the treatment of ARB infections.
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Affiliation(s)
- Ethan Khong
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Joseph J Oh
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Julian M Jimenez
- Department of Bioengineering, University of California San Diego, La Jolla, California, USA
| | - Roland Liu
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Sage Dunham
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, California, USA
| | - Alisha Monsibais
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, California, USA
| | - Alison Rhoads
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Pooja Ghatbale
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Andrew Garcia
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | | | - Alisha N Blanc
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Megan Chiu
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Peiting Kuo
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Marissa Proost
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Ahnika Kline
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Saima Aslam
- Department of Medicine, University of California San Diego, La Jolla, California, USA
| | - Robert T Schooley
- Department of Medicine, University of California San Diego, La Jolla, California, USA
| | - Katrine Whiteson
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, California, USA
| | - Stephanie I Fraley
- Department of Bioengineering, University of California San Diego, La Jolla, California, USA
| | - David T Pride
- Department of Pathology, University of California San Diego, La Jolla, California, USA
- Department of Medicine, University of California San Diego, La Jolla, California, USA
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Cobián Güemes AG, Ghatbale P, Blanc AN, Morgan CJ, Garcia A, Leonard J, Huang L, Kovalick G, Proost M, Chiu M, Kuo P, Oh J, Karthikeyan S, Knight R, Pogliano J, Schooley RT, Pride DT. Jumbo phages are active against extensively drug-resistant eyedrop-associated Pseudomonas aeruginosa infections. Antimicrob Agents Chemother 2023; 67:e0065423. [PMID: 37931230 PMCID: PMC10720484 DOI: 10.1128/aac.00654-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 09/08/2023] [Indexed: 11/08/2023] Open
Abstract
Antibiotic-resistant bacteria present an emerging challenge to human health. Their prevalence has been increasing across the globe due in part to the liberal use of antibiotics that has pressured them to develop resistance. Those bacteria that acquire mobile genetic elements are especially concerning because those plasmids may be shared readily with other microbes that can then also become antibiotic resistant. Serious infections have recently been related to the contamination of preservative-free eyedrops with extensively drug-resistant (XDR) isolates of Pseudomonas aeruginosa, already resulting in three deaths. These drug-resistant isolates cannot be managed with most conventional antibiotics. We sought to identify alternatives to conventional antibiotics for the lysis of these XDR isolates and identified multiple bacteriophages (viruses that attack bacteria) that killed them efficiently. We found both jumbo phages (>200 kb in genome size) and non-jumbo phages that were active against these isolates, the former killing more efficiently. Jumbo phages effectively killed the three separate XDR P. aeruginosa isolates both on solid and liquid medium. Given the ongoing nature of the XDR P. aeruginosa eyedrop outbreak, the identification of phages active against them provides physicians with several novel potential alternatives for treatment.
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Affiliation(s)
| | - Pooja Ghatbale
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Alisha N. Blanc
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Chase J. Morgan
- Department of Biology, University of California San Diego, La Jolla, California, USA
| | - Andrew Garcia
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Jesse Leonard
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Lina Huang
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Grace Kovalick
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Marissa Proost
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Megan Chiu
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Peiting Kuo
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Joseph Oh
- Department of Pathology, University of California San Diego, La Jolla, California, USA
| | - Smruthi Karthikeyan
- Department of Environmental Science and Engineering, Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California, USA
- Department of Pediatrics, University of California San Diego, La Jolla, California, USA
| | - Rob Knight
- Department of Pediatrics, University of California San Diego, La Jolla, California, USA
- Center for Microbiome Innovation, University of California San Diego, La Jolla, California, USA
- Department of Bioengineering, University of California San Diego, La Jolla, California, USA
- Department of Computer Sciences & Engineering, University of California San Diego, La Jolla, California, USA
| | - Joe Pogliano
- Department of Biology, University of California San Diego, La Jolla, California, USA
- Howard Hughes Medical Institute, University of California San Diego, La Jolla, California, USA
| | - Robert T. Schooley
- Department of Medicine, University of California San Diego, La Jolla, California, USA
| | - David T. Pride
- Department of Pathology, University of California San Diego, La Jolla, California, USA
- Howard Hughes Medical Institute, University of California San Diego, La Jolla, California, USA
- Department of Medicine, University of California San Diego, La Jolla, California, USA
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Abstract
Objectives: Breastfeeding and human milk (HM) improve maternal and infant morbidities and mortality. Therefore, monitoring the safety of breastfeeding and access to HM is of critical importance. In this study, we assessed tools to monitor the presence of monkeypox virus (MPXV) in HM and whether standard Holder pasteurization inactivates MPXV. Materials and Methods: Heat-inactivated MPXV was added to HM or viral transport media (VTM) and analyzed using both research and clinical MPXV quantitative polymerase chain reaction (qPCR) tests. Infectious MPXV was added to HM and was exposed to 1 cycle of freeze-thaw, incubation for 1 hour at room temperature, or conditions of Holder pasteurization (62.5°C for 30 minutes) followed by infectious unit quantification by plaque assay. Results: Research and clinical nucleic acid tests detect MPXV that was added to HM but with reduced sensitivity compared with equivalent samples in VTM at low virus inoculum. MPXV added to HM to achieve a starting concentration of 225,000 plaque forming units (pfu)/mL remains infectious after freeze-thaw or 1 hour storage at room temperature. However, Holder pasteurization reduced infectious virus below the limit of detection, >2,000-fold reduction in viral titer. Conclusion: MPXV can be detected when added to HM using a clinical laboratory-developed qPCR test without modification, but the detection limit is reduced compared with equivalent samples in VTM. MPXV remains viable in HM should the virus ever gain access to HM, but Holder pasteurization reduces infectious MPXV to below detection limits and can be used to reduce the risk of MPXV transmission to infants who receive pasteurized (donor) HM.
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Affiliation(s)
- Alex E. Clark
- Department of Medicine, University of California, San Diego, La Jolla, California, USA
| | - Annalee Furst
- Department of Pediatrics, and University of California, San Diego, La Jolla, California, USA
| | - Kristija Sejane
- Department of Pediatrics, and University of California, San Diego, La Jolla, California, USA
| | - Lisa Stellwagen
- UC Health Milk Bank, University of California, San Diego, La Jolla, California, USA
- Human Milk Institute (HMI), University of California, San Diego, La Jolla, California, USA
| | - Marissa Proost
- Department of Pathology, University of California, San Diego, La Jolla, California, USA
| | - David Pride
- Department of Pathology, University of California, San Diego, La Jolla, California, USA
| | - Davey M. Smith
- Department of Medicine, University of California, San Diego, La Jolla, California, USA
- VA San Diego Healthcare System, San Diego, California, USA
| | - Aaron F. Carlin
- Department of Medicine, University of California, San Diego, La Jolla, California, USA
- Department of Pathology, University of California, San Diego, La Jolla, California, USA
| | - Lars Bode
- Department of Pediatrics, and University of California, San Diego, La Jolla, California, USA
- Human Milk Institute (HMI), University of California, San Diego, La Jolla, California, USA
- Larsson-Rosenquist Foundation Mother-Milk-Infant Center of research Excellence (MOMI CORE), University of California, San Diego, La Jolla, California, USA
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Khong E, Oh J, Jimenez JM, Liu R, Dunham S, Monsibais A, Rhoads A, Ghatbale P, Garcia A, Cobián Güemes AG, Blanc AN, Chiu M, Kuo P, Proost M, Kline A, Aslam S, Schooley RT, Whiteson K, Fraley SI, Pride DT. A simple solid media assay for detection of synergy between bacteriophages and antibiotics. bioRxiv 2023:2023.08.23.554535. [PMID: 37662290 PMCID: PMC10473724 DOI: 10.1101/2023.08.23.554535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
The emergence of antibiotic resistant bacteria (ARB) has necessitated the development of alternative therapies to deal with this global threat. Bacteriophages (viruses that target bacteria) that kill ARB are one such alternative. While phages have been used clinically for decades with inconsistent results, a number of recent advances in phage selection, propagation and purification have enabled a reevaluation of their utility in contemporary clinical medicine. In most phage therapy cases, phages are administered in combination with antibiotics to ensure that patients receive the standard-of-care treatment. Some phages may work cooperatively with antibiotics to eradicate ARB, as often determined using non-standardized broth assays. We sought to develop a solid media-based assay to assess cooperativity between antibiotics and phages to offer a standardized platform for such testing. We modeled the interactions that occur between antibiotics and phages on solid medium to measure additive, antagonistic, and synergistic interactions. We then tested the method using different bacterial isolates, and identified a number of isolates where synergistic interactions were identified. These interactions were not dependent on the specific organism, phage family, or antibiotic used. A priori susceptibility to the antibiotic or the specific phage were not requirements to observe synergistic interactions. Our data also confirm the potential for the restoration of vancomycin to treat Vancomycin Resistant Enterococcus (VRE) when used in combination with phages. Solid media assays for the detection of cooperative interactions between antibiotics and phages can be an accessible technique adopted by clinical laboratories to evaluate antibiotic and phage choices in phage therapy.
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