Strains of Neisseria meningitidis responsible for an epidemic of meningococcal disease occurring in Norway since the mid-1970s and for recent increases in the incidence of disease in several other parts of Europe have been identified by multilocus enzyme electrophoresis as members of a distinctive group of 22 closely related clones (the ET-5 complex). Clones of this complex have also colonized South Africa, Chile, Cuba, and Florida, where they have been identified as the causative agents of recent outbreaks of meningococcal disease. There is strong circumstantial evidence that outbreaks of disease occurring in Miami in 1981 and 1982 were caused in large part by bacteria that reached Florida via human immigrants from Cuba.

Variation in nine enzymes in 152 isolates of Neisseria meningitidis from Norway (118 from blood or cerebrospinal fluid of patients with systemic disease and 34 from the pharynx of healthy carriers) was analysed by starch-gel electrophoresis. All nine enzymes were polymorphic and the number of allozymes (electromorphs) identified per locus ranged from 3 to 12, with a mean of 6.1. Among the 152 isolates, 55 unique combinations of electromorphs (electrophoretic types, ETs) were distinguished. Twenty ETs were represented among the carrier isolates and 37 among the systemic isolates; hence, only two ETs were found in both groups of isolates. ET-5 was identified 67 times among the 118 systemic isolates (58%), indicating an association of this ET with invasiveness; ET-5 was also the most common type among the carrier isolates (18%). Genetic similarity between ETs was analysed by pairwise comparison of all 55 ETs with respect to the number of electromorphs by which they differed. No evidence of a general genetic difference between carrier and case isolates was found. Two well-defined clusters of ETs were observed, each including one of the two most common ETs identified among the systemic isolates (ET-5 and ET-37), together with isolates differing from them only at one or two loci. All isolates of ET-5 and ET-37, as well as their closely related variants defined by the similarity matrix, were resistant to sulphonamide, independent of their antigenic characteristics and isolation site. The extensive allozyme variation among isolates of the same serogroup demonstrated the limited value of serogrouping as an epidemiological tool. All but one isolate of serotype 15:P1.16 were electrophoretically similar, as were all the 2a:P1.2 isolates. The 15:P1.15 isolates, however, were genetically heterogeneous. The distribution of alleles in genotypes identified among the systemic isolates indicated that genetic recombination may occur in natural populations of N. meningitidis.

Genetic diversity and relationships among 109 isolates ofNeisseria meningitidis obtained from throat cultures of healthy individuals in Norway in 1984 were assessed by analyzing electrophoretically demonstrable alielic variation at 15 enzyme-encoding chromosomal genes. Seventy-eight distinctive electrophoretic types (ETs), representing multilocus genotypes, were identified. The mean genetic diversity per locus among the 78 ETs (0.538) was equivalent to that among 19 ETs represented by 66 isolates collected from patients with meningococcal disease in Norway in the first 5 months of 1984. The clonal composition of the collection of carrier strains was, however, quite different from that of strains from patients. The two groups of clones, the ET-5 complex and the ET-37 complex, that were responsible for 91% of the cases of systemic disease in Norway in 1984 were identified in only 7 and 9%, respectively, of the throat cultures from healthy individuals, and their frequencies in the human population sampled were only 0.7% for clones of the ET-5 complex and 0.9% for those of the ET-37 complex. The complex of clones that was most frequently represented by isolates from carriers (19%) has never been recovered from patients with meningococcal disease in Norway or elsewhere, which suggests that these clones have a low virulence potential. Children attending the same day care center or school seldom harbored the same clone in their throats.

No abstract

A rod-shaped, non-motile, Gram-negative, oxidase-positive and asaccharolytic organism found in the human nasopharynx is allotted to genus Neisseria and named Neisseria elongata. The strain M 2, which is the only isolate, is proposed as the type strain. The average guanine + cytosine (G + C ) content of its DNA is 53 mole yo. Genetic transformation of streptomycin resistance reveals a comparatively high compatibility with N. rneningitidis and a strain designated N. Jlava, with ratios of interstrain to autologous transformation frequency in the range 0.01 to 0.1. On the other hand, there is no affinity in streptomycin-resistance transformation between N . elongata and members of genus Moraxella, including the old concepts N . catarrhalis and N. ovis. The family Neisseriaceae now appears to consist of two genera, Neisseria and Moraxella, each containing both coccal and rod-shaped species, which makes cell shape questionable as a highly weighted criterion in the construction of bacterial genera and higher taxa.