Potential Capsule Switching from Serogroup Y to B: The Characterization of Three suchNeisseria meningitidisIsolates Causing Invasive Meningococcal Disease in Canada

Gwen S Stephens,Shaun D Tyler,Dennis Ks Law,Raymond Sw Tsang,Wendell D Zollinger,Mark Bigham

doi:10.1155/2005/216369

Abstract

Three group B Neisseria meningitidis isolates, recovered from meningococcal disease cases in Canada and typed as B:2c:P1.5, were characterized. Multilocus sequence typing showed that all three isolates were related because of an identical sequence type (ST) 573. Isolates typed as 2c:P1.5 are common in serogroup Y meningococci but rare in isolates from serogroups B or C. Although no serogroup Y isolates have been typed as ST-573, eight isolates showed five to six housekeeping gene alleles that were identical to that of ST-573. This suggested that the B:2c:P1.5 isolates may have originated from serogroup Y organisms, possibly by capsule switching.

Highlights

Three group B Neisseria meningitidis isolates, recovered from meningococcal disease cases in Canada and typed as B:2c:P1.5, were characterized
DNA sequencing of their porB genes confirmed that they were serotype 2c because their PorB variable regions (VR) types were identified as C, 2c, 2bb and Db for their VR1 to VR4 regions, respectively [9], showing 100% identity with that of the serotype 2c prototype strain 2396, B:2c:P1.5,2 (GenBank accession number U92911)
The PorB VR amino acid sequences of these three B:2c:P1.5 isolates were identical to the sequence of the variable loop V.5 described in the PorB typing database for N meningitidis [13]

Summary

Introduction

Three group B Neisseria meningitidis isolates, recovered from meningococcal disease cases in Canada and typed as B:2c:P1.5, were characterized. No serogroup Y isolates have been typed as ST-573, eight isolates showed five to six housekeeping gene alleles that were identical to that of ST-573 This suggested that the B:2c:P1.5 isolates may have originated from serogroup Y organisms, possibly by capsule switching. Serotyping and serosubtyping rely on the detection of distinct epitopes present on three of five different classes of OMPs of N meningitidis. Serosubtyping epitopes are present on the class 1 OMP ( called PorA) Based on this nomenclature scheme, a strain can be characterized by its antigenic formula; for example, B:15:P1.7,16 refers to serogroup B, serotype 15 and serosubtype P1.7,16. Capsule switching has been demonstrated in vivo and in vitro by specific gene replacement within the cps loci between different

Methods

Results

Conclusion