[1] Cent Publ Hlth Lab, Antibiot Resistance Monitoring & Reference Lab, London NW9 5HT, England
[2] Addenbrookes Hosp, Clin Microbiol & Publ Hlth Lab, Cambridge, England
[3] Cook Cty Hosp, Dept Med, Chicago, IL 60612 USA
[4] Rush Univ, Chicago, IL 60612 USA
[5] Beth Israel Deaconess Med Ctr, Boston, MA 02215 USA
[6] Univ Pittsburgh, Med Ctr, Div Infect Dis, Pittsburgh, PA 15213 USA
[7] VA Med Ctr, Infect Dis Sect, Pittsburgh, PA 15240 USA