Characterization of a stx2a prophage present in STEC O145:H- isolated from cattle

KRÜGER, A.; ROSSEN, J. W. A.; FRIEDRICH, A. W.; LUCCHESI, P. M. A.

Boston

Simposio; 9th INTERNACIONAL SYMPOSIUM ON SHIGA TOXIN (VEROCYTOTOXIN) - PRODUCING Escherichia coli INFECTIONS; 2015

IntroductionPhages carrying Shiga toxin genes (stx phages) regulate Stx production and dissemination of stx genes. Furthermore, the gastrointestinal tract of ruminants plays an important role in the emergence of STEC strains. The aims of this study were to determine the whole genome sequence of the stx2a prophage present in the STEC strain representing the first described stx2-positive O145:H- isolation from a cow in Argentina, and to perform a comparative analysis with complete stx-phage sequences available in databases.MethodsGenomic DNA from the FB5 strain was prepared using the Ultraclean Microbial DNA isolation kit (MoBio). Paired-end and mate-paired libraries were generated and sequenced on the Illumina Miseq platform. Combined reads were de novo assembled using CLC Genomics Workbench and the contig of interest was detected by BLAST using the stx2a sequence from the phage 933W. The sequence of the stx2a phage was identified and annotated using PHAST and RAST. Comparative analyses were performed using BLAST programs.Results and DiscussionThe complete sequence of the stx2a phage (66,618 bp) was detected in a contig of 279,109 bp. The phage was named ArgO145. Sequence annotation revealed the presence of 89 predicted coding sequences, most of them previously detected in other stx phages. Whole genome comparison of ArgO145 with stx phages collected in databases revealed high similarities with those identified in STEC from other countries. Particularly, ArgO145 showed 99% identity (90% query coverage) with VT2phi-272, a stx phage from anO157:H7 strain, and 98% identity (86-88% coverage) with stx phages from human O104:H4 strains.ImplicationsTo our knowledge, this is the first report describing the genome of a stx2a phage from a bovine strain. Since stx phages are considered highly diverse, it is remarkably that ArgO145 showed similarities with stx phages present in strains isolated from patients and belonging to other serotypes.