1. Max Planck Institute for Extraterrestrial Physics; Plasma Medicine; PO Box 1312 Giessenbachst. 1 85741 Garching Germany
2. Institute for Hygiene and Public Health; University Bonn; Sigmund-Freud-St. 25 53105 Bonn Germany
3. Max Planck Institute for Plasma Physics; EURATOM Association; Boltzmannst. 2 85741 Garching Germany
4. Department of Microbiology; Städtisches Klinikum München GmbH; 80804 Munich Germany