ALTERING THE HOST RANGE OF THE FIRST DISCOVERED LYTIC STAPHYLOCOCCUS PSEUDINTERMEDIUS BACTERIOPHAGES

Jon Johnson

Date of Award

2023

Document Type

Thesis

Degree Name

Bachelors

Department

Natural Sciences

First Advisor

Diaz Almeyda, Erika

Area of Concentration

Microbiology

Abstract

With the rising prevalence of antibiotic-resistant Staphylococcus strains, utilization of lytic bacteriophages, or simply phages, is gathering interest among the scientific and biomedical communities. Three novel lytic phages for Staphylococcus pseudintermedius were recently discovered in canine microbiomes from skin, hair, and fecal samples. In this study, these three S. pseudintermedius phages DH2, DH5, and DS10 were challenged against a dozen strains of S. aureus and S. pseudintermedius strains permissive to at least one of the phages. A modified Appelmans Protocol, which functions to alter the host range of phages, was employed to attempt host range changes for the three phages. After 6 rounds of host range expansion experiments, the evolved DH2 phage, DH2-A, had a significant increase in both host range and efficacy of plating (EOP) values, the measure of a phage’s infectivity, on tested strains. DH5-A experienced significant decreases to host range and EOP values while DS10-A experienced a modest increase in host range at the cost of infectivity efficiency. Overall, the application of experimental evolution protocols to alter the host range of bacteriophages was shown to be possible, but not guaranteed, with success varying on a species-by-species basis.

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