A direct polymerase chain reaction method to EC cultured broth (named EC-PCR) for screening detection of enteropathogenic
E. coli (ETEC, VTEC and EIEC) in foods and feces is described.
Eleven
E. coli strains belonging to three groups (4ETEC: 06, 025, 0128, 0148; 4VTEC: 026, 0111, 0145, 0157; and 3EIEC: 028ac, 0124, 0164) were used for this study. Four pairs of oligonucleotide primers homologous to LT, ST, VT and EIEC genes were used in combination. The culture condition at 37-43°C for 16-20 h in EC broth was most suitable for the EC-PCR method, and no cross readings were observed with other bacteria, substances in meats or feces.
After a 20-h enrichment step, it was possible to detect fewer than 10 to 10
2 bacteria per g of the aritificially inoculated meat.
E. coli was easily detected because of low contamination with other bacteria which disturb the detection of
E. coli. However, in feces, it ranged from 10
3 to 10
4 cfu per g. The large number of bacteria with feces are the main limiting factor of the EC-PCR detection assay. All
E. coli strains examined were detected from all the enrichment cultures on both the EC-PCR and the culture methods. In two sporadic cases and two food poisoning cases, the enteropathogenicity of
E. coli isolates from patients was rapidly judged by the EC-PCR method.
These findings were consistent with those of the culture method. Thus, the findings suggest that the EC-PCR method is a suitable, sensitive and rapid method for detection of the potentially enteropathogenic
E. coli.
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