Molecular Study of Phase Variation of Type ۱ Fimbriae in Uropathogenic Escherichia coli O۴۴ Serotypes during Touching with Solid Surfaces

Background & Aims: Type ۱ fimbriae is the most common adhesion factor in urine tract infection. In this Study, presence of virulence genes in isolated strains of uropathogenic E.Coli, O serotyping and molecular detection of phase variation of type ۱ fimbriae were assessed during solid surfaces exposure. Methods: Isolated E.coli from urine samples of patients were serotyped by using serologic methods. Phenotypic estimation of phase variation was applied by mannose – resistant hemagglutination (MRHA). Fim opron phase variation was studied by HinFI digestion and PCR reaction. Results: For all ۱۵۸ E.coli strains, the most occurrences belonged to O۴۴. Forty nine percent of the isolates were mannose-sensitive and expressed fim operon in agar medium. While, ۵۱% of strains were resistant to mannose in the same position. In Broth medium ۶۸% of isolates were mannose-sensitive and ۳۲% were mannose-resistant. PCR products with ۳۵۹bp and ۲۰۰bp long fragment demonstrated ON position and those with ۴۸۹bp and ۷۰bp long fragment indicated ON and OFF positions. Conclusion: Uropathologic E.coli strains posses few number of O serotypes. Environmental factors play an important role in regulation of fimberiae operon expression. Strains recovered from these urine samples, however, were shown capable to switch the fim operon to the ON position after culture in broth medium. Type ۱ fimbrial expression and flagella motility are probably representative of an essential dynamic interplay between bacterial adhesion and motility. The strains present in urine samples but nonattached to the epithelium are inactive for type ۱ fimbriae expression.

Keywords:

Escherichia coli , Serotyping , PCR