1. Lehrstuhl für Bakteriologie, Max von Pettenkofer‐Institut für Hygiene und Medizinische Mikrobiologie, München, Germany.
2. Department of Infectious Diseases, Royal Postgraduate Medical School, Hammersmith Hospital, London W12 ONN, UK.
3. Department of Microbiology and Immunology, Stanford School of Medicine, Stanford University, Stanford, California 94305, USA.