Phage Therapy Is Partially Successful in Rescuing Hornworms from Pseudomonas Infections

Background: Phage therapy is one of the few alternatives to confront the tide of drug-resistant bacteria. Yet phage therapy is often applied knowing little more than that the therapeutic phages can grow on the infecting bacterium. The lack of convenient, inexpensive infection models slows progress in discovering principles that may improve phage therapy success. Here we explore hornworms, the larvae of hawkmoths, as a new model host for phage therapy. Methods: We injected fifth instar hornworms with Pseudomonas aeruginosa and, in some, also simultaneously administered a single dose of one of three phages. Results: Phage treatment significantly improved survival relative to bacteria-only controls, although only modestly. Phages did not significantly affect hornworm weight gain among survivors. Differences in survival and weight among the three phage treatments were not statistically significant despite large genomic differences among the phages. Conclusions: Comparing hornworms to the more commonly used waxworms, hornworms, offers additional phenotypes that can be easily assayed, but their need to be housed individually increases the effort to provide large numbers.