Electropherotyping of plasmid DNA of different serotypes ofShigella flexneriisolated in Bangladesh

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Abstract
SUMMARY: One hundred and twenty-fiveShigella flexneristrains, isolated during January-December 1984, at the Dhaka treatment centre of the International Centre for Diarrhoeal Disease Research, Bangladesh, were serotyped using absorbed rabbit antisera specific for all type-and group-factor antigens, as well as a group of ten mouse and rat monoclonal antibodies. Electropherotypes of the plasmid deoxyribonucleic acid (DNA) were also determined.S. flexneri2a was the predominant serotype followed by 3b, 1a, and 2b.The recently described E1037 antigen was also found in three strains ofS. flexneriserotype 6. Electropherotyping of the plasmid DNA showed that three plasmids of approximately 140. 2·7. and 2 megadalton (MDa) were present, respectively, in 97, 97 and 94% of the 125 strains. Additional plasmids of various other sizes were also present in different serotypes except in serotype 2a. The additional plasmids again appeared to be specific for that particular serotype. For example, all 12 strains ofS. flexneri2b harboured an additional plasmid of approximately 1 MDa. Thus, electropherotyping of plasmid DNA of different serotypes ofS. flexnerimight be useful to differentiateS. flexnerifrom other species ofShigellaand in identifying different serotypes ofS. flexneri. Therefore, the common plasmids, plus the additional plasmids. could be used to identify epidemic, as well as sporadic, subclones ofS. flexneristrains.