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

Department of Food Sanitation, Tajen Junior College of Pharmacy, Ping Tung 907, *Department of Microbiology, Kaohsiung Medical College, Kaohsiung 807 and National Institute of Preventive Medicine, Department of Health, Taipei 115, Taiwan, ROC Corresponding author: Dr S.-F. Chang (e-mail: shui{at}mail nsysu.edu.tw). Received 1 April 1999; revised version accepted 13 Sept. 1999. Abstract Fifty-eight isolates of Shigella sonnei from three outbreaks in school children and eight control isolates from epidemiologically unrelated sporadic clinical infections in Taiwan were compared by antibiotic susceptibility testing and molecular typing. Antibiotic susceptibility testing showed that all strains except one sporadic isolate were multi-resistant. Ribotyping after restriction endonuclease digestion with Sal I, Pvu II and Hin dII generated the same ribosomal pattern in 65 of the 66 isolates. Plasmid profile analysis and pulsed-field gel electrophoresis (PFGE) produced eight and nine distinct patterns, respectively, and were in agreement with the epidemiological relationship of the outbreak strains. Nevertheless, some of the sporadic isolates could be discriminated only by a combination of these two methods. This study showed that plasmid profiling in combination with PFGE may be superior to ribotyping in molecular epidemiological investigations of S. sonnei .