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Abstract :
[en] Enteropathogenic Escherichia coli (EPEC) are subdivided into “typical (t) EPEC” producing the “Bundle Forming Pili” (BFP) type 4 fimbriae and isolated from humans, and “atypical (a) EPEC” not producing the BFP and isolated from animals and humans. aEPEC are indeed quite frequently associated with diarrhoea in young calves. Although calf aEPEC can belong to the O26:H11 and O80:H2 serotypes, most serotypes remain unidentified (Mainil and Fairbrother, 2014). The general purpose of this project is to identify the serotypes of aEPEC isolated from diarrheic calves and to compare them with calf and human Shiga toxin-producing E. coli (STEC) belonging to the same serotypes.
The specific purpose of the study reported here was therefore to test 41 and 35 un-typed aEPEC and STEC for five non-conventional O serogroups (O123/186, O156, O177, O182, O183) recently identified in 5 calf aEPEC and STEC that previously tested negative, using two multiplex PCRs and to confirm the positive results with the uniplex PCRs. Twenty-three aEPEC (56%) tested positive with the multiplex and uniplex PCRs: 9 for the O123/186 serogroups (these two serogroups cannot be distinguished by PCR), 12 for the O177 and 2 for the O182 serogroups. In addition, the PCRs also detected 8 STEC (23%): 1 for the O123/186, 2 for the O156, 1 for the O177, 2 for the O182 and 2 for the O183 serogroups. Besides the classical O26:H11 serotype, calf aEPEC belong to several non-conventional serogroups/-types, like O80:H2 and those identified in this study, though still other serogroups/-types remain to identify. The further steps are: (i) comparison of these calf aEPEC with calf and human STEC belonging to the same serogroups/-types; (ii) investigation to answer the following question: are these calf aEPEC true aEPEC, or STEC derivatives that have lost stx genes, or STEC precursors that could acquire stx genes in the future? (iii) identification of still other serogroups/-types amongst the remaining un-typed calf aEPEC.
