[1] Univ Concepcion, Dept Microbiol, Fac Ciencias Biol, Concepcion, Chile
[2] Univ Concepcion, Dept Med Interna, Fac Med, Concepcion, Chile
[3] Univ San Sebastian, Fac Med, Concepcion, Chile
[4] Univ Dundee, Dept Biol Sci, Dundee DD1 4HN, Scotland
[5] Univ Edinburgh, Sch Med, Dept Med Microbiol, Edinburgh EH8 9AG, Midlothian, Scotland