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The increase in antibiotic resistance among Gram-positive bacteria underscores the urgent need to develop new antibiotics. New antibiotics should target actively growing susceptible bacteria that are resistant to clinically accepted antibiotics including bacteria that are not growing or are protected in a biofilm environment. In this paper, we compare the in vitro activities of two new semisynthetic glycopeptide antibiotics, MA79 and ERJ390, with two clinically used glycopeptide antibiotics—vancomycin and teicoplanin. The new antibiotics effectively killed not only exponentially growing cells of Staphylococcus aureus, but also cells in the stationary growth phase and biofilm.

We investigated the genetic basis of glycopeptide resistance in laboratory-derived strains of S. haemolyticus with emphasis on differences between vancomycin and teicoplanin. The genomes of two stable teicoplanin-resistant laboratory mutants selected on vancomycin or teicoplanin were sequenced and compared to parental S. haemolyticus strain W2/124. Only the two non-synonymous mutations, VraS Q289K and WalK V550L were identified. No other mutations or genome rearrangements were detected. Increased cell wall thickness, resistance to lysostaphin-induced lysis and adaptation of cell growth rates specifically to teicoplanin were phenotypes observed in a sequenced strain with the VraS Q289K mutation. Neither of the VraS Q289K and WalK V550L mutations was present in the genomes of 121S. haemolyticus clinical isolates. However, all but two of the teicoplanin resistant strains carried non-synonymous SNPs in vraSRTU and walKR-YycHIJ operons pointing to their importance for the glycopeptide resistance.

Objectives The aim of this study was to analyse the DNA sequences of three teicoplanin-resistant Staphylococcus epidermidis isolates collected from patients not previously treated with glycopeptide antibiotics. Methods The minimum inhibitory concentrations (MICs) of 12 antibiotics, including teicoplanin and vancomycin, were determined by the broth microdilution method. Genomic DNA was isolated, was sequenced by HiSeqX paired-end sequencing and was assembled into draft genome sequences using MyPro pipeline. Results Analysis of the draft genome sequences demonstrated that the teicoplanin-resistant S. epidermidis isolates belonged to multilocus sequence typing (MLST) sequence types ST5 and ST87 and encoded multiple antimicrobial resistance genes, including the methicillin resistance gene mecA. Conclusions This report highlights the risk of dissemination of S. epidermidis strains resistant to a wide range of clinically important antibiotics.

Here, we describe a fluorescent assay developed to study competitive binding of the glycopeptide antibiotics to live bacteria cells. This assay demonstrated that the mechanism of action of the lipoglycopeptide antibiotics strongly depends on the hydrophobicity of the substitutes, with the best antibacterial activity of the glycopeptide antibiotics equally sharing properties of binding to D-Ala-D-Ala residues of the nascent peptidoglycan and to the membrane.