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

Fifty-eight isolates of Shigella sonnei from three outbreaks in school chil dren and eight control isolates from epidemiologically unrelated sporadic c linical infections in Taiwan were compared by antibiotic susceptibility tes ting and molecular typing. Antibiotic susceptibility testing showed that al l strains except one sporadic isolate were multi-resistant. Ribotyping afte r restriction endonuclease digestion with SalI, PvuII and HindII generated the same ribosomal pattern in 65 of the 66 isolates. Plasmid profile analys is and pulsed-field gel electrophoresis (PFGE) produced eight and nine dist inct patterns, respectively, and were in agreement with the epidemiological relationship of the outbreak strains. Nevertheless, some of the sporadic i solates could be discriminated only by a combination of these two methods. This study showed that plasmid profiling in combination with PFGE may be su perior to ribotyping in molecular epidemiological investigations of S, sonn ei.