| Summary: | Catheter associated urinary tract infection seriously complicates the care of an already vulnerable patient set and has been estimated to cost the UK National Health Service in excess of one billion pounds per annum. Approximately 50 % of patients catheterised for more than 28 days will experience catheter blockage due to the formation of crystalline biofilm on the eye holes, balloon and lumen of the catheter(Getliffe, 1994) as a result of colonisation by Proteus mirabilis. Blockage can lead to significant complications such as pyelonephritis and septicaemia. To date, strategies to reduce or prevent these infections from occurring have met with limited success. One potential approach to prevent catheter colonisation and blockage is the application of bacteriophages as a catheter coating. Natural parasites of bacteria, bacteriophages offer several advantages over conventional antimicrobial treatment including replication at the site of infection, specificity and, in some cases, biofilm degrading ability. Three novel bacteriophages vB_PmiS_NSM6, vB_PmiP_#3 and vB_PmiM_D3 were isolated from environmental sources and characterised phenotypically and genetically utilising electron microscopy, host range analysis and, for phages vB_PmiS_NSM6 and vB_PmiP_#3, genome sequencing via hybrid assembly. The isolated phages belong to the Caudovirales order and sequence data analysis indicated that they were lysogenic. They possess the characteristic modular architecture of their dsDNA genomes that are densely packed with coding sequence. Both phages displayed terminal redundancy which is indicative of a headful packaging strategy and both appear to be circularly permuted. Putative function was obtained for 63 % of the coding sequences for phage vB_PmiS_NSM6 and 52 % of genes identified in phage vB_PmiP_#3. The effect of these phages, either individually or as a cocktail, on P. mirabilis colonisation of urinary catheters in an in vitro bladder model was investigated. Models were run for 24 h and adhered bacteria used as an indicator of phage activity. A reduction of greater than 3 log10 was observed for phage vB_PmiS_NSM6 treated catheters in comparison to untreated controls across all three sections of catheter analysed. Phage vB_PmiP_#3 reduced bacterial adherence by 1 log10 across all sections and a similar reduction was observed with phage vB_PmiM_D3 of greater than 1 log10. These data were confirmed with scanning electron microscopy (SEM) which showed a significant reduction in crystalline deposits on the phage treated catheters. The time taken for the mineralised biofilm to occlude the catheter lumen in the presence of bacteriophages was also investigated. Time to blockage was extended by 61.49 %, 25.67 % and 52.31 % for phages vBPmiS_NSM6, vB_PmiP_#3 and vB_PmiM_D3, respectively, in comparison to controls. Phages vB_PmiS_NSM6 and vB_PmiM_D3 displayed activity on each other’s isolating strain. This enabled the assessment of a two phage cocktail. The cocktail increased time to blockage by approximately 7 % compared to single phage treatment for both bacterial isolates. These data provide some evidence of efficacy of bacteriophage pre-treatment of urinary catheters in an in vitro model of P. mirabilis infection of the catheterised bladder, despite the lysogenic nature of the phages investigated. As such, this suggests phage treatment of catheters warrants further investigation.
|
|---|
