Dalfopristin

About: Dalfopristin is a research topic. Over the lifetime, 696 publications have been published within this topic receiving 26621 citations. The topic is also known as: RP-54476 & Dalfopristina.

Assessment of linezolid resistance mechanisms among Staphylococcus epidermidis causing bacteraemia in Rome, Italy

Abstract: Objectives: To characterize linezolid resistance among blood cultured Staphylococcus epidermidis from patients at the Polyclinic Agostino Gemelli (2006-08). Isolates also showed elevated MICs of macrolide, lincosomide and streptogramin (MLS) compounds, which were investigated. Methods: Ten S. epidermidis exhibiting linezolid MICs≥4 mg/L were included. Isolates were screened for cfr mutations in 23S rRNA, L3, L4 and L22, and MLS genes by PCR/sequencing. Ribosomal proteins were compared with those from a linezolid-susceptible (MIC, 1 mg/L) clinical strain and ATCC 12228. cfr location was determined by Southern blot/hybridization. The cfr strain was submitted to plasmid curing. Epidemiology was assessed by PFGE and multilocus sequence typing (MLST). Results: S. epidermidis displayed linezolid MICs of 4 or 8 mg/L, except for strain 4303A (MIC, 64 mg/L). These organisms and a linezolid-susceptible strain exhibited L3 Leu101Val compared with ATCC 12228. Isolates also showed L3 Phe147Leu and A1a157Arg, and L4 Asn158Ser. Strain 12375A possessed L4 Lys68Arg. Isolates were wild-type for 23S rRNA and L22. cfr was plasmid located in strain 4303A and the plasmid-cured strain exhibited a linezolid MIC (4 mg/L) similar to that for cfr-negative strains (4-8 mg/L). All organisms harboured erm(A) and msr(A), while vga(A) was detected in several isolates. All isolates were clonally related and ST-23. Conclusions: L3 Phe147Leu and/or Ala157Arg appeared responsible for the elevated linezolid MIC, since adjacent alterations have been associated with resistance. L4 Asn158Ser has been reported in a linezolid-susceptible isolate and Lys68Arg detected here did not seem to provide an additive effect. Acquisition of cfr markedly increased (8- to 16-fold) the linezolid MICs. vga(A) was associated with higher MICs of quinupristin/dalfopristin and retapamulin.

Antibiotic pressure can induce the viable but non-culturable state in Staphylococcus aureus growing in biofilms

Abstract: Objectives: Staphylococcal biofilms are among the main causes of chronic implant-associated infections. We have recently suggested that their transformation into viable but non-culturable (VBNC) forms (i.e. forms capable of resuscitation) could be responsible for the recurrent symptoms. This work aims to establish whether Staphylococcus aureus biofilms can give rise to VBNC forms capable of being resuscitated in suitable environmental conditions, the role of different stressors in inducing the VBNC state and the conditions favouring resuscitation. Methods: S. aureus 10850 biofilms were exposed to different concentrations of antibiotic (vancomycin or quinupristin/dalfopristin) and/or to nutrient depletion until loss of culturability. The presence of viable cells and their number were examined by epifluorescence microscopy and flow cytometry. Gene expression was measured by real-time PCR. Resuscitation ability was tested by growth in rich medium containing antioxidant factors. Results: Viable subpopulations were detected in all non-culturable biofilms. However, viable cell numbers and gene expression remained constant for 150 days from loss of culturability in cells from antibiotic-exposed biofilms, but not in those that had only been starved. Resuscitation was obtained in rich medium supplemented with 0.3% sodium pyruvate or with 50% filtrate of a late-log culture. Conclusions: Our findings demonstrate that S. aureus can enter the VBNC state in infectious biofilms. The presence of vancomycin or quinupristin/dalfopristin can inadvertently induce a true VBNC state or its persistence in S. aureus cells embedded in biofilms, supporting previous findings on the role of staphylococcal biofilms in recurrent infections.

Antimicrobial susceptibility of Bifidobacterium strains from humans, animals and probiotic products

Abstract: Objectives: The aim of this study was to assess the antimicrobial susceptibility of a taxonomically diverse set of Bifidobacterium strains to different classes of antimicrobial agents using a recently described medium. Methods: The susceptibility of 100 strains encompassing 11 bifidobacterial species originating from humans, animals and probiotic products to 12 antimicrobial agents was tested by agar overlay disc diffusion. Based on these results, one or two strains per species were selected for susceptibility testing to nine antibiotics by broth microdilution using the Lactic acid bacteria Susceptibility test Medium (LSM) supplemented with cysteine. The genotypic basis of atypical tetracycline resistance was further characterized using PCR, Southern blotting and partial sequencing. Results: Based on the distribution of inhibition zone diameters and MIC values, all strains tested were susceptible to amoxicillin, chloramphenicol, erythromycin, quinupristin/dalfopristin, rifampicin and vancomycin. Our data also reinforce earlier observations indicating that bifidobacteria are intrinsically resistant to gentamicin, sulfamethoxazole and polymyxin B. Susceptibility to trimethoprim, trimethoprim/ sulfamethoxazole, ciprofloxacin, clindamycin, tetracycline and minocycline was variable. The tet(W) gene was responsible for tetracycline resistance in 15 strains including 7 probiotic isolates belonging to the taxa Bifidobacterium animalis subsp. lactis and Bifidobacterium bifidum. This gene was present in a single copy on the chromosome and did not appear to be associated with the conjugative transposon TnB1230 previously found in tet(W)-containing Butyrivibrio fibrisolvens. Conclusions: The use of the LSM + cysteine medium allowed us to discriminate between intrinsic and atypical resistance properties of bifidobacteria and sets the scene for future definition of epidemiological cut-off values for all important Bifidobacterium species. The presence of an acquired tet(W) gene in several probiotic product isolates stresses the need for a minimal safety evaluation during the selection of Bifidobacterium strains for probiotic use.

Mechanisms of resistance to quinupristin-dalfopristin among isolates of Enterococcus faecium from animals, raw meat, and hospital patients in Western Europe.

Abstract: Twenty-eight quinupristin-dalfopristin-resistant isolates of Enterococcus faecium from hospital patients and nonhuman sources in European countries were studied. High-level resistance (MICs, >/=32 microg/ml) was associated with the presence of vat(E) (satG) (14 isolates ?50%) or vat(D) (satA) (6 isolates ?21%). These genes were not detected in eight (29%) isolates with lower levels of quinupristin-dalfopristin resistance (MICs, 4 to 16 microg/ml). This suggests the presence of further mechanisms of resistance to quinupristin-dalfopristin in E. faecium.