Fimbriae have distinguishable roles inProteus mirabilisbiofilm formation

Abstract

Proteus mirabilis is one of the most common etiological agents of complicated urinary tract infections, especially those associated with catheterization. This is related to the ability of P. mirabilis to form biofilms on different surfaces. This pathogen encodes 17 putative fimbrial operons, the highest number found in any sequenced bacterial species so far. The present study analyzed the role of four P. mirabilis fimbriae (MR/P, UCA, ATF and PMF) in biofilm formation using isogenic mutants. Experimental approaches included migration over catheter, swimming and swarming motility, the semiquantitative assay based on adhesion and crystal violet staining, and biofilm development by immunofluorescence and confocal microscopy. Different assays were performed using LB or artificial urine. Results indicated that the different fimbriae contribute to the formation of a stable and functional biofilm. Fimbriae revealed particular associated roles. First, all the mutants showed a significantly reduced ability to migrate across urinary catheter sections but neither swimming nor swarming motility were affected. However, some mutants formed smaller biofilms compared with the wild type (MRP and ATF) while others formed significantly larger biofilms (UCA and PMF) showing different bioarchitecture features. It can be concluded that P. mirabilis fimbriae have distinguishable roles in the generation of biofilms, particularly in association with catheters.

Pathogenesis of Proteus mirabilis Infection

“…Biofilm formation ( link biofilm section ), measured in plastic multi-well plates, on glass coverslips, as pellicles in culture tubes, or in static cultures in glass tubing, is dependent on MR/P fimbriae (156, 244, 256). Interestingly, phase variation contributes to biofilm development.…”

“…This suggests that ATF may play a role in infection that is masked by other fimbriae, such as MR/P, and also there may be a fimbrial hierarchy that determines gene expression. ATF may contribute to biofilm formation under some conditions (256). …”

“…In particular, MR/P fimbriae have been linked to biofilm formation using multiple methods, including crystal violet-stained multi-well plates (256, 275), confocal microscopy on glass coverslips (244), glass tubing (256), bacterial clustering within the bladder lumen (44), and aggregative adherence to cultured cells (275). MR/P fimbriae allow complex biofilm architecture to develop, but only if the bacteria are allowed to modulate their fimbrial production ( link fimbrial section ).…”

“…The major advantage is that this assay allows for simultaneous screening of many samples; it is also easily quantifiable by dissolving the crystal violet and measuring the dye with a spectrophotometer. For this reason, the assay has been used to screen P. mirabilis clinical isolates and transposon mutants, as well as screening of targeted mutants (53, 177, 256, 275, 280, 281, 293, 294). Other variations on this assay include the addition of short catheter segments to multiwall plates and culture in static, closed tubes (283, 295).…”

From Catheter to Kidney Stone: The Uropathogenic Lifestyle of Proteus mirabilis

“…MR/P is critical for biofilms in microtiter plate models [35,69]. However, it remains untested whether MR/P is important for mediating crystalline biofilm formation on catheters.…”