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Clinically relevant extended-spectrum beta-lactamase (ESBL)-producing multi-resistant Escherichia (E.) coli are increasingly detected in various habitats, not only in a human and veterinary clinical context but also in extra-clinical settings such as communities, the environment and wildlife. Infections including diarrhea, septicemia, pneumonia, and wound and urinary tract infections these bugs cause are not only severe but also difficult to treat due to limitations in antimicrobial therapy possibilities.
This thesis is based on a total of 100 samples from environmental dog feces and 320 cloacal samples from wild birds, which were collected in Berlin, Germany, between 2008 and 2014. Of these 10 % (dogs) respectively 7.5 % (birds) harbored ESBL-producing E. coli. In addition, eleven canine clinical and 40 human clinical (bacteremia) ESBL-producing E. coli isolates from the same area were included and pheno- and genotypically analyzed. To determine the phylogenetic population structure of ESBL-producing isolates, multi-locus sequence typing (MLST) was performed. The sequence type (ST) occurring in all sample groups was ST410. All ST410 isolates were initially clonally analyzed using pulsed-field gel electrophoresis (PFGE). Ten isolates from one clonal PFGE group with identical or almost identical macrorestriction patterns were then chosen for whole-genome sequencing using the MiSeq platform (Illumina). Following raw data reprocessing through standard bioinformatics pipelines it was possible to perform detailed phylogenetic and clonal as well as molecular analyses, again including both chromosomal and episomal (plasmids) determinants.
Besides ST410, various sequence types frequently described in both humans and animals worldwide were detected in environmental dog feces and wild birds (ST10, ST131, ST224) with all isolates harboring the typical beta-lactamase (bla)-gene blaCTX-M-1 or blaCTX-M-15. Within the ten ST410 strains from different hosts in the same region, almost genetically identical isolates were identified. As some of the isolates differed by a few single-nucleotide polymorphisms (SNPs) only, the study gives initial evidence for an ongoing interspecies transmission of a putative successful new E. coli clone of ST410 between avian wildlife, humans, companion animals and the environment. This underlines the zoonotic potential of ESBL-producing E. coli as well as the mandatory nature of the One Health approach to address the threat of antimicrobial resistance. Future investigations call for long-scale and comprehensive epidemiological studies and functional analyses to reinforce the proposed transmission scenarios and to identify infection sources and underlying molecular mechanisms of successful pandemic clones.