Evaluation of pulsed-field gel electrophoresis in epidemiological investigations of meningococcal disease outbreaks caused by Neisseria meningitidis serogroup C

Since 1990, the frequency of Neisseria meningitidis serogroup C (NMSC) outb reaks in the United States has increased. Based on multilocus enzyme electr ophoresis (MEE), the current molecular subtyping standard, most of the NMSC outbreaks have been caused by isolates of several closely related electrop horetic types (ETs) within the ET-37 complex. We chose 66 isolates from fou r well-described NMSC outbreaks that occurred in the United States from 199 3 to 1995 to evaluate the potential of pulsed-field gel electrophoresis (PF GE) to identify outbreak-related isolates specific for each of the four out breaks and to differentiate between them and 50 sporadic isolates collected during the outbreak investigations or through active laboratory-based surv eillance from 1989 to 1996. We tested all isolates collected during the out break investigations by four other molecular subtyping methods: MEE, riboty ping (ClaI), random amplified polymorphic DNA assay (two primers), and sero typing and serosubtyping. Among the 116 isolates, we observed 11 clusters o f 39 NheI PFGE patterns. Excellent correlation between the PFGE and the epi demiological data was observed, with an overall sensitivity of 85% and spec ificity of 71% at the 95% pattern relatedness breakpoint using either 1.5 o r 1.0% tolerance. For all four analyzed outbreaks, PFGE would have given pu blic health officials additional support in declaring an outbreak and makin g appropriate public health decisions.