1. From the Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, San Antonio, Texas; 2Department of Microbiology, University of South China, Hengyang, Hunan, China;
2. Department of Clinical Research, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom; and 4MRC Laboratories, Fajara, Banjul, The Gambia, West Africa.
3. From the Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, San Antonio, Texas;
4. Department of Clinical Research, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom; and
5. Department of Microbiology, University of South China, Hengyang, Hunan, China;