Coagulase-negative staphylococci (CoNS) are the most frequently isolated bacteria from the blood and the predominant cause of nosocomial infections. Macrolides, lincosamides and streptogramin B (MLSB) antibiotics, especially erythromycin and clindamycin, are important therapeutic agents in the treatment of methicillin-resistant staphylococci infections. Among CoNS, Staphylococcus hominis represents the third most common organism. In spite of its clinical significance, very little is known about its mechanisms of resistance to antibiotics, especially MLSB. Fifty-five S. hominis isolates from the blood and the surgical wounds of hospitalized patients were studied. The erm(C) gene was predominant in erythromycin-resistant S. hominis isolates. The methylase genes, erm(A) and erm(B), were present in 15 and 25% of clinical isolates, respectively. A combination of various erythromycin resistance methylase (erm) genes was detected in 15% S. hominis isolates. The efflux gene msr(A) was detected in 18% of isolates, alone in four isolates, and in different combinations in a further six. The lnu(A) gene, responsible for enzymatic inactivation of lincosamides was carried by 31% of the isolates. No erythromycin resistance that could not be attributed to the genes erm(A), erm(B), erm(C) and msr(A) was detected. In S. hominis, 75 and 84%, respectively, were erythromycin resistant and clindamycin susceptible. Among erythromycin-resistant S. hominis isolates, 68% of these strains showed the inducible MLSB phenotype. Four isolates harbouring the msr(A) genes alone displayed the MSB phenotype. These studies indicated that resistance to MLSB in S. hominis is mostly based on the ribosomal target modification mechanism mediated by erm genes, mainly the erm(C), and enzymatic drug inactivation mediated by lnu(A).

• MeSH
• Anti-Bacterial Agents pharmacology   MeSH
• Bacterial Proteins genetics   metabolism   MeSH
• Humans MeSH
• Lincosamides pharmacology   MeSH
• Macrolides pharmacology   MeSH
• Methyltransferases genetics   metabolism   MeSH
• Microbial Sensitivity Tests MeSH
• Drug Resistance, Multiple, Bacterial MeSH
• Staphylococcal Infections microbiology   MeSH
• Staphylococcus hominis classification   drug effects   enzymology   genetics   MeSH
• Streptogramins pharmacology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Anti-Bacterial Agents MeSH
• Bacterial Proteins MeSH
• ErmA protein, Bacteria MeSH Browser
• Lincosamides MeSH
• Macrolides MeSH
• Methyltransferases MeSH
• Streptogramins MeSH

The lincomycin biosynthetic gene lmbX was deleted in Streptomyces lincolnensis ATCC 25466, and deletion of this gene led to abolition of lincomycin production. The results of complementation experiments proved the blockage in the biosynthesis of lincomycin precursor 4-propyl-L-proline. Feeding this mutant strain with precursor derivatives resulted in production of 4'-butyl-4'-depropyllincomycin and 4'-pentyl-4'-depropyllincomycin in high titers and without lincomycin contamination. Moreover, 4'-pentyl-4'-depropyllincomycin was found to be more active than lincomycin against clinical Staphylococcus isolates with genes determining low-level lincosamide resistance.

• MeSH
• Anti-Bacterial Agents chemistry   metabolism   pharmacology   MeSH
• Bacterial Proteins genetics   metabolism   MeSH
• Humans MeSH
• Lincomycin analogs & derivatives   chemistry   metabolism   pharmacology   MeSH
• Microbial Sensitivity Tests MeSH
• Molecular Structure MeSH
• Proline analogs & derivatives   metabolism   MeSH
• Staphylococcal Infections microbiology   MeSH
• Staphylococcus drug effects   MeSH
• Streptomyces genetics   metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Anti-Bacterial Agents MeSH
• Bacterial Proteins MeSH
• Lincomycin MeSH
• Proline MeSH

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
• Anti-Bacterial Agents pharmacology   MeSH
• Drug Resistance, Bacterial genetics   MeSH
• Erythromycin pharmacology   MeSH
• Ketolides pharmacology   MeSH
• Clindamycin pharmacology   MeSH
• Coagulase metabolism   MeSH
• Macrolides pharmacology   MeSH
• Microbial Sensitivity Tests MeSH
• Methicillin Resistance drug effects   MeSH
• Staphylococcus drug effects   MeSH
• Streptogramin A pharmacology   MeSH
• Streptogramin B pharmacology   MeSH
• Virginiamycin pharmacology   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Anti-Bacterial Agents MeSH
• Erythromycin MeSH
• Ketolides MeSH
• Clindamycin MeSH
• Coagulase MeSH
• Macrolides MeSH
• quinupristin-dalfopristin MeSH Browser
• Streptogramin A MeSH
• Streptogramin B MeSH
• telithromycin MeSH Browser
• 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
• Genes, Bacterial MeSH
• Bacterial Proteins chemistry   genetics   metabolism   physiology   MeSH
• DNA, Bacterial genetics   isolation & purification   MeSH
• Genetic Variation * MeSH
• Humans MeSH
• Lincosamides MeSH
• Macrolides pharmacology   MeSH
• Microbial Sensitivity Tests MeSH
• Drug Resistance, Multiple, Bacterial MeSH
• Evolution, Molecular * MeSH
• Amino Acid Sequence MeSH
• Base Sequence MeSH
• Sequence Analysis, DNA MeSH
• Staphylococcus aureus drug effects   genetics   MeSH
• Staphylococcus haemolyticus drug effects   genetics   isolation & purification   MeSH
• Streptogramin A pharmacology   MeSH
• Amino Acid Substitution MeSH
• Substrate Specificity MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Comparative Study MeSH
• Names of Substances
• Bacterial Proteins MeSH
• DNA, Bacterial MeSH
• Lincosamides MeSH
• Macrolides MeSH
• Streptogramin A MeSH