Investigation for a more virulent variant among the C:2b:P1.2,5 Spanish meningococcal epidemic strains by molecular epidemiology

Laboratorio de Referencia de Meningococos, Servicio de Bacteriología, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid and *Dirección Xeral de Saúde Pública, Xunta de Galicia, Spain Corresponding author: Dr J. A. Vázquez (e-mail: jv\|[aacute]\|zquez{at}isciii.es ). Received 7 Oct. 1999; revised version received 5 April 2000; accepted 14 April 2000. Abstract A rise in the incidence of meningococcal disease has occurred in Spain in recent years, especially in some regions in the north-west of the country. Most cases have been caused by meningococci characterised as Neisseria meningitidis C:2b:P1.2,5. A total of 107 C:2b:P1.2,5 meningococcal isolates (60 from patients and 47 from carriers) and 12 isolates showing related antigenic combinations (C:2b:NST, C:2b:P1.2, C:2b:P1.5, C:NT:P1.2,5) was analysed by pulsed-field gel electrophoresis to determine the genetic variability of the epidemic and related strains. Endonucleases Bgl II and Nhe I were used to cut chromosomal DNA. When Bgl II was used, most of the C:2b:P1.2,5 isolates showed the same pulsotype regardless of whether they were from clinical cases or carriers. Isolates showing the principal profile after digestion with endonuclease Bgl II were analysed with Nhe I. Four pulsotypes were identified, of which two were found in only one isolate each. The major profiles (1 and 2) showed differential distribution among clinical and carrier isolates; pulsotype 1 was the most frequent among clinical isolates. However, the proportions of isolates showing profiles 1 and 2 were similar among carrier isolates. This could indicate that there are two variants of the C:2b:P1.2,5 strain with differing pathogenicity.