Cerebrospinal fluid linezolid concentrations in postneurosurgical central nervous system infections

Linezolid Population Pharmacokinetic Model in Plasma and Cerebrospinal Fluid Among Patients With Tuberculosis Meningitis

BACKGROUND

Linezolid is evaluated in novel treatment regimens for tuberculous meningitis (TBM). Linezolid pharmacokinetics have not been characterized in this population, particularly in cerebrospinal fluid (CSF), as well as, following its co-administration with high-dose rifampicin. We aimed to characterize linezolid plasma and CSF pharmacokinetics in adults with TBM.

METHODS

In the LASER-TBM pharmacokinetic substudy, the intervention groups received high-dose rifampicin (35 mg/kg) plus 1200 mg/day of linezolid for 28 days, which was then reduced to 600 mg/day. Plasma sampling was done on day 3 (intensive) and day 28 (sparse). A lumbar CSF sample was obtained on both visits.

RESULTS

Thirty participants contributed 247 plasma and 28 CSF observations. Their median age and weight were 40 years (range, 27-56) and 58 kg (range, 30-96). Plasma pharmacokinetics was described by a 1-compartment model with first-order absorption and saturable elimination. Maximal clearance was 7.25 L/h, and the Michaelis-Menten constant was 27.2 mg/L. Rifampicin cotreatment duration did not affect linezolid pharmacokinetics. CSF-plasma partitioning correlated with CSF total protein up to 1.2 g/L, where the partition coefficient reached a maximal value of 37%. The plasma-CSF equilibration half-life was ∼3.5 hours.

CONCLUSIONS

Linezolid was readily detected in CSF despite high-dose rifampicin coadministration. These findings support continued clinical evaluation of linezolid plus high-dose rifampicin for the treatment of TBM in adults. Clinical Trials Registration.  ClinicalTrials.gov (NCT03927313).

Linezolid brain penetration in neurointensive care patients

BACKGROUND

Linezolid exposure in critically ill patients is associated with high inter-individual variability, potentially resulting in subtherapeutic antibiotic exposure. Linezolid exhibits good penetration into the CSF, but its penetration into cerebral interstitial fluid (ISF) is unknown.

OBJECTIVES

To determine linezolid penetration into CSF and cerebral ISF of neurointensive care patients.

PATIENTS AND METHODS

Five neurocritical care patients received 600 mg of linezolid IV twice daily for treatment of extracerebral infections. At steady state, blood and CSF samples were collected from arterial and ventricular catheters, and microdialysate was obtained from a cerebral intraparenchymal probe.

RESULTS

The median fAUC0-24 was 57.6 (24.9-365) mg·h/L in plasma, 64.1 (43.5-306.1) mg·h/L in CSF, and 27.0 (10.7-217.6) mg·h/L in cerebral ISF. The median penetration ratio (fAUCbrain_or_CSF/fAUCplasma) was 0.5 (0.25-0.81) for cerebral ISF and 0.92 (0.79-1) for CSF. Cerebral ISF concentrations correlated well with plasma (R = 0.93, P < 0.001) and CSF levels (R = 0.93, P < 0.001).The median fAUC0-24/MIC ratio was ≥100 in plasma and CSF for MICs of ≤0.5 mg/L, and in cerebral ISF for MICs of ≤0.25 mg/L. The median fT>MIC was ≥80% of the dosing interval in CSF for MICs of ≤0.5 mg/L, and in plasma and cerebral ISF for MICs of ≤0.25 mg/L.

CONCLUSIONS

Linezolid demonstrates a high degree of cerebral penetration, and brain concentrations correlate well with plasma and CSF levels. However, substantial variability in plasma levels, and thus cerebral concentrations, may result in subtherapeutic tissue concentrations in critically ill patients with standard dosing, necessitating therapeutic drug monitoring.

Validation of a quantitative liquid chromatography tandem mass spectrometry assay for linezolid in cerebrospinal fluid and its application to patients with HIV-associated TB-meningitis

Tuberculous meningitis treatment outcomes are poor and alternative regimens are under investigation. Reliable methods to measure drug concentrations in cerebrospinal fluid are required to evaluate distribution into the cerebrospinal fluid. A simple and quick method was developed and validated to analyse linezolid in human cerebrospinal fluid. Samples were prepared by protein precipitation followed by isocratic liquid chromatography and tandem mass spectrometry. The run time was 3.5 min. Accuracy and precision were assessed in three independent validation batches with a calibration range of 0.100-20.0 μg/mL. The method was used to analyse cerebrospinal fluid samples from patients with tuberculous meningitis enrolled in a clinical trial. Potentially infective patient samples could be decontaminated using Nanosep® nylon and Costar® nylon filter tubes under biosafety level 3 conditions before analysis. The filtration process did not significantly affect the quantification of linezolid. Linezolid concentration in cerebrospinal fluid obtained from tuberculous meningitis patients ranged from 0.197 μg/mL to 15.0 μg/mL. The ratio between average CSF and plasma linezolid concentrations varied with time, reaching a maximum of 0.9 at 6 h after dosing.

Linezolid population pharmacokinetic model in plasma and cerebrospinal fluid among patients with tuberculosis meningitis

Background

Linezolid is being evaluated in novel treatment regimens for tuberculous meningitis (TBM). The pharmacokinetics of linezolid have not been characterized in this population, particularly in cerebrospinal fluid (CSF) where exposures may be affected by changes in protein concentration and rifampicin co-administration.

Methods

This was a sub-study of a phase 2 clinical trial of intensified antibiotic therapy for adults with HIV-associated TBM. Participants in the intervention groups received high-dose rifampicin (35 mg/kg) plus linezolid 1200 mg daily for 28 days followed by 600 mg daily until day 56. Plasma was intensively sampled, and lumbar CSF was collected at a single timepoint in a randomly allocated sampling window, within 3 days after enrolment. Sparse plasma and CSF samples were also obtained on day 28. Linezolid concentrations were analyzed using non-linear mixed effects modelling.

Results

30 participants contributed 247 plasma and 28 CSF linezolid observations. Plasma PK was best described by a one-compartment model with first-order absorption and saturable elimination. The typical value of maximal clearance was 7.25 L/h. Duration of rifampicin co-treatment (compared on day 3 versus day 28) did not affect linezolid pharmacokinetics. Partitioning between plasma and CSF correlated with CSF total protein concentration up to 1.2 g/L where the partition coefficient reached a maximal value of 37%. The equilibration half-life between plasma and CSF was estimated at ∼3.5 hours.

Conclusion

Linezolid was readily detected in CSF despite co-administration of the potent inducer rifampicin at high doses. These findings support continued clinical evaluation of linezolid plus high-dose rifampicin for the treatment of TBM in adults.

Effectiveness and Safety of Linezolid Versus Vancomycin, Teicoplanin, or Daptomycin against Methicillin-Resistant Staphylococcus aureus Bacteremia: A Systematic Review and Meta-Analysis

Vancomycin (VCM) and daptomycin (DAP) are standard therapies for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia, despite concerns regarding clinical utility and growing resistance. Linezolid (LZD) affords superior tissue penetration to VCM or DAP and has been successfully used as salvage therapy for persistent MRSA bacteremia, indicating its utility as a first-choice drug against MRSA bacteremia. In a systematic review and meta-analysis, we compared the effectiveness and safety of LZD with VCM, teicoplanin (TEIC), or DAP in patients with MRSA bacteremia. We evaluated all-cause mortality as the primary effectiveness outcome, clinical and microbiological cure, hospital length of stay, recurrence, and 90-day readmission rates as secondary effectiveness outcomes, and drug-related adverse effects as primary safety outcomes. We identified 5328 patients across 2 randomized controlled trials (RCTs), 1 pooled analysis of 5 RCTs, 1 subgroup analysis (1 RCT), and 5 case-control and cohort studies (CSs). Primary and secondary effectiveness outcomes were comparable between patients treated with LZD versus VCM, TEIC, or DAP in RCT-based studies and CSs. There was no difference in adverse event incidence between LZD and comparators. These findings suggest that LZD could be a potential first-line drug against MRSA bacteremia as well as VCM or DAP.

New and Repurposed Drugs for the Treatment of Active Tuberculosis: An Update for Clinicians

Although tuberculosis (TB) is preventable and curable, the lengthy treatment (generally 6 months), poor patient adherence, high inter-individual variability in pharmacokinetics (PK), emergence of drug resistance, presence of comorbidities, and adverse drug reactions complicate TB therapy and drive the need for new drugs and/or regimens. Hence, new compounds are being developed, available drugs are repurposed, and the dosing of existing drugs is optimized, resulting in the largest drug development portfolio in TB history. This review highlights a selection of clinically available drug candidates that could be part of future TB regimens, including bedaquiline, delamanid, pretomanid, linezolid, clofazimine, optimized (high dose) rifampicin, rifapentine, and para-aminosalicylic acid. The review covers drug development history, preclinical data, PK, and current clinical development.

Tissue Penetration of Antimicrobials in Intensive Care Unit Patients: A Systematic Review-Part II

In patients that are admitted to intensive care units (ICUs), the clinical outcome of severe infections depends on several factors, as well as the early administration of chemotherapies and comorbidities. Antimicrobials may be used in off-label regimens to maximize the probability of therapeutic concentrations within infected tissues and to prevent the selection of resistant clones. Interestingly, the literature clearly shows that the rate of tissue penetration is variable among antibacterial drugs, and the correlation between plasma and tissue concentrations may be inconstant. The present review harvests data about tissue penetration of antibacterial drugs in ICU patients, limiting the search to those drugs that mainly act as protein synthesis inhibitors and disrupting DNA structure and function. As expected, fluoroquinolones, macrolides, linezolid, and tigecycline have an excellent diffusion into epithelial lining fluid. That high penetration is fundamental for the therapy of ventilator and healthcare-associated pneumonia. Some drugs also display a high penetration rate within cerebrospinal fluid, while other agents diffuse into the skin and soft tissues. Further studies are needed to improve our knowledge about drug tissue penetration, especially in the presence of factors that may affect drug pharmacokinetics.

Pharmacokinetics and Pharmacodynamics of Tedizolid

Tedizolid is an oxazolidinone antibiotic with high potency against Gram-positive bacteria and currently prescribed in bacterial skin and skin-structure infections. The aim of the review was to summarize and critically review the key pharmacokinetic and pharmacodynamic aspects of tedizolid. Tedizolid displays linear pharmacokinetics with good tissue penetration. In in vitro susceptibility studies, tedizolid exhibits activity against the majority of Gram-positive bacteria (minimal inhibitory concentration [MIC] of ≤ 0.5 mg/L), is four-fold more potent than linezolid, and has the potential to treat pathogens being less susceptible to linezolid. Area under the unbound concentration–time curve (fAUC) related to MIC (fAUC/MIC) was best correlated with efficacy. In neutropenic mice, fAUC/MIC of ~ 50 and ~ 20 induced bacteriostasis in thigh and pulmonary infection models, respectively, at 24 h. The presence of granulocytes augmented its antibacterial effect. Hence, tedizolid is currently not recommended for immunocompromised patients. Clinical investigations with daily doses of 200 mg for 6 days showed non-inferiority to twice-daily dosing of linezolid 600 mg for 10 days in patients with acute bacterial skin and skin-structure infections. In addition to its use in skin and skin-structure infections, the high pulmonary penetration makes it an attractive option for respiratory infections including Mycobacterium tuberculosis. Resistance against tedizolid is rare yet effective antimicrobial surveillance and defining pharmacokinetic/pharmacodynamic targets for resistance suppression are needed to guide dosing strategies to suppress resistance development.

Early intravenous immunoglobulin therapy for group A β-haemolytic streptococcal meningitis with toxic shock syndrome

A woman in her forties was transferred to a Sydney (Australia)-based tertiary hospital, following presentation to a regional hospital with group A Streptococcus (GAS) otomastoiditis; complicated by meningitis, venous sinus thrombosis, haemorrhagic cerebral infarction and subdural empyema. She rapidly deteriorated with profound cardiovascular collapse. Despite initiation of high dose vasoactive therapy, she remained shocked and developed multiorgan dysfunction syndrome. Early intravenous immunoglobulin therapy (140 g in two doses) was initiated as an adjunct to antimicrobial, surgical and supportive care for refractory streptococcal toxic shock syndrome. Over the course of a twelve-day intensive care unit stay she made good progress with de-escalation of her vasoactive supportive care and reversal of her organ injuries. She was subsequently discharged to ward-based care. At her three-month follow-up appointment she had significantly reduced neurological deficit. Five months following her presentation to hospital she had returned to full-time work.

A retrospective test for a possible relationship between linezolid-induced thrombocytopenia and hyponatraemia

WHAT IS KNOWN AND OBJECTIVE

Thrombocytopenia is one of the typical adverse events caused by linezolid (LZD). Recently, some cases of severe hyponatraemia occurring while receiving LZD have been reported. This study investigated a possible relationship between LZD-induced hyponatraemia and thrombocytopenia and identified the risk factors for hyponatraemia and/or thrombocytopenia.

METHODS

In this retrospective, single-centre, observational cohort study, 63 hospitalized patients aged over 18 years who received intravenous injection of LZD for more than seven consecutive days in Oita University Hospital between April 2015 and March 2018 were analysed.

RESULTS

Thrombocytopenia occurred in 25 (39.7%) patients and hyponatraemia in 11 (17.5%) patients. Seven of 11 patients with hyponatraemia had concurrent thrombocytopenia. Although both serum sodium level and platelet count declined in most patients who developed hyponatraemia, no significant association between thrombocytopenia and hyponatraemia was found. Creatinine clearance level (Ccr) was significantly lower not only in the thrombocytopenia (vs no-thrombocytopenia) but also in the hyponatraemia group (vs no-hyponatraemia group). Univariate and multivariate logistic regression analyses identified different risk factors for thrombocytopenia and/or hyponatraemia (thrombocytopenia: Ccr and administration period; hyponatraemia: serum albumin; thrombocytopenia and hyponatraemia: administration period and serum albumin).

WHAT IS NEW AND CONCLUSION

In conclusion, this study found no significant relationship between LZD-induced thrombocytopenia and hyponatraemia and identified some possible risk factors associated with onset of the two adverse events. These require further validation.

Prolonged infusion of linezolid is associated with improved pharmacokinetic/pharmacodynamic (PK/PD) profiles in patients with external ventricular drains

OBJECTIVE

We previously investigated the pharmacokinetic and pharmacodynamic (PK/PD) parameters of routine linezolid infusions (1 h) in patients with external ventricular drains (EVD). The aim of the study was to determine whether extended linezolid infusions (200 mg/h for 3 h) were more efficacious than short linezolid infusions (600 mg/h for 1 h).

METHODS

We collected cerebrospinal fluid (CSF) and plasma samples from 10 patients who received linezolid infusions after cerebral hemorrhage surgery with EVDs. Linezolid concentrations were measured by high-performance liquid chromatography (HPLC). A Monte Carlo simulation was used to measure the probability of target attainments (PTA) and the PK/PD indexes at four minimum inhibitory concentrations (MIC).

RESULTS

When the same dose (600 mg) was given as an extended infusion (3 h), linezolid reached its maximum concentrations in the plasma and CSF at 3.00 h and 4.40 h, respectively. The mean penetration of linezolid in CSF was 41.31%. Using the parameter of AUC_{0-24 h}/MIC ≥ 100, the plasma PTA provided good coverage at > 90% when MIC was ≤ 1 μg/mL, while the values were 0 in CSF. Using the parameter %T (time) > MIC ≥ 85%, the PTA in both the plasma and CSF provided good coverage when MIC ≤ 2 μg/mL. Compared with routine infusions, prolonged infusion times (3 h) showed increased PTA of linezolid.

CONCLUSIONS

Prolonged infusion times increased the concentration of linezolid in the plasma, leading to improved therapeutic outcomes. However, this improvement did not exist in CSF. Lastly, the PK/PD indicator AUC/MIC ≥ 100 may be used to achieve improved outcomes in patients with critical infections.

Linezolid for therapy of Staphylococcus aureus meningitis: a cohort study of 26 patients

BACKGROUND

Linezolid has good penetration to the meninges and could be an alternative for treatment of Staphylococcus aureus meningitis. We assessed the efficacy and safety of linezolid therapy for this infection.

METHODS

Retrospective multicenter cohort study of 26 adults treated with linezolid, derived from a cohort of 350 cases of S. aureus meningitis diagnosed at 11 university hospitals in Spain (1981-2015).

RESULTS

There were 15 males (58%) and mean age was 47.3 years. Meningitis was postoperative in 21 (81%) patients. The infection was nosocomial in 23 (88%) cases, and caused by methicillin-resistant S. aureus in 15 cases and methicillin-susceptible S. aureus in 11. Linezolid was given as empirical therapy in 10 cases, as directed therapy in 10, and due to failure of vancomycin in 6. Monotherapy was given to 16 (62%) patients. Median duration of linezolid therapy was 17 days (IQR 12-22 days) with a daily dose of 1,200 mg in all cases. The clinical response rate to linezolid was 69% (18/26) and microbiological response was observed in 14 of 15 cases evaluated (93%). Overall 30-day mortality was 23% and was directly associated with infection in most cases. When compared with the patients of the cohort, no significant difference in mortality was observed between patients receiving linezolid or vancomycin for therapy of methicillin-resistant S. aureus meningitis (9% vs. 20%; p = .16) nor between patients receiving linezolid or cloxacillin for therapy of methicillin-susceptible S. aureus meningitis (20% vs 14%; p = .68). Adverse events appeared in 14% (3/22) of patients, but linezolid was discontinued in only one patient.

CONCLUSIONS

Linezolid appears to be effective and safe for therapy of S. aureus meningitis. Our findings showed that linezolid may be considered an adequate alternative to other antimicrobials in meningitis caused by S. aureus.

Linezolid for the treatment of postneurosurgical infection caused by methicillin-resistant Staphylococcus

Background

Postneurosurgical infection (PNSI) is a major problem. Linezolid is a bacteriostatic oxazolidinone antibiotic with a highly activity against Gram-positive cocci resistant to methicillin and a good cerebrospinal fluid penetration. The purpose of this study is to evaluate the efficacy of linezolid in the treatment of PNSI caused by methicillin-resistant Staphylococcus (MRS).

Methods

We conducted an observational study for all patients over 14 years old and diagnosed with MRS PNSI. Demographic, clinical, and laboratory information were collected prospectively.

Results

A total of 10 patients with PNSI (6 meningitis, 2 ventriculitis, and 2 subdural empyema) received linezolid. MRS isolated was Staphylococcus aureus in seven cases and Staphylococcus epidermidis in three cases. All isolated microorganisms were susceptible to vancomycin (minimum inhibitory concentration (MIC) = 2 mg/L) and linezolid (MIC = 1). The rate of microbiologic efficacy was 100% for patients with meningitis or ventriculitis. In the case of subdural empyema, focal infection had improved between 14 and 18 days. No adverse effects occurred during this study.

Conclusion

Our results suggest that linezolid as an alternative to vancomycin for the treatment of PNSI caused by MRS with a high rate of efficacy.

La pharmacologie des antibiotiques dans le liquide cérébrospinal

Le liquide cérébrospinal (LCS) est produit par les plexus choroïdes des ventricules cérébraux avec pour rôle de protéger le système nerveux central des agressions mécaniques (chocs) et infectieuses (virus, bactéries, parasites) et de lui apporter des nutriments essentiels à son fonctionnement optimal. Il est anatomiquement à l'interface entre le compartiment sanguin, le liquide interstitiel cérébral et le compartiment lymphatique. Sa composition est fortement influencée par ces structures. Deux barrières permettent de réguler le passage moléculaire dans le système nerveux central et limitent fortement l'accès à ce dernier : la barrière hématoencéphalique et la barrière hématoméningée. La diffusion des antibiotiques dans le LCS, mais également dans le parenchyme cérébral dépend de plusieurs facteurs : la taille de la molécule, sa lipophilie, la liaison aux protéines plasmatiques et l'intégrité des barrières hématoencéphalique et hématoméningée. Les phénomènes d'inflammation méningée observés dans les méningites bactériennes augmentent la perméabilité des barrières et facilitent la diffusion des agents antibiotiques. Les molécules diffusant le mieux dans le LCS sont les fluoroquinolones, le linézolide, l'association triméthoprime- sulfaméthoxazole, la rifampicine et la fosfomycine. Les bêtalactamines présentent une diffusion assez faible mais qui augmente fortement en cas d'inflammation méningée. Des posologies journalières très élevées permettent de contourner l'écueil de la diffusion. De nombreux paramètres influencent la diffusion des antibiotiques dans le LCS. Le choix de l'antibiothérapie adaptée se fait en fonction de ces paramètres et du type d'infection à traiter en concertation pluridisciplinaire.

Clinical Pharmacokinetics and Pharmacodynamics of Oxazolidinones

Oxazolidinones are a class of synthetic antimicrobial agents with potent activity against a wide range of multidrug-resistant Gram-positive pathogens including methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. Oxazolidinones exhibit their antibacterial effects by inhibiting protein synthesis acting on the ribosomal 50S subunit of the bacteria and thus preventing formation of a functional 70S initiation complex. Currently, two oxazolidinones have been approved by the US Food and Drug Administration: linezolid and more recently tedizolid. Other oxazolidinones are currently under investigation in clinical trials. These antimicrobial agents exhibit a favourable pharmacokinetic profile with an excellent bioavailability and a good tissue and organ penetration. In-vitro susceptibility studies have shown that oxazolidinones are bacteriostatic against enterococci and staphylococci, and bactericidal for the majority of strains of streptococci. In the context of emergence of resistance to glycopeptides, oxazolidinones have become an effective alternative to vancomycin treatment frequently associated with nephrotoxicity. However, oxazolidinones, and linezolid in particular, are associated with significant adverse events, myelosuppression representing the main unfavourable side effect. More recently, tedizolid has been shown to effectively treat acute bacterial skin and skin structure infections. This newer oxazolidinone offers the advantages of once-daily dosing and a better safety profile in healthy volunteer studies (fewer gastrointestinal and haematological side effects). The potential use of tedizolid for other infections that could require longer therapy warrants further studies for positioning this new oxazolidinone in the available antimicrobial armamentarium. Moreover, other oxazolidinones are currently under active investigation.

Central Nervous System Infections Caused by Mycobacterium abscessus: Ventricular Shunt Infection in Two Pediatric Patients and Literature Review

A 4-year-old former 24-week gestation male and an 18-month-old former 26-week gestation female, both with history of intraventricular hemorrhage resulting in hydrocephalus, presented with Mycobacterium abscessus ventricular shunt infections affecting both the shunt track and the ventricular fluid. Both children required prolonged combination antimycobacterial therapy; the 4 years old required more than 2 months of triple intravenous antibiotics and intraventricular amikacin to sterilize the cerebrospinal fluid. Each infection came under control only after removal of all foreign material and multiple and extensive adjunctive surgical procedures to excise infected shunt track tissue. Central nervous system infections caused by M. abscessus are rare, and their management is challenging: prolonged antimicrobial therapy is required, adverse effects from antibiotics are common and rates of mortality and morbidity are high.

Effects of Epacadostat on Brain Extracellular Fluid Concentrations of Serotonin-an Intracerebral Microdialysis Study in Sprague-Dawley Rats

Epacadostat (EPAC) is an indoleamine 2,3-dioxygenase 1 (IDO1) inhibitor that has been examined in multiple clinical trials. The substrate for IDO1 is tryptophan and there is a theoretical concern that inhibition of IDO1 may increase the concentrations of tryptophan and subsequently serotonin, potentially leading to serotonin syndrome (SS). The objective of this study was to evaluate the effect of EPAC, either alone or with linezolid, a monoamine oxidase inhibitor (MAOI), on brain extracellular fluid (ECF) concentrations of serotonin in rats, using microdialysis. While fluoxetine, a selective serotonin reuptake inhibitor, increased the serotonin ECF concentration by 2-fold, the combination of fluoxetine with linezolid (a positive control used in the study) resulted in a 9-fold increase. Neither EPAC monotherapy nor combination with linezolid had any effect on serotonin concentration. In addition, EPAC was shown to have poor penetration across the rat blood-brain barrier. Across multiple phase I/II clinical studies with EPAC, four SS-like episodes were observed out of 2490 subjects, but none of the incidences were confirmed as a true case of SS. These data suggest that EPAC is unlikely to cause SS following either monotherapy or in combination with MAOIs. Thus, the exclusion of MAOI from clinical studies with EPAC has been lifted.

Therapeutic Effect of Linezolid in Children With Health Care-Associated Meningitis or Ventriculitis

We evaluated the efficacy of linezolid treatment in 6 children with health care-associated meningitis or ventriculitis (HCAMV) caused by gram-positive cocci. All children were diagnosed and treated at the Ehime University Hospital between January 2010 and December 2017. Of these, 5 were treated with linezolid as an empirical therapy. In these 5 patients, vancomycin was initially used but was changed to linezolid because of cerebrospinal fluid (CSF) culture positivity (n = 3) and a high minimum inhibitory concentration of vancomycin (n = 2). The most common HCAMV pathogens were methicillin-resistant coagulase-negative staphylococci (n = 3). In 3 patients, vancomycin concentration was low in CSF but reached the target concentration in serum, while linezolid concentration was high in both CSF and serum. HCAMV treatment using antimicrobial agents with poor CSF penetration may increase the likelihood of therapy failure. Linezolid is more susceptible as the first-line treatment for HCAMV compared with vancomycin.

[Antibiotic diffusion to central nervous system]

Central nervous system (CNS) infections caused by pathogens with a reduced sensitivity to drugs are a therapeutic challenge. Transport of fluid and solutes is tightly controlled within CNS, where vasculature exhibits a blood-brain barrier (BBB).The entry of drugs, including antibiotics, into the cerebro-spinal fluid (CSF) is governed by molecular size, lipophilicity, plasma protein binding and their affinity to transport systems at the BBB. The ratio of the AUCCSF (Area under the curve in CSF)/AUCS (Area under the curve in serum) is the most accurate parameter to characterize drug penetration into the CSF. Linezolid, some fluoroquinolones and metronidazole get high CSF concentrations and are useful for treating susceptible pathogens. Some highly active antibiotic compounds with low BBB permeability can be directly administered into the ventricles together with concomitant intravenous therapy. The ideal antibiotic to treat CNS infections should be that with a small moderately lipophilic molecule, low plasma protein binding and low affinity to efflux pumps at BBB. Knowledge of the pharmacokinetics and pharmacodynamics of antibiotics at the BBB will assist to optimize antibiotic treatment in CNS infections. This article reviews the physicochemical properties of the main groups of antibiotics to assess which compounds are most promising for the treatment of CNS infections and how to use them in the daily clinical practice.

Successful Treatment and Cerebrospinal Fluid Penetration of Oral Linezolid in a Patient with Coagulase-Negative Staphylococcus Ventriculitis

Objective:

TO describe a case of coagulase-negative Staphylococcus ventriculitis successfully treated with oral linezolid, for which good cerebrospinal fluid (CSF) penetration was observed.

Case Summary:

A 69-year-old man had an extraventricular drain inserted following a right cerebellar infarct. On day 6, the CSF culture was positive for coagulase-negative staphylococci; intravenous vancomycin 1 g daily was initiated to treat ventriculitis. A ventriculoperitoneal shunt, inserted on day 35 to manage communicating hydrocephalus, was subsequently removed as symptoms suggesting infection presented. Coagulase-negative Staphylococcus was isolated from shunt reservoir aspirate, and intrathecal vancomycin 10 mg daily was added to the treatment regimen. On day 61, vancomycin was stopped and oral linezolid 600 mg twice daily was started. Linezolid was discontinued 22 days later, with no evidence of ongoing infection. Four blood samples were collected around the seventh dose of linezolid and 5 CSF samples were collected on separate days during treatment. Linezolid concentrations were measured in plasma and CSF by HPLC. Using an ADAPT II maximum a priori Bayesian estimator module, a 2 compartment pharmacokinetic model was fitted to the plasma linezolid concentration data and CSF:predicted plasma concentration ratios (ranging from 0.27 to 1.02) were derived. All CSF concentrations exceeded the reported 90% minimum inhibitory concentration of 2 mg/L for linezolid against coagulase-negative staphylococci.

Discussion:

Evidence of the effectiveness of linezolid against central nervous system infections is growing; however, limited data exist describing its CSF penetration. Oral linezolid exhibited good CSF penetration in this patient, which corresponded to positive clinical response.

Conclusions:

Oral linezolid may play a valuable role in the treatment of multiresistant gram-positive central nervous system infections.

LInezolid for the Treatment of Nocardia spp. Infections

Objective:

To review the available evidence regarding the use of linezolid for the treatment of Nocardia spp. infections.

Data Sources:

Data were identified through a search of MEDLINE (1966-May 2007), American Search Premier (1975-May 2007), International Pharmaceutical Abstracts (1960-2007), Science Citation Index Expanded (1996-2007), and Cochrane Databases (publications archived until May 2007) using the terms linezolid and Nocardia.

Study Selection and Data Extraction:

Prospective and retrospective studies, case reports, case series, and in vitro studies were eligible for inclusion if they used linezolid for nocardiosis regardless of site of infection and outcome.

Data Synthesis:

We identified 11 published cases of linezolid use for Nocardia spp. infections. The predominant species isolated were N. asteroides (n=4; 36%) and N. farcinica (n= 3; 27%). Nocardiosis with central nervous system involvement (n= 7; 64%) or disseminated disease (n= 4; 36%) were most common. The main reason for discontinuation of previous antimicrobials was most often related to adverse effects (n= 5; 45%), followed by clinical failure (n = 3; 27%). Linezolid was associated with cure or improvement in all cases (n =11; 100%). However, the majority of patients developed serious complications that may have led to premature discontinuation of therapy with linezolid, including myelosuppression (n = 5; 45%) or possible/confirmed peripheral neuropathy (n = 2; 18%).

Conclusions:

The limited published data suggest that linezolid appears to be an effective alternative to trimethoprim/sulfamethoxazole for the treatment of nocardiosis. Unfortunately, the high cost and potentially serious long-term toxicities of linezolid appear to limit its use and relegate it to salvage therapy alone or in combination with other antimicrobials.

Sequential antimicrobial treatment with linezolid for neurosurgical infections: efficacy, safety and cost study

BACKGROUND

Evidence for the effectiveness of linezolid in neurosurgical infections (NSIs) is growing. The comfortable oral dosage and tolerance of linezolid opens the possibility for sequential antimicrobial treatment (SAT) in stable patients after a period of intravenous treatment.

METHODS

To evaluate the efficacy and safety of SAT with oral linezolid in patients with NSI and to analyse the cost implications, an observational, non-comparative, prospective cohort study was conducted on clinically stable consecutive adult patients at the Neurosurgical Service. Following intravenous treatment, patients were discharged with SAT with oral linezolid.

RESULTS

A total of 77 patients were included. The most common NSIs were: 41 surgical wound infections, 20 subdural empyemas, 18 epidural abscesses, and 16 brain abscesses. Forty-four percent of patients presented two or more concomitant NSIs. Aetiological agents commonly isolated were: Propionibacterium acnes (36 %), Staphylococcus aureus (23 %), Staphylococcus epidermidis (21 %) and Streptococcus spp. (13 %). The median duration of the SAT was 15 days (range, 3-42). The SAT was interrupted in five cases due to adverse events. The remainder of the patients were cured at the end of the SAT. A total of 1,163 days of hospitalisation were saved. An overall cost reduction of €516,188 was attributed to the SAT. Eight patients with device infections did not require removal of the device, with an additional cost reduction of €190,595. The mean cost saving per patient was €9,179.

CONCLUSIONS

SAT with linezolid was safe and effective for the treatment of NSI. SAT reduces hospitalisation times, which means significant savings of health and economic resources.

Treatment strategies for central nervous system infections: an update

INTRODUCTION

Central nervous system infection continues to be an important cause of mortality and morbidity worldwide. Our incomplete knowledge on the pathogenesis of how meningitis-causing pathogens cause CNS infection and emergence of antimicrobial resistance has contributed to the mortality and morbidity. An early empiric antibiotic treatment is critical for the management of patients with bacterial meningitis, but early recognition of bacterial meningitis continues to be a challenge.

AREAS COVERED

This review gives an overview on current therapeutic strategies for CNS infection with a focus on recent literature since 2010 on bacterial meningitis. Bacterial meningitis is a medical emergency, requiring early recognition and treatment. The selection of appropriate empiric antimicrobial regimen, after incorporating the epidemiology of bacterial meningitis, impact of vaccination, emergence of antimicrobial-resistant bacteria, role of adjunctive therapy and the current knowledge on the pathogenesis of meningitis and associated neuronal injury are covered.

EXPERT OPINION

Prompt treatment of bacterial meningitis with an appropriate antibiotic is essential. Optimal antimicrobial treatment of bacterial meningitis requires bactericidal agents able to penetrate the blood-brain barrier, with efficacy in cerebrospinal fluid. Emergence of CNS-infecting pathogens with resistance to conventional antibiotics has been increasingly recognized, but development of new antibiotics has been limited. More complete understanding of the microbial and host factors that are involved in the pathogenesis of bacterial meningitis and associated neurologic sequelae is likely to help in developing new strategies for the prevention and therapy of bacterial meningitis.

Centers for disease control and prevention expert panel meetings on prevention and treatment of anthrax in adults

The Centers for Disease Control and Prevention convened panels of anthrax experts to review and update guidelines for anthrax postexposure prophylaxis and treatment. The panels included civilian and military anthrax experts and clinicians with experience treating anthrax patients. Specialties represented included internal medicine, pediatrics, obstetrics, infectious disease, emergency medicine, critical care, pulmonology, hematology, and nephrology. Panelists discussed recent patients with systemic anthrax; reviews of published, unpublished, and proprietary data regarding antimicrobial drugs and anthrax antitoxins; and critical care measures of potential benefit to patients with anthrax. This article updates antimicrobial postexposure prophylaxis and antimicrobial and antitoxin treatment options and describes potentially beneficial critical care measures for persons with anthrax, including clinical procedures for infected nonpregnant adults. Changes from previous guidelines include an expanded discussion of critical care and clinical procedures and additional antimicrobial choices, including preferred antimicrobial drug treatment for possible anthrax meningitis.

Retrospective analysis of the risk factors for linezolid-induced thrombocytopenia in adult Japanese patients

BACKGROUND

Thrombocytopenia is a major side effect of linezolid therapy. However, there are few reports about the risk factors for linezolid-induced thrombocytopenia.

OBJECTIVE

The aim of this study is to evaluate the risk factors for thrombocytopenia in patients who undergo linezolid therapy.

SETTING

Aomori Prefectural Central Hospital in Japan, a tertiary 695 beds hospital.

METHOD

A retrospective review was performed using the hospital's medical records. From January 2010 to August 2012, 75 adult patients who received linezolid therapy were enrolled in this study.

MAIN OUTCOME MEASURE

Linezolid-induced thrombocytopenia was defined as a decrease in the patient's platelet count to <10 × 10⁴/μL or a reduction of ≥30 % from their baseline value. Odds ratios (OR) for thrombocytopenia were analyzed using multivariate stepwise logistic regression analysis.

RESULTS

Thrombocytopenia occurred in 29 patients (38.6 %), seven of whom required platelet transfusions. The patients who developed thrombocytopenia were significantly older, displayed a significantly higher frequency of renal insufficiency, and received linezolid therapy for significantly longer than the patients without thrombocytopenia. Stepwise logistic regression analysis suggested that receiving linezolid therapy for ≥14 days was a significant risk factor for thrombocytopenia [OR 13.3, 95 % confidence interval (CI) 3.2-55.6, p < 0.01], whereas the creatinine clearance rate exhibited a significant negative correlation with the incidence of the condition [OR 0.98, 95 % CI 0.96-0.99, p = 0.037]. The incidence of thrombocytopenia among the patients who demonstrated creatinine clearance rates of <30 mL/min was 60 % (12/20), which was significantly higher than that observed among the patients who displayed creatinine clearance rates of more than 60 mL/min (26.4 %, 9/34, p = 0.014).

CONCLUSION

Receiving linezolid therapy for ≥14 days and a low creatinine clearance rate were suggested to be risk factors for linezolid-induced thrombocytopenia. The platelet counts of patients with these risk factors should be closely monitored.

Pediatric anthrax clinical management

Anthrax is a zoonotic disease caused by Bacillus anthracis, which has multiple routes of infection in humans, manifesting in different initial presentations of disease. Because B anthracis has the potential to be used as a biological weapon and can rapidly progress to systemic anthrax with high mortality in those who are exposed and untreated, clinical guidance that can be quickly implemented must be in place before any intentional release of the agent. This document provides clinical guidance for the prophylaxis and treatment of neonates, infants, children, adolescents, and young adults up to the age of 21 (referred to as "children") in the event of a deliberate B anthracis release and offers guidance in areas where the unique characteristics of children dictate a different clinical recommendation from adults.

Treatment with linezolid in a neonate with meningitis caused by methicillin-resistant Staphylococcus epidermidis

Recent findings have focused on the possible role of linezolid (LZD) as a suitable candidate for the treatment of central nervous system infections. LZD treatment for meningitis has been sporadically reported in adults, but there are no reports in neonates or infants. We report a case of meningitis caused by methicillin-resistant Staphylococcus epidermidis (MRSE) in a neonatal girl. The patient had intraventricular hemorrhage on postnatal day 1 and was treated with ventricular drainage. Twenty-two days after drainage, the patient developed a fever and seizure. Although ampicillin and ceftriaxone were given empirically for meningitis, an increased cell count and protein were observed in cerebrospinal fluid (CSF). Vancomycin (VCM) was administered intravenously because MRSE was detected from CSF 2 days after the administration of ampicillin and ceftriaxone. However, intravenous administration of VCM did not show any effect. Subsequent treatment of LZD successfully reduced the cell count and protein in CSF.

CONCLUSION

LZD may be a treatment option for neonates and infants for drain-associated meningitis caused by MRSE.

Bacterial meningitis: new therapeutic approaches

Bacterial meningitis remains a disease with high mortality and long-term morbidity. Outcome critically depends on the rapid initiation of effective antibiotic therapy. Since a further increase of the incidence of pathogens resistant to antibacterials can be expected both in community-acquired and nosocomial bacterial meningitis, the choice of an optimum initial empirical antibiotic regimen will gain significance. In this context, the use of antibiotics which are bactericidal but do not lyse bacteria, may emerge as a therapeutic option. Conversely, the role of corticosteroids, which decrease the entry of hydrophilic antibacterials into the cerebrospinal fluid, as adjunctive therapy will probably decline as a consequence of the increasing antibiotic resistance of bacteria causing meningitis. Consequent vaccination of all children at present is the most efficient manner to reduce disease burden.

Surveillance and management of multidrug-resistant microorganisms

Multidrug-resistant organisms are an established and growing worldwide public health problem and few therapeutic options remain available. The traditional antimicrobials (glycopeptides) for multidrug-resistant Gram-positive infections are declining in efficacy. New drugs that are presently available are linezolid, daptomicin and tigecycline, which have well-defined indications for severe infections, and talavancin, which is under Phase III trial for hospital-acquired pneumonia. Unfortunately the therapies available for multidrug-resistant Gram-negatives, including carbapenem-resistant Pseudomonas aeruginosa, Acinetobacter baumannii and Enterobacteriaceae, are limited to only colistin and tigecycline. Both of these drugs are still not registered for severe infections, such as hospital acquired pneumonia. Consequently, as confirmed by scientific evidence, a multidisciplinary approach is needed. Surveillance, infection control procedures, isolation and antimicrobial stewardship should be implemented to reduce multidrug-resistant organism diffusion.

Vancomycin versus linezolid in the treatment of methicillin-resistant Staphylococcus aureus meningitis in an experimental rabbit model

Background

The aim of this study was to compare the antibacterial efficacy of vancomycin and linezolid in a rabbit model of methicillin-resistant Staphylococcus aureus (MRSA) meningitis.

Material/Methods

Meningitis was induced by intracisternal inoculation of ATCC 43300 strain. After 16 h incubation time and development of meningitis, the vancomycin group received vancomycin 20 mg/kg every 12 h. The linezolid-10 and linezolid-20 groups received linezolid in 10 and 20 mg/kg dosages every 12 h, respectively. The control group did not receive any antibiotics. Cerebrospinal fluid bacterial counts were measured at the end of 16-h incubation time and at the end of 24-h treatment.

Results

Bacterial counts were similar in all groups at 16 h. At the end of treatment the decrease in bacterial counts in the vancomycin group was approximately 2 logs higher than the linezolid-20 group (p>0.05) and approximately 4 logs higher than in the linezolid-10 group (p: 0.037) (Vancomycin group: −2.860±4.495 versus Linezolid-20: −0.724±4.360, versus Linezolid-10: 1.39±3.37). Full or partial bacteriological response was higher in vancomycin versus linezolid-10 (p: 0.01), but not vancomycin versus linezolid-20 or linezolid-10 versus-linezolid-20 groups.

Conclusions

Our results suggest that linezolid is not statistically inferior to vancomycin in the treatment of MRSA meningitis in an experimental rabbit model in 20 mg/kg q12 h dosage; however, it is inferior in 10 mg/kg q12 h dosage. Additional data should gathered to confirm these findings in advance of clinical trials to assess efficacy in humans.

Daptomycin plus trimethoprim/sulfamethoxazole combination therapy in post-neurosurgical meningitis caused by linezolid-resistant Staphylococcus epidermidis

Post-neurosurgical infection is a serious complication that occurs in approx. 4% of all patients undergoing neurosurgical procedures and is associated with high morbidity and mortality rates and prolonged length of intensive care unit (ICU) stay. Coagulase-negative staphylococci (CoNS), especially methicillin-resistant Staphylococcus epidermidis (MRSE), are the most frequent pathogens involved in CNS post-neurosurgical meningitis. Treatment is challenging especially in patients with meningitis due to multidrug- resistant (MDR) CONS. Herein, we report a unique case of post-neurosurgical meningitis due to MRSE resistant to linezolid (a molecular analysis revealed the presence of the mutation G2576T on domain V of the 23S rRNA gene) and with reduced susceptibility to glycopeptides, successfully treated with a combination of daptomycin at 10 mg/kg daily plus trimethoprim/sulfamethoxazole (TMP/SMX). This antibiotic combination showed an indifferent interaction in in vitro studies. Daptomycin serum and cerebrospinal fluid (CSF) concentrations, determined through blood and CSF samples drawn just prior to and 4 h after the third dose, were 18.9-0.78 and 51.65-3.1 mg/L, respectively. These values allowed us to approximate a 5-6% penetration rate of the drug through an inflamed blood-brain barrier. In conclusion, although further studies are needed, combination of high-dose daptomycin plus TMP/SMX is a reasonable option for treatment of meningitis caused by multidrug-resistant S. epidermidis.

In vitro electrophysiological investigations of the acute effects of linezolid and novel oxazolidinones on central nervous system neurons

Oxazolidinones are a novel class of antibacterial agents with demonstrated activity against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and enterococci. Prolonged clinical use of linezolid, the prototypical oxazolidinone, results in peripheral, central and optic neuropathies. The cellular mechanism by which it may alter neuronal function to produce these effects is not known. This study examined the in vitro effects of clinically relevant concentrations of linezolid and four selected potent antibacterial oxazolidinones on neuronal responses to determine if they are neuroactive and their possible neurotoxic mechanism(s). Using in vitro slice preparations of the rat nucleus accumbens (NAc) and hippocampus, we examined the effects of linezolid and the potent antibacterial triazolyl oxazolidinones, PH027, PH036, PH084 and PH108 on synaptic transmission and neuronal excitability recorded in voltage or current clamp mode. PH027 and PH084 generally depressed all excitatory and inhibitory postsynaptic currents. Linezolid, at the highest concentration tested, depressed NMDA receptor-mediated currents while PH036 and PH108 had no significant effect on any of these responses. The synaptic depression by PH084 was without effect on the resting membrane conductance at resting or relatively hyperpolarized voltage and could be blocked by GABA(B), dopamine D1-like and α-adrenergic receptor antagonists but not by an adenosine A1 receptor antagonist. Finally, PH084 decreased action potential firing frequency of NAc and hippocampal cells elicited at depolarized potentials. Our data indicate that, while oxazolidinones containing both the morpholine and triazole functional groups, as in PH027 and PH084, have neuroactivity, those containing morpholine and acetamide (linezolid) or piperazine and triazolyl (PH036 and PH108) functional groups have minimal acute neuroactivity and therefore may be safer antibacterial agents.

Penetration of drugs through the blood-cerebrospinal fluid/blood-brain barrier for treatment of central nervous system infections

The entry of anti-infectives into the central nervous system (CNS) depends on the compartment studied, molecular size, electric charge, lipophilicity, plasma protein binding, affinity to active transport systems at the blood-brain/blood-cerebrospinal fluid (CSF) barrier, and host factors such as meningeal inflammation and CSF flow. Since concentrations in microdialysates and abscesses are not frequently available for humans, this review focuses on drug CSF concentrations. The ideal compound to treat CNS infections is of small molecular size, is moderately lipophilic, has a low level of plasma protein binding, has a volume of distribution of around 1 liter/kg, and is not a strong ligand of an efflux pump at the blood-brain or blood-CSF barrier. When several equally active compounds are available, a drug which comes close to these physicochemical and pharmacokinetic properties should be preferred. Several anti-infectives (e.g., isoniazid, pyrazinamide, linezolid, metronidazole, fluconazole, and some fluoroquinolones) reach a CSF-to-serum ratio of the areas under the curves close to 1.0 and, therefore, are extremely valuable for the treatment of CNS infections. In many cases, however, pharmacokinetics have to be balanced against in vitro activity. Direct injection of drugs, which do not readily penetrate into the CNS, into the ventricular or lumbar CSF is indicated when other effective therapeutic options are unavailable.

Postoperative meningitis in patients with cervical cord tumor: a case report

Postoperative meningitis after spinal surgery is a rare complication that can result in a life-threatening condition. Linezolid (LZD) is an oxazolidinone which has been approved in Japan for infections caused by methicillin-resistant Staphylococcus aureus. The authors encountered a case of postoperative meningitis with cerebrospinal fluid leakage (liquorrhoea) that occurred after resection of a cervical cord tumor. The infection was caused by methicillin-resistant Staphylococcus epidermidis(MRSE). Debridement and suture of the dura matter was carried out. LZD was given intravenously. The infection was cured without any sequelae. Based on this result, we concluded that LZD might be considered as one of the first choices for the treatment of postsurgical meningitis caused by MRSE.

Pharmacokinetics and distribution of linezolid in cerebrospinal fluid in children and adolescents

BACKGROUND

Two studies in hydrocephalic children and adolescents were performed to assess the penetration of linezolid into cerebrospinal fluid and its relation to meningeal inflammation.

METHODS

Each patient was administered intravenous linezolid 10 mg/kg every 12 hours for 3 days (study 1) or every 8 hours for 2 days (study 2). Pharmacokinetic indices (Cmax, Cmin, Tmax, AUC) were determined for plasma and ventricular fluid (VF) after the first and last doses.

RESULTS

In study 1, after the last dose, the mean Cmax values for plasma and VF were 10.30 microg/mL (range, 3.95-16.6 microg/mL) and 7.54 microg/mL (range, 2.26-12.6 microg/mL), respectively; mean Cmin values were 1.32 microg/mL (range, 0.08-3.66 microg/mL) and 1.26 microg/mL (range, 0.19-2.58 microg/mL), respectively. The VF:plasma ratio based on last dose AUC0-12 was 0.98 microg h/mL (range, 0.64-1.22 microg h/mL). In study 2, after the last dose, the mean plasma and VF Cmax levels were 9.83 microg/mL (range, 3.19-16.5 microg/mL) and 5.84 microg/mL (range, 1.82-9.34 microg/mL), respectively; mean plasma and VF Cmin levels were 1.12 microg/mL (range, 0.10-3.39 microg/mL) and 1.94 microg/mL (range, 0.34-4.62 microg/mL), respectively. The VF:plasma ratio based on last dose AUC0-8 was 0.95 microg h/mL (range, 0.62-1.31 microg h/mL). Inflammation of the meninges did not seem to influence penetration of linezolid to the VF.

CONCLUSIONS

: Both studies showed that VF concentrations were variable. Further investigation of the role of linezolid in the treatment of CNS infection is needed.