Multilocus Genotypes Determined by Enzyme Electrophoresis of Neisseria meningitidis Isolated from Patients with Systemic Disease and from Healthy Carriers

Abstract

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.

Phylogenetic and epidemiological analysis ofNeisseria meningitidisusing DNA probes

“…2(A and B); only minor variations were found between the branching orders obtained using probes derived from different genetic loci. The value of RFLP analysis for examining the relationships between the serogroups, serotypes and sero-subtypes of N. me.ningitidis is also supported by the similarity of the phylogenetic trees presented here and those obtained by ET-typing [4,21]. RFLP analysis permits classification of strains which cannot be grouped or typed with current serological reagents.…”

Transmission ofNeisseria meningitidisamong asymptomatic military recruits and antibody analysis

“…The meningococcal blood isolate (11/86) from the patient was serogroup B, serotype 15:P1.7,16 and ET-5, as the majority of the strains isolated from patients in Norway since the beginning of the present epidemic in the mid-1970s [10] has been.…”

“…conventional methods of typing are generally unsatisfactory for characterizing N. meningitidis strains from carriers. Consequently, multilocus enzyme electrophoresis was employed to identify the meningococcal clones [10].…”

Meningococcal infection: --a review based upon papers presented at the 155th Meeting of the Pathological Society of Great Britain and Ireland at Southampton; 8 July, 1987

“…Currently available serological typing of serogroup-A bacteria has been based on outer-membrane protein and LPS antigens (Frasch et al, 1976;Zollinger and Mandrell, 1980) but has not yielded any striking epidemiological conclusions (Olyhoek et al, 1987). Very recently, the techniques of clonal analysis (Selander et al, 1986Achtman and Pluschke, 1986) have been applied to Neisseria meningitidis (Caugant et al, 1986a andOlyhoek et al, 1987) and the results with serogroup-A organisms have revealed world-wide patterns to the epidemic waves seen since 1962 (Olyhoek et al, 1987).…”

“…Clonal typing methods have now been used in epidemiological studies of serogroup-A meningococci (Olyhoek et al, 1987), and of other serogroups (Caugant et al, 1986a and. The method is based on either the isoenzyme analysis of soluble cytoplasmic enzymes or on a combination of isoenzyme analysis and outermembrane-protein analysis (Achtman and Pluschke, 1986).…”