F17-like fimbriae from an invasive Escherichia coli strain producing cytotoxic necrotizing factor type 2 toxin

Abstract

The F17b fimbriae encoded by the transmissible virulence plasmid Vir, also coding for cytotoxic necrotizing factor type 2, were characterized. A 5.7-kb region of Vir mediates in vitro N-acetylglucosamine-sensitive adhesion to calf intestinal villi. Sequence analysis revealed that this region codes for a structural subunit and an adhesin closely related to the F17-A and F17-G proteins encoded by the F17 fimbrial gene cluster. The F17b-A gene presents an open reading frame of 540 bp encoding a polypeptide of 180 amino acids with a putative signal peptide of 21 residues. The mature protein shows an identity of 74% with the F17-A structural subunit. This 20-kDa protein is recognized by antiserum directed against F17 fimbriae. The F17b-G gene shows an open reading frame of 1,029 bp encoding a polypeptide of 343 amino acids with a putative signal peptide of 22 residues. The F17b-G polypeptide exhibits 95% identity with the F17-G adhesin. The functional homology of the gene products was further confirmed by demonstrating that mutants in the F17-A gene can be complemented by the F17b-A gene and vice versa. These results prove that fimbriae belonging to the F17 family are also found on pathogenic Escherichia coli strains other than enterotoxigenic isolates producing heat-labile or heat-stable enterotoxin.

A new cytolethal distending toxin (CDT) from Escherichia coli producing CNF2 blocks HeLa cell division in G2/M phase

“…This region is a pathogenicity island (PAI) inserted near the pheR tRNA gene (Swenson et al, 1996). Conversely, most of the CNF2-producing strains are not haemolytic and produce a F17 fimbrial adhesin which mediates adhesion to calf villi (El Mazouari et al, 1994;Oswald et al, 1991). Certain CNF2-producing strains may also produce an AFA-like adhesin (Mainil et al, 1997).…”

“…Certain CNF2-producing strains may also produce an AFA-like adhesin (Mainil et al, 1997). All these factors, CNF2 and adhesins, are encoded by the Vir plasmid (El Mazouari et al, 1994;Mainil et al, 1997;Oswald et al, 1989). This plasmid is a large F-like conjugative plasmid of 140 kb which was first described in E. coli strains isolated from septicaemic calves (Lopez-Alvarez et al, 1980;Smith, 1974).…”

Association of genes encoding P fimbriae, CS31A antigen and EAST 1 toxin among CNF1-producing Escherichia coli strains from cattle with septicemia and diarrhea

“…Interestingly, CS31A was prominent among CNF1-producing strains but was not detected among bovine E. coli strains producing the closely related CNF2 toxin [10]. In contrast, previous studies have demonstrated that CNF2 toxin is often associated with F17 ¢mbriae [3,10].…”

“…The cytotoxic necrotizing factor type I (CNF1) is a chromosome-encoded toxin produced by E. coli strains isolated from diarrhea, septicemia or UTI in humans, piglets or calves [2]. The cytotoxic necrotizing factor type II (CNF2) expressed by E. coli strains isolated from calves and lambs with enteritis or bacteremia is highly homologous to CNF1 [3]. More recently, a low-molecularmass peptide named enteroaggregative E. coli heatstable enterotoxin I (EAST 1) produced by enteroag-gregative E. coli (EAggEC) has been described [4].…”

Characterization of Necrotoxigenic Escherichia coli (NTEC) Strains Isolated from Healthy Calves in Poland

“…Whereas CNF1 is encoded by the chromosome (Falbo et al, 1993), CNF2 is determined by a Vir plasmid . At least two other virulence markers are encoded by Vir plasmids along with CNF2: an F17-related ®mbria, which mediates the adherence of bacterial cells to calf intestinal villi (Oswald et al, 1991;El Mazouari et al, 1994) and a new type of ®mbrial adhesin, called AFA (Mainil et al, 1997). The role of CNF1 and CNF2 in the pathogenesis of E. coli infections is still uncertain but their necrotic and lethal properties in vivo and their ability to alter the cytoskeleton of cultured cells in vitro suggest that both cytotoxins may be true virulence factors Pohl et al, 1992).…”