Characterization and genomic analysis of phage vB_SmaP_c9-N, a novel Stenotrophomonas maltophilia podophage with antibiofilm activity

Stenotrophomonas maltophilia strains are increasingly emerging as multidrug-resistant pathogens. Moreover, S. maltophilia commonly produces biofilms that enhance antibiotic resistance in bacteria. Phages are effective alternative drugs for treating S. maltophilia infections. In this study, the lytic phage vB_SmaP_c9-N (abbreviated as Φc9-N), which is specific for S. maltophilia, was isolated from Nanhu Lake, Wuhan, China. Electron microscopy observation revealed that Φc9-N is a podophage. Φc9-N is stable over a wide pH range, from pH 4 to 10, and its activity did not change after storage at 4 °C for 2 months. The latency period of Φc9-N is 5 min, and its outbreak period is 35 min. Antibacterial tests showed that Φc9-N could effectively inhibit the growth of S. maltophilia c24. Moreover, the biofilm production of S. maltophilia c24 decreased when Φc9-N was administered either to the forming biofilm or to the mature biofilm. These results suggest that Φc9-N has application potential in clinical treatment. The genome of Φc9-N is a dsDNA of 43,170 bp with 55 putative unidirectional genes, 18 of which were assigned putative functions, while other genes encoded hypothetical proteins. Genome sequence comparisons and phylogenetic analysis indicated that Φc9-N represents a new species, and, together with the Stenotrophomonas phages BUCT700, BUCT703, BUCT598, and vB_SmaS_P15, can be included in the newly proposed genus “Maltovirus” in the family Autographiviridae.