Phage Isolation and Enrichment

Phage therapy overcomes the limitations of traditional broad-spectrum antibiotic applications and has attracted a lot of attention from researchers in the medical health field. The development pipeline for traditional broad-spectrum antibiotics faces a number of well-known obstacles, including a resistance crisis and high R&D costs. In the not so promising situation that antibiotics find themselves in, phage therapy, a century-old technology, has stepped back into the spotlight in recent years as an alternative to antibiotics. Creative Biolabs has become a well-known company in the industry with its advanced technology platform and extensive experience in phage research, and is committed to providing the best phage isolation and enrichment services.

Overview of Phage Isolation and Enrichment

Along with the increasing attention and interest in phage therapy, the isolation and enrichment of phages are of great importance for the enrichment of phage libraries. Phages are widely present in environmental samples, and corresponding phages can be found in their host strains. For example, phages of enteric bacteria can be isolated in human feces and gutter effluent, and phages of a variety of soil microorganisms can be isolated in the soil.

The direct isolation method is difficult to obtain high titers of phage products, which affects the usefulness of effective bacterial infection. Therefore, performing phage enrichment can not only increase the titer of phages, but also further expand the range of infecting bacteria through multi-host variant culture. The isolation and enrichment of phages are the basis for their biological properties and applications.

Fig.1 Overview of bacteriophage cultivation and purification. (Luong, 2020)

Principles of Phage Isolation and Enrichment

Phages are specialized parasites and are highly host specific, so their hosts can be used as sensitive strains for phage isolation and enrichment. The presence of phage is characterized by cloudy to clear suspensions containing specific hosts or by the formation of clear or cloudy empty plates called phage spots on agar plates with host cell growth. Multiple phages may be isolated from one host organism, and their corresponding phage spots vary in morphology and size.

Since it is difficult to isolate the required high concentration of phage directly from the host strain, further enrichment of phage is still necessary. By repeating multiple rounds of adsorption-elution-amplification procedures with competing receptors, high titers of phage capable of effectively infecting bacteria can be obtained.

Workflow of Phage Isolation and Enrichment

Phage isolation is a process of removing bacteria from a mixture with host bacteria that has phage proliferation by centrifugation and filtration. After the host bacteria have completed phage amplification and fermentation in the production medium, phage isolation is performed by repeated filtration and chromatography unit operations, including ultrafiltration, dialysis filtration, ion exchange chromatography, affinity chromatography, and size exclusion chromatography. In this process, the optimal choice of isolation method varies depending on the phage, while endotoxin and protease contamination should be avoided.

Phage enrichment is the process of obtaining sufficient titers of phage in appropriate media to meet effective infection. Preparation of high-titer phage can be achieved by keeping the receptor-binding protein of the phage exposed and adsorbed to a single strain or multiple host strains of the same host as the isolated host, followed by multiple rounds of adsorption, elution, and amplification. In addition, the use of multiple strains of the same species for adsorption, or sequential multiplication of phages in multiple hosts, allows for the expansion of the range of phage hosts and the improvement of their infection efficacy.

Fig.2 Schematic of phage lysate dead-end filtration (Step 91) and cross-flow filtration (Steps 93-104) removal of impurities. (Luong, 2020)

Reliable phage isolation and purification procedures facilitate the acquisition of efficient phages with a broad host range and provide a decisive foundation for the construction of rich phage libraries and the advancement of superbug therapeutics. Creative Biolabs has a dedicated team of phage research experts to provide you with high quality phage isolation and enrichment services. Please contact us with your specific requirements.

Reference:

1. Luong, T.; et al. Standardized bacteriophage purification for personalized phage therapy. Nat Protoc. 2020, 15(9): 2867-2890.