Bacteriophages. Host range: What to consider as a standard procedure

During July 3rd - 7th our Research & Development team participated in the Viruses of Microbes 2023, which took place in Tbilisi, Georgia. Our Chief Research Officer, dr Ewelina Wójcik, presented the results of one of the recently conducted studies on the Host range – what to consider as standard procedure?

The implementation of bacteriophage preparations requires confirmation of their safety and effectiveness. While for safety assessment, there are clear regulatory guidelines, in line with the standards developed for all biological products, efficacy assessment of bacteriophage product is missing well defined and regulatory acceptable standards.

One important problem is the gap between methods and standards broadly accepted in phage scientific community and methodology accepted by regulatory bodies. While extrapolation of spectrum of antibiotic activity observed in vitro to in vivo efficacy is broadly accepted in regulatory process extrapolation of in vitro host range of bacteriophages to their in vivo efficacy seems to be not so obvious.

One of the reasons is the lack of gold standard for determination of bacteriophage lytic strength. Experimental techniques such as spot test, spot test in serial dilutions of phage suspension and liquid assay are commonly used for this purpose, although novel methods based on viral tagging, microfluidic PCR, phageFISH and single-cell genomics are recently gaining interest.

However, discrepancies between the results obtained for the same phages and bacteria, but with the use of each of the presented methods and the dependence of the outcome on physiological state of bacterial cells exposed to phage and environmental conditions suggest need for development of validated standard for testing phage activity.

In this work, we present a comparison of host range determination of bacteriophage preparation BAFASAL® carried out on the library of Salmonella field isolates with the use of various bacteriophage lytic activity assays.

Proteon Pharmaceuticals is a leader in bacteriophage (phage) technology for livestock farming and aquaculture. Our mission is to eliminate the need for unnecessary antibiotic use, reducing the risk of antimicrobial resistance (AMR), as well as to increase the sustainability of protein production through the reduction of waste and improvement of on-farm efficiency. Our products function by modulating the microbiome enabling prophylactic health. We have created a precision phage product development platform using -omics technologies, molecular biology, bioinformatics, and artificial intelligence (AI) to create effective, reliable, and safe antibacterial solutions for animal and human health.