Abstract
BackgroundRuminants, in particular bovines, are the primary reservoir of Shiga toxin-producing E. coli (STEC), but whole genome analyses of the current German ESBL-producing O104:H4 outbreak strain of sequence type (ST) 678 showed this strain to be highly similar to enteroaggregative E. coli (EAEC). Strains of the EAEC pathotype are basically adapted to the human host. To clarify whether in contrast to this paradigm, the O104:H4 outbreak strain and/or EAEC may also be able to colonize ruminants, we screened a total of 2.000 colonies from faecal samples of 100 cattle from 34 different farms - all located in the HUS outbreak region of Northern Germany - for genes associated with the O104:H4 HUS outbreak strain (stx2, terD, rfbO104, fliCH4), STEC (stx1, stx2, escV), EAEC (pAA, aggR, astA), and ESBL-production (blaCTX-M, blaTEM, blaSHV).ResultsThe faecal samples contained neither the HUS outbreak strain nor any EAEC. As the current outbreak strain belongs to ST678 and displays an en-teroaggregative and ESBL-producing phenotype, we additionally screened selected strains for ST678 as well as the aggregative adhesion pattern in HEp-2 cells. However, we were unable to find any strains belonging to ST678 or showing an aggregative adhesion pattern. A high percentage of animals (28%) shed STEC, corroborating previous knowl-edge and thereby proving the validity of our study. One of the STEC also harboured the LEE pathogenicity island. In addition, eleven animals shed ESBL-producing E. coli.ConclusionsWhile we are aware of the limitations of our survey, our data support the theory, that, in contrast to other Shiga-toxin producing E. coli, cattle are not the reservoir for the O104:H4 outbreak strain or other EAEC, but that the outbreak strain seems to be adapted to humans or might have yet another reservoir, raising new questions about the epidemiology of STEC O104:H4.
Highlights
Ruminants, in particular bovines, are the primary reservoir of Shiga toxin-producing E. coli (STEC), but whole genome analyses of the current German extended-spectrum beta-lactamase (ESBL)-producing O104:H4 outbreak strain of sequence type (ST) 678 showed this strain to be highly similar to enteroaggregative E. coli (EAEC)
While the reasons for this are currently unknown, it has already been proven that the outbreak strain has an unusual genome make up, as it shows a strong similarity to an enteroaggregative E. coli (EAEC) of the same serotype, which was previously isolated from a patient in Africa
Screening bovine faecal E. coli for the haemolytic uremic syndrome (HUS) O104:H4 outbreak strain In the first part of the present study, the strains were tested using the Multiplex-PCR developed by Bielaszewska et al (2011) for rapid detection of the outbreak strain
Summary
In particular bovines, are the primary reservoir of Shiga toxin-producing E. coli (STEC), but whole genome analyses of the current German ESBL-producing O104:H4 outbreak strain of sequence type (ST) 678 showed this strain to be highly similar to enteroaggregative E. coli (EAEC). While the reasons for this are currently unknown, it has already been proven that the outbreak strain has an unusual genome make up, as it shows a strong similarity to an enteroaggregative E. coli (EAEC) of the same serotype, which was previously isolated from a patient in Africa. This E. coli strain combines virulence traits of EAEC and STEC [3,5,6,7,8]
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