Human megbetegedeseket okozo Escherichia coli torzsek patogenetikai jellemzese.

摘要

Pathogenic Escherichia coli strains can cause severe illnesses in significant number worldwide. They can be categorized in different groups by the harbouring virulence factors: EPEC, VTEC, EHEC, ETEC, EIEC, EAggEC and DAEC, which are responsible for diarrheal diseases, while the UPEC and MAEC for extraintestinal manifestations.;The aim of this study was to introduce molecular methods in the National Reference Laboratory of Enteral Pathogen Bacteria to enhace the efficacy of the diagnostics of pathogenic Escherichia coli. In the course of my work I have adapted and optimized PCR methods using previously collected E. coli strains, so I could detect the genes of intimin ( eae), enterohaemolysin (ehlyA), enteroaggregative heat-stable toxin (ast1), ETEC heat-lable enterotoxin ( elt), ETEC heat-stable enterotoxin (est) and the invasion-related plasmid (Ipa). Besides the serotyping these assays seem to be useful tools to classify the isolates into different pathogroups. The next step of the development of laboratory diagnostics was to exchange the tube-agglutination for microplate-agglutination. The latter is a simplier, more sensible as well as more economical method than the conventional tube agglutination Widal test. Application of these new molecular methods enabled the characterization of all the VTEC strains isolated from 2000 to 2006 in a retrospective study. Our results reflected expected values in the field of serogroup distribution as well as of related verotoxin subtypes. The most frequent group proved to be the O157 type (58%), while the most severe outbreaks were due to vt2 and vt2c toxintypes producing E. coli strains. Surprisingly the two described HUS cases were not caused by O157 but vt2-producing O26 strains. Five non-O157 isolates harboured ast1 gene often described in the literature. We have observed no association between the temporal and geographical origin and the PFGE patterns among the isolates. The results of the serotyping suggest that the verotoxigenic E. coli strains are underrepresented in Hungary, however we expect to reveal their etiologic role in more cases after improving the surveillance systems.;The other purpose of our investigations was to determine the serotypes of ESBL-producing strains. The results showed that two groups: O25 and O15 appeared in significant by high numbers. Much of the O25 isolates were confirmed by PCR to belong to the worldwide- spread O25b-ST131 clone.