The reservoir in the reservoir: Genotypic and phenotypic characteristics of persistent Shiga toxin-producing Escherichia coli in cattle herds

• Applicant: Dr. Lutz Geue
• Subject Area: Veterinary Medical Science
• Term: from 2012 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 221245401

Cattle are a major reservoir for Shiga toxin (Stx) producing Escherichia coli (STEC), including human-pathogenic enterohemorrhagic E. coli (EHEC). Clones form outbreaks that were epidemiologically linked to cattle herds have a high zoonotic potential, but these clones are usually only sporadically detectable in humans and cattle. So far, little attention has been paid to the fact that there are STEC clones in cattle that may persist in individual animals or cattle herds. As stx is bacteriophage encoded in the genome of STEC, these persistent STEC clones can constantly produce new clones with an incalculable hazard potential for humans. Since valid predictive genetic markers for the zoonotic potential of STEC clones are missing, control strategies should focus on those clones that form a bacterial reservoir for the stx-converting phage in the gastrointestinal tract of cattle.Persistence of bovine STEC infection is supported by the capability of the bacteria to form Stx. However, not all STEC have the capacity for persistence. We think that persistence is not linked to a single bacterial factor, but on the result of a combination of features, which may not have been noticed in the recent virulence gene based characterization of bovine STEC. In order to identify genotypic and phenotypic patterns characteristic for these clones, sporadically and persistent bovine STEC clones should be typed by using miniaturized E. coli oligonucleotide arrays with a view on the occurrence of STEC / EHEC and other E. coli-specific virulence genes and fitness genes. Transcriptome, proteome and metabolome after interaction of the clones with intestine epithelium cell cultures and effector mechanisms of the innate immune system may clarify the regulatory circuits between the genetic background of STEC, the adherence properties, the clone-specific host cell responses and host-induced bacterial gene expression. Analysis of the complex mechanisms for the persistence of STEC in cattle should help to understand the persistence of human-adapted EHEC clones in humans, such as the current outbreak strain HUSEC 041 (O104:H4) and should open new approaches for reduction strategies of this pathovar in humans and animals.

• DFG Programme: Research Grants