Phage Resistance Detection

As the world's leading service provider, Creative Biolabs focuses on providing customized phage resistance detection services for global customers. Relying on our state-of-the-art experimental facilities and dedicated team, we are confident in providing one-stop phage resistance detection services, from experimental design to final result analysis.

Background

The development of resistance to phage therapy means that bacteria are initially susceptible to phages, and this sensitivity is critical for clinical applications. There are many methods available for determining phage sensitivity or resistance. Common methods include spot testing, the efficiency of plating (EOP), viable counts of phage and/or bacteria, and turbidity reduction as a visual indicator of phage-lysed bacteria. Some methods, such as turbidity reduction, have been automated through the use of plate readers, which increases screening throughput and enables more quantitative inferences of phage sensitivity than visual inspection.

Phage Resistance Detection

• Spot test

The spot test is a technique to quickly check whether a sample of bacteriophages can infect bacteria. The method is to spot dilutions of phage lysates on bacterial inoculated plates for the determination of phage susceptibility. This test involves mainly qualitative analysis and is an inexpensive and commonly used method.

• EOP

Another common method to determine host range is to measure the EOP by adding a diluted phage stock to newly seeded lawns of the strain. Host range and titers are determined by the formation of single plaques within the spot area at the final dilution. Plaque formation is a better indicator of productive phage infection because it is the result of multiple rounds of infection, lysis and release of progeny. Compared with spot tests, EOP is more quantitative. But this method is time-consuming and prone to human error in counting.

Fig.1 Assays validating phage receptors of well-characterized phages. (Kortright, 2020)

• Turbidity reduction assay

In this assay, different strains are grown to the appropriate extent in the medium. Each culture is centrifuged under specific conditions, and the cells are then resuspended in a medium and then stored on ice until use. Start the turbidity reduction assay by adding the same amount of purified endolysin or each domain deletion mutant, then monitor the OD value using a plate reader. This is a high-throughput approach, but assay results are affected by growth conditions.

What Can We Do?

The development of reliable phage susceptibility testing systems is an area of continuous innovation. At Creative Biolabs, in addition to the assays mentioned above, we have also developed faster and more efficient detection methods. Our multidisciplinary experts focus on predicting bacteria-phage interactions with genomic data using in silico, where the genomes of target isolates are sequenced and screened against existing phage genome databases to determine matches. We offer a variety of different assay options to meet the needs of different clients.

With our proven capabilities and regulatory expertise, we are confident in offering many flexible options for phage resistance detection, from which you can always find one that is better suited to your specific project. If you are interested in our phage resistance detection service, please contact us for more details.

Reference:

1. Kortright, K. E.; et al. High-throughput discovery of phage receptors using transposon insertion sequencing of bacteria. Proceedings of the National Academy of Sciences. 2020, 117(37): 18670-18679.