title: Construction of an MR/P fimbrial mutant of Proteus mirabilis: role in virulence in a mouse model of ascending urinary tract infection.
abstract: Proteus mirabilis, a cause of acute pyelonephritis, produces at least four types of fimbriae, including MR/P (mannose-resistant/Proteus-like) fimbriae. To investigate the contribution of MR/P fimbriae to colonization of the urinary tract, we constructed an MR/P fimbrial mutant by allelic exchange. A 4.2-kb BamHI fragment carrying the mrpA gene was subcloned into a mobilizable plasmid, pSUP202. A 1.3-kb Kanr cassette was inserted into the mrpA open reading frame, and the construct was transferred to the parent P. mirabilis strain by conjugation. Following passage on nonselective medium, 1 of 500 transconjugants screened was found to have undergone allelic exchange as demonstrated by Southern blot. Colony immunoblot, Western immunoblot, and immunogold labeling with a monoclonal antibody to MR/P fimbriae revealed that MrpA was not expressed. Complementation with cloned mrpA restored MR/P expression as shown by hemagglutination, Western blot, and immunogold electron microscopy. To assess virulence, we challenged 40 CBA mice transurethrally with 10(7) CFU of wild-type or mutant strains. After 1 week, geometric means of log10 CFU per milliliter of urine or per gram of bladder or kidney for the wild-type and mutant strains were as follows: urine, 7.79 (wild type) versus 7.02 (mutant) (P = 0.035); bladder, 6.22 versus 4.78 (P = 0.019); left kidney, 5.02 versus 3.31 (P = 0.009); and right kidney, 5.28 versus 4.46 (P = 0.039). Mice challenged with the wild-type strain showed significantly more severe renal damage than did mice challenged with the MR/P-negative mutant (P = 0.007). We conclude that MR/P fimbriae contribute significantly to colonization of the urinary tract and increase the risk of development of acute pyelonephritis.
authors.affiliation: Department of Medicine, University of Maryland School of Medicine, Baltimore 21201.
authors.forename: F K
authors.initials: FK
authors.lastname: Bahrani
authors.forename: G
authors.initials: G
authors.lastname: Massad
authors.forename: C V
authors.initials: CV
authors.lastname: Lockatell
authors.forename: D E
authors.initials: DE
authors.lastname: Johnson
authors.forename: R G
authors.initials: RG
authors.lastname: Russell
authors.forename: J W
authors.initials: JW
authors.lastname: Warren
authors.forename: H L
authors.initials: HL
authors.lastname: Mobley
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D005260:Female; D010861:Fimbriae, Bacterial / Q000502:physiology*; D005816:Genetic Complementation Test; D007668:Kidney / Q000473:pathology; D051379:Mice; D009154:Mutation; D011512:Proteus Infections / Q000473:pathology; D011513:Proteus mirabilis / Q000472:pathogenicity*; D011704:Pyelonephritis / Q000209:etiology; D014552:Urinary Tract Infections / Q000209:etiology*; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; C079120:mrpA protein, Proteus mirabilis