Molecular characterisation of Neisseria meningitidis serogroup B isolates in South Africa, 2002- 2006
Date
2011-10-17
Authors
Moodley, Chivonne
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Abstract
Despite being a fulminant pathogen, Neisseria meningitidis (meningococcus) is
part of the commensal flora of the human nasopharynx. Globally, five
meningococcal serogroups (A, B, C, Y and W135) cause the majority of invasive
disease. Most serogroup B cases occur sporadically but may be endemic or
epidemic within a geographic region. In South Africa, there are limited data on
invasive serogroup B clones and the antigenic diversity of certain meningococcal
outer membrane proteins. This study examined the molecular epidemiology of
serogroup B meningococci in South Africa from 2002 through 2006.
Invasive meningococcal isolates were submitted to a national laboratory-based
surveillance system. For this study, serogroup B isolates were characterised by
pulsed-field gel electrophoresis (PFGE), PorA, FetA and multilocus sequence
(MLST) typing. PorA, FetA and multilocus sequence (MLST) typing were
performed on all 2005 isolates (n=58) and randomly selected isolates from other
years (n=25).
A total of 2144 invasive cases were reported over the study period. Of these, 76%
(1627/2144) had viable isolates available for serogrouping and 307 (19%) were
serogroup B. Serogroup B cases were reported from across the country however
the majority were from the Western Cape province. The highest incidence of
serogroup B was in children less than 5 years of age.
Isolates displayed a high level of diversity by PFGE. Despite this diversity the
majority of serogroup B meningococci collected over the 5-year period could be
grouped into several clonal clusters representative of global invasive MLST
clonal complexes. Overall, the most predominant MLST clones in South Africa
were ST-32/ET-5 and ST-41/44/lineage 3. In addition, at least 19 PorA types and
16 FetA types were determined among selected isolates.
Globally invasive serogroup B disease is caused by heterogeneous strains
however, prolonged outbreaks in several countries have been due to strains of
the ST-32/ET-5 and ST-41/44/lineage 3 clonal complexes. At present, serogroup
B disease in South Africa is not dominated by an epidemic clone, however, global
clonal complexes ST-32/ET-5 and ST-41/44/lineage 3 are circulating in Western
Cape and Gauteng, respectively.
Description
MSc (Med), Faculty of Health Sciences, University of the Witwatersrand, 2011
Keywords
Neisseria meningitidis, meningococcal infections, serogroup B meningococci