title: Shigella flexneri serotype 1c derived from serotype 1a by acquisition of gtrIC gene cluster via a bacteriophage.
abstract: Shigella spp. are the primary causative agents of bacillary dysentery. Since its emergence in the late 1980s, the S. flexneri serotype 1c remains poorly understood, particularly with regard to its origin and genetic evolution. This article provides a molecular insight into this novel serotype and the gtrIC gene cluster that determines its unique immune recognition.
  
  
  
  A PCR of the gtrIC cluster showed that serotype 1c isolates from different geographical origins were genetically conserved. An analysis of sequences flanking the gtrIC cluster revealed remnants of a prophage genome, in particular integrase and tRNA(Pro) genes. Meanwhile, Southern blot analyses on serotype 1c, 1a and 1b strains indicated that all the tested serotype 1c strains may have had a common origin that has since remained distinct from the closely related 1a and 1b serotypes. The identification of prophage genes upstream of the gtrIC cluster is consistent with the notion of bacteriophage-mediated integration of the gtrIC cluster into a pre-existing serotype.
  
  
  
  This is the first study to show that serotype 1c isolates from different geographical origins share an identical pattern of genetic arrangement, suggesting that serotype 1c strains may have originated from a single parental strain. Analysis of the sequence around the gtrIC cluster revealed a new site for the integration of the serotype converting phages of S. flexneri. Understanding the origin of new pathogenic serotypes and the molecular basis of serotype conversion in S. flexneri would provide information for developing cross-reactive Shigella vaccines.
authors.affiliation: Division of Biomedical Science and Biochemistry, Research School of Biology, The Australian National University, Bldg #134 Linnaeus Way, Canberra, ACT 0200, Australia. sstang@um.edu.my.|Division of Microbiology, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603, Kuala Lumpur, Malaysia. sstang@um.edu.my.
authors.forename: Swee-Seong
authors.identifier: 0000-0002-6996-441X
authors.initials: SS
authors.lastname: Tang
authors.affiliation: Etvax AB, Gunnar Asplunds Allé 16, SE-171 63, Solna, Stockholm, Sweden.
authors.forename: Nils I A
authors.initials: NI
authors.lastname: Carlin
authors.affiliation: International Centre for Diarrhoeal Diseases Research, Dhaka, Bangladesh.
authors.forename: Kaisar A
authors.initials: KA
authors.lastname: Talukder
authors.affiliation: Department of Microbiology, National Institute of Hygiene and Epidemiology, Hanoi, Vietnam.
authors.forename: Phung D
authors.initials: PD
authors.lastname: Cam
authors.affiliation: Division of Biomedical Science and Biochemistry, Research School of Biology, The Australian National University, Bldg #134 Linnaeus Way, Canberra, ACT 0200, Australia.
authors.forename: Naresh K
authors.initials: NK
authors.lastname: Verma
mesh_terms: D015373:Bacterial Typing Techniques; D001435:Bacteriophages / Q000235:genetics*; D001483:Base Sequence; D015139:Blotting, Southern; D004269:DNA, Bacterial / Q000235:genetics*; D004405:Dysentery, Bacillary / Q000382:microbiology; D019143:Evolution, Molecular; D016679:Genome, Viral; D005964:Glucosyltransferases / Q000235:genetics; D005810:Multigene Family / Q000235:genetics*; D019081:O Antigens / Q000235:genetics; D016133:Polymerase Chain Reaction; D039002:Prophages / Q000235:genetics; D012343:RNA, Transfer; D017421:Sequence Analysis; D065288:Serogroup; D012703:Serotyping; D012763:Shigella flexneri / Q000235:genetics* / Q000276:immunology / Q000821:virology*; D016662:Virus Integration / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial; D019081:O Antigens; D012343:RNA, Transfer; D005964:Glucosyltransferases
keywords: Bacillary dysentery; Evolutionary origin; Glucosyltransferase; Serotype 1c; Serotype-conversion; Shigella flexneri