title: Molecular diagnosis of non-serotypeable Shigella spp.: problems and prospects.
abstract: It is not always possible to identify Shigella serogroups/serotypes by biochemical properties alone. Specific identification requires serotyping. Occasionally, isolates that resemble Shigella spp. biochemically, but are non-agglutinable with available antisera, have been observed. Several mechanisms have been reported to limit the efficiency of the serotyping assay. Serotype conversion is a major mechanism in Shigella spp. to escape protective host immune responses. This easy conversion through significant modification of the O-antigen backbone results in different serotypes, which makes laboratory identification difficult. Furthermore, members of the family Enterobacteriaceae are closely related and there is antigenic cross-over (intra- and inter-specific cross-reaction) which affects the agglutination reaction. The performance of the available methods for identification of non-serotypeable Shigella is discussed here, and reveals them to be non-reliable. This shows a need for an alternative method for identification and typing of Shigella spp.
authors.affiliation: Department of Clinical Microbiology, Christian Medical College, Vellore 632 004, India.
authors.forename: Dhiviya Prabaa
authors.initials: DP
authors.lastname: Muthuirulandi Sethuvel
authors.affiliation: Department of Clinical Microbiology, Christian Medical College, Vellore 632 004, India.
authors.forename: Naveen Kumar
authors.initials: NK
authors.lastname: Devanga Ragupathi
authors.affiliation: Department of Clinical Microbiology, Christian Medical College, Vellore 632 004, India.
authors.forename: Shalini
authors.initials: S
authors.lastname: Anandan
authors.affiliation: Division of Epidemiology and Communicable Diseases, Indian Council of Medical Research, New Delhi 110 029, India.
authors.forename: Kamini
authors.initials: K
authors.lastname: Walia
authors.affiliation: Department of Clinical Microbiology, Christian Medical College, Vellore 632 004, India.
authors.forename: Balaji
authors.initials: B
authors.lastname: Veeraraghavan
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D005243:Feces / Q000382:microbiology; D056726:Genetic Association Studies; D006801:Humans; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D005810:Multigene Family; D019081:O Antigens / Q000032:analysis / Q000235:genetics / Q000276:immunology; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D065288:Serogroup; D012703:Serotyping; D012760:Shigella / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification*
chemical_list: D001426:Bacterial Proteins; D019081:O Antigens; D012336:RNA, Ribosomal, 16S; C079397:rfb protein, Bacteria