[1] ACIA, Dept Microbiol, E-08080 Barcelona, Spain
[2] Univ Basque Country, Fac Med, Dept Inmunol Microbiol & Parasitol, E-48080 Bilbao, Spain
[3] Hosp Valle De Hebron, Microbiol Serv, Barcelona, Spain
[4] Hosp Inmaculada, Microbiol Serv, Huercal Overa, Almeria, Spain
[5] Schering Plough Res Inst, Kenilworth, NJ USA
[6] Hosp Pediat Pablo Garrahan, Buenos Aires, DF, Argentina