Isolation and Characterization of the Novel Bacteriophage AXL3 against Stenotrophomonas maltophilia

Abstract

The rapid increase in the number of worldwide human infections caused by the extremely antibiotic resistant bacterial pathogen Stenotrophomonas maltophilia is cause for concern. An alternative treatment solution in the post-antibiotic era is phage therapy, the use of bacteriophages to selectively kill bacterial pathogens. In this study, the novel bacteriophage AXL3 (vB_SmaS-AXL_3) was isolated from soil and characterized. Host range analysis using a panel of 29 clinical S. maltophilia isolates shows successful infection of five isolates and electron microscopy indicates that AXL3 is a member of the Siphoviridae family. Complete genome sequencing and analysis reveals a 47.5 kb genome predicted to encode 65 proteins. Functionality testing suggests AXL3 is a virulent phage and results show that AXL3 uses the type IV pilus, a virulence factor on the cell surface, as its receptor across its host range. This research identifies a novel virulent phage and characterization suggests that AXL3 is a promising phage therapy candidate, with future research examining modification through genetic engineering to broaden its host range.

Antimicrobial Treatment Strategies for Stenotrophomonas maltophilia: A Focus on Novel Therapies

“…Bacterial phage therapy is gaining traction as a novel approach to refractory cases of extremely multidrug resistant (XDR) bacterial infections; advantages include specificity to the target, limited side effects on the host biome, and lack of major end organ damage [82]. In 2004, Chang et al reported a series of Stenotrophomonas bacteriophages, φSMA1-φSMA8, with an in-depth characterization and discussion of one phage, φSMA5 [83].…”

The Characterization of a Novel Phage, pPa_SNUABM_DT01, Infecting Pseudomonas aeruginosa

“…Previous studies have shown that this protein is essential to DNA ejection and phage morphogenesis [44]. However, no comprehensive description exists of the protein's exact activities [45].…”

The Potential of Phage Therapy against the Emerging Opportunistic Pathogen Stenotrophomonas maltophilia

“…Strain FDAARGOS_1044 (accession: NZ_CP065965.1) was predicted to have the most prophage regions with 11, three of which were classified as intact, six as incomplete, and two as questionable, whereas only one strain, AA1 (accession: NZ_CP018756.1), had zero predicted prophage regions. Although many bacteria have phage defense systems to protect against phage predation and possibly prophage integration, these systems, including CRISPR-Cas immunity, have not yet been characterized in S. maltophilia [111][112][113], potentially contributing to the high prevalence of prophage DNA in their genomes.…”

“…intact, six as incomplete, and two as questionable, whereas only one strain, AA1 (accession: NZ_CP018756.1), had zero predicted prophage regions. Although many bacteria have phage defense systems to protect against phage predation and possibly prophage integration, these systems, including CRISPR-Cas immunity, have not yet been characterized in S. maltophilia [111][112][113], potentially contributing to the high prevalence of prophage DNA in their genomes. The high prevalence of prophages in bacterial genomes suggests that phages have played an important role in bacterial evolution [108,114].…”

“…The final S. maltophilia phage paper published by our group characterizes a novel virulent Siphoviridae phage, AXL3 [113]. This phage has a narrow host range and long productive cycle, with approximately 38 phages released per cell after 6.5 h, and was identified to also use the type IV pilus as its host receptor.…”