Microbiological analysis of tunneled hemodialysis catheters isolated from patients receiving hemodialysis in Saskatchewan

<b>Aim:</b> To compare the microbial communities inside hemodialysis catheters from symptomatic and asymptomatic patients to determine their differences. <b>Materials &amp; methods:</b> Catheters (<i>n</i> = 41) were removed from patients in the Saskatchewan Health Authority over an 18-month period. The catheter section inside the body was flushed and the contents were evaluated using culture-dependent and culture-independent analysis. <b>Results:</b> All catheters were colonized by bacteria, with considerable overlap between groups based on microbial communities and the individual species detected. More Gram-negative species were detected by sequencing, whereas predominantly Gram-positive strains were cultured. Antibiotic resistance and biofilm formation was widespread and not correlated with either catheter group. <b>Conclusion:</b> Common pathogens were detected in each set of catheters, therefore predicting infections based on the microbiology is difficult. Many patients use catheters to help clean their blood, a process called hemodialysis. The use of catheters is also associated with complications, such as blood infections. We looked at the types of bacteria associated with catheters from patients who had infections (<i>n</i> = 21) and compared them to catheters from patients who had no signs of infection (<i>n</i> = 20). Once removed from the patient, we flushed out each catheter and tried to grow bacteria in different conditions. We also looked at DNA from within the catheter to identify bacterial species that were present. All 41 catheters had bacteria and there were many common species detected. We detected species known to cause illness such as <i>Staphylococcus aureus</i>, <i>Staphylococcus epidermidis</i>, <i>Escherichia coli</i> and <i>Pseudomonas</i>, <i>Enterobacter</i>, <i>Morganella</i> and <i>Stenotrophomonas</i> species. <i>S. aureus</i> was only grown from patients that had infections. Resistance to antibiotics was found to be common in bacteria grown from catheters. This did not seem to be influenced by whether patients were infected or not. Finally, we identified several catheters where two species, <i>S. epidermidis</i> and <i>P. aeruginosa</i>, were detected together. Our main conclusion was that bacteria are commonly present inside catheters that are used for hemodialysis, regardless of whether patients are infected or not. For patients with non resolving infections (i.e., exit-site infections, tunneled infections or bloodstream infections), the catheter was removed urgently and was considered infected (symptomatic; <i>n</i> = 21). For patients with no signs of catheter related infections, the catheters were removed electively when the patient no longer needed dialysis (i.e., recovered kidney function) or another dialysis access was used (i.e., arteriovenous fistula or peritoneal dialysis) (asymptomatic; <i>n</i> = 20). Analyzing the microbiology by standard culturing and 16S sequencing showed that all 41 catheters were colonized by bacteria. Symptomatic and asymptomatic catheter groups had significant overlap in their microbial communities, with common pathogens detected in each group. Gram-negative bacterial species were most abundant based on 16S sequencing, whereas Gram-positive species were most abundant by culturing. <i>Staphylococcus aureus</i> was only cultured from symptomatic catheters and was the dominant colonizing organism in several cases. Biofilm formation and antimicrobial resistance was widespread among the catheter isolates and was not correlated with either catheter group. There were no clear microbiology signatures to differentiate between symptomatic and asymptomatic hemodialysis catheters or predict if a catheter infection will arise in the future.