Activity of a new oral streptogramin, XRP2868, against gram-positive cocci harboring various mechanisms of resistance to streptogramins.
The antibacterial activity of XRP2868, a new oral streptogramin composed of a combination of RPR132552 (streptogramin A) and RPR202868 (streptogramin B), was evaluated against a collection of clinical gram-positive isolates with characterized phenotypes and genotypes of streptogramin resistance. The effects of genes for resistance to streptogramin A or B on the activity of XRP2868 and its components were also tested by cloning these genes individually or in various combinations in gram-positive recipient strains susceptible to quinupristin-dalfopristin. The species tested included Staphylococcus aureus, coagulase-negative staphylococci, Enterococcus faecalis, Enterococcus faecium, Streptococcus pneumoniae, and other species of streptococci. XRP2868 was generally fourfold more potent than quinupristin-dalfopristin against S. aureus, E. faecium, and streptococci and had activity against E. faecalis (MICs = 0.25 to 1 microg/ml). XRP2868 appeared to be affected by the same mechanisms of resistance as those to quinupristin-dalfopristin. Nevertheless, the strong activity of factor A of the oral streptogramin enabled the combination to be very potent against streptogramin-susceptible staphylococci, streptococci, and E. faecium (MICs = 0.03 to 0.25 microg/ml) and to retain low MICs against the strains harboring a mechanism of resistance to factor A or factor B of the streptogramin. However, the combination of mechanisms of resistance to factors A and B caused an increase in the MICs of XRP2868, which reached 1 to 4 mug/ml. As with the other streptogramins, there was a reduction in the bactericidal effect of XRPR2868 when the staphylococcal strains acquired a constitutively expressed erm gene.
Dupuis
Michel
M
Service de Microbiologie and EA 2128 Relations Hôte et Microorganismes de Epithéliums, Hôpital Côte de Nacre, Université de Caen, France.
Leclercq
Roland
R
D000284:Administration, Oral; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004338:Drug Combinations; D004353:Drug Evaluation, Preclinical; D004352:Drug Resistance, Microbial; D006095:Gram-Positive Cocci / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D025364:Streptogramin A / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D025381:Streptogramin B / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D025361:Streptogramins / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D004338:Drug Combinations; D025361:Streptogramins; C509060:flopristin, linopristin drug combination; D025381:Streptogramin B; D025364:Streptogramin A