1. Wellcome Trust Centre for the Epidemiology of Infectious Disease, Department of Zoology, University of Oxford, Oxford OX1 3FY,1 and
2. Laboratorio de Referencia de Neumococos, Servicio de Bacteriologı́a, Centro Nacional de Microbiologı́a, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain2
3. Department of Microbiology, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU,3 United Kingdom, and