A multilocus sequence typing (MLST) system for group B streptococcus (GBS) has been developed and validated on a global collection of human GBS strains isolated from carriage and invasive disease. A carriage study was performed, over a 3-year period, to establish the rate of carriage ofGBS in pregnant women in Oxford, UK. Invasive isolates were collected, prospectively and retrospectively over a similar time period. Twenty-one percent of women studied were asymptomatic carriers of GBS. The incidence of invasive GBS was 0.9/1000 live births in neonates and 6.11100,000 population >60 years. The population structure of GBS is best depicted. using MLST. as a network of related clusters indicating the presence of recomb inationa I events occurring in the population that interfere with a tree like branching structure of the population. A single hypervirulent clone ofGBS (ST-17 complex) is responsible for an excess of neonatal disease in Oxford (odds ratio 3.4). The possibility that a factor other than capsular type IIImay be responsible for virulence of this clonal complex in neonates is raised. Intriguingly this clonal complex was unique among human lineages in that it has emerged from bovine GBS. It was not however associated with increased invasiveness amongst adult (> 60 years). Further study ofthis hypervirulent clone of GBS is likely to contribute to the understanding of the pathogenesis of neonatal GBS disease.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:402623 |
| Date | January 2004 |
| Creators | Jones, Nicola |
| Publisher | Open University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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