Analysis of clonal relationships among isolates of Shigella sonnei by different molecular typing methods

Abstract

Shigella sonnei is a major cause of diarrheal disease in developed as well as in developing countries. Epidemiologic studies of this organism have been limited by the lack of a simple and effective method for comparing strains. In this study, we have compared different molecular typing methods, i.e., plasmid profile analysis, restriction endonuclease analysis of plasmids, rRNA gene restriction analysis (ribotyping), pulsedfield gel electrophoresis (PFGE), and enterobacterial repetitive intergenic consensus (ERIC) sequence-based PCR (ERIC-PCR) for typing 20 clinical isolates of S. sonnei collected from six incidents of infection. PFGE and ERIC-PCR fingerprintings had the highest discriminatory power for discrimination of epidemiologically related isolates from epidemiologically unrelated strains of S. sonnei, and both gave seven distinct strain types among these isolates and the type strain of the species. Plasmid study and ribotyping produced only six and two distinct patterns, respectively, among these strains. All of these molecular typing techniques demonstrated an identical fingerprint for eight temporally related sporadic isolates. It is possible that these temporally related isolates belonged to a single bacterial clone and circulated obscurely through the community. Our results indicate that the ERIC-PCR technique represents a rapid and simple means for typing S. sonnei with a level of discrimination equivalent to that of PFGE but greater than those of plasmid profile analysis, restriction endonuclease analysis of plasmids, and ribotyping.

Molecular analysis of Shigella sonnei isolated from three well-documented outbreaks in school children

“…The present study showed the poor discriminatory power of ribotyping for S. sonnei isolates. This ®nding is similar to an earlier report on strains from Taiwan [14]. This limits the usefulness of ribotyping in epidemiological investigations of S. sonnei.…”

“…Recently, approaches at the DNA level have been used to discriminate between bacterial isolates. Plasmid pro®le analysis [9,10], ribotyping [11,12] and pulsed-®eld gel electrophoresis (PFGE) [13,14] have proved to be useful in discriminating isolates of Shigella spp.…”

Outbreak of Shigella sonnei in a clinical microbiology laboratory

“…The S. sonnei isolates were characterized by preparing total genomic DNA in agarose plugs and carrying out pulsed-field gel electrophoresis (PFGE) (1,7). After growth overnight in Trypticase soy broth (Difco Laboratories, Detroit, Mich.), 2 ml of each culture was washed in cell suspension buffer and resuspended in 0.5 ml of the same buffer.…”

Identification of shiga toxin-producing bacteria by a new immuno-capture toxin gene PCR

“…DNA genotyping methods have been increasingly used for bacterial characterization. The most commonly used techniques remain analysis by restriction fragment length polymorphism [2], single-stranded conformational polymorphism [3], randomly ampli¢ed polymorphic DNA [4], pulse ¢eld electrophoresis [5] and ribotyping [6]. However, these techniques are laborious, expensive and not suitable for studying a large number of bacterial strains [7].…”