tedizolid and Staphylococcal-Infections

Acute bacterial skin and skin structure infections (ABSSSI) are among the most frequent infectious diseases. Recently, several new antibiotics with activity against MRSA have been approved. Tedizolid, a second-generation oxazolidinone approved for ABSSSI offers theoretical advantages over first-generation oxazolidinones.. A comprehensive online search of Medline, ClinicalTrials.gov, and conference presentations was made, selecting articles between January 2000 and April 2020. In this review, the authors discuss the chemical and microbiological properties of tedizolid, summarize its efficacy, safety, and potential role in the treatment of ABSSSI as well as the potential for future indications.. Tedizolid has proven to be non-inferior compared to linezolid for the treatment of ABSSSI in two registrational phase III clinical trials, being well tolerated. Tedizolid exhibits antibacterial activity against the most important ABSSSI pathogens (including multidrug-resistant strains of MRSA), as well as mycobacteria and Nocardia. It appears to have a safe profile, including decreased myelotoxicity and no significant drug interactions. Preliminary studies with longer duration of therapy seem to confirm these potential benefits. Overall, tedizolid expands the newly acquired armamentarium to treat ABSSSI. The role of tedizolid for other indications is under investigation and has yet to be determined.

Topics: Animals; Anti-Bacterial Agents; Drug Interactions; Humans; Linezolid; Methicillin-Resistant Staphylococcus aureus; Oxazolidinones; Skin Diseases, Bacterial; Staphylococcal Infections; Tetrazoles

Methicillin-resistant Staphylococcus aureus (MRSA)is a common pathogen in acute bacterial skin and soft tissue infections (ABSSSIs), nosocomial pneumonia, bacteremia, endocarditis, as well as diabetic foot, bone, and joint infections. Areas covered: This review summarizes the randomized controlled trials that evaluated the clinical efficacy of tedizolid in ABSSSIs, which is currently the only United States Food and Drug Administration-labeled indication for tedizolid. Expert opinion: Tedizolid has several potential advantages over linezolid including once-daily dosing, shorter duration of therapy, and increased tolerability. However, its cost will likely limit its adoption for ABSSSIs with MRSA because other oxazolidinone antibiotics are available in less costly generic versions. Tedizolid is also currently being investigated for its use in other MRSA infections including nosocomial pneumonia as well as diabetic foot, bone, and joint infections and tedizolid's use in these disease states appears more promising. Potential indications for future clinical investigation of tedizolid's efficacy and safety include bacteremia and meningitis.

Topics: Anti-Bacterial Agents; Humans; Linezolid; Methicillin-Resistant Staphylococcus aureus; Oxazolidinones; Randomized Controlled Trials as Topic; Soft Tissue Infections; Staphylococcal Infections; Tetrazoles

Tedizolid, the active moiety of tedizolid phosphate, is approved in the United States, the European Union, Canada and a number of other countries for the treatment of acute bacterial skin and skin structure infections (ABSSSI) caused by certain susceptible bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). This network meta-analysis (NMA) evaluates the comparative effectiveness of tedizolid and other antibacterials indicated for the treatment of ABSSSI caused by MRSA.. Systematic review of 10 databases was undertaken to inform an NMA to estimate the relative effectiveness of tedizolid and established monotherapy comparators (ceftaroline, daptomycin, linezolid, teicoplanin, tigecycline, vancomycin) for treating MRSA-associated ABSSSI. Randomized controlled trials enrolling adults with ABSSSI or complicated skin and skin structure infections caused by suspected/documented MRSA were eligible for inclusion. Networks were developed based on similarity of study design, patient characteristics, outcome measures and available data. Outcomes of interest included clinical response at end of therapy (EOT), post-therapy evaluation (PTE) or test-of-cure assessment and treatment discontinuations resulting from adverse events (AEs). Bayesian NMA was conducted for each outcome using fixed-effects and random effects models.. Literature searches identified 3,618 records; 15 trials met the inclusion criteria and were considered suitable for NMA comparison. In fixed-effects models, tedizolid had higher odds of clinical response at EOT (odds ratio [OR], 1.7; credible interval, 1.0, 3.0) and PTE than vancomycin (OR, 1.6; credible interval, 1.1, 2.5). No differences in odds of clinical response at EOT or PTE were observed between tedizolid and other comparators. There was no evidence of a difference among treatments for discontinuation due to AEs. Results from random effects and fixed-effects models were generally consistent.. Tedizolid was superior to vancomycin for clinical response at EOT and PTE. There was no evidence of a difference between tedizolid and other comparators and no evidence of a difference between tedizolid and all comparators when evaluating discontinuation due to AEs. These findings suggest that tedizolid provides an alternative option for the management of serious skin infections caused by suspected or documented MRSA. This study is subject to the limitations inherent in all NMAs, and the results should be interpreted accordingly.

Topics: Anti-Bacterial Agents; Bayes Theorem; Ceftaroline; Cephalosporins; Daptomycin; Humans; Linezolid; Methicillin-Resistant Staphylococcus aureus; Organophosphates; Oxazoles; Oxazolidinones; Skin Diseases, Bacterial; Staphylococcal Infections; Tetrazoles; Vancomycin

Vancomycin has been the cornerstone of treatment for methicillin-resistant Staphylococcus aureus (MRSA) infections. This review describes new MRSA-active antibiotics that have recently been introduced and highlights emerging resistance.. Elevations in the vancomycin minimum inhibitory concentration within the susceptible range are associated with treatment failure and mortality in the treatment of MRSA infections. Ceftaroline and ceftobiprole are anti-MRSA cephalosporins and are noninferior to comparator agents in the treatment of acute bacterial skin and skin structure infections (ABSSSIs) and pneumonia. Tedizolid is more potent than linezolid, has improved pharmacokinetics and reduced toxicity and is active against cfr-containing S. aureus. Telavancin now has approval for treatment of hospital-acquired pneumonia, and recent phase 2 trial data showed similar cure rates in S. aureus bacteremia. Dalbavancin and oritavancin are administered once weekly and are noninferior to comparators for acute bacterial skin and skin structure infections. Resistance has emerged against many new anti-MRSA antimicrobials including ceftaroline. Combination therapy of β-lactams with vancomycin or daptomycin is increasing.. Several new MRSA-active agents are now approved for use, although much of the data is derived from treatment of acute bacterial skin and skin structure infections or pneumonia. Further studies are required for more invasive infections, such as bacteremia and endocarditis.

Topics: Acetamides; Anti-Bacterial Agents; Cephalosporins; Cost-Benefit Analysis; Drug Administration Routes; Drug Therapy, Combination; Glycopeptides; Humans; Linezolid; Lipoglycopeptides; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Oxazolidinones; Severity of Illness Index; Skin Diseases, Bacterial; Staphylococcal Infections; Tetrazoles; Vancomycin

Tedizolid is a protein synthesis inhibitor in clinical use for the treatment of Gram-positive infections. Pulmonary MRSA infections are a growing problem in patients with cystic fibrosis (CF) and the efficacy of tedizolid-based therapy in CF pulmonary infections is unknown.. To evaluate the in vitro and in vivo activity of tedizolid and predict the likelihood of tedizolid resistance selection in CF-background Staphylococcus aureus strains.. A collection of 330 S. aureus strains (from adult and paediatric patients), either of normal or small colony variant (SCV) phenotypes, gathered at three CF centres in the USA was used. Tedizolid activity was assessed by broth microdilution, Etest and time-kill analysis. In vivo tedizolid efficacy was tested in a murine pneumonia model. Tedizolid in vitro mutants were obtained by 40 days of exposure and progressive passages. Whole genome sequencing of clinical S. aureus strains with reduced susceptibility to tedizolid was performed.. MRSA strain MIC90s were tedizolid 0.12-0.25 mg/L and linezolid 1-2 mg/L; for MSSA strains, MIC90s were tedizolid 0.12 mg/L and linezolid 1-2 mg/L. Two strains, WIS 441 and Seattle 106, with tedizolid MICs of 2 mg/L and 1 mg/L, respectively, had MICs above the FDA tedizolid breakpoint (0.5 mg/L). Tedizolid at free serum concentrations exhibited a bacteriostatic effect. Mean bacterial burdens in lungs (log10 cfu/g) for WIS 423-infected mice were: control, 11.2±0.5; tedizolid-treated (10 mg/kg), 3.40±1.87; linezolid-treated (40 mg/kg), 4.51±2.1; and vancomycin-treated (30 mg/kg), 5.21±1.93. For WIS 441-infected mice the (log10 cfu/g) values were: control, 9.66±0.8; tedizolid-treated, 3.18±1.35; linezolid-treated 5.94±2.19; and vancomycin-treated, 4.35±1.7.. These results suggest that tedizolid represents a promising therapeutic option for the treatment of CF-associated MRSA/MSSA infections, having potent in vivo activity and low resistance potential.

Topics: Adult; Animals; Anti-Bacterial Agents; Child; Coinfection; Cystic Fibrosis; Humans; Larva; Mice; Microbial Sensitivity Tests; Moths; Oxazolidinones; Pneumonia, Bacterial; Protein Synthesis Inhibitors; Sputum; Staphylococcal Infections; Staphylococcus aureus; Tetrazoles; Whole Genome Sequencing

Tedizolid (TZD) and daptomycin (DAP) were assessed in a rat endocarditis model against

Topics: Animals; Anti-Bacterial Agents; Colony Count, Microbial; Daptomycin; Endocarditis, Bacterial; Enterococcus; Enterococcus faecalis; Enterococcus faecium; Gram-Positive Bacterial Infections; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Oxazolidinones; Rats; Staphylococcal Infections; Tetrazoles; Vancomycin Resistance; Vancomycin-Resistant Staphylococcus aureus

Prolonged use of linezolid for bone and joint infection (BJI) is limited by its long-term toxicity. The better safety profile of tedizolid, a recently developed oxazolidinone, could offer an alternative. However, its efficacy against biofilm-embedded and intracellular Staphylococcus aureus, the two main bacterial reservoirs associated with BJI chronicity, is unknown.. Using three S. aureus strains (6850 and two clinical BJI isolates), linezolid and tedizolid were compared regarding their ability: (i) to target the S. aureus intracellular reservoir in an in vitro model of osteoblast infection, using three concentrations increasing from the bone concentration reached with standard therapeutic doses (Cbone = 2.5 × MIC; Cplasm = 10 × MIC; Cmax = 40 × MIC); (ii) to eradicate mature biofilm [minimal biofilm eradication concentration (MBEC)]; and (iii) to prevent biofilm formation [biofilm MIC (bMIC) and confocal microscopy].. Linezolid and tedizolid weakly reduced the intracellular inoculum of S. aureus in a strain-dependent manner despite the similar MICs for the tested strains, but improved cell viability even in the absence of an intracellular bactericidal effect. Conversely, linezolid and tedizolid were ineffective in eradicating mature biofilm formed in vitro, with MBEC >2000 and >675 mg/L, respectively. bMICs of tedizolid were 4-fold lower than those of linezolid for all strains.. Linezolid and tedizolid alone are not optimal candidates to target bacterial phenotypes associated with chronic forms of BJI. Despite weak intracellular activity, they both reduce infection-related cytotoxicity, suggesting a role in modulating intracellular expression of staphylococcal virulence factors. Although inactive against biofilm-embedded S. aureus, both-but particularly tedizolid-are able to prevent biofilm formation.

Topics: Anti-Bacterial Agents; Biofilms; Granulocyte Precursor Cells; Humans; Linezolid; Microbial Sensitivity Tests; Models, Theoretical; Osteoarthritis; Oxazolidinones; Staphylococcal Infections; Staphylococcus aureus; Tetrazoles

Glycopeptides are widely used for the treatment of meticillin-resistant Staphylococcus aureus (MRSA) infections. Although difficult to detect, isolates with reduced (GISA), hetero (hGISA) or complete (GRSA) resistance to glycopeptides are increasingly reported. Optimal therapy for such strains is unknown. We compared the in vitro and in vivo activity of tedizolid (TED), a recently licensed oxazolidonone, with vancomycin (VAN) and teicoplanin (TEIC) combined with fusidic acid (FD) or rifampicin (RIF) against S. aureus (SA) with reduced susceptibility to glycopeptides.. Susceptibility was determined for six (GISA, hGISA and GRSA) reference strains and 72 clinical MRSA isolates screened for hGISA/GISA-like phenotypes. Synergy and bactericidal activity were assessed using chequerboard and time-kill assays. The G. mellonella wax moth caterpillar model was used to measure the activity of TED and the combinations in vivo.. Glycopeptide MICs (VAN/TEIC) ranged from 0.5-8/4 and 0.125-1 for TED. No significant synergy was noted when VAN/TEIC were combined with either RIF or FD. Time-kill assays confirmed that TED was bacteriostatic but superior to VAN and TEIC against GISA strains. In G. mellonella TED was more effective than TEIC monotherapy versus GISA strains. The combination of TEIC with RIF was the most effective combination overall, both in vitro and in vivo.. TED had good in vitro activity versus MRSA including those with reduced susceptibility to glycopeptides. Although bacteriostatic, it was effective in the G. mellonella model and superior to TEIC in the treatment of GISA. Although this supports the use of TED for MRSA and GISA, the TEIC/RIF combination also warrants further study.

Topics: Animals; Anti-Bacterial Agents; Drug Therapy, Combination; Humans; Larva; Lepidoptera; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Oxazolidinones; Staphylococcal Infections; Staphylococcus aureus; Teicoplanin; Tetrazoles; Vancomycin

Topics: Aged; Bacteremia; Endovascular Procedures; Humans; Male; Methicillin-Resistant Staphylococcus aureus; Oxazolidinones; Recurrence; Staphylococcal Infections; Tetrazoles; Time Factors; Transplants

Topics: Aged; Anti-Bacterial Agents; Cross Infection; Drug Resistance, Bacterial; Fatal Outcome; Genes, Bacterial; Humans; Linezolid; Male; Multiple Organ Failure; Mutation; Oxazolidinones; Staphylococcal Infections; Staphylococcus epidermidis; Tetrazoles; Turkey

Methicillin-resistant Staphylococcus aureus (MRSA) is a threat to the success of clinical treatment. Besides high antimicrobial resistance rates, the presence of heterogeneous vancomycin-intermediate S. aureus (hVISA) and heterogeneous daptomycin-non-susceptible S. aureus (hDNSSA) in the hospital environment is underestimated and is associated with treatment failure. The aim of this study was to investigate MRSA dissemination in a Brazilian hospital and to evaluate the efficacy of various treatment options in vitro.. MRSA strains were typed by MLST, PFGE and SCCmec typing. Minimum inhibitory concentrations (MICs) to daptomycin, linezolid, quinupristin/dalfopristin, teicoplanin, tetracycline, tigecycline, vancomycin and tedizolid were determined by broth microdilution. The presence of a heterogeneous population was detected by population analysis profile (PAP). Regarding hVISA and hDNSSA strains, the sequences and expression levels of genes involved in resistance to daptomycin and vancomycin were determined as well as cell wall thickness and autolysis.. ST5/ST105-SCCmecII lineage was prevalent amongst 27 clinical MRSA characterised in this study. Two hDNSSA strains (one also hVISA) were detected and were confirmed by PAP. Isolate SCMSC29 (hVISA and hDNSSA) showed increased expression of genes involved in cell wall metabolism, slight cell wall thickening, reduction of autolysis, and single nucleotide polymorphisms (SNPs) in the rpoB and mprF genes compared with the susceptible strain SCMSC31. SCMSC35 (hDNSSA) presented SNPs in the rpoB and mprF genes as well as a thickened cell wall.. Despite this worrying and hard to detect phenotype, treatment alternatives such as teicoplanin, linezolid, tetracycline, tigecycline, quinupristin/dalfopristin and tedizolid were all active against these isolates.

Topics: Bacterial Proteins; Bacteriolysis; Brazil; Cell Wall; Daptomycin; Drug Resistance, Bacterial; Humans; Linezolid; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Multilocus Sequence Typing; Oxazolidinones; Polymorphism, Single Nucleotide; Staphylococcal Infections; Tetrazoles; Vancomycin

Topics: Anti-Bacterial Agents; Humans; Linezolid; Methicillin-Resistant Staphylococcus aureus; Oxazolidinones; Soft Tissue Infections; Staphylococcal Infections; Tetrazoles

Tedizolid is an orally bioavailable oxazolidinone with once-daily dosing and broad-spectrum Gram-positive activity. Combination therapy is commonly indicated to improve efficacy against difficult-to-treat pathogens and biofilms. There are no studies describing the pharmacodynamic interactions between tedizolid and other orally bioavailable antimicrobials.. MICs of tedizolid, rifampicin, trimethoprim/sulfamethoxazole, doxycycline and moxifloxacin were determined by broth microdilution against a convenience sample of 45 staphylococcal isolates. Seven MRSA isolates and three Staphylococcus epidermidis were evaluated by time-kill using concentrations equal to 0.5× the MIC. These strains had variable susceptibility to the investigated antimicrobials. Synergy was defined as a ≥2 log 10 cfu/mL reduction of the combination over the most active single agent, antagonism was defined as ≥1 log 10 cfu/mL growth compared with the most active single agent, and other interactions were indifferent.. Three of 45 strains tested were non-susceptible to tedizolid (MIC = 1 mg/L), but the MIC 90 was 0.5 mg/L. Interactions between tedizolid and other agents were largely indifferent (80%). Tedizolid was synergistic with doxycycline and rifampicin against 2/10 and 3/10 strains, respectively. Tedizolid was antagonistic with moxifloxacin against 3/10 strains. Other interactions were indifferent.. The addition of rifampicin to tedizolid appears to be the most likely to improve activity but synergy was not universal. The combination of tedizolid plus moxifloxacin should be avoided due to the risk of antagonism. The addition of other orally bioavailable anti-staphylococcal agents to tedizolid may be unlikely to improve killing but further research is warranted to assess the impact of these combinations on resistance prevention, or against biofilm-embedded organisms.

Topics: Acetamides; Administration, Oral; Anti-Bacterial Agents; Drug Interactions; Fluoroquinolones; Humans; Kinetics; Linezolid; Microbial Sensitivity Tests; Moxifloxacin; Oxazolidinones; Rifampin; Staphylococcal Infections; Staphylococcus aureus; Staphylococcus epidermidis; Tetrazoles; Trimethoprim, Sulfamethoxazole Drug Combination

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in Spain is approximately 20-30%. However, resistance to linezolid is rare, and the main reports are from nosocomial outbreaks. The objective of the present study was to compare the in vitro susceptibility of linezolid with that of tedizolid against MRSA isolates and methicillin-and linezolid-resistant isolates (MLRSA) mediated by the cfr gene.. The in vitro susceptibility of linezolid and tedizolid was determined using the E-test with 18 MRSA strains and 18 cfr-mediated MLRSA strains obtained from clinical isolates in the microbiology service of a tertiary university hospital.. All MRSA strains were susceptible to both antibiotics. Analysis of the MRSA isolates revealed that the MIC50 and MIC90 of linezolid were 1.5 and 2 mg/L, respectively; those of tedizolid were 0.25 and 0.4 mg/L. The MIC50 and MIC90 of tedizolid remained at 0.75 and 1 mg/L against the MLRSA strains (MIC90 ≥ 8 mg/L).. Both for MRSA and for MLRSA, the MICs obtained for tedizolid were at least 2 dilutions lower than those of linezolid, thus demonstrating between 2 and 4 times greater activity in vitro than linezolid.

Topics: Anti-Bacterial Agents; Bacterial Proteins; Drug Resistance, Bacterial; Linezolid; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Oxazolidinones; Staphylococcal Infections; Staphylococcus aureus; Tetrazoles

Tedizolid phosphate is a novel antibacterial prodrug that is rapidly and extensively converted to its active moiety, tedizolid. We developed a population pharmacokinetics (PK) model for tedizolid using pooled data from seven densely and sparsely sampled clinical trials evaluating oral and intravenous tedizolid. Model-derived exposure estimates were evaluated for relationships to select efficacy and safety outcomes. A two-compartment model with sigmoidal absorption, absolute bioavailability, and linear elimination described the PK data well. Variability was small (clearance, 31% coefficient of variation; volume, 13.4% coefficient of variation), and absolute bioavailability was high (86%). No clinically significant covariate effects on tedizolid PK were found. Based on phase 3 data evaluating 200-mg once-daily tedizolid for acute bacterial skin and skin structure infections (ABSSSI), no relationships were seen between various efficacy outcomes and estimated tedizolid exposure; the estimated exposure range (free-drug area under the concentration-time curve over 24 h at steady state [AUCss(0-24)], 7 to 50 μg · h/ml) in these patients was modest. Safety data modeling, using once-daily doses of up to 400 mg, showed a small increase in the probability of an adverse event with increasing model-estimated tedizolid exposure; no such relationship was observed when specifically evaluating the 200-mg dose. There were no trends in neutrophil or platelet counts with increasing tedizolid exposure. Target attainment simulations for 200-mg tedizolid indicated a 98.31% probability of attaining the target measure (AUC for the free, unbound fraction of a drug [fAUC]/MIC = 3) against a Staphylococcus aureus strain for which the MIC was ≤0.5 μg/ml. These findings support 200-mg tedizolid once daily as the optimum dose for treatment of ABSSSI.

Topics: Adolescent; Adult; Aged; Anti-Bacterial Agents; Area Under Curve; Biological Availability; Female; Humans; Male; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Middle Aged; Neutrophils; Organophosphates; Oxazoles; Oxazolidinones; Platelet Count; Prodrugs; Skin Diseases, Bacterial; Staphylococcal Infections; Tetrazoles; Young Adult

To compare the activity of tedizolid (formally known as torezolid and TR-700) with that of 15 agents against a collection of linezolid-resistant staphylococci (164 coagulase-negative staphylococci and 5 Staphylococcus aureus).. Antimicrobial susceptibility tests were performed using the broth microdilution method following the recommendations of the CLSI.. All isolates were susceptible to vancomycin and tigecycline. Based on the MIC(90) values, the potency of tedizolid against coagulase-negative staphylococci was >16-fold greater than that of linezolid. Tedizolid retained activity against most of the linezolid-resistant staphylococci tested, including multidrug-resistant isolates with elevated linezolid MICs (32 to >128 mg/L). Of the isolates, 79.2% and 31.4% were inhibited by tedizolid at ≤ 4 mg/L and ≤ 2 mg/L, respectively.. The results of this study confirm the activity of tedizolid against linezolid-resistant staphylococci. This new oxazolidinone could have an important role as a potential therapeutic agent against multidrug-resistant staphylococci.

Topics: Acetamides; Anti-Bacterial Agents; Drug Resistance, Bacterial; Humans; Linezolid; Microbial Sensitivity Tests; Oxazolidinones; Staphylococcal Infections; Staphylococcus; Tetrazoles

Torezolid phosphate (TR-701) is the phosphate monoester prodrug of the oxazolidinone TR-700 which demonstrates potent in vitro activity against Gram-positive bacteria, including methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA). The pharmacodynamics of TR-701 or TR-700 (TR-701/700) against S. aureus is incompletely defined. Single-dose pharmacokinetic studies were conducted in mice for TR-701/700. Forty-eight-hour dose range and 24-hour dose fractionation studies were conducted in a neutropenic mouse thigh model of S. aureus infection using MRSA ATCC 33591 to identify the dose and schedule of administration of TR-701/700 that was linked with optimized antimicrobial effect. Additional dose range studies compared the efficacies of TR-701/700 and linezolid for one MSSA strain and one community-associated MRSA strain. In dose range studies, TR-701/700 was equally bactericidal against MSSA and MRSA. Mean doses of 37.6 and 66.9 mg/kg of body weight/day of TR-701/700 resulted in stasis and 1 log CFU/g decreases in bacterial densities, respectively, at 24 h, and mean doses of 35.3, 46.6, and 71.1 mg/kg/day resulted in stasis and 1 and 2 log CFU/g reductions, respectively, at 48 h. Linezolid administered at doses as high as 150 mg/kg/day did not achieve stasis at either time point. Dose fractionation studies demonstrated that the area under the concentration-time curve over 24 h in the steady state divided by the MIC (AUC/MIC ratio) was the pharmacodynamic index for TR-701/700 that was linked with efficacy. TR-701/700 was highly active against MSSA and MRSA, in vivo, and was substantially more efficacious than linezolid, although linezolid's top exposure has half the human exposure. Dose fractionation studies showed that AUC/MIC was the pharmacodynamic index linked with efficacy, indicating that once-daily dosing in humans is feasible.

Topics: Acetamides; Animals; Anti-Bacterial Agents; Female; Humans; Linezolid; Methicillin; Methicillin-Resistant Staphylococcus aureus; Mice; Microbial Sensitivity Tests; Organophosphates; Oxazoles; Oxazolidinones; Serum; Staphylococcal Infections; Staphylococcus aureus; Tetrazoles; Thigh

Tedizolid (TR-700, formerly torezolid) is the active component of the new oxazolidinone prodrug tedizolid phosphate (TR-701). We had previously demonstrated that tedizolid possessed potent antistaphylococcal activity superior to that of linezolid in a neutropenic mouse thigh infection model (A. Louie, W. Liu, R. Kulawy, and G. L. Drusano, Antimicrob. Agents Chemother. 55:3453-3460, 2011). In the current investigation, we used a mouse thigh infection model to delineate the effect of an interaction of TR-700 and granulocytes on staphylococcal cell killing. We compared the antistaphylococcal killing effect of doses of TR-701 equivalent to human exposures ranging from 200 to 3,200 mg/day in both granulocytopenic and normal mice. The mice were evaluated at 24, 48, and 72 h after therapy initiation. In granulocytopenic mice, a clear exposure response in which, depending on the time point of evaluation, stasis was achieved at "human-equivalent" doses of slightly below 2,300 mg/day (at 24 h) to slightly below 2,000 mg/day (at 72 h) was observed. In immune-normal animals, stasis was achieved at human-equivalent doses of slightly greater than 100 mg/day or less. The variance in bacterial cell killing results was attributable to the presence of granulocytes (without drug), the direct effect of TR-700 on Staphylococcus aureus, and the effect of the drug on Staphylococcus aureus mediated through granulocytes. The majority of the bacterial cell killing in normal animals was attributable to the effect of TR-700 mediated through granulocytes. Additional studies need to be undertaken to elucidate the mechanism underlying this observation.

Topics: Animals; Anti-Infective Agents; Female; Granulocytes; Mice; Microbial Sensitivity Tests; Models, Theoretical; Organophosphates; Oxazoles; Oxazolidinones; Staphylococcal Infections; Staphylococcus aureus; Tetrazoles; Thigh

The in vitro activity of TR-700 (torezolid) was evaluated against a collection of 660 staphylococcal blood isolates. TR-700 showed excellent activity against all the staphylococci tested. The MIC(50) and MIC(90) values of TR-700, linezolid, daptomycin, and vancomycin against methicillin-resistant Staphylococcus aureus (MRSA) isolates were 0.25 and 0.5, 2 and 4, 0.5 and 0.5, and 1 and 2 microg/ml, respectively. TR-700 demonstrated greater in vitro potency than linezolid against staphylococci, including linezolid-resistant and vancomycin-nonsusceptible strains, and was 32-fold more active than linezolid against the seven cfr-positive MRSA strains tested.

Topics: Acetamides; Anti-Bacterial Agents; Daptomycin; Drug Resistance, Bacterial; In Vitro Techniques; Linezolid; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Oxazolidinones; Sepsis; Spain; Staphylococcal Infections; Tetrazoles; Vancomycin

Following recent reports of ribosomal protein L3 mutations in laboratory-derived linezolid-resistant (LZD(r)) Staphylococcus aureus, we investigated whether similar mutations were present in LZD(r) staphylococci of clinical origin. Sequence analysis of a variety of LZD(r) isolates revealed two L3 mutations, DeltaSer145 (S. aureus NRS127) and Ala157Arg (Staphylococcus epidermidis 1653059), both occurring proximal to the oxazolidinone binding site in the peptidyl transferase center. The oxazolidinone torezolid maintained a >or=8-fold potency advantage over linezolid for both strains.

Topics: Acetamides; Binding Sites; Drug Resistance, Bacterial; Linezolid; Mutation; Oxazolidinones; Protein Structure, Secondary; Ribosomal Protein L3; Ribosomal Proteins; RNA, Ribosomal, 23S; Staphylococcal Infections; Staphylococcus; Staphylococcus aureus; Tetrazoles