Abstract
To investigate the sources and routes of long-term bacterial colonization in the dialysate supply system in Tokatsu Clinic Hospital, pulsed-field gel electrophoresis (PFGE) was used to analyze genomic DNA of Burkholderia pickettii which was the most predominant isolate from the fluid pathway.
Genomic DNA of B. pickettii was digested with a Spe I restriction enzyme, and DNA fragment separation was performed using the GenePathTM system (Bio-Rad, Japan). Thirty-one strains of B. pickettii isolated from dialysis centers associated with Tokatsu Clinic Hospital were divided into 8 genotypes (A-H) by PFGE. All B. pickettii isolates from the reverse osmosis (RO) water tank and mixing tank, and almost all isolates from a region just before the dialysis monitor in a dialysis unit (A-5), exhibited identical PFGE restriction profiles (type A). Isolates from the fluid pathway (RO water, bicarbonate solution, mixing tank and terminal portion of the pathway) in another unit (A-4) of the same dialysis center, showed 2 different profiles (types C and D) distinct from those in the A-5 unit. These results suggested that the contaminated bacteria escaped from the daily routine disinfection procedures by forming biofilms on the internal wall of the distribution piping, and the survivors flowed downward to the pathway. There was no direct evidence to show cross transmission among different dialysis units, showing that a characteristic type of bacteria colonized each dialysis unit.
The results of genotypic analysis for 10 strains of Pseudomonas spp. isolated from the fluid pathway in a A-5 unit suggested artificial backward transfer of bacteria from a contaminated sampling port on the lower pathway to the upper mixing tank, caused by insufficient aseptic procedures by the dialysis unit staff in obtaining test materials.
There was no close correlation between the endotoxin concentrations and viable bacterial numbers for samples from the fluid pathway of A-5 unit.
