Molecular Epidemiological Study of a Shigellosis Outbreak in
John JY Lu
1999 Vol.15 NO.11
A Shigellosis outbreak occurred on October 15, 1997 at a primary school in Kuanhsi Township of Hsinchu County. Both the plasmid profile analysis and the polymerase chain reaction methods were used to investigate study the 50 strains of Shigella sonnei isolated in the outbreak, to compare them with the Shigella sonnei strains isolated at different times from the central part of Taiwan, for the molecular epidemiological study of this Shigellosis outbreak. The findings by plasmid profile analysis indicated that three different molecular types could be differentiated; and by ploymerase chain reaction, six molecular types could be differentiated. Although most Shigella sonnei strains in this outbreak were of the same serotype (plasmid type I or polymerase chain reaction type E), some strains were of other plasmid profile or polymerase chain reaction molecular type. The Shigella sonnei strains isolated from this outbreak were of different molecular types from strains isolated elsewhere at different times. This fact indicated that the outbreak was a local incident. Strains isolated from family members, by analysis, were of the same molecular type, indicating that the mode of transmission was also by way of familial contact. By analysis of transmissions through school and family contacts, it was noted that molecular typing was useful in identifying major strains of shigellosis outbreaks. Though the present outbreak was caused primarily by a single strain, strains of other molecular types were also found in school children. A further study of the inapparent Shigellae in the environment and their anti-microbial drugs resistance would be useful in the control of shigellosis outbreaks.