Isolation and characterisation of Klebsiella phages for phage therapy

Klebsiella is a clinically important pathogen causing a variety of antimicrobial resistant infections in both community and nosocomial settings, particularly pneumonia, urinary tract infection and sepsis. Bacteriophage (phage) therapy is being considered as a primary option for the treatment of drugresistant infections of these types. We report the successful isolation and characterisation of 30 novel, genetically diverse Klebsiella phages. The isolated phages span six different phage families and nine genera, representing both lysogenic and lytic lifestyles. Individual Klebsiella phage isolates infected up to 11 of the 18 Klebsiella capsule types tested, and all 18 capsule-types were infected by at least one of the phages. Of the Klebsiella -infecting phages presented in this study, the lytic phages are most suitable for phage therapy, based on their broad host range, high virulence, short lysis period and given that they encode no known toxin or antimicrobial resistance genes. Importantly, when applied alone, none of the characterised phages were able to suppress the growth of Klebsiella for more than 12 hours, with some phages only able to suppress growth for 3 hours, likely due to inherent ease of Klebsiella to generate spontaneous phage-resistant mutants. This indicates that for successful phage therapy, a cocktail of multiple phages would be necessary to treat Klebsiella infections. ### Competing Interest Statement The authors have declared no competing interest.