Closed genome and comparative phylogenetic analysis of the clinicalmultidrug resistant shigella sonnei strain 866

Abstract

Shigella sonnei is responsible for themajority of shigellosis infections in the USwith over 500,000 cases reported annually. Here, we present the complete genome of the clinical multidrug resistant (MDR) strain 866, which is highly susceptible to bacteriophage infections. The strain has a circular chromosome of 4.85Mb and carries a 113 kbMDR plasmid. This IncB/O/K/Z-type plasmid, termed p866, confers resistance to five different classes of antibiotics including β-lactamase, sulfonamide, tetracycline, aminoglycoside, and trimethoprim. Comparative analysis of the plasmid architecture and gene inventory revealed that p866 shares its plasmid backbone with previously described Inc B/O/K/Z-type Shigella spp. andEscherichia coli plasmids, but is differentiated by the insertion of antibiotic resistance cassettes, which we found associated with mobile genetic elements such as Tn3, Tn7, and Tn10.Awholegenome-derived phylogenetic reconstruction showed the evolutionary relationships of S. sonnei strain 866 and the four established Shigella species, highlighting the clonal nature of S. sonnei.