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In order to understand the mechanism(s) of the resistance/reduced susceptibility of Staphylococcus aureus to glycopeptide antibiotics, the current data on the modes of action of glycopeptides were reviewed. In addition, the different test systems for detecting vancomycin resistance and the clinical relevance of resistant Staphylococcus aureus were analyzed. Finally, strategies to prevent the nosocomial spread of these bacteria are presented, as are new therapeutic options.

The SENTRY Antimicrobial Surveillance Programme was established to provide a coordinated, standardised, international surveillance on antimicrobial resistance. In one part of the programme, isolates from skin and soft tissue infections sent from 20 hospitals in 12 different European countries were investigated in the European coordinating centre. Of 1013 isolates, Staphylococcus aureus and Pseudomonas aeruginosa were the most significant species, constituting almost 50% of the referred isolates. Methicillin resistance in Staphylococcus aureus averaged 22% across Europe, only slightly less than that in isolates derived from blood. Less than 5% of the enterococcal isolates were resistant to vancomycin. Piperacillin/tazobactam was the most active penicillin-derived beta-lactam compound against Pseudomonas aeruginosa, inhibiting 91.3% of the isolates, while ceftazidime and cefepime were the most active cephalosporins, inhibiting 85.8% and 80.3% of the isolates, respectively. Putative extended-spectrum beta-lactamase production was not detected in Escherichia coli and was found in only 5.1% of the Klebsiella pneumoniae isolates. In general, strains of the family Enterobacteriaceae remained mostly susceptible to carbapenems, cefepime, and amikacin.

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The quinolones are a potent class of antimicrobial agents that target two essential enzymes of bacterial cells: DNA gyrase and topoisomerase IV. Resistance is mediated chiefly through stepwise mutations in the genes that encode these enzymes, leading to alterations of the target site. These mutations occur in an area called the "quinolone resistance determining region". In gram-positive organisms, mutations occur more often in topoisomerase IV than in DNA gyrase. This target preference appears to depend upon two factors: the species of organism and the selecting drug. Resistance can be enhanced by a decrease in intracellular drug concentration, which is mediated through efflux pumps. The newer generation of fluoroquinolones and non-fluorinated quinolones exhibits enhanced activity against gram-positive organisms compared to the older members of this drug class, although development of resistance to these drugs has been demonstrated in vitro. This review gives a chronological perspective of the literature on the action of DNA gyrase and topoisomerase IV and the mechanisms of resistance to quinolones in staphylococci, streptococci and enterococci.

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Implant-associated Staphylococcus aureus infections are difficult to treat because of biofilm formation. Bacteria in a biofilm are often insensitive to antibiotics and host immunity. Monoclonal antibodies (mAbs) could provide an alternative approach to improve the diagnosis and/or treatment of biofilm-related infections. Here we show that mAbs targeting common surface components of S. aureus can recognize clinically relevant biofilm types. We identify two groups of antibodies: one group that uniquely binds S. aureus in biofilm state and one that recognizes S. aureus in both biofilm and planktonic state. In a mouse model, we show that mAb 4497 (recognizing wall teichoic acid (WTA)) specifically localizes to biofilm-infected implants. In conclusion, we demonstrate the capacity of several human mAbs to detect S. aureus biofilms in vitro and in vivo. This is an important first step to develop mAbs for imaging or treating S. aureus biofilms.