We determined the activities of new antibiotics telithromycin (ketolide) and quinupristin/dalfopristin (streptogramins) against 88 macrolide and/or lincosamide resistant coagulase-negative staphylococci (CoNS) isolates with defined resistance gene status. Telithromycin susceptibility was determined only in erythromycin-sensitive isolates (15) indicating the same mechanisms of resistance. In contrast, all erythromycin-resistant isolates (73) were either constitutively resistant to telithromycin (13 isolates with constitutive erm genes) or demonstrated telithromycin D-shaped zone (60 isolates with inducible msr(A) and/or erm). However, the level of inducible resistance conferred by msr(A) (35 isolates) was borderline even after induction by erythromycin. No quinupristin/dalfopristin resistant isolate was observed if tested by disk-diffusion method (DDM) but 18 isolates were intermediate (MIC = 1-3 mg/L) and two isolates resistant (MIC = 8 mg/L) if tested by E-test. All these isolates were resistant to streptogramin A and harbored vga(A) gene (1 isolate) or vga(A)LC gene (19 isolates). MICs for quinupristin/dalfopristin were higher for isolates with combination of streptogramin A resistance and constitutive MLSB resistance (MIC = 3-8 mg/L in 4 isolates) than for streptogramin A-resistant isolates susceptible to streptogramin B (MIC = 0.5-2 mg/L in 16 isolates). In addition to S. haemolyticus, vga(A)LC was newly identified in S. epidermidis and S. warnerii indicating its widespread occurrence in CoNS. Misidentification of low-level resistant isolates by DDM may contribute to dissemination of streptogramin A resistance.

• MeSH
• antibakteriální látky farmakologie   MeSH
• bakteriální léková rezistence genetika   MeSH
• erythromycin farmakologie   MeSH
• ketolidy farmakologie   MeSH
• klindamycin farmakologie   MeSH
• koagulasa metabolismus   MeSH
• makrolidy farmakologie   MeSH
• mikrobiální testy citlivosti MeSH
• rezistence na methicilin účinky léků   MeSH
• Staphylococcus účinky léků   MeSH
• streptogramin A farmakologie   MeSH
• streptogramin B farmakologie   MeSH
• virginiamycin farmakologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antibakteriální látky MeSH
• erythromycin MeSH
• ketolidy MeSH
• klindamycin MeSH
• koagulasa MeSH
• makrolidy MeSH
• quinupristin-dalfopristin MeSH Prohlížeč
• streptogramin A MeSH
• streptogramin B MeSH
• telithromycin MeSH Prohlížeč
• virginiamycin MeSH

We found a new variant of the streptogramin A resistance gene, vga(A)LC, in clinical isolates of Staphylococcus haemolyticus resistant to lincomycin and clindamycin but susceptible to erythromycin and in which no relevant lincosamide resistance gene was detected. The gene vga(A)LC, differing from the gene vga(A) at the protein level by seven amino acid substitutions, was present exclusively in S. haemolyticus strains resistant to both lincosamides and streptogramin A (LS(A) phenotype). Antibiotic resistance profiles of the ATP-binding cassette (ABC) proteins Vga(A)(LC) and Vga(A) in the antibiotic-susceptible host S. aureus RN4220 were compared. It was shown that Vga(A)LC conferred resistance to both lincosamides and streptogramin A, while Vga(A) conferred significant resistance to streptogramin A only. Detailed analysis of the seven amino acid substitutions, distinguishing the two related ABC proteins with different substrate specificities, identified the substrate-recognizing site: four clustered substitutions (L212S, G219V, A220T, and G226S) in the spacer between the two ATP-binding cassettes altered the substrate specificity and constituted the lincosamide-streptogramin A resistance phenotype. A transport experiment with radiolabeled lincomycin demonstrated that the mechanism of lincosamide resistance in S. haemolyticus was identical to that of the reported macrolide-streptogramin B resistance conferred by Msr(A).

• MeSH
• bakteriální geny MeSH
• bakteriální proteiny chemie   genetika   metabolismus   fyziologie   MeSH
• DNA bakterií genetika   izolace a purifikace   MeSH
• genetická variace * MeSH
• lidé MeSH
• linkosamidy MeSH
• makrolidy farmakologie   MeSH
• mikrobiální testy citlivosti MeSH
• mnohočetná bakteriální léková rezistence MeSH
• molekulární evoluce * MeSH
• sekvence aminokyselin MeSH
• sekvence nukleotidů MeSH
• sekvenční analýza DNA MeSH
• Staphylococcus aureus účinky léků   genetika   MeSH
• Staphylococcus haemolyticus účinky léků   genetika   izolace a purifikace   MeSH
• streptogramin A farmakologie   MeSH
• substituce aminokyselin MeSH
• substrátová specifita MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• srovnávací studie MeSH
• Názvy látek
• bakteriální proteiny MeSH
• DNA bakterií MeSH
• linkosamidy MeSH
• makrolidy MeSH
• streptogramin A MeSH