Molecular profile and genetic diversity of cytolethal distending toxin (CDT)‐producing Escherichia coli isolates from diarrheal patients

Abstract

Cytolethal distending toxin (CDT)-producing Escherichia coli strains are considered to be a heterogeneous group of E. coli. In the present investigation, 20 CDT-producing E. coli strains, which had already been shown to be cytotoxic necrotizing factor (cnf) gene positive, were selected by PCR. Since these strains proved to be CDT producers on CHO cells but were partially characterized by PCR, they were subjected to PCR analysis to amplify the complete coding region of cdt genes. Moreover, the genetic relatedness of these strains was examined by pulse field gel electrophoresis (PFGE). To check the extent of homogeneity of these strains at the chromosomal level, tRNA insertion site analysis was performed. The CDT-producing E. coli strains under investigation were shown to be heterogeneous and diverse in regard to their genetic analysis. This observed diversity could be an independent acquisition of virulence genes that might occur through horizontal gene transfer by mobile genetic elements. This conclusion is based on the fact that data shown by tRNA insertion site analysis revealed that there is no common pattern of insertion among these isolates although they do share a common trait of CDT production.

Preliminary virulence genotyping and phylogeny of Escherichia coli from the gut of pigs at slaughtering stage in Brazil

“…In this work, 2.2% of strains were positive for cdtB. Contrary to preceding studies on human and cattle E. coli (Bouzari et al, 2005;Clark, Johnson, Easy, Campbell, & Rodgers, 2002;Oloomi & Bouzari, 2008), none of the CDT harbouring isolates were positive for eae, stx or cnf genes. Similarly, Fratamico, Bhagwat, Injaian, and Fedorka-Cray (2008) asserted a low prevalence (0.46%) of cdt genes in stx positive E. coli from faeces of five months old pigs.…”

“…Cytotoxic Necrotizing Factor (CNF) and Cytolethal Distending Toxin (CDT) positive E coli have also attracted the attention of research efforts because of their potential animal and human health significance (Kadhum, Ball, Oswald, & Rowe, 2006). The association of CNF and CDT is reported in several previous investigations and their acquisition is supposed to occur by horizontal gene transfer or through a phage, which provides genetic diversity and versatility to strains (Friedrich et al, 2006;Oloomi & Bouzari, 2008).…”

In Silico Signature Prediction Modeling in Cytolethal Distending Toxin-Producing Escherichia coli Strains

“…The heterogeneous nature of CDT-producing strains might arise from horizontal gene transfer through mobile genetic elements. These genetic exchanges that occur in bacteria provide genetic diversity and versatility [19]. …”

Horizontal Gene Transfer and the Diversity of <i>Escherichia coli</i>

“…EHEC strains also possess a LEE which has 54 ORFs; 41 are common to the LEE of both EPEC and EHEC. The remaining 13 ORFs belong to a putative prophage, designated 933L (P4-like prophage), which is located close to the selC locus [7]. In contrast to the LEE of EPEC, cloned EHEC LEE is not able to induce A/E lesions.…”

“…Alphahemolysin belongs to the RTX toxins with pore-forming activities in erythrocytes and other eukaryotic cells. The alpha-hemolysin operon (hly gene) of UPEC can be located either on a plasmid or on the chromosome [7].…”