Molecular investigation of tRNA genes integrity and its relation to pathogenicity islands in Shiga toxin-producing Escherichia coli (STEC) strains

Abstract

AbstracttRNA genes are known target sites for the integration of pathogenicity islands (PAI) and other genetic elements, such as bacteriophages, into bacterial genome. In most STEC (Shiga toxin-producing Escherichia coli), the PAI called LEE (locus of enterocyte effacement) is related to bacterial virulence and is mostly associated to the tRNA genes selC and pheU. In this work, we first investigated the relationship of LEE with tRNA genes selC and pheU in 43 STEC strains. We found that 28 strains (65%) had a disrupted selC and/or pheU. Three of these strains (637/1, 650/5 and 654/3) were chosen to be submitted to a RAPD-PCR technique modified by the introduction of specific primers (corresponding to the 5'end of genes selC and pheU) into the reaction, which we called "anchored RAPD-PCR". The PCR fragments obtained were transferred onto membranes, and those fragments which hybridized to selC and pheU probes were isolated. One of these fragments from strain 637/1 was partially sequenced. An 85-nucleotide sequence was found to be similar to the cfxA2 gene that encodes a beta-lactamase and is part of transposon Tn4555, a pathogenicity island originally integrated into the Bacteroides genome.

<p>Ribaxamase, an Orally Administered β-Lactamase, Diminishes Changes to Acquired Antimicrobial Resistance of the Gut Resistome in Patients Treated with Ceftriaxone</p>

“…49 Furthermore, the cfxA genes in Bacteroides are associated with the Tn4555 transposon which could facilitate gene transfer to other microbiota species in the gut. 50 Indeed, Tn4555 has been identified in Shiga toxin producing E. coli 51 and cfxA genes are associated with β-lactam resistance in oral pathogens Prevotella and Capnocytophaga. 52,53 The two vancomycin resistance genes, vanSD and vanRD, that displayed increased frequency in placebo vs ribaxamase patients, are variants of the vanS/vanR two component regulator system that result in constitutive expression of vanD and confer high-level vancomycin resistance in E. faecium, E. faecalis and E. avium.…”