[1] Ludwig Maximilian Univ Munich, Fac Vet Med, Dept Vet Sci, Schonleutnerstr 8, D-85764 Oberschleissheim, Germany
[2] Univ Vet Med Vienna, Inst Microbiol, Funct Microbiol, Dept Pathobiol, A-1210 Vienna, Austria
[3] Norwegian Univ Life Sci, Fac Vet Med, Dept Food Safety & Infect Biol, POB 5003 NMBU, N-1432 As, Norway