A study of enteroaggregative Escherichia coli (EAggEC) which was recently reported as a causative agent of diarrhea was attemped, by isolating these organisms from the fecal samples collected from sporadic diarrhea patients in Miyazaki Prefecture during the period from January 1993 to April 1998, and by investigating several characteristics of the isolates.
By using the PCR method targetting aggR gene which was a transcriptional activator of aggregative adherence fimbria I expression, thirty four strains of aggR (+)-Escherichia coli (E. coli) were detected from 2, 652 fecal samples. Twenty nine of these 34 isolates were confirmed as EAggEC by demonstration of aggregative adherence to HEp-2 cells, and the other 5 isolates were not EAggEC because they showed negative adherence to HEp-2 cells. The above mentioned, aggR-PCR method revealed that there were a few non-EAggEC strains with aggR gene.
It has been reported that aggregative adherence fimbriae are encoded by the plasmid of about 60Md. All of the 29 EAggEC isolates possessed plasmids of about 50Md or more, and these plasmids were suggested to relate to aggregative adherence fimbriae. Sixteen (55%) of the 29 isolates were classified serologically into two serotypes, O111: H21 and 0126: H27, and the other 13 isolates were classified into ten groups or more which included a few strains in a group. EAggEC heat-stable enterotoxin 1 (EAST1) gene was demonstrated in nineteen of 29 isolates. In drug susceptibility test, 72%, 59% and 21% of the 29 isolates showed resistance to Ampicillin, Cefazolin, and Streptomycin, respectively.