[1] Univ Antwerp, Microbiol Lab, B-2610 Antwerp, Belgium
[2] Univ Antwerp, Dept Gen Practice, B-2610 Antwerp, Belgium
[3] Fund Sci Res Flanders, Brussels, Belgium
[4] Sci Inst Publ Hlth, Epidemiol Unit, Brussels, Belgium
[5] Leiden Univ, Med Ctr, Microbiol Lab, NL-2300 RA Leiden, Netherlands