Necrotoxic Escherichia coli (NTEC) are relatively new group of pathogenic E. coli first described by CAPRIOLI et al. (1983) in diarrheal children. The necrotic toxin produced by these strains has been termed cytotoxic necrotic factor (CNF). Since then the NTEC bacteria were found in several animal species (mostly porcine, bovine, ovine and canine) and in man in several countries of Europe and North America as well as in Japan and there could be two types of this toxin distinguished (CNF1 and CNF2), but so far there have been no report about such strains from Central Europe. In this study 1215 E. coli strains of human (202), porcine (452), bovine (150), avian (303), lapine (102) and canine/feline (6) strains were tested for the presence of genes responsible for production of cytotoxic necrotic factors (CNF1 and CNF2) using PCR. Most of the strains were isolated in Hungary, but an essential part of the porcine, bovine, lapine and canine/feline strains were isolated in Austria and in the Czech Republic. Selected CNF1+ strains were tested for production of toxin using in vitro (HeLa cell culture) and in vivo (rabbit skin) systems. Most of the CNF+ strains were also tested for the presence of adhesive fimbrial genes (pap, sfa) and for afimbrial adhesin (afa) genes by PCR. In case of porcine enteric CNF+ strains the presence of F4 and F18 fimbriac was also tested. The CNF1+ strains were further tested for the presence of the genes of a newly discovered cytolethal distending toxin (CDT). Results of the CNF studies are summarized in Table 3., indicating that CNF1+ strains could be detected among human porcine and canine/feline E. coli. Antibiotic resistance of the NTEC strains did not show any typical pattern and the multiresistance (resistance against 3 or more drugs) was most frequent among porcine NTEC strains (66,6%), followed by human (23%) and bovine (15%) strains. As a result of further characterization of CNF1+ strains, the genes of P and S fimbriae were detected in most human and porcine NTEC strains (Figure 2.). CDT genes were detected in several human, porcine and bovine NTEC strains. Based on these latter observations 202 porcine E. coli (enteric, postweaning diarrhea and oedema isolates) were tested for CDT and further 6 non-NTEC strains were detected as CDT+. The serotypes and virulence factors of several porcine NTEC strains were the same as those of human strains. Consequently, the potential zoonotic significance of NTEC strains from pigs (and possibly those from other animals) should be pointed out. As a conclusion, these studies represent the first organized effort to explore the presence and characteristics of NTEC strains in Hungary (and In Central Europe) in animals and man as well as they represent the first indication of possible significance of CDT in postweaning enteric diseases of swine.
|Number of pages||8|
|Journal||Magyar Allatorvosok Lapja|
|Publication status||Published - Dec 1 2000|
ASJC Scopus subject areas