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Fecal isolates of E. coli strains which were collected from healthy domestic animals belonging to seven different species (cattle, sheep, goats, pigs, chickens, dogs and cats) were examined. These animals were kept in 15 different locations in Berlin (Geier 1992). The examined E. coli strains produced verotoxin (VT) and haemolysin (Hly) in different combinations. Both, verotoxigenic and haemolytic as well as non-verotoxigenic but haemolytic E. coli are isolated from farm and pet animals. The aim of this work was to study the relationships between these different typs of E. coli. The examined 301 E. coli strains in this work distinguish phenotypical and genotypical from each other, which does not seem to suggest a relationship. Of the 301 E. coli strains which were examined, 126 showed a combination of VT+ and Hly+, 81 strains were VT+ and Hlyand 94 strains were VT- and Hly+. The characteristics (Hamagglutination, Colicin, Aerobaktin, Auxotrophie, Serotype, PAGE, PFGE and ET) are more frequently associated with strains belonging to the group of verotoxigenic and haemolytic E. coli than with strains which are either VT or Hly negative. The expression of the examined characteristics was independent of the location and species of the animals and was not closely associated with the serotype of the E. coli strains. These results could indicate that verotoxin and haemolysin producing strains are have an advantage, when colonizing their hosts as opposed to the other examined strains.Regarding the species, from which the strains were isolated, some phenotypical and genotypical characteristics of bacteria remained constant, thus could making it possible o identify strains. Thie is especially true for characteristics e.g. the MRHA of the canine E. coli strains or the prototrophy of strains wich were isolated from chicken, which remained constant, regardless of location and serotype.It is generally assumed that plasmid-encoded characteristics are more varied than chromosomal-encoded characteristics. The main serotypes are divided into four groups which differ in their expression of phenotypical and genotypical traits. In the first group (e.g.: 021:K5:H14 and 070:H11) are types among the main serotypes which express many common phenotypical and genotypical characteristics, and which may be related. In the second group are serotypes which express a wide variation of phenotypical characteristics (e.g.:
0108:H9, 0113:H21) but the PFGE pattern of them were location related constant. The strains of the third group within the main serotypes (e.g.: 05:H-, 077:H4) express the phenotypical characteristics constant, but the PFGE pattern are variable. Whereas the fourth group of serotype strains (e.g.: 091:H-) express a wide variation of phenotypical and genotypical characteristics.In an effort to evaluate the relationship of strains (Serotype, PAGE, PFGE, ET, MRAH, Colicin, Aerobactin and Auxotrophie), the examined characteristics of strains is of limited use. A relationship of E. coli stains can only be proven and confirmed with the aid of PFGE. A location related relationship could be established in many cases (e.g.: 0108:H9, 0113:H21, OX3:H8) only with he aid of PFGE. The PFGE is a very good method for exactcharacterisation of bacteria.