AUTHOR=Stephenson Stacy Ann-Marie , Brown Paul D. 

TITLE=Epigenetic Influence of Dam Methylation on Gene Expression and Attachment in Uropathogenic Escherichia coli

JOURNAL=Frontiers in Public Health

VOLUME=Volume 4 - 2016

YEAR=2016

URL=https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2016.00131

DOI=10.3389/fpubh.2016.00131

ISSN=2296-2565

ABSTRACT=Urinary tract infections (UTI) are among the most frequently encountered infections in clinical practice globally. Predominantly a burden among female adults and infants, UTIs primarily caused by uropathogenic Escherichia coli (UPEC) results in high morbidity and fiscal health strains. During pathogenesis, colonization of the urinary tract via fimbrial adhesion to mucosal cells is the most critical point in infection and has been linked to DNA methylation. Furthermore, with continuous exposure to antibiotics as the standard therapeutic strategy, UPEC has evolved to become highly adaptable in circumventing the effect of antimicrobial agents and host defenses. Hence, the need for alternative treatment strategies arises. Since differential DNA methylation is observed as a critical precursor to virulence in various pathogenic bacteria, this study sought to assess the influence of the DNA adenine methylase (dam) gene on gene expression and cellular adhesion characteristics in UPEC and its potential as a therapeutic target. To assess the influence of dam on attachment and fluoroquinolone resistance, selected wild-type UPEC strains were compared with their dam mutants and qnrA and dam complemented transformants in terms of fitness, antimicrobial susceptibility, biofilm formation, recA and papI gene expression and attachment to HEK-293 and HTB-9 cell monolayers. DNA methylation was notably absent among dam mutants, and phenotypic characteristics of wild type strains were restored in dam complement strains. While there were observed deficiencies in cell growth, antimicrobial resistance and biofilm formation among dam mutants, increases in gene expression and adherence to mammalian cells were detected as a factor of SOS induction in the absence of methyl-directed mismatch repair. These data underscore the critical role of dam-mediated DNA methylation and gene expression in UPEC. Together, these findings suggest that the application of Dam inhibitors against UPEC or utility of dam-deficient UPEC strains as attenuated live vaccines might be problematic. Further investigations will shed light on the post-transcriptional influence of dam on the regulatory network of virulence genes central to pathogenesis.