Characterization of Serogroup ANeisseria meningitidisfrom Invasive Meningococcal Disease Cases in Canada Between 1979 and 2006: Epidemiological Links to Returning Travellers

Abstract

INTRODUCTION: Serogroup ANeisseria meningitidishas repeatedly caused epidemics of invasive meningococcal disease (IMD) in developing nations since the 1960s. The present study is the first detailed study of serogroup A bacteria isolated in Canada.METHODS: Thirty-four serogroup A meningococcal isolates collected from individuals with IMD in Canada between 1979 and 2006 were characterized by serology and multilocus sequence typing of seven housekeeping enzyme genes and genes encoding three outer membrane protein antigens.RESULTS: Isolates were assigned to either the sequence type (ST)-1 or the ST-5 clonal complex. Clones within the ST-1 complex were recovered between 1979 and 1992, while clones of the ST-5 complex were isolated between 1987 and 2006; respectively, they accounted for 70.6% and 29.4% of all isolates studied. Isolates of the ST-1 complex were characterized by serosubtype antigen P1.3 or P1.3,6 with PorB allele 60 (serotype 4) and FetA sequence F5-1, while isolates of the ST-5 complex were characterized by serosubtype antigen P1.9 with PorB allele 47 (also serotype 4) and FetA sequence F3-1.CONCLUSIONS: The Canadian serogroup A IMD isolates likely originated in travellers returning from hyperendemic or epidemic areas of the globe where serogroup A bacteria circulate. Although the Canadian cases of serogroup A IMD were caused by clones known to have caused epidemics in developing countries, disease incidence remained low in Canada.