Strain differentiation of Neisseria meningitidis by small-fragment restriction endonuclease analysis (SF-REA)

Following an outbreak involving 3 cases of serogroup B meningococcal disease in a rural part of Western Norway, 2 clinical and 99 carrier isolates of Neisseria meningitidis were examined by small-fragment restriction endonuclease analysis (SF-REA) using EcoRI, to determine its potential for strain differentiation. SF-REA characterized all isolates and provided reproducible results with acceptable inter-clonal differentiation. The results of SF-REA correlated well with those of serological typing and were used to determine clonal diversity and prevalence of invasive strains among the carrier isolates. SF-REA was also useful in demonstrating acquisition of a new carrier strain after eradication of the initial strain by ofloxacin. Thirty-one different restriction patterns/pattern complexes were recognized among the 101 isolates. The two clinical isolates had identical restriction patterns and showed > or = 90% similarity to those of six carrier isolates. In three out of six apparent treatment failures, successful eradication of the original strain by ofloxacin was demonstrated by SF-REA. SF-REA proved valuable in strain differentiation of Neisseria meningitidis, complemented serology, and characterized all isolates which could not be typified by serology.