Cytolethal distending toxin producing Escherichia coli O157:H43 strain T22 represents a novel evolutionary lineage within the O157 serogroup.
Enterohemorrhagic Escherichia coli (EHEC) O157:H7/NM strains are significant foodborne pathogens intensively studied, while other sero- and pathotypes of the O157 serogroup only began to receive more attention. Here we report the first genome sequence of a cytolethal distending toxin (CDT-V) producing E. coli O157:H43 strain (T22) isolated from cattle. The genome consists of a 4.9Mb chromosome assembled into three contigs and one plasmid of 82.4kb. Comparative genomic investigations conducted with the core genomes of representative E. coli strains in GenBank (n=62) confirmed the separation of T22 from the EHEC and enteropathogenic (EPEC) O157 lineages. Gene content based pangenome analysis revealed as many as 261 T22-specific coding sequences without orthologs in EDL933 EHEC O157 prototypic and two phylogenetically related commensal E. coli strains. The genome sequence revealed 10 prophage-like regions which harbor several virulence-associated genes including cdt and heat-labile enterotoxin (LT-II) encoding operons. Our results indicate that the evolutionary path of T22 is largely independent from that of EHEC and EPEC O157:H7/NM strains. Thus, the CDT-producing T22 E. coli O157:H43 strain represents a unique lineage of E. coli O157.
Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary. Electronic address: svab.domonkos@agrar.mta.hu.
Domonkos
D
Sváb
Seqomics Biotechnology Ltd., Mórahalom, Hungary. Electronic address: balintb@seqomics.hu.
Balázs
B
Bálint
Institute of Biochemistry, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary. Electronic address: marotig@brc.hu.
Gergely
G
Maróti
Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary. Electronic address: toth.istvan@agrar.mta.hu.
István
I
Tóth
D000818:Animals; D001427:Bacterial Toxins / Q000235:genetics*; D002417:Cattle; D019453:Escherichia coli O157 / Q000145:classification* / Q000235:genetics*; D019143:Evolution, Molecular; D016680:Genome, Bacterial / Q000235:genetics; D023281:Genomics; D008892:Milk / Q000382:microbiology; D010802:Phylogeny
D001427:Bacterial Toxins; C067044:cytolethal distending toxin
CDT; Comparative genomics; Escherichia; LT-II; O157:H43; Phylogeny