Fachbereich Veterinärmedizin



    Molekulare Charakterisierung und Typisierung von Escherichia coli-Stämmen der Serogruppe O78 aus Durchfallgeschehen von Rind und Kalb (2003)

    Schüffner, Claudia
    Berlin: Pro Business, 2003 — VI, 138 Seiten
    ISBN: 3-937343-70-9
    Institut für Mikrobiologie und Tierseuchen

    Robert-von-Ostertag-Str. 7-13
    Gebäude 35
    14163 Berlin
    +49 30 838 51840 / 51843

    Abstract / Zusammenfassung

    Summary E. coli of the serogroup 078 are regarded as a typical cause for septicaemia in cattle. During the last years E. coli, which reacted with 078:K80 antiserum on live slide agglutination, were increasingly isolated in acute diarrhoea cases. In the present study the virulence properties of 117 of such field isolates originating from cattle and calves were characterized molecularbiologically. By means of PCR and DNA hybridization the field isolates were screened for the presence of 17 defined virulence genes [est, elt, f5, f41, stx, eae, hlyA, hlyEHEC, fyuA, irp2, iucD, astA, cdt-IIB, cnf-1/2, pssA, tia, ipaC] which are associated with intestinal pathogenicity (toxicity, adhesion, invasiveness) in human E. coli isolates. Furthermore, a special diagnostic technique (Multiplex-PCR) which is also applicable for additional epidemiological surveys was developed. Prior to molecularbiological characterization, the serogroup of the 117 isolated E. coli was determined bacteriologically- serologically using boiled cultures. The result was that only 22 (18,8%) of the E. coli field isolates could be assigned to serogroup 078. The remaining isolates, classified as non-078- E. coli, belonged to various serogroups. For further characterization, the 078 field strains were subjected to genomic affinity analysis. Additionally, bovine 078 isolates from diarrhoea cases were phenotypically screened in a cell culture model (gentamycin resistence test) for adhesion properties and invasiveness. Virulence genes (est, elt, f5, and f4l) characteristic for enterotoxic E. coli (ETEC) were not demonstrated in any of the 117 examined bovine E. coli isolates. In the non-078-E. coli, eae (4,2%), stx (3,2%), hlyA (1,1%) hlyEHEC(4,2%) and ipaC (1,1%) were seldom demonstrated. Virulence genes astA, cdt-IIIB, cnf-1/2, fuA, irp2, pssA, tia and iucD were isolated in both 078-E. coli as well as non-078-E. coli. Virulence genes fyuA and irp2 were only demonstrated in combination. In both, 078- and non-078-E. coli the toxin gene astA (63,6%/24,4%) as well as the iron acquiring genes fuA, irp2 (59,1%/33,7%) and meD (72,7%/53,7%) were most frequently encountered. In 078-E. coli, cdt-IIIB (13,6%), cnf-1/2 (13,6%,pssA (22,7%) and tia (22,7%) were more common than in non-078-E. coli. Close genetic relationship of the isolated 078 strains was demonstrated following analysis of cional affinities. It was also demonstrated that 6 strains belong to one clone. When comparing bovine 078 isolates with the human 078 reference strain E38 as well as Salmonella control strains in Madin Darby bovine kidney cell cultures, bovine 078-E. coli demonstrated the ability of adhesion properties and invasion. The results demonstrate the multiple virulence properties of bovine E. coli of serogroup 078 isolated from diarrhoea cases. Although primarily genotypic characteristics of enteroaggregative (EAEC) and necrotoxic (NTEC) E. coli were demonstrated, the examined 078 strains can not be assigned to any of the described human enteropathogenic E. coli groups. The data rather indicate the presence of group-overlapping properties, with the result that the differentiation from septicaemic 078-E. coli is impeded as well. The entire results indicate that also the enterogenic 078-E. coli examined constitute a possible anthropozoonotic risk, as is already described for septicaemic 078-E. coli.