Liposome capsules improve phage therapy

WRITTEN BY: Kerry Evans

Researchers devised a method to improve oral bacteriophage therapy.

The group, made up of investigators from the Autonomous University of Barcelona and the Catalan Institute for Nanoscience and Nanotechnology, encapsulated bacteriophages within liposomes. The liposomes make the phages more resistant to stomach acid and increase the amount of time they spend in the intestinal tract.

Bacteriophages (red) target and kill bacteria (blue).

These researchers already demonstrated that oral phage therapy is effective against Salmonella infection in chickens. However, they needed some way to keep the phages from being destroyed by the chicken’s stomach acid and to increase retention time in the intestines.

Enter liposome nanoencapsulation. The capsules have an average diameter of 320 nm and are positively charged. Conveniently, this technique can also be applied to bacteriophages of any shape and size.

The group first showed that encapsulation could protect the phages from stomach acid. When exposed to simulated gastric fluid with a pH of 2.8, the number of “viable” nonencapsulated phages decreased by as much as 7.8 log units. However, the number of encapsulated phages only decreased by around 5.4 log units.

Next, they tested whether encapsulation increased the retention time of phages in the intestinal tract. Sure enough, 38.1% of chickens retained the encapsulated phages in their ceca after 72 hours compared to only 9.5% of chickens that were given nonencapsulated phages.

Finally, they needed to know whether the encapsulated phages could effectively kill Salmonella in the chickens. They tested this by infecting broiler chickens with Salmonella and treating them orally with nonencapsulated or encapsulated phages. Both nonencapsulated and encapsulated phages decreased the Salmonella concentration in the cecum within the first 6 days after infection. However, from days 8 to 15, the encapsulated phages decreased the Salmonella concentration to a much greater degree than the nonencapsulated phages.

Does this mean phage therapy is one step closer to becoming a mainstream antibacterial therapy? Guess we’ll wait and see.

Sources: Applied and Environmental Microbiology, AlphaGalileo