INVIVO DEVELOPMENT OF TEICOPLANIN RESISTANCE IN A VANB ENTEROCOCCUS-FAECIUM ISOLATE

Acquired vancomycin resistance in enterococci may be associated with t eicoplanin susceptibility (VanB) or teicoplanin resistance (VanA). Thi s paper characterizes the first instance of in vivo emergence of teico planin resistance in an Enterococcus faecium strain of VanB phenotype. Vancomvcin-resistant (MIC, 256/512 mug/mL) E. faecium was isolated in termittently from a patient' s blood over 4 months. The MIC of teicopl anin for the first 5 isolates was 1.0 mug/mL; it was 64 mug/mL for the final 2. Analysis of plasmid and chromosomal DNA revealed the isolate s to be of clonal origin. Conjugal transfer of vancomycin resistance w as not obtained. A vanB DNA probe hybridized with both teicoplanin-sus ceptible and resistant isolates, but a vanA probe failed to hybridize with any isolate. SDS-PAGE of membrane proteins from a teicoplanin-res istant isolate revealed constitutive production of a normally inducibl e 41-kDa protein. These findings challenge the ultimate utility of tei coplanin for treatment of infections caused by vancomycin-resistant en terococci.