Abstract
BackgroundKlebsiella pneumoniae is an important gram-negative opportunistic pathogen causing primarily urinary tract infections, respiratory infections, and bacteraemia. The ability of bacteria to form biofilms on medical devices, e.g. catheters, has a major role in development of many nosocomial infections. Most clinical K. pneumoniae isolates express two types of fimbrial adhesins, type 1 fimbriae and type 3 fimbriae. In this study, we characterized the role of type 1 and type 3 fimbriae in K. pneumoniae biofilm formation.ResultsIsogenic fimbriae mutants of the clinical K. pneumoniae isolate C3091 were constructed, and their ability to form biofilm was investigated in a flow cell system by confocal scanning laser microscopy. The wild type strain was found to form characteristic biofilm and development of K. pneumoniae biofilm occurred primarily by clonal growth, not by recruitment of planktonic cells. Type 1 fimbriae did not influence biofilm formation and the expression of type 1 fimbriae was found to be down-regulated in biofilm forming cells. In contrast, expression of type 3 fimbriae was found to strongly promote biofilm formation.ConclusionBy use of well defined isogenic mutants we found that type 3 fimbriae, but not type 1 fimbriae, strongly promote biofilm formation in K. pneumoniae C3091. As the vast majority of clinical K. pneumoniae isolates express type 3 fimbriae, this fimbrial adhesin may play a significant role in development of catheter associated K. pneumoniae infections.
Highlights
Klebsiella pneumoniae is an important gram-negative opportunistic pathogen causing primarily urinary tract infections, respiratory infections, and bacteraemia
Construction of fluorescently-tagged strains To observe biofilm formation by confocal laser scanning microscopy (CLSM), the C3091 wild type and its fimbriae-mutants were chromosomally-tagged by allelic exchange of the lacIZ genes with a cassette encoding fluorescent protein (yellow fluorescent protein (YFP) or cyan fluorescent protein (CFP)) under control of the modified lac promotor PA1/04/03, and chloramphenicol resistance flanked by regions homologous to regions upand down-stream the lacIZ genes
To further characterize the influence of fimbriae on K. pneumoniae biofilm formation, flow cell experiments were performed with the different fimbriae mutants in direct competition with the wild type strain
Summary
Klebsiella pneumoniae is an important gram-negative opportunistic pathogen causing primarily urinary tract infections, respiratory infections, and bacteraemia. The ability of bacteria to form biofilms on medical devices, e.g. catheters, has a major role in development of many nosocomial infections. Klebsiella pneumoniae is an important gram-negative opportunistic pathogen causing primarily urinary tract infections (UTIs), respiratory infections and bacteraemia especially in immunocompromised individuals [1]. The ability of bacteria to form biofilms on medical devices, e.g. catheters, is believed to play a major role in development of nosocomial infections including CAUTIs [2,5,6,7]. Biofilm formation, i.e. bacteria form an organized matrix-enclosed community adhering to the surface and the first time reported type 3 fimbriae expression in E. coli strains encoded by conjugative plasmids [16,17]
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