ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Phage Biology
This article is part of the Research TopicInnovations in Phage Biocontrol: Advancing Technology and ApplicationsView all 8 articles
Two Virulent Bacteriophages Targeting Carbapenem-Resistant Raoultella planticola
Provisionally accepted
Cuong Hoang1Jonathan Fan1Lauren Bhasin1Anthony Del Mundo1Vanessa Law1Dominic Nguyen1Suraj Ganiger1Ashley Mansour1Christi L McElheny2
Yohei Doi2,3
Olakunle Olawole1*- 1Department of Microbiology & Plant Pathology, University of California, Riverside, CA, USA, Riverside, United States
- 2Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA, Pittsburgh, United States
- 3Departments of Microbiology, and Infectious Diseases, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
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Carbapenem-resistant Raoultella planticola (CRRP) is an emerging nosocomial pathogen with limited therapeutic options. Here, we describe the comparative characterization of two novel virulent bacteriophages, Macy and Sally, both isolated from the same soil microenvironment. Macy exhibits exceptional lytic potency, with a burst size of 8,375 PFU per infected cell, narrow host specificity, and pronounced biofilm-disrupting activity likely mediated by a putative depolymerase. In contrast, Sally displays a broader host range, infecting both R. planticola and R. ornithinolytica (including a clinical CRRP isolate), while maintaining moderate lytic activity, notable acid tolerance, and substantial biofilm reduction. SNP analysis revealed that resistant isolates carried mutations in genes linked to surface polysaccharide biosynthesis and LysR-family transcriptional regulation, conferring resistance at a measurable cost to bacterial growth fitness. Genomic and phylogenomic analyses further revealed distinct evolutionary trajectories: Macy is a large (147.8 kb) myovirus with a mosaic genome related to Raoultella phages, whereas Sally is a compact (48.5 kb) siphovirus more closely aligned with Klebsiella and Enterobacter phages. Pangenomic comparisons highlighted Macy's strain-specific gene expansions versus Sally's cross-genus homology, emphasizing divergent adaptation strategies. Together, these findings illustrate the complementary therapeutic potential of Macy and Sally and establish a genomic and phenotypic foundation for developing effective phage cocktails against multidrug-resistant Raoultella infections.
Keywords: Carbapenem-resistant Raoultella planticola, Bacteriophage therapy, Host range, Clinical strains, Multidrug-resistant pathogens
Received: 22 Oct 2025; Accepted: 18 Nov 2025.
Copyright: © 2025 Hoang, Fan, Bhasin, Del Mundo, Law, Nguyen, Ganiger, Mansour, McElheny, Doi and Olawole. 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: Olakunle Olawole, olakunlo@ucr.edu
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