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Abstract :
[en] Escherichia coli producing the Shiga toxins (STEC) and/or the attaching-effacing (AE) lesion (EPEC) cause enteritis and (bloody) diarrhoea in young calves and in humans. STEC and EPEC can belong 7 serogroups frequently identified worldwide: O26, O103, O111, O121, O145, O157 and O165. Beside these classical “gang of 7” serogroups, unconventional serogroups can be identified as previously demonstrated with the O80 EPEC. The use of active and specific bacteriophages as biocontrol agents seems to be a promising alternative against unconventional STEC/EPEC and have been employed for diagnostic. The first aim of this project was to identify those 6 unconventional serogroups among 76 STEC and EPEC isolated between 2008 and 2015 from diarrheic calves at ARSIA. Two triplex PCRs have been applied either for the O146_O182_O183 serogroups or for the O123/186_O156_O177 serogroups. The second objective of this project was to isolate specific bacteriophages against these unconventional serogroups from wastewater or farm slurry. So far, the first triplex PCR identified 4 O182-positive and 2 O183-positive STEC and EPEC. The second triplex PCR identified 10 O123-186-positive, 2 O156-positive and 13 O177-positive STEC and EPEC. A total of 4 potentially specific bacteriophages respectively active against O5, O123, O146, O186 were obtained. The further steps of this study will be to perform: (i) the PFGE profile comparison of the calf and healthy cattle PCR-positive STEC and EPEC between themselves and with human STEC and EPEC; (ii) the identification of still other unconventional serogroups among STEC and EPEC from diarrheic calves; (iii) the host range spectrum of the 4 potentially specific bacteriophages.
