Colicine production as an epidemiological marker for Shigella sonnei

SUMMARY The reliability of colicine typing of Shigella sonnei: as an epidemiological marker ha,s been investigated. Strains from 13 of 110 exeretors showed variation in type as determined by typing serial isolates and in 14 of 106 epidemics there was a lack of uniformity in typing results. The simultaneous presence of two types was found in 11@4 °/O of patients. In vitro variation was seen after 10 days in 6o8 °/O of isolates from 44 stools; variation had risen to 9 °/O when isolates were re-examined after one month. These results suggest that restrictions should be placed on the use of colicine typing as an epidemiologic tool.