ISOLATION OF SHIGATOXIGENIC ESCHERICHIA COLI SEROGROUPS O157 AND O111 BY

Abstract

The objective of this study was to verify the isolation tax by immunomagnetic separation (IMS) of strains of Shigatoxin producing Escherichia coli serogroups O157 and O111 in dairy farms in Jaboticabal-SP, Brazil, starting from positive samples, detected by the polimerase chain reaction (PCR). Initially feces, water and milk samples were submitted to a selection process, through a PCR multiplex, in order to detect the presence of sequences stx₁, stx₂ and eae. All of the positive samples in this first phase were submitted to a new PCR reaction targeting the sequences rfb O157 and rfb O111, what resulted in, respectively, 14.8% and 0.2% of positive feces samples for those serogroups and 2.4% and 10.0%, respectively, of water and milk positive samples for the serogroup O157. Those PCR positive samples were submitted to IMS, isolated strains of E. coli O157, were obtained of only 53.6% of the feces samples. There were no isolated strains of E. coli O157 from water and milk samples, they were not also isolated strains of E. coli O111 from any sample type. In conclusion, IMS, although more sensitive than other techniques, still doesn’t allow the isolation of E. coli O157 and O111 strains, of 100% of the PCR positive samples.

KEY WORDS: E coli O111, E. coli O157, immunomagnetic separation, PCR, shigatoxin.