Detecting the prevalence of bacterial colonization on tunneled cuffed hemodialysis catheters using quantitative PCR targeting 16S rRNA and scanning electron microscopy

Background and objectives: Tunneled cuffed hemodialysis catheters (TCC) get colonized by microorganisms, increasing risk for catheter related bacteremia (CRB). Our objective was to detect the prevalence of bacterial colonization of TCC by using quantitative PCR (qPCR) targeting 16S rRNA and by determining the intraluminal adherent biological material (ABM) coverage. Methods: A total of 45 TCC were investigated. The 16S rRNA qPCR technique was used to detect bacterial colonization after scraping the intraluminal ABM. Proximal, middle, and distal TCC were evaluated by scanning electron microscopy (SEM) to determine the percentage (%) of intraluminal ABM coverage. All catheters were cultured following sonication. Results: A total of 45 TCC were removed: 7 due to CRB, 3 for suspected CRB and 35 were removed for non-infectious etiologies. Bacterial colonization was detected in 27 TCC by documenting 16S rRNA qPCR (+) results (60%). Seven of these 16S rRNA qPCR (+) catheters were removed due to CRB. There was no difference in demographic, clinical, or laboratory values between the 16S rRNA (+) versus (−) TCC. The 16S rRNA qPCR (−) outcome was highly associated with CRB-free status with negative predictive value of 100%. Bacterial colonization was documented in 10 TCC using catheter cultures (22%), which was significantly less compared to qPCR method (p = 0.0002). ABM were detected in all catheter pieces, with mean intraluminal surface coverage (ABMC) of 68.4 ± 26.1%. ABM was unlikely to be microbial biofilm in at least 36% of removed TCC as their 16S rRNA qPCR and catheter culture results were both negative. Conclusions: Detecting bacterial colonization of TCC was significantly higher with 16S rRNA qPCR compared to catheter cultures. The 16S rRNA qPCR (−) cannot be predicted and was strongly associated with absence of CRB. Intraluminal ABM was not associated with microbial presence in about 1/3 of the TCC. These pieces of evidence may help to improve prophylactic strategies against CRB.