Novel membrane proteins present in teicoplanin-resistant, vancomycin sensitive, coagulase-negative Staphylococcus spp

Abstract

Clinical isolates of Staphylococcus epidermids and Staphylococcus haemolyticus resistant to teicoplanin (MIC 64 mg/L) and sensitive to vancomycin (MIC 2 mg/L), were compared with vancomycin- and teicoplanin-sensitive isolates (MICs I mg/L) of the same species. No apparent differences between the sensitive and resistant strains of either pair were found with respect to binding of teicoplanin to the bacteria, or to the amino acid content or degree of cross-linkage of purified peptidoglycan. The resistant strains did not inactivate teicoplanin in the surrounding medium. Analysis of the membrane proteins of the resistant S. epidermidis strain grown in the presence or absence of sub-inhibitory levels of teicoplanin (4 mg/L), showed the presence of a 39 kDa protein which was either absent, or present in considerably reduced amounts, in the sensitive strain. Fractionation of cell components after lysis of protoplasts showed that the 39 kDa protein was present predominantly in the membrane fraction but also in small amounts in the wall fraction. Similar investigations with S. haemolyticus revealed the presence of a 35 kDa protein in membranes of the resistant strain: the amount was increased substantially by growth in sub-inhibitory levels of teicoplanin. Membranes prepared by mechanical disintegration of bacteria or by osmotic lysis of protoplasts showed large apparent differences in the amounts of the 39 kDa protein.