1. Department of Microbiology, Institute of Tropical Medicine, B-2000 Antwerp, Belgium and Medical Research Council Laboratories, Banjul, The Gambia
2. Department of Microbiology, Institute of Tropical Medicine, B-2000 Antwerp, Belgium
3. Department of Microbiology, Institute of Tropical Medicine, B-2000 Antwerp, Belgium and Flanders Interuniversity Institute for Biotechnology, VIB, B-9052 Ghent, Belgium.
4. Medical Research Council Laboratories, Banjul, The Gambia