Isolation of a PRD1-like Phage Uncovers the Carriage of Three Putative Conjugative Plasmids in Clinical Burkholderia Contaminans

Abstract

The Burkholderia cepacia complex (Bcc) are a group of increasingly multi-drug resistant opportunistic bacteria that can cause severe pulmonary infections. This resistance is driven through a combination of intrinsic factors and the carriage of a broad range of conjugative plasmids harbouring virulence determinants. Therefore, novel treatments are required to not only treat Bcc infection but also to prevent further spread of these virulence determinants. In the search for phages infective for two clinical Bcc isolates, CSP1 phage, a PRD1-like phage was isolated. CSP1 phage was found to require pilus machinery commonly encoded on conjugative plasmids to facilitate infection of multiple Gram-negative bacteria genera including Escherichia and Pseudomonas. Whole genome sequencing and characterisation of one of the clinical Burkholderia isolates revealed it to be Burkholderia contaminans. B. contaminans 5080 was found to contain a genome of over 8 Mbp encoding multiple intrinsic resistance factors, such as efflux pump systems, but more interestingly, carried three novel plasmids encoding multiple putative virulence factors for increased host fitness, including antimicrobial resistance. Even though PRD1-like phages are broad host range, their use in novel antimicrobial treatments shouldn’t be dismissed, as the dissemination potential of conjugative plasmids is extensive. Continued survey of clinical bacterial strains is

Burkholderia contaminans Bacteriophage CSP3 Requires O-Antigen Polysaccharides for Infection

“…After screening various environmental samples, single plaques were produced on clinical isolate Burkholderia contaminans (strain 5080) ( 23 ) and another Bcc (strain 3726) from soil samples collected from Darwin, Australia. After purification and whole-genome sequencing, it was revealed that there was one distinct phage, CSP3.…”

“…Here, we describe novel phage CSP3, isolated against two clinical isolates of Bcc organisms, one confirmed as Burkholderia contaminans ( 23 ). CSP3 is a new member of the Lessievirus genus, the first to be isolated from Australia.…”

Diverse and abundant phages exploit conjugative plasmids

“…are known hosts of IncP-type conjugative plasmids 31 we expect that the Burkholderia cenocepacia host used to isolate BCE1 carried such a plasmid (highlighting the serendipitous nature by which PDPs are often found) and we include BCE1 in our known plasmiddependent tectivirus phylogeny. Novel conjugative plasmids have recently been detected in Burkholderia contaminans isolates, after their existence was implicated by the isolation of alphatectiviruses on these strains 32 , suggesting Burkholderia species may be common hosts for these plasmids and phages. While the new plasmid-dependent tectiviruses we report greatly expand the known diversity of this group of phages, we found that all 51 phages in our collection had perfectly conserved gene synteny (Figure S1b).…”