Biology subjects

Bucher, M. J.

Publications and source records attributed to Bucher, M. J..

3 recordsLinked to original sources

bioRxiv2025

Mechanistic insights and clinical implications of cross-reactive anti-prophage antibodies and bacterial heteroresistance on phage therapeutic failure

Phage therapy is an exciting strategy against antimicrobial-resistant bacterial infections, but critical knowledge gaps regarding its clinical application persist. Studying a patient with a life-threatening, chronic bacterial infection who failed phage therapy, we uncovered important biological concepts with direct translational impact. Using longitudinal clinical samples, we found that patients can harbour pre-existing antibodies against active prophages induced from the genome of the causative pathogen. Notably, these antibodies can contribute to clinical failure by cross-reacting with and effectively neutralising therapeutic phage. We also uncovered bacterial heteroresistance, characterised by bacterial subpopulations from the initial infection with reduced phage susceptibility, as a further contributor to treatment failure. These findings highlight the intricate interplay between host immunology, bacterial genetic diversity and phage biology, bearing broad significance for clinical phage therapy. Future phage therapy patients, especially those with chronic infections, should be screened for antiphage immunity and bacterial heteroresistance prior to phage treatment.

microbiology↗

bioRxiv2025

High-content assessment of Pseudomonas aeruginosa bacteriophage efficacy reveals host genetic factors involved in phage specificity

Pseudomonas aeruginosa infects immunocompromised and hospitalized individuals, resulting in over 500,000 annual deaths. With emerging multidrug resistance and stagnating antibiotic development, alternative antimicrobials are desperately needed. Bacteriophages (phages) offer a promising, effective, and safe alternative. We developed and optimized a high-content liquid assay screen and a stringent assessment of efficacy to isolate and characterize seven novel P. aeruginosa phages. Phages were screened individually and in cocktail, inhibiting the growth of over 90% (50/55) of multidrug-resistant clinical strains and [~]75% (102/137) of animal, environmental, and human isolates. When tested in a mouse bacteremia model, the phage cocktail successfully eradicated P. aeruginosa. A proteome-wide bi-directional BLAST identified eight proteins that influenced phage infection. The functional analysis of the corresponding genes reveals their putative roles involving genome modification and transcriptional regulation, metabolic processes, and structural components essential for phage docking. Collectively, we have developed a rigorous high-content approach to identify effective phages, which, coupled with functional genomics, revealed genes that affect phage-bacteria interaction. Author SummaryIn this study, we explored the potential of bacteriophages (phages) isolated from municipal and hospital wastewater sources for combating multidrug-resistant Pseudomonas aeruginosa, an opportunistic pathogen known for posing significant clinical challenges. A rigorous stepwise screen aimed at enhancing specificity against a broad set of 55 clinical P. aeruginosa strains allowed us to isolate diverse class phages that can target over 90% of the clinical isolates. Our phage efficacy assessments employed a colorimetric MTT assay to measure the metabolic activity of P. aeruginosa strains in response to phage exposure. Notably, the phages demonstrated broad coverage against the P. aeruginosa library, with individual phages showing varying degrees of efficacy and a cocktail exhibiting superior inhibitory properties. Further validation using a mouse bacteremia model confirmed the exceptional efficacy of the cocktail, supported by a complete attenuation of clinical signs of infection and a significant reduction of bacterial loads across all organs, supporting their utility as potential phage therapy. Finally, a comprehensive comparative genomic analysis of target bacteria combined with phage efficacy revealed novel genes that are potentially involved in phage infection. These findings provide a foundation for understanding phage-host interactions and pave the way for the development of targeted phage therapies against antibiotic-resistant bacterial infections.

microbiology↗

bioRxiv2024

Sub-therapeutic Concentrations of Antibiotics Induce Prophage-driven Superinfection Exclusion and Fitness Cost in Pseudomonas aeruginosa

Bacteria and other microbes can naturally produce antibiotics within their native soil environment, but often at sub-inhibitory concentrations; consequently, the exact role of antibiotics within bacterial native communities remains unknown. We have shown that subtherapeutic quantities of naturally occurring antibiotics can induce the Pseudomonas prophage Pf4, and superinfection of Pseudomonas aeruginosa cells by this phage leads to their reduced virulence, as demonstrated by impaired twitching motility, compromised macrophage evasion, and increased killing by macrophages in vitro. Thus, the production of subtherapeutic concentrations of antibiotics by environmental microbes may provide the producers an evolutionary advantage associated with reduced fitness induced by prophages in the competing bacteria. Collectively, these results reveal the role of naturally occurring antibiotics in altering fitness by phage-mediated superinfection exclusion and provide potential clinical implications in the application of phage therapy. Significance StatementThis study provides insights into the mechanisms by which sub-inhibitory concentrations of environmentally-produced antibiotics induce Pseudomonas aeruginosa prophages, revealing a potential evolutionary strategy for competitive advantage among bacteria. By activating prophages, antibiotics can induce fitness defects in neighboring bacteria, impacting their motility, phagocytosis, and survival within macrophages. Such previously unrecognized role for environmental antibiotics in bacterial ecosystems may offer insights into enhancing phage therapy by exploiting phage-antibiotic synergies. Understanding phage-host interactions can enhance therapeutic strategies to mitigate bacterial infections and antimicrobial resistance.

microbiology↗