New Bacteriophage Pseudomonas Phage Ka2 from a Tributary Stream of Lake Baikal

<i>Pseudomonas aeruginosa</i>, an opportunistic pathogen, causes various biofilm-associated infections like pneumonia, infections in cystic fibrosis patients, and urinary tract and burn infections with high morbidity and mortality, as well as low treatment efficacy due to the extremely wide spread of isolates with multidrug resistance. Here, we report the new bacteriophage <i>Pseudomonas</i> phage Ka2 isolated from a tributary stream of Lake Baikal and belonging to the <i>Pbunavirus</i> genus. Transmission electron microscopy resolved that <i>Pseudomonas</i> phage Ka2 has a capsid of 57 ± 9 nm and a contractile and inflexible tail of 115 ± 10 nm in the non-contracted state. The genome consists of 66,310 bp with a GC content of 55% and contains 96 coding sequences. Among them, 52 encode proteins have known functions, and none of them are potentially associated with lysogeny. The bacteriophage lyses 21 of 30 <i>P. aeruginosa</i> clinical isolates and decreases the MIC of amikacin, gentamicin, and cefepime up to 16-fold and the MIC of colistin up to 32-fold. When treating the biofilms with Ka2, the biomass was reduced by twice, and up to a 32-fold decrease in the antibiotics MBC against biofilm-embedded cells was achieved by the combination of Ka2 with cefepime for the PAO1 strain, along with a decrease of up to 16-fold with either amikacin or colistin for clinical isolates. Taken together, these data characterize the new <i>Pseudomonas</i> phage Ka2 as a promising tool for the combined treatment of infections associated with <i>P. aeruginosa</i> biofilms.