Characteristics of Escherichia coli strains belonging to enteropathogenic E. coli serogroups isolated in Italy from children with diarrhea

Abstract

Fifty-five Escherichia coli strains belonging to enteropathogenic E. coli (EPEC) serogroups were examined for phenotypic and genetic factors associated with virulence. The strains were isolated in Italy from children with diarrhea and identified as EPEC by clinical laboratories using commercially available antisera. O:H serotyping showed that 35 strains (27 of O26, O111, and O128 serogroups) belonged to 11 serotypes considered to be classical EPEC O:H serotypes. The other 20 isolates were classified as 15 nonclassical EPEC O:H serotypes. All the potential EPEC virulence factors associated with bacterial adhesion (localized adherence, fluorescentactin staining test positivity, presence of the attaching and effacing [eaeA] gene), the production of verotoxin, and the positivity with the enterohemorrhagic E. coli probe were significantly more frequent among isolates belonging to classical than nonclassical serotypes. Strains displaying an aggregative adhesion and hybridizing with the enteroaggregative DNA probe were found in serogroups O86, O111, and O126. Verotoxin-producing isolates belonged to serogroups O26, O111, and O128. Only one of the isolates hybridized with the EPEC adherence factor (EAF) probe, but 33 strains gave positive results with the eae probe, confirming that the former is more suitable in epidemiological studies in European countries. These results indicate that up to 75% of strains identified as EPEC by commercial antisera may possess potential virulence properties and/or belong to classical EPEC O:H serotypes and suggest that O grouping is still a useful diagnostic tool for presumptive identification of diarrheagenic E. coli in clinical laboratories.

Virulence-related DNA sequences and adherence patterns in strains of enteropathogenic Escherichia coli

“…EAF plasmids have been implicated in the initial adhesion of EPEC strains to intestinal mucosal surfaces [22], but data concerning the association between LA and EAF plasmids are varied. Results reported from Italy and UK [15,21] have shown low circulation of EAF plasmids among strains showing LA, whereas in a study conducted in Sao Paulo 100% association between LA and EAF had been observed [17]. In the present study this association was observed in 76% of the isolates, but similar to the data reported by Rosa et al [23] some LA strains were negative for all three genetic markers described for EPECs ( Table 2).…”

“…Comparison of the circulation rate of DNA sequences associated with A/E lesions and EAF plasmid in Italy [15] and those previously reported from UK [21] has led to the conclusion that eae might be a more suitable marker for epidemiological studies in Europe, while the EAF-related probe has been proposed as more appropriate for developing countries. However, in the present study in which isolates were classi¢ed, as EPEC on the basis of serogrouping and serotyping was not performed, no signi¢cant di¡erence between the circulation rate of EAF and eae sequences was observed (EAF = 44.4%, eae = 50%).…”

Role of non-O157 VTEC

“…Serotype 026:H11 appears to be the predominant VTEC serotype of this serogroup, and isolations of this serotype have been reported from Germany (Bockemuhl et al 1992), Japan (Kudoh et al 1994), Australia (Goldwater and Bettelheim 1994) and the Czech Republic (Bielaszewska et al 1994(Bielaszewska et al , 1996 from cases of HUS. In addition, Thomas et al (1993Thomas et al ( , 1996 and Scotland et al (1988) in the United Kingdom reported cases of diarrhoea, bloody diarrhoea and HUS, and Pierard et al (1994and Pierard et al ( , 1997, Giammanco et al (1996), Huppertz et al (1996 and Czirok and Herpay (1995) reported cases of diarrhoea from Belgium, Italy, Germany, Hungary and Denmark, respectively. Caprioli and Luzzi (1995) and Farina et al (1996) reported cases of diarrhoea and HUS from Italy.…”

“…As in groups 026 and 0111, the 0128 group has for many years been associated with EPEC Isolates of this group from human disease are predominantly of serotypes 0128:H-and 0128:H2. VTEC 0128:H-has been isolated from human cases of diarrhoea and HUS in Asia (Tamura et al 1996) andGermany (Bockemtihl et al 1992), and VTEC 0128:H2 has been isolated from cases of diarrhoea in Belgium (Pierard et al 1994(Pierard et al , 1997, Italy (Giammanco et al 1996), Japan (Kudoh et al 1994) and New Zealand (Brooks et al 1997). In addition, VTEC 0128:H7 has been isolated from a case of HUS in the United Kingdom (Thomas et al 1996), VTEC 0128:H8 from a case of diarrhoea in Asia (Tamura et al 1996) and VTEC 0128:H45 from a case of diarrhoea in the USA (Strockbine et al 1997).…”

Attaching and effacing Escherichia coli isolates from Danish children: clinical significance and microbiological characteristics

“…The pathogenic ability of some of the classical EPEC serotypes has been demonstrated in several studies [5–7], and classical EPEC strains are well‐recognised as being diarrhoeagenic. However, their diarrhoeagenic potential cannot be inferred from the serotype itself, because strains belonging to the classical EPEC serotypes may not necessarily possess the virulence properties characteristic of EPEC [8–13]. Classical EPEC eae ‐positive O:H serotypes are grouped into typical EPEC, possessing a large virulence plasmid (the EPEC adherence factor (EAF) plasmid), and atypical EPEC (EAF‐negative) [14].…”