Culture-Dependent and-Independent Investigations of Microbial Diversity on Urinary Catheters

Catheter-associated urinary tract infection is caused by bacteria, which ascend the catheter along its external or internal surface to the bladder and subsequently develop into biofilms on the catheter and uroepithelium. Antibiotic-treated bacteria and bacte-ria residing in biofilm can be difficult to culture. In this study we used culture-based and 16S rRNA gene-based culture-indepen-dent methods (fingerprinting, cloning, and pyrosequencing) to determine the microbial diversity of biofilms on 24 urinary cath-eters. Most of the patients were catheterized for<30 days and had undergone recent antibiotic treatment. In addition, the corresponding urine samples for 16 patients were cultured. We found that gene analyses of the catheters were consistent with cultures of the corresponding urine samples for the presence of bacteria but sometimes discordant for the identity of the species. Cultures of catheter tips detected bacteria more frequently than urine cultures and gene analyses; coagulase-negative staphylo-cocci were, in particular, cultured muchmore often from catheter tips, indicating potential contamination of the catheter tips during sampling. The external and internal surfaces of 19 catheters were separately analyzed by molecular methods, and discor-dant results were found in six catheters, suggesting that bacterial colonization intra- and extraluminally may be different. Molec-ular analyses showed that most of the species identified in this study were known uropathogens, and infected catheters were gen-erally colonized by one to two species, probably due to antibiotic usage and short-term catheterization. In conclusion, our data showed that culture-independent molecular methods did not detect bacteria from urinary catheters more frequently than cul-ture-based methods