Characterization of endemic Shigella boydii strains isolated in Iran by serotyping, antimicrobial resistance, plasmid profile, ribotyping and pulsed-field gel electrophoresis

BACKGROUND: Shigellosis is one of the major causes of morbidity in children with diarrhea in Iran. The present study was undertaken to characterize apparently sporadic Shigella boydii strains isolated from pediatric patients in Iran. FINDINGS: Ten S. boydii strains isolated from pediatric cases of gastroenteritis and acute diarrhea in Tehran between December 2002 and November 2003 were submitted to serotyping, antimicrobial susceptibility testing, plasmid profile analysis, ribotyping and pulsed field gel electrophoresis (PFGE). Seven isolates were attributed to serotype 2, whereas the remaining three belonged to serotypes 14, 18, 19, respectively. Six drug resistance phenotypes (R1 to R6) were defined with R4 – streptomycin (STR), ampicillin (AMP), sulfamethoxazole-trimethoprim (SXT) – being the most prevalent. Plasmid analysis resulted in seven different plasmid profiles with one to five DNA bands. All strains, but one, shared the same ribotype, but PFGE differentiated them in four groups. CONCLUSION: Based upon ribotyping and PFGE results, endemic circulation of S. boydii in Tehran, Iran, could be attributed to a few clones. Resistance pattern and plasmid profile analysis proved to be very effective in discriminating apparently unrelated strains of S. boydii.