Abstract
The adherence of Proteus mirabilis to the surface of urinary catheters leads to colonization and eventual blockage of the catheter lumen by unique crystalline biofilms produced by these opportunistic pathogens, making P. mirabilis one of the leading causes of catheter-associated urinary tract infections. The Proteus biofilms reduce efficiency of antibiotic-based treatment, which in turn increases the risk of antibiotic resistance development. Bacteriophages and their enzymes have recently become investigated as alternative treatment options. In this study, a novel Proteus bacteriophage (vB_PmiS_PM-CJR) was isolated from an environmental sample and fully characterized. The phage displayed depolymerase activity and the subsequent genome analysis revealed the presence of a pectate lyase domain in its tail spike protein. The protein was heterologously expressed and purified; the ability of the purified tail spike to degrade Proteus biofilms was tested. We showed that the application of the tail spike protein was able to reduce the adherence of bacterial biofilm to plastic pegs in a MBEC (minimum biofilm eradication concentration) assay and improve the survival of Galleria mellonella larvae infected with Proteus mirabilis. Our study is the first to successfully isolate and characterize a biofilm depolymerase from a Proteus phage, demonstrating the potential of this group of enzymes in treatment of Proteus infections.
Highlights
Proteus mirabilis is a Gram-negative, opportunistically pathogenic bacterium which is widespread in natural and built environments and commonly present in gastrointestinal tracts of healthy humans
We performed the isolation of Proteus bacteriophages from a number of environmental samples collected in Northern Ireland
The plaque assay conducted with the material from one of the phage-positive samples led to the formation of medium-sized (1–3 mm) clear plaques on a lawn of P. mirabilis BB2000, surrounded by semi-transparent haloes (Figure 2a, top)
Summary
Proteus mirabilis is a Gram-negative, opportunistically pathogenic bacterium which is widespread in natural and built environments and commonly present in gastrointestinal tracts of healthy humans. One of the distinguishing features of P. mirabilis is its swarming motility, resulting in formation of characteristic “bull’s-eye” patterns when grown on solid media. This is the result of sequential rounds of formation of elongated swarming cells, capable of flagella-assisted migration across surfaces, followed by deconsolidation into rod-shaped swimmer cells. The readiness with which the bacterium forms biofilms on a variety of abiotic surfaces in combination with its ability to rapidly spread by swarming makes it a clinically important pathogen, capable of colonizing a variety of indwelling medical devices, including urinary catheters.
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