TEICOPLANIN-RESISTANT STAPHYLOCOCCUS-AUREUS EXPRESSES A NOVEL MEMBRANE-PROTEIN AND INCREASES EXPRESSION OF PENICILLIN-BINDING PROTEIN-2 COMPLEX

In the recent clinical trials of teicoplanin therapy of endocarditis c aused by Staphylococcus aureus, at least one instance of the emergence of teicoplanin-resistant strains during therapy has been reported (G. W. Kaatz, S. M. Seo, N. J. Dorman, and S. A. Lerner, J. Infect. Dis 1 62:103-108, 1990). We have confirmed, using conventional electrophores is of EcoRI-digested chromosomal DNA and pulsed-field gel electrophore sis of SmaI-digested chromosomal DNA, that the resistant strain (12873 ) (MIC, 16 mug/ml) is genetically very similar to the susceptible pare nt (12871) (MIC, 4 mug/ml). Kaatz et al. were able to select spontaneo us teicoplanin-resistant mutants (10(-9)), suggesting that a single ge ne might be involved. We have shown that the mutation is highly stable during growth in the absence of teicoplanin. Using Tn551, we have sel ected insertion mutants of 12873 that become teicoplanin susceptible. We have examined a number of aspects of cell wall physiology in strain s 12871 and 12873 and the teicoplanin-susceptible Tn551 mutants of 128 73. 12873 was more susceptible to lysostaphin lysis than 12871 and the susceptible Tn551 derivatives of 12873. Autolysis in phosphate buffer (pH 7.5) and cell wall turnover rates were similar in 12871 and 12873 . An analysis of membrane proteins revealed the expression of a ca. 35 -kDa protein and increased expression of both polypeptides of penicill in-binding protein (PBP) 2 (PBP2) in 12873 relative to 12871 and the T n551 mutants of 12873. This increased expression was not related to PB P2', since both strains were susceptible to oxacillin in 2% NaCl (MIC, less-than-or-equal-to 0.25 mug/ml) and cellular DNA from neither stra in hybridized with a specific mec gene probe. Two independent Tn551 in serts have been mapped to a ca. 117-kb SmaI fragment of the chromosome . These data suggest the possibility that the mutation resulting in re sistance to teicoplanin involves the regulation of expression of both polypeptides of PBP2 and a 35-kDa membrane protein.