Occurrence and structure of cyclic Enterobacterial Common Antigen in Escherichia coli O157:H−

Two cyclic forms of the Enterobacterial Common Antigen were isolated from Escherichia coli O157:H−. These antigenic determinants were purified from the biomass through extensive chemical, enzymatic and chromatographic procedures whereas MALDI MS spectrometry indicated their cyclic nature with a polymerization degree of 4 or 5. The two species, denoted as ECACYC-4 and ECACYC-5, were assigned by NMR and showed no further substitution with other appendages such as acetyl groups as usually described for similar cyclic antigens from other Enterobacteriaceae.

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► Escherichia coli growth on agar.
► Water phase of the hot water/phenol extraction.
► Two cyclic forms of the Enterobacterial Common Antigen.
► E. coli growth in liquid medium.
► No Enterobacterial Common Antigen observed.