ANALYSIS OF BORDETELLA-PERTUSSIS ISOLATES FROM AN EPIDEMIC BY PULSED-FIELD GEL-ELECTROPHORESIS

We examined genetic variation among 78 clinical isolates of Bordetella pertussis, including 54 strains recovered during a 1986 pertussis epi demic, A total of 16 pulsed-field gel electrophoresis (PFGE) profiles, generated with each of three different enzymes (XbaI, SpeI, and DraI) , were obtained from the epidemic and sporadic isolates included in th e study. Indistinguishable profiles were seen among strains unrelated temporally or geographically, as well as among strains isolated sporad ically from the same geographic areas. All isolates from the epidemic had indistinguishable PFGE profiles. The PFGE pattern of the epidemic strains was shared with only 1 of 25 strains isolated independently of the outbreak. This isolate was cultured from a specimen from a labora tory scientist who had been working with the epidemic strains, further implicating the usefulness of PFGE for the epidemiologic study of cli nical strains of B. pertussis, Differences in PFGE profiles for single epidemic strains occurred occasionally upon repeated passage on agar medium, suggesting that subculturing of initial isolates should be min imized before pulsed-field analysis.