Klebsiella pneumoniae type 3 pili facilitate adherence and biofilm formation on abiotic surfaces.

The role of type 1 and type 3 pili in mediating Klebsiella pneumoniae colonization of inert surfaces was assessed by analysis of 26 clinical, 7 water distribution system and four reference strains. Amongst the 33 wild type strains tested, 57.6% expressed type 1 pili, 54.5% expressed type 3 pili, 42.4% were highly hydrophobic, 69.7% were highly adherent to both glass and polypropylene surfaces, and 48.5% were efficient biofilm-forming strains on polystyrene dishes. High adherence and biofilm formation were positively correlated with bacterial surface hydrophobicity, type 3 fimbriae expression but not with type 1 pili expression and were not dependent upon the strain's origin. The K. pneumoniae CF3051 reference strain expressing only type 1 fimbriae adhered slightly to glass and polypropylene and did not form biofilm on polystyrene. K. pneumoniae IA565 and CF3097 reference strains producing type 1 and type 3 fimbriae showed efficient adherence to both glass and polypropylene and biofilm formation on polystyrene. Moreover, transformation of the afimbriated, weakly-adherent CF3172 strain with the recombinant pFK10 plasmid carrying the mrk gene cluster resulted in type 3 fimbriae expression, increased surface hydrophobicity, increased adherence to abiotic surfaces and biofilm formation. Thus, type 3 pili constitute the main K. pneumoniae adhesive factor, facilitating adherence and biofilm formation on abiotic surfaces of strains of different origins.