Commensal and pathogenic Escherichia coli use a common pilus for epithelial cell colonization. G-quadruplex interactive compounds as broad spectrum antimicrobials.

Abstract

Diarrheagenic Escherichia coli (E. coli) and Neisseria sp. are Gram-negative pathogens that cause high disease burden, especially in low-income countries.Enterohemorrhagic E. coli (EHEC) and enteropathogenic E. coli (EPEC) are a subset of E. coli that can cause disease. The sequence of E. coli genomes revealed the presence of at least 16 putative pili operons, it is still unknown if they encode functional pili. Several adhesins have been described in EPEC; however it is still an enigma if EHEC produces pili. In this dissertation the identification and characterization of a new pilus in EHEC is described. The main pilin subunit is encoded in the yagZ gene (renamed ecpA) and is present in all E. coli. We demonstrate ECP production in 137 (70%) of a total of 197 ecpA+ strains representing different categories of E. coli. Isogenic ecpA mutants of EHEC O157:H7 and fecal commensal E. coli showed significant reduction in adherence to cultured epithelial cells. Adherence levels were not hampered after single mutation of ecpA in EPEC. Only after the removal of the known EPEC adhesins such as BFP and intimin we were able to see significant reduction in adherence levels. In sum, ECP is the first pilus of EHEC O157:H7 with a potential role in host epithelial cell colonization. However, EPEC-ECP plays a secondary role in adherence.Since 2007 the CDC recommends only third generation cephalosporins as the elected treatment for Neisseria gonorrhoeae infections. There is an urgent need to search for new drug targets and to development new drugs. Regions rich in guanine in the DNA are able to form secondary structures known as G-quadruplexes. It has been shown that G-quadruplexes are involved in control of transcription, translation and telomere elongation in mammalian cells. G-quadruplex interactive compounds are being developed for cancer therapy. G-quadruplex motifs are also present in bacteria. The fact that G-quadruplex interactive compounds can impair cancer development leads us to hypothesize that these drugs can be used as antimicrobials. This work presents evidence for the potential of G-quadruplex interactive compounds as broad-spectrum antimicrobials.