Karen Fong

The Pseudomonas syringae complex (Psc) is a group of globally distributed phytopathogens responsible for substantial agricultural losses. Although bacteriophage‐based biocontrol has shown promise against Psc, no studies have examined phages targeting blueberry‐tropic Psc lineages. Here, we isolated phages infecting Psc strains from diseased highbush blueberry ( Vaccinium corymbosum ), and evaluated their suitability for biocontrol using a multi‐stage screening pipeline incorporating host‐range analysis, comparative genomics, environmental stability testing, in vitro antibacterial efficacy assays and ex planta validation. Twelve of the isolated phages exhibited favourable host‐range characteristics. Genomic analyses revealed substantial phylogenetic diversity among these candidates but simultaneously identified multiple clonal groups, reducing the collection to eight non‐redundant phages spanning five distinct genera. Candidate phages generally retained infectivity under environmentally relevant conditions and exhibited heterogeneous but largely favourable stability profiles. Planktonic killing assays uncovered considerable variation in antibacterial efficacy, but phage performance appeared to be driven by infection compatibility and host‐specific factors rather than properties intrinsic to individual phages. Notably, the jumbo phage CB10 emerged as a particularly promising candidate due to its strong antibacterial activity (median GRC = 0.943), favourable environmental stability and unique genomic features. Cocktails containing the most effective candidates produced substantial and longitudinally sustained reductions in epiphytic colonization of detached blueberry leaves by Psc, exceeding five orders of magnitude at peak efficacy and demonstrating robust activity in a biologically relevant ex planta system. Importantly, in vitro antibacterial efficacy was predictive of performance in our ex planta model ( r = 0.67; p = 0.0003), supporting the utility of tiered screening approaches for candidate selection. Taken together, these findings establish a framework for the systematic identification and evaluation of phages targeting Psc, and support the development of phage‐based interventions for managing plant diseases.

Non-typhoidal Salmonella is estimated to cause up to 1 billion cases of global foodborne illness per year. Salmonella Typhimurium is a serovar of gravest worldwide concern as it is capable of infecting animal and human hosts and can also acquire antimicrobial resistance (AMR) determinants at a rapid rate. Recent advances in phage research have positioned them as especially useful for inactivation of Salmonella where antibiotics have proven no longer effective. Even more recently, phage-antibiotic synergy (PAS) has been proposed as a solution for AMR Salmonella , where synergistic combinations of phages and antibiotics are more effective than application of phage or antibiotic alone. Utilizing an in-house phage isolate, SeKF_13, we sought to determine the existence of PAS against a strain of Salmonella enterica serovar Typhimurium 14028 2a that is clinically resistant to bacteriostatic antibiotics chloramphenicol and tetracycline. Checkerboard assays revealed the presence of synergy when sub-lethal (sub-MIC) levels of either tetracycline or chloramphenicol were combined with phage SeKF_13 ( P < 0.05; two-way ANOVA). Compared to tetracycline or chloramphenicol alone, the addition of phage also decreased the MICs of both antibiotics twofold. We also monitored the development of resistance and found that PAS significantly suppressed emergence of resistance compared to the antibacterial agents alone ( P < 0.05; Tukey’s HSD). Whole-genome sequencing revealed that SeKF_13 is devoid of genes encoding integrase, antimicrobial resistance, and virulence, ensuring safety in future applications. Together, our results suggest that combined treatment of phage and antibiotic can improve antimicrobial efficacy against antibiotic-resistant Salmonella enterica . IMPORTANCE: Salmonella enterica is a foodborne pathogen that causes one of the highest rates of foodborne illness worldwide. They are also capable of becoming resistant to antimicrobials very rapidly (i.e., antimicrobial resistance; AMR) due to their ability to acquire AMR determinants, undermining the effectiveness of current treatments. Bacteriophages (phages), viral predators of bacteria, have been proven to be effective in some cases, but recently, phage-antibiotic synergy has been proposed as a more effective solution than phages or antibiotics alone. We found this was, indeed, the case; using phage SeKF_13 and tetracycline or chloramphenicol (to which the Salmonella strain was resistant), we found that combination treatment was significantly more effective than either treatment alone. These results demonstrate that combined treatment of phage and antibiotic can bolster treatment efficacy against AMR Salmonella.

Bacteriophages, viral predators of bacteria, have been well-studied for their capacity to control diverse pathogens and as promising alternatives to antibiotics across healthcare, food and agriculture sectors (Guo et al., 2020;Mahony et al., 2020;Pye et al., 2024). Phage selection for biocontrol applications typically includes isolation and characterization of novel phages that perform well during in vitro studies against target pathogen. Phage characterization involves bioinformatic analysis of the phage genome to confirm the absence of genes that could pose a risk during biocontrol applications (i.e., encoding for antimicrobial resistance, virulence, lysogeny). There is inherent value in such approaches as the discovery of novel phages further enrich and expand the pre-existing repertoire of known and characterized phages, particularly those possessing ultranarrow host ranges whose biocontrol potential can be quite limited. Recently, there has been a surge of innovative approaches that capitalize on the existing diversity and ease of phage isolation and characterization. This Research Topic aims to showcase recent discoveries, developments and innovations in the utility of phage applications in diverse settings. Our Topic comprises nine articles, including six original research articles and three review articles. Topics span from perspectives on phage-based biocontrol in One Health, agriculture and healthcare to understanding phage components and systems to achieve optimal outcomes. The contributed papers present phage innovation in diverse applications across three themes: (1) discovery and characterization of novel phages; (2) phages and their components as alternative therapeutics; and (3) engineering and precision targeting using CRISPR-Phage systems.There were three manuscripts that focused on the isolation and characterization of phages for biocontrol applications. Hoang et al. provided comparative genomics and host interaction insights into two novel lytic phages, Macy and Sally, against carbapenem-resistant Raoultella planticola, an emerging nosocomial pathogen. Features attractive for biocontrol were described, including high burst sizes, broad host ranges and the ability to degrade biofilms. Additionally, Zhang et al. described the characterization of phages PSV6 and PSV3 against Pseudomonas syringae pv. syringae (Pss). They noted effective in vivo efficacy against Pss, potentiating their utility in biocontrol applications. Interestingly, Cheng et al. isolated a novel phage capable of cross-genus infection, vB_SmaS_QH3, that was able to lyse both Stenotrophomonas maltophilia and Pseudomonas aeruginosa. This phage exhibited significant antimicrobial activity against both hosts, along with good stability and infection kinetics.A large-scale bibliometric study on research into Acinetobacter baumanii phages revealed research hotspots and trends in this area, highlighting the trend towards targeting antimicrobial resistance (AMR) strains (Jiang et al.). Two reviews highlighted the growing need for alternative therapeutics to AMR. Wang et al. provided perspectives on the utility of phage therapy for intestinal bacterial infections. They elucidated clear benefits of using phages in such applications, including the promotion of microbiome stability, potential synergistic effects and the ability to treat AMR or multidrug-resistant intestinal infections. Plat et al. further discussed application of phage in clinical and veterinary medicine and food in their narrative review. Additionally, they discussed the utility of phage-derived components such as endolysins and depolymerases for the replacement of antibiotics. To this end, Schwarzkopf et al. further elucidated the role of holins, phage-encoded hole-forming membrane proteins, in endolysin release. They provide evidence for the existence of a ring-shaped holin complex in phage T4 that enables endolysin release.A novel predictive approach was developed by Ortiz-Cartagena et al. that utilizes the LAMP-CRISPR-Cas13a rapid-technique for detecting bacterial resistance mechanisms and predicting potential incompatibilities of therapeutic phages in the treatment of Klebsiella pneumoniae. Separately, Lee et al. cloned CRISPR-Cas12a genes into temperate phage λ and found it could selectively eliminate E. coli carrying target genomic sequences. Together, these two approaches advance the science on precision microbiome engineering tools to potentially overcome the inherent disadvantage of infection of non-target strains.In conclusion, phage research, still in its infancy, is ever-evolving as there are still many avenues worth exploring. Fundamental work involving discovery and characterization of novel phages provides a solid foundation for application-driven work on studying phage-host interactions. As phages are being increasingly recognized globally for their therapeutic applications, further research is needed to enhance their potential across One Health, agriculture, food production and medicine.

Salmonella enterica is a Gram-negative inhabitant of the gastrointestinal tract of warm-blooded animals and commonly implicated in foodborne illness. Here, we describe the isolation of Salmonella enterica phage SeKF_80. The 89,965 bp genome contains 174 predicted coding sequences with 44 predicted functions. Phage SeKF_80 shares species-level similarity with Salmonella phages 7–11.

Predicting the post-storage quality of cherry fruits is crucial for determining their suitability for long-distance shipping or domestic distribution. This study aimed to forecast key quality attributes of Staccato sweet cherries after storage, simulating shipping conditions, by analyzing spring soil, leaf, fruitlet, and at-harvest data from thirty orchards in the Okanagan Valley, British Columbia, Canada, over two years. A support vector machine (SVM) was used to predict post-storage variables, with pre-harvest and at-harvest data selected by a genetic algorithm. The SVM accurately predicted soluble solids (R² = 0.88), firmness (R² = 0.83), and acidity (R² = 0.79) after four weeks of storage, as well as visual disorders like slip skin and stem browning. Spring soil properties (Ca, Mg), leaf (N, Ca, Mg, Fe, Zn, B), and fruitlet data (N, Ca, Mg, B) were key predictors. Leaf Ca was vital for firmness and total soluble solids (TSS) prediction, while N in leaves and fruitlets influenced firmness, acidity, and disorders. Leaf Zn helped predict weight and acidity/TSS ratio, and Mg impacted fruit color. Pre-harvest leaf nutrition measured 3–4 weeks before harvest, proved most effective in predicting post-storage quality.

Novel bacteriophages (phages) possessing a broad host range are consistently and routinely reported, yet there is presently no consensus on the definition of “broad host range.” As phages are increasingly being used in the development of methods for the detection and biocontrol of human pathogens, it is important to address the limitations associated with the host range. For instance, unanticipated host range breadth may result in the detection of nonpathogenic targets, thereby increasing the false-positive rate. Moreover, a broad host range is generally favored in biocontrol applications despite the risk of undesirable ancillary effects against nontarget species. Here, we discuss the research progress, applications, and implications of broad host range phages with a focus on tailed broad host range phages infecting human pathogens of concern in the Agri-Food sector.