All are true about EHEC except -

Ans. is 'a' i.e., Sereny test is positive . Sereny test is done for enteroinvasive E. coli (EIEC). "Although screening for E. coli strains that do not ferment sorbital and subsequent serotyping for 0 157 constitute the most common method presently used to detect STEC (EHEC), testing for shiga toxin or toxin genes is more senstive, specific, and rapid. The latter approach offers another advantage as well it detects both non - 0 157 strains and sorbitol fermenting strains of 0 157, which otherwise are difficult to identify ". From above lines it is clear that EHEC has both sorbital fermenting and sorbital nonfermenting strains. . EHEC elobrates shiga like toxin and can cause HUS, especially in young children and the elderly.