[1] Bulgarian Acad Sci, Stephan Angeloff Inst Microbiol, Sect Microbial Biochem, Acad G Bonchev St,Bl 26, BU-1113 Sofia, Bulgaria
[2] Med Univ Sofia, Dept Med Microbiol, 2 Zdrave St, Sofia 1431, Bulgaria
[3] Bulgarian Acad Sci, Inst Expt Morphol Pathol & Anthropol Museum, Acad G Bonchev St,Bl 25, BU-1113 Sofia, Bulgaria
[4] Natl Ctr Infect & Parasit Dis, NRL Enter Pathogens, 26 Yanko Sakazov Blvd, Sofia 1504, Bulgaria
[5] Natl Ctr Infect & Parasit Dis, NRL Biohazard Level Infect 3, 26 Yanko Sakazov Blvd, Sofia 1504, Bulgaria