Molecular Analysis of Cytolysin A (ClyA) in Pathogenic Escherichia coli Strains

Abstract

Cytolysin A (ClyA) of Escherichia coli is a pore-forming hemolytic protein encoded by the clyA (hlyE, sheA) gene that was first identified in E. coli K-12. In this study we examined various clinical E. coli isolates with regard to the presence and integrity of clyA. PCR and DNA sequence analyses demonstrated that 19 of 23 tested Shiga toxin-producing E. coli (STEC) strains, all 7 tested enteroinvasive E. coli (EIEC) strains, 6 of 8 enteroaggregative E. coli (EAEC) strains, and 4 of 7 tested enterotoxigenic E. coli (ETEC) strains possess a complete clyA gene. The remaining STEC, EAEC, and ETEC strains and 9 of the 17 tested enteropathogenic E. coli (EPEC) strains were shown to harbor mutant clyA derivatives containing 1-bp frameshift mutations that cause premature termination of the coding sequence. The other eight EPEC strains and all tested uropathogenic and new-born meningitis-associated E. coli strains (n ‫؍‬ 14 and 3, respectively) carried only nonfunctional clyA fragments due to the deletion of two sequences of 493 bp and 204 or 217 bp at the clyA locus. Expression of clyA from clinical E. coli isolates proved to be positively controlled by the transcriptional regulator SlyA. Several tested E. coli strains harboring a functional clyA gene produced basal amounts of ClyA when grown under standard laboratory conditions, but most of them showed a clyA-dependent hemolytic phenotype only when SlyA was overexpressed. The presented data indicate that cytolysin A can play a role only for some of the pathogenic E. coli strains.

A novel PhoP-regulated locus encoding the cytolysin ClyA and the secreted invasin TaiA of Salmonella enterica serovar Typhi is involved in virulence

“…By comparative genomic hybridization, serovars Montevideo, Oranienfoburg, Sendai and Muenchen were also shown to possess these genes, although only one strain per serovar was tested (Porwollik et al, 2004). The presence of clyA, by itself, has been observed in E. coli, in both pathogenic and K-12 strains (Ludwig et al, 2004). BLAST analysis with the nucleotide sequence revealed that clyA is also present in Shigella flexneri serotypes 2a and 5.…”

Bacillus cereus Nhe is a pore-forming toxin with structural and functional properties similar to the ClyA (HlyE, SheA) family of haemolysins, able to induce osmotic lysis in epithelia

“…It is also present in enteropathogenic E. coli (Ludwig et al, 2004), Shigella flexneri (Wallace et al, 2000) and Salmonella enterica serovars Typhi and Paratyphi A (Oscarsson et al, 2002). ClyA is haemolytic and causes LDH release in nucleated cells (delCastillo et al, 1997;Oscarsson et al, 1996Oscarsson et al, , 1999, which has led to the suggestion that it too mediates osmotic lysis through the formation of transmembrane homo-oligomeric pores (Eifler et al, 2006;Tzokov et al, 2006;Wallace et al, 2000).…”

Virulence Genes and Antimicrobial Susceptibilities of Hemolytic and Nonhemolytic Escherichia coli Isolated from Post-Weaning Piglets in Central Thailand

“…-hemolysin is a pore-forming cytolysin causing cells to swell and eventually burst [21]. Even though the hemolysis traits of E. coli isolates have been used as presumptive evidence of virulence, the pathogenesis involves exotoxinmediated secretion into the gut lumen [3,26,33].…”