Linezolid in the Starter Combination for Multidrug-Resistant Tuberculosis: Time to Move on to Group Four?

Linezolid (LNZ), a group 5 antituberculous drug (unclear efficacy), was used in the starter regimens of 23 adults with multidrug-resistant tuberculosis. The LNZ-containing regimens were effective in achieving culture conversions and relapse-free outcomes. The most frequent LNZ-related side effect was neuropathy. We propose that LNZ should be reclassified among bactericidal second-line drugs.

A 1 year retrospective audit of quality indicators of clinical pharmacological advice for personalized linezolid dosing: one stone for two birds?

AIM

This study explored the clinical and economic impact of clinical pharmacological advice (CPA) (based on therapeutic drug monitoring [TDM] results, and on patients' characteristics and co-medications) on personalized linezolid therapy in a tertiary care hospital.

METHODS

A 1 year retrospective analysis of quality indicators of CPA (clinicians' adherence rate to CPA, pre-post rate of linezolid trough concentrations within the desired range and cost balance analysis) was conducted.

RESULTS

Five hundred and forty-four CPAs were provided to clinicians during 2014 for personalizing linezolid therapy in 168 patients. Clinicians' adherence to CPAs was very high (94.7%). The pre-post rate of linezolid Cmin distribution showed a favourable impact of CPA on patient care (pre-post ratio of Cmin within the desired range + 23.4%, pre, 51.2% vs. post, 74.6%). Overall, linezolid dosage was mainly reduced (56.9% of cases), whereas dose augmentation was needed only in a minority of cases (7.7%). Cost balance analysis showed that overall 1258 standard doses of linezolid (unitary dose 600 mg) were spared for treating 168 patients with a personalized dosage for a median duration of 11 days (range 3-128 days) with a cost saving of 60038.05 €.

CONCLUSION

Active computerized advice elaborated by the clinical pharmacologist on the basis of TDM results and of patient's pathophysiological data and co-medications may be cost-effective for personalizing linezolid treatment.

Pancytopenia due to linezolid treatment

Antibiotic-resistant infections constitute a significant portion of severe childhood infections. A gradually increasing resistance and treatment difficulty are observed in infections caused by enterococci, staphylococci and pneumococci. Linezolid is one of the new antibiotics which has recently been introduced for clinical use with gram positive efficiency. In this article, a pediatric patient with vancomycin-resistant enterococcus infection who developed reversible bone marrow supression related with use of linesolid was presented. A shunt was inserted in a ten-month old female patient who had been operated at the age of one month because of meningomyelocele and who had developed hydrocephalus. Linezolid and meropenem treatment was started when vancomycin-resistant Enterococcus faecium and extended-spectrum beta-lactamase positive Escherichia coli grew in cerebrospinal fluid culture. In the second week of treatment, cerebrospinal fluid findings improved. However, bone marrow supression was observed. Linezolid treatment was discontinued. In the follow-up, the blood cell counts returned to normal levels.

Design, Synthesis, and Identification of Silicon Incorporated Oxazolidinone Antibiotics with Improved Brain Exposure

Therapeutic options for brain infections caused by pathogens with a reduced sensitivity to drugs are limited. Recent reports on the potential use of linezolid in treating brain infections prompted us to design novel compounds around this scaffold. Herein, we describe the design and synthesis of various oxazolidinone antibiotics with the incorporation of silicon. Our findings in preclinical species suggest that silicon incorporation is highly useful in improving brain exposures. Interestingly, three compounds from this series demonstrated up to a 30-fold higher brain/plasma ratio when compared to linezolid thereby indicating their therapeutic potential in brain associated disorders.

Linezolid-Associated Thrombocytopenia in Children With Renal Impairment

Impaired renal function has been associated with an increased risk of thrombocytopenia in adults receiving linezolid. Findings from this retrospective cohort demonstrate an association between thrombocytopenia and lower creatinine clearance in children receiving linezolid.

Successful Treatment of a Child With Extensively Drug-Resistant Tuberculous Meningitis

Unlike in pulmonary multidrug-resistant (MDR) tuberculosis, the clinical outcome of MDR tuberculous meningitis (TBM) in children, including extensively drug-resistant tuberculosis, is poor and management is challenging. We report the successful treatment of a case of extensively drug-resistant TBM in a 4-year-old girl, and we discuss implications for tuberculosis diagnosis and chemotherapy.

Linezolid induced black hairy tongue

Black hairy tongue (BHT) also called as lingua villosa nigra, is a self limiting benign condition characterized by hypertrophy and elongation of filiform papillae of tongue with brown or black discoloration. Smoking, poor oral hygiene, xerostomia, using peroxide containing mouth washes, substance abuse and drugs (steroids, methyldopa, olanzapine, etc) are the predisposing factors. However its occurrence in relation to linezolid ingestion among south Indians has not been reported in PubMed database. Here we report a case, where significant association of linezolid intake with BHT was found in a 10-year-old boy, who was treated with tablet linezolid for post surgical infection of left side radial neck fracture. This case is reported for the rarity of occurrence with linezolid therapy. According to Naranjo adverse drug reaction (ADR) causality scale, the association of BHT due to linezolid in our case was probable.

Isoniazid-induced polyneuropathy in a tuberculosis patient - implication for individual risk stratification with genotyping?

BACKGROUND

Development of polyneuropathy (PNP) under treatment for tuberculosis (TB), including isoniazid (INH), is a highly relevant adverse drug effect. The NAT2 acetylation status is a predictor of potential toxic effects of INH. The question as to whether individual risk stratification by genotyping is useful to avoid suffering of patients and to lower costs for the health care system is of considerable clinical importance.

CASE PRESENTATION

After drug treatment for TB, including INH, a 23-year-old man developed severe PNP. During the treatment, laboratory results have been indicating incipient liver and renal injury. Later, molecular genetic analyses were performed and revealed a variation in the NAT2 gene and the c1/c2 genotype of the CYP2E1 gene, both described to contribute to an elevated risk for anti-tuberculostatic-induced liver damages (ATIL).

CONCLUSION

The combination of metabolizer genotypes should be taken into account as a cause for toxic effects and the development of PNP. Individual genotyping, performed before medication or at least if an elevation of liver parameters is observed, may reduce the risk of severe cases of PNP by early adjustment of treatment. Our case study indicates that evaluation of individual risk stratification with systematic pharmacogenetic genotyping of metabolizer gene combinations in the context of TB treatment should be addressed in clinical studies with larger cohorts.

Linezolid Versus Vancomycin in the Empiric Treatment of Nosocomial Pneumonia: A Cost-Utility Analysis Incorporating Results from the ZEPHyR Trial

OBJECTIVE

To examine the cost-effectiveness of vancomycin versus linezolid in the empiric treatment of nosocomial pneumonias incorporating results from a recent prospective, double-blind, multicenter, controlled trial in adults with suspected methicillin-resistant Staphylococcus aureus (MRSA) nosocomial pneumonia.

METHODS

A decision-analytic model examining the cost-effectiveness of linezolid versus vancomycin for the empiric treatment of nosocomial pneumonia was created. Publicly available cost, efficacy, and utility data populated relevant model variables. A probabilistic sensitivity analysis varied parameters in 10,000 Monte-Carlo simulations, and univariate sensitivity analyses assessed the impact of model uncertainties and the robustness of our conclusions.

RESULTS

Results indicated that the cost per quality-adjusted life-year (QALY) increased 6% ($22,594 vs. $23,860) by using linezolid versus vancomycin for nosocomial pneumonia. The incremental cost per QALY gained by using linezolid over vancomycin was $6,089, and the incremental cost per life saved was $68,615 with the use of linezolid. Vancomycin dominated linezolid in the subset of patients with documented MRSA. The incremental cost per QALY gained using linezolid if no mortality benefit exists between agents or a 60-day time horizon was analyzed was $19,608,688 and $443,662, respectively.

CONCLUSIONS

Linezolid may be a cost-effective alternative to vancomycin in the empiric treatment of patients with suspected MRSA nosocomial pneumonia; however, results of our model were highly variable on a number of important variables and assumptions including mortality differences and time frame analyzed.

Comparing the ocular surface effects of topical vancomycin and linezolid for treating bacterial keratitis

BACKGROUND

Vancomycin is the gold standard in combination therapy for severe and resistant gram-positive keratitis and in particular for Methicillin-resistant Staphylococcus aureus (MRSA) infections. The aim of this study was to report the ocular surface toxicity and scoring in patients whose treatment shifted to topical linezolid/ceftazidime from topical vancomycin/ceftazidime due to their vancomycin intolerance.

METHODS

A retrospective, interventional case series of bacterial keratitis was treated with topical linezolid (one drop of 0.2% solution per eye), administered hourly until epithelization and then gradually decreased. The number and extent of punctate epithelial erosions were noted across the entire surface of the cornea. Ocular discomfort was assessed by means of (a) patient-reported pain upon instillation of the medication (vancomycin/linezolid), (b) reported burning sensation between doses and (c) reported foreign-body sensation. No ocular surface toxicity related to linezolid use was noted. Patients were followed for at least 2 months after treatment between April and December 2013.

RESULTS

Of the seven patients included in the study (age range: 2-88 years; five females, two males), complete epithelization and resolution was achieved in five patients. One patient was treated with linezolid after penetrating keratoplasty. The second culture of another patient with impending perforation despite linezolid/ceftazidime therapy yielded Fusarium spp., so he underwent tectonic keratoplasty. The mean ocular surface score was 9.4 ± 1.6 during vancomycin treatment and 5.9 ± 1.3 during linezolid treatment after discontinuation of vancomycin. The topical linezolid score was significantly lower (p = 0.027).

CONCLUSIONS

Topical linezolid may be better tolerated, according to the mean ocular surface score, than topical vancomycin by some patients and can be considered an alternative for patients who do not well tolerate vancomycin.

Clinical pharmacological approach for balancing the use of daptomycin and linezolid in comparison with that of vancomycin in the treatment of MRSA-related infections

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most challenging bacterial pathogens responsible for severe infections among hospitalized patients. In recent years there is increasing evidence that the clinical efficacy of vancomycin is progressively decreasing. Although daptomycin and linezolid are valuable alternatives to vancomycin for the treatment of MRSA-related bloodstream infections and pneumonia, respectively, a great deal of debate exists about their role in daily clinical practice due to cost-effectiveness issues. In this article we put into perspective the importance of pharmacokinetic/pharmacodynamic (PK/PD) considerations based on recent experimental and clinical data to argue whether they could be helpful in identifying clinical conditions in which these agents could be advantageous as compared to vancomycin.

Comparison of the Effectiveness and Safety of Linezolid and Daptomycin in Vancomycin-Resistant Enterococcal Bloodstream Infection: A National Cohort Study of Veterans Affairs Patients

BACKGROUND

Vancomycin-resistant Enterococcus bloodstream infections (VRE-BSIs) are becoming increasingly common. Linezolid and daptomycin are the primary treatment options for VRE-BSI, but optimal treatment is unclear.

METHODS

This was a national retrospective cohort study comparing linezolid and daptomycin for the treatment of VRE-BSI among Veterans Affairs Medical Center patients admitted during 2004-2013. The primary outcome was treatment failure, defined as a composite of (1) 30-day all-cause mortality; (2) microbiologic failure; and (3) 60-day VRE-BSI recurrence. Poisson regression was conducted to determine if antimicrobial treatment was independently associated with clinical outcomes.

RESULTS

A total of 644 patients were included (linezolid, n = 319; daptomycin, n = 325). Overall, treatment failure was 60.9% (n = 392/644), and 30-day all-cause mortality was 38.2% (n = 246/644). Linezolid was associated with a significantly higher risk of treatment failure compared with daptomycin (risk ratio [RR], 1.37; 95% confidence interval [CI], 1.13-1.67; P = .001). After adjusting for confounding factors in Poisson regression, the relationship between linezolid use and treatment failure persisted (adjusted RR, 1.15; 95% CI, 1.02-1.30; P = .026). Linezolid was also associated with higher 30-day mortality (42.9% vs 33.5%; RR, 1.17; 95% CI, 1.04-1.32; P = .014) and microbiologic failure rates (RR, 1.10; 95% CI, 1.02-1.18; P = .011). No difference in 60-day VRE-BSI recurrence was observed between treatment groups.

CONCLUSIONS

Treatment with linezolid for VRE-BSI resulted in significantly higher treatment failure in comparison to daptomycin. Linezolid treatment was also associated with greater 30-day all-cause mortality and microbiologic failure in this cohort.

A novel gene, optrA, that confers transferable resistance to oxazolidinones and phenicols and its presence in Enterococcus faecalis and Enterococcus faecium of human and animal origin

OBJECTIVES

The oxazolidinone-resistant Enterococcus faecalis E349 from a human patient tested negative for the cfr gene and 23S rRNA mutations. Here we report the identification of a novel oxazolidinone resistance gene, optrA, and a first investigation of the extent to which this gene was present in E. faecalis and Enterococcus faecium from humans and food-producing animals.

METHODS

The resistance gene optrA was identified by whole-plasmid sequencing and subsequent cloning and expression in a susceptible Enterococcus host. Transformation and conjugation assays served to investigate the transferability of optrA. All optrA-positive E. faecalis and E. faecium isolates of human and animal origin were analysed for their MICs and their genotype, as well as the location of optrA.

RESULTS

The novel plasmid-borne ABC transporter gene optrA from E. faecalis E349 conferred combined resistance or elevated MICs (when no clinical breakpoints were available) to oxazolidinones (linezolid and tedizolid) and phenicols (chloramphenicol and florfenicol). The corresponding conjugative plasmid pE349, on which optrA was located, had a size of 36 331 bp and also carried the phenicol exporter gene fexA. The optrA gene was functionally expressed in E. faecalis, E. faecium and Staphylococcus aureus. It was detected more frequently in E. faecalis and E. faecium from food-producing animals (20.3% and 5.7%, respectively) than from humans (4.2% and 0.6%, respectively).

CONCLUSIONS

Enterococci with elevated MICs of linezolid and tedizolid should be tested not only for 23S rRNA mutations and the gene cfr, but also for the novel resistance gene optrA.

Systematic review and meta-analysis of the efficacy and safety of therapy with linezolid containing regimens in the treatment of multidrug-resistant and extensively drug-resistant tuberculosis

BACKGROUND

Linezolid containing regimens have been proposed as potentially valuable alternatives for the treatment of patients with multidrug-resistant tuberculosis (MDR-TB) or extensively drug-resistant TB (XDR-TB).

METHODS

A systematic review and meta-analysis was conducted to assess the efficacy, safety and tolerability of linezolid for drug-resistant TB (DR-TB) treatment. We searched the Cochrane Controlled Trial Registry, PubMed, Embase, Science Citation Index Expanded (SCI) and China National Knowledge Infrastructure (CNKI), database up to May 2014 to identify studies providing data of the use of linezolid for the treatment of DR-TB.

RESULTS

The search yielded 15 studies (367 patients) including one randomized controlled trial (RCT), covering 239 patients who could be evaluated for effectiveness; 83% [95% confidence interval (CI), 75-90%; I(2)=62.8%] had a favorable outcome, defined as either cure or treatment completion. The pooled rate of culture conversion was 89% (95% CI, 83-95%; I(2)=49.6%). Between the group receiving daily linezolid doses of ≤600 or >600 mg, the mortality was considerably lower in patients treated with less than 600 mg/day (P value <0.001). Of 367 patients for whom data on safety was available, peripheral neuropathy (31%, 95% CI, 19-42%; I(2)=81.7%) and anemia (25%, 95% CI, 15-34%; I(2)=76.6%) were the main adverse effects. Patients receiving less than 600 mg/day were more likely to experience nervous system adverse events (P value <0.01).

CONCLUSIONS

The available evidence suggests that linezolid could be considered as a promising option as treatment of MDR/XDR TB. Randomized trials are warranted to define the dose and frequency of administration.

Update on the emerging role of telavancin in hospital-acquired infections

Telavancin is a lipoglycopeptide that has activity against Gram-positive aerobic and anaerobic bacteria. It has activity against methicillin-resistant Staphylococcus aureus, vancomycin-intermediate S. aureus and non-Van-A strains of vancomycin-resistant enterococci. It has been approved by the US Food and Drug Administration (FDA) for complicated skin and skin structure infections and hospital-acquired pneumonia. There is a need for more clinical studies to determine the role of telavancin in treating bacteremia and prosthetic device infections. In this review, we discuss the published data on the use of telavancin in treating hospital-acquired infections and provide an update on new research.

The association between risk factors and time of onset for thrombocytopenia in Japanese patients receiving linezolid therapy: a retrospective analysis

WHAT IS KNOWN AND OBJECTIVE

Linezolid (LZD) is an oxazolidinone antibiotic that is active against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. The major adverse effect related to its use in humans is reversible myelosuppression, which mostly manifests as thrombocytopenia. This retrospective study was conducted to identify risk factors that might contribute towards the development of thrombocytopenia due to intravenous administration of LZD.

METHOD

Patients who were administered LZD between January 2008 and March 2013 were included. Thrombocytopenia was defined as a decrease in platelet count of ≥10 × 10(4) cell/μL from baseline or of ≥30%.

RESULTS

A total of 47 patients were included in this study. These patients were divided into two groups: 22 patients (46·8%) were assigned to a non-thrombocytopenia group and 25 patients (53·2%) to a thrombocytopenia group. Multivariate logistic regression analysis revealed significant intergroup differences in duration of LZD treatment [odds ratio (OR) = 1·278; 95% confidence interval (CI) = 1·068-1·529; P = 0·007] and white blood cell (WBC) count (>12000 cells/μL; OR = 10·399; 95% CI = 1·667-64·882; P = 0·012).

WHAT IS NEW AND CONCLUSIONS

This finding suggests that duration of LZD treatment and WBC count (>12000 cells/μL) are risk factors associated with thrombocytopenia resulting from LZD administration.

A simple high-performance liquid chromatography for the determination of linezolid in human plasma and saliva

Linezolid is an antimicrobial agent for the treatment of multiresistant Gram-positive infections. A practical high-performance liquid chromatography method was developed for the determination of linezolid in human plasma and saliva. Linezolid and an internal standard (o-ethoxybenzamide) were extracted from plasma and saliva with ethyl acetate and analyzed on a Capcell Pak C18 MG column with UV detection at 254 nm. The calibration curve was linear through the range 0.5-50 µg/mL using a 200 μL sample volume. The intra- and interday precisions were all <6.44% for plasma and 5.60% for saliva. The accuracies ranged from 98.8 to 110% for both matrices. The mean recoveries of linezolid were 80.8% for plasma and 79.0% for saliva. This method was used to determine the plasma and saliva concentrations of linezolid in healthy volunteers who were orally administered a 600 mg dose of linezolid. Our liquid-liquid extraction procedure is easy and requires a small volume of plasma or saliva (200 μL). This small volume can be advantageous in clinical pharmacokinetic studies, especially if children participate.

Linezolid bladder irrigation as adjunctive treatment for a vancomycin-resistant Enterococcus faecium catheter-associated urinary tract infection

OBJECTIVE

To describe the first reported successful use of adjunctive linezolid bladder irrigation.

CASE SUMMARY

An 89-year-old woman with 10% TBSA burns developed septic shock and anuric acute kidney insufficiency. She acquired a urinary tract infection caused by vancomycin-resistant Enterococcus faecium (VREfm). Based on clinical status, a linezolid bladder irrigation was initiated in addition to high-dose intravenous linezolid and demonstrated microbiological cure with 7 days of treatment.

DISCUSSION

Linezolid is primarily hepatically cleared and has no labeled indication for urinary tract infections. Anuria adds an additional complication of potentially reduced urinary drug concentrations. Bladder irrigation offers the benefit of achieving high local drug concentrations, but there are no data regarding such a route for linezolid. This case report is the first demonstrating the use, stability, safety, and efficacy of linezolid as a continuous bladder irrigation.

CONCLUSIONS

Linezolid use as a bladder irrigation may be a feasible route of administration in anuric, critically ill patients with VREfm and few antimicrobial options. Further studies are warranted.

Relationship between consumption of MRSA-active antibiotics and burden of MRSA in acute care hospitals in Catalonia, Spain

OBJECTIVES

To analyse the possible relationship between consumption of old and new MRSA-active antibiotics and burden of MRSA in acute care hospitals in Catalonia during the period 2007-12.

METHODS

Fifty-four hospitals participating in the VINCat Programme were included. Proportion of MRSA (resistant isolates of Staphylococcus aureus per 100 isolates of S. aureus tested), incidence of new cases of infection [new cases of MRSA per 1000 occupied bed-days (OBD)] and incidence of cases of bacteraemia (MRSA bacteraemia cases per 1000 OBD) were determined to estimate the annual MRSA burden. Antibiotic consumption was calculated in DDD/100 OBD. Cost was expressed in euros/100 OBD.

RESULTS

MRSA rates remained stable over the study period, with the proportion of MRSA ranging from 20% to 22.82% in 2007 and 2012, respectively (P=0.864). Consumption of old MRSA-active antibiotics (vancomycin and teicoplanin) did not change significantly, with values from 1.51 to 2.07 DDD/100 OBD (P=0.693). Consumption of new MRSA-active antibiotics (linezolid and daptomycin) increased significantly, with values rising from 0.24 to 1.49 DDD/100 OBD (P<0.001). Cost increased by almost 200%.

CONCLUSIONS

A widespread and steady increase in consumption of new MRSA-active antibiotics was observed among acute care hospitals in Catalonia, in spite of a stable MRSA burden. At the same time, consumption of old drugs remained stable. Such trends resulted in a significant increase in cost. Our findings suggest that factors other than the proportion of methicillin resistance among S. aureus may influence the use of old and new MRSA-active antibiotics in the clinical setting.

Transfer of linezolid into breast milk

Linezolid, a broad-spectrum antibiotic used primarily for treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections, is the first oxazolidinone approved for clinical use. This is a case report of a 30-year-old woman who was exclusively breastfeeding her infant prior to taking linezolid 600 mg orally every 12 hours to treat a MRSA mastitis. Breast milk samples were obtained over a 12-hour dosing interval on day 1 (after a single dose of therapy) and again on day 14 (at steady state). The relative infant dose at steady state was found to be 15.61% on day 14 of therapy. Using the average concentration at steady state, the estimated infant dose would have been 1.84 mg/kg/day, which is well below the recommended dose given to neonates requiring linezolid drug therapy. The infant did not breastfeed during maternal treatment with linezolid.

An economic model to compare linezolid and vancomycin for the treatment of confirmed methicillin-resistant Staphylococcus aureus nosocomial pneumonia in Germany

BACKGROUND

Across Europe, methicillin-resistant Staphylococcus aureus (MRSA) is considered to be the primary cause of nosocomial pneumonia (NP). In Germany alone, approximately 14,000 cases of MRSA-associated NP occur annually, which may have a significant impact on health care resource use and associated economic costs. The objective of this study was to investigate the economic impact of linezolid compared with that of vancomycin in the treatment of hospitalized patients with MRSA-confirmed NP in the German health care system.

METHODS

A 4-week decision tree model incorporated published data and expert opinion on clinical parameters, resource use, and costs (2012 euros) was constructed. The base case first-line treatment duration for patients with MRSA-confirmed NP was 10 days. Treatment success (survival), failure due to lack of efficacy, serious adverse events, and mortality were possible outcomes that could impact costs. Alternate scenarios were analyzed, such as varying treatment duration (7 or 14 days) or treatment switch due to a serious adverse event/treatment failure (at day 5 or 10).

RESULTS

The model calculated total base case inpatient costs of €15,116 for linezolid and €15,239 for vancomycin. The incremental cost-effectiveness ratio favored linezolid (versus vancomycin), with marginally lower costs (by €123) and greater efficacy (+2.7% absolute difference in the proportion of patients successfully treated for MRSA NP). Approximately 85%-87% of the total treatment costs were attributed to hospital stay (primarily in the intensive care unit). Sensitivity analysis yielded similar results.

CONCLUSION

The model results show that linezolid is a cost-effective alternative to vancomycin for MRSA-confirmed NP, largely attributable to the higher clinical response rate of patients treated with linezolid.

In vitro susceptibility to methicillin, vancomycin and linezolid of staphylococci isolated from bloodstream infections in eastern Turkey

Staphylococcus species are one of the major causes of bacterial bloodstream infections. Multi-resistant staphylococci infections are major therapeutic problems. This study was aimed to detect methicillin, linezolid and vancomycin susceptibilities of Staphylococcus isolates. A total of 870 Staphylococcus strains isolated from blood cultures of hospitalized patients with BSI. Antimicrobial susceptibilities of methicillin, linezolid and vancomycin were detected according to the Clinical and Laboratory Standards Institute (CLSI). A total of 771 (88.6%) isolates were coagulase-negative staphylococci (CoNS). 700 (80.5%) isolates were methicillin-resistant (MR) and 170 (19.5%) were methicillin-susceptible (MS). All the MS isolates were also susceptible to linezolid. However 15 (1.7%) of MR strains were resistant to linezolid. The minimum inhibitory concentration range for the linezolid-resistant isolates by Etest was 6–32 μg/mL. The difference between linezolid susceptibilities for MS and MR staphylococci was not quite statistically significant (p = 0.052). There was no statistically significant difference between S. aureus and CoNS isolates for linezolid susceptibility. All of the isolates were susceptible to vancomycin. In conclusion, linezolid is currently an efficient option for the treatment of methicillin-resistant staphylococci infections.

European perspective and update on the management of nosocomial pneumonia due to methicillin-resistant Staphylococcus aureus after more than 10 years of experience with linezolid

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of antimicrobial-resistant hospital-acquired infections worldwide and remains a public health priority in Europe. Nosocomial pneumonia (NP) involving MRSA often affects patients in intensive care units with substantial morbidity, mortality and associated costs. A guideline-based approach to empirical treatment with an antibacterial agent active against MRSA can improve the outcome of patients with MRSA NP, including those with ventilator-associated pneumonia. New methods may allow more rapid or sensitive diagnosis of NP or microbiological confirmation in patients with MRSA NP, allowing early de-escalation of treatment once the pathogen is known. In Europe, available antibacterial agents for the treatment of MRSA NP include the glycopeptides (vancomycin and teicoplanin) and linezolid (available as an intravenous or oral treatment). Vancomycin has remained a standard of care in many European hospitals; however, there is evidence that it may be a suboptimal therapeutic option in critically ill patients with NP because of concerns about its limited intrapulmonary penetration, increased nephrotoxicity with higher doses, as well as the emergence of resistant strains that may result in increased clinical failure. Linezolid has demonstrated high penetration into the epithelial lining fluid of patients with ventilator-associated pneumonia and shown statistically superior clinical efficacy versus vancomycin in the treatment of MRSA NP in a phase IV, randomized, controlled study. This review focuses on the disease burden and clinical management of MRSA NP, and the use of linezolid after more than 10 years of clinical experience.

Peritonitis in a continuous ambulatory peritoneal dialysis patient by two different species of enterococci: A rare finding

Peritonitis in a continuous ambulatory peritoneal dialysis patient by two different species of enterococci is a rare condition. We report a case of peritonitis from which vancomycin sensitive Enterococcus faecalis and vancomycin resistant Enterococcusc faecium were isolated. It also emphasizes the effectiveness of linezolid for the treatment of vancomycin resistant enterococcal infection.

Optimization of nebulized delivery of linezolid, daptomycin, and vancomycin aerosol

BACKGROUND

At this time, several antibiotics have been investigated as possibilities for aerosol administration, but local therapy has been found to be more efficient in several diseases.

MATERIALS AND METHODS

The drugs linezolid (Zyvox), vancomycin (Voncon), and daptomycin (Cubicin) were tested with three jet nebulizers with seven different residual cups and different loadings. Moreover, three ultrasound nebulizers were again tested with these drugs, with different loadings and mouthpiece attachments.

RESULTS

When drugs are combined with particular cup designs, they significantly lower the droplet size to 1.60 and 1.80 μm, which represents the best combination of Zyvox and cup G and Cubicin and cup D, respectively. Cup design D is suggested as the most effective cup for lowering the droplet size (2.30 μm) when considering a higher loading level (8 mL).

CONCLUSION

Modification of current drugs from dry powder to solution is possible, and the residual cup design plays the most important role in droplet size production when the nebulization systems have the same properties.

Methicillin-resistant Staphylococcus aureus pneumonia in adults

Methicillin-resistant Staphylococcus aureus (MRSA) has become one of the leading etiologies of nosocomial pneumonia as a result of an increase in staphylococcal infections caused by methicillin-resistant strains paired with extended ventilatory support of critically, and often, chronically ill patients. The prevalence of community-acquired MRSA pneumonia, which historically affects younger patients and is often preceded by an influenza-like illness, is also increasing. A high index of suspicion and early initiation of appropriate antibiotics are key factors for the successful treatment of this disease. Even with early diagnosis and appropriate treatment, MRSA pneumonia still carries an unacceptably high mortality rate. This article will review historical differences between hospital-acquired and community-acquired MRSA pneumonia, as well as, clinical features of, diagnosis and treatment of MRSA pneumonia.

Hypoglycemia in patients treated with linezolid

Hypoglycemia was not previously known to be a linezolid-associated adverse reaction. A case report describing symptomatic hypoglycemia in a linezolid recipient prompted a review of the US Food and Drug Administration Adverse Event Reporting System, which demonstrated a relationship between linezolid and hypoglycemia. A warning with this information was added to the linezolid package insert.

Linezolid effects on bacterial toxin production and host immune response: review of the evidence

BACKGROUND

Linezolid is active against a broad range of gram-positive pathogens and has the potential to also affect production of bacterial toxins and host immune function.

OBJECTIVE

To assess the evidence for direct effects of linezolid on bacterial toxin synthesis and modulation of host immune responses.

METHODS

Literature searches were performed of the PubMed and OVID databases. Reviews and non-English language articles were excluded. Articles with information on the effect of linezolid on bacterial toxin synthesis and immune responses were selected for further review, and data were summarized.

RESULTS

Substantial in vitro evidence supports effects of linezolid on bacterial toxin production; however, the strength of the evidence and the nature of the effects are mixed. In the case of Staphylococcus aureus, repeated observations support the inhibition of production of certain staphylococcal toxins (Panton-Valentine leukocidin, protein A, and α- and β-hemolysin) by linezolid, whereas only solitary reports indicate inhibition (toxic shock syndrome toxin-1, coagulase, autolysins, and enterotoxins A and B) or stimulation (phenol-soluble modulins) of toxin production by linezolid. In the case of Streptococcus pyogenes, there are solitary reports of linezolid inhibition (protein M, deoxyribonuclease, and streptococcal pyrogenic exotoxins A, B, and F) or stimulation (immunogenic secreted protein 2 and streptococcal inhibitor of complement-mediated lysis) of toxin production, whereas published evidence for effects on streptolysin O production is conflicting. In vitro data are limited, but suggest that linezolid might also have indirect effects on host cytokine expression through inhibition of bacterial production of toxins. In vivo data from preclinical animal studies and a single clinical study in humans are limited and equivocal insofar as a potential role for linezolid in modulating the host inflammatory response; this is due in part to the difficulty in isolating antimicrobial effects and toxin synthesis inhibitory effects of linezolid from any secondary effects on host inflammatory response.

CONCLUSIONS

Available evidence supports the possibility that linezolid can inhibit, and in some cases stimulate, toxin production in clinically relevant pathogens. However, more research will be needed to determine the potential clinical relevance of those findings for linezolid.

Target site pharmacokinetics of linezolid after single and multiple doses in diabetic patients with soft tissue infection

The underlying pathology of diabetic wounds, i.e. impairment of macro- and microcirculation, might also impact target site penetration of antibacterial drugs. To compare tissue concentrations of linezolid in infected and not infected tissue 10 patients suffering from type 2 diabetes with foot infection were included in the study. Tissue penetration of linezolid was assessed using in vivo microdialysis at the site of infection as well as in non-inflamed subcutaneous adipose tissue. All patients were investigated after receiving a single dose of linezolid and five patients in addition at steady state. After a single dose of linezolid significantly higher area under the concentration vs. time curve over 8 hours (AUC0-8 ) and maximum concentrations (Cmax )-values were observed in plasma (65.5 ± 21.2 mg*h/L and 16.4 ± 4.6 mg/L) as compared to inflamed (36.3 ± 22.9  mg*h/L and 6.6 ± 3.6 mg/L) and non-inflamed tissue (33.0 ± 17.7 mg*h/L and 6.7 ± 3.6 mg/L). Multiple administrations of linezolid led to disappearance of significant differences in Cmax and AUC0-8 between plasma, inflamed, and non-inflamed tissue. Approximately 2-fold increase of Cmax and AUC0-8 -values in tissue was observed at steady state as compared to the first administration. Penetration of linezolid is not impaired in diabetic foot infection but equilibrium between plasma and tissue might be delayed.

Cost-Effectiveness of Linezolid versus Vancomycin among Patients with Methicillin-Resistant Staphylococcus aureus Confirmed Nosocomial Pneumonia in China

OBJECTIVE

To estimate the cost-effectiveness of intravenous linezolid as a first-line agent against intravenous vancomycin in treating methicillin-resistant Staphylococcus aureus-confirmed nosocomial pneumonia in four Chinese cities.

METHODS

A decision-analytic model of 4-week time horizon was used to conduct cost-effectiveness analyses from the payer's perspective. Clinical outcomes and resource use data were derived from a head-to-head trial, supplemented with local cost estimates based on hospital data via an expert panel. A series of scenario analyses were conducted to evaluate the impact of uncertainty around model inputs. All results were reported in 2012 Chinese Renminbi.

RESULTS

The predicted probability of overall treatment success was 0.629 and 0.602 for linezolid and vancomycin, respectively. Total inpatient costs varied across the four cities, ranging from ¥58,835 to ¥86,894 for linezolid and ¥58,390 to ¥87,033 for vancomycin, respectively. Linezolid was demonstrated to be a dominant treatment strategy in Guangzhou. In Beijing, Nanjing, and Xi'an, incremental cost-effectiveness ratios in terms of additional successfully treated patient were ¥1,861, ¥163, and ¥16,509, respectively. Dominance by linezolid was observed in some scenario analyses with parameters such as treatment duration, inclusion of cost of managing adverse events, and drug acquisition costs being the main drivers of cost-effectiveness results.

CONCLUSIONS

Despite linezolid's higher drug acquisition cost, its superior clinical efficacy renders it a likely cost-effective alternative for the treatment of methicillin-resistant Staphylococcus aureus-confirmed nosocomial pneumonia as compared with branded vancomycin from the payer perspectives of Beijing, Guangzhou, Nanjing, and Xi'an.

Pharmacokinetics and safety of recently approved drugs used to treat methicillin-resistant Staphylococcus aureus infections in infants, children and adults

Methicillin-resistant Staphylococcus aureus (MRSA) remains a significant cause of morbidity in hospitalized infants. Over the past 15 years, several drugs have been approved for the treatment of S. aureus infections in adults (linezolid, quinupristin/dalfopristin, daptomycin, telavancin, tigecycline and ceftaroline). The use of the majority of these drugs has extended into the treatment of MRSA infections in infants, frequently with minimal safety or dosing information. Only linezolid is approved for use in infants, and pharmacokinetic data in infants are limited to linezolid and daptomycin. Pediatric trials are underway for ceftaroline, telavancin, and daptomycin; however, none of these studies includes infants. Here, we review current pharmacokinetic, safety and efficacy data of these drugs with a specific focus in infants.

Carbonate apatite nephrolithiasis associated with Corynebacterium urealyticum urinary tract infection in a dog

BACKGROUND

Urinary tract infections caused by Corynebacterium urealyticum are uncommon in veterinary medicine. Encrusted cystitis, encrusted pyelitis and uroliths have been described as complications in humans, but only encrusted cystitis and cystoliths have been reported in dogs so far. Because C. urealyticum is usually resistant to all standard antibacterial drugs, antimicrobial treatment and elimination of this microorganism are challenging.

CASE REPORT

An 11-month-old female spayed mixed-breed dog was evaluated because of a C. urealyticum urinary tract infection, mineralisation within both renal pelvises and failure of antimicrobial treatment. Physical examination, haematology and biochemistry were unremarkable. Radiographic and ultrasonographic examinations confirmed bilateral nephrolithiasis. Voided uroliths were composed of 100% carbonate apatite. Urinalysis was indicative of bacterial infection. Aerobic culture of the urine and 16S rRNA sequencing identified significant growth of C. urealyticum and susceptibility testing revealed sensitivity to only vancomycin and linezolid.

CONCLUSION

Treatment with the oxazolidinone antibacterial, linezolid, in combination with a urine-acidifying diet resulted in elimination of this multiresistant microorganism and complete resolution of nephrolithiasis.

A phase 3 randomized double-blind comparison of ceftobiprole medocaril versus ceftazidime plus linezolid for the treatment of hospital-acquired pneumonia

BACKGROUND

Ceftobiprole, the active moiety of ceftobiprole medocaril, is a novel broad-spectrum cephalosporin, with bactericidal activity against a wide range of gram-positive bacteria, including Staphylococcus aureus (including methicillin-resistant strains) and penicillin- and ceftriaxone-resistant pneumococci, and gram-negative bacteria, including Enterobacteriaceae and Pseudomonas aeruginosa.

METHODS

This was a double-blind, randomized, multicenter study of 781 patients with hospital-acquired pneumonia (HAP), including 210 with ventilator-associated pneumonia (VAP). Treatment was intravenous ceftobiprole 500 mg every 8 hours, or ceftazidime 2 g every 8 hours plus linezolid 600 mg every 12 hours; primary outcome was clinical cure at the test-of-cure visit.

RESULTS

Overall cure rates for ceftobiprole vs ceftazidime/linezolid were 49.9% vs 52.8% (intent-to-treat [ITT], 95% confidence interval [CI] for the difference, -10.0 to 4.1) and 69.3% vs 71.3% (clinically evaluable [CE], 95% CI, -10.0 to 6.1). Cure rates in HAP (excluding VAP) patients were 59.6% vs 58.8% (ITT, 95% CI, -7.3 to 8.8), and 77.8% vs 76.2% (CE, 95% CI, -6.9 to 10.0). Cure rates in VAP patients were 23.1% vs 36.8% (ITT, 95% CI, -26.0 to -1.5) and 37.7% vs 55.9% (CE, 95% CI, -36.4 to 0). Microbiological eradication rates in HAP (excluding VAP) patients were, respectively, 62.9% vs 67.5% (microbiologically evaluable [ME], 95% CI, -16.7 to 7.6), and in VAP patients 30.4% vs 50.0% (ME, 95% CI, -38.8 to -0.4). Treatment-related adverse events were comparable for ceftobiprole (24.9%) and ceftazidime/linezolid (25.4%).

CONCLUSIONS

Ceftobiprole is a safe and effective bactericidal antibiotic for the empiric treatment of HAP (excluding VAP). Further investigations are needed before recommending the use of ceftobiprole in VAP patients. Clinical Trials Registration. NCT00210964, NCT00229008.

Predictors of clinical success among a national Veterans Affairs cohort with methicillin-resistant Staphylococcus aureus pneumonia

BACKGROUND

The treatment of methicillin-resistant Staphylococcus aureus (MRSA) pneumonia is exceedingly complicated, which is concerning because of the high mortality rate associated with the infection. Identification of independent predictors of clinical success can optimize patient care by assisting clinicians in treatment decisions.

OBJECTIVES

Our goal was to identify independent predictors of clinical success in a national Veterans Affairs (VA) cohort of patients with MRSA pneumonia.

METHODS

A nested case-control study was conducted among a cohort of VA patients with MRSA pneumonia receiving linezolid or vancomycin between January 2002 and September 2010. Cases included those demonstrating clinical success, defined as discharge from the hospital or intensive care unit by day 14 after treatment initiation, in the absence of death, therapy change, or intubation by day 14. Control subjects represented nonsuccess, defined as therapy change, intubation, intensive care unit admission, readmission, or death between treatment initiation and day 14. The potential predictors assessed included treatment, patient demographic and admission characteristics, previous health care and medication exposures, comorbidities, and medical history. Odds ratios (ORs) and 95% CIs were calculated from logistic regression.

RESULTS

Our study included 2442 cases of clinical success and 1290 control subjects. Demographic characteristics varied between the clinical success and nonsuccess groups, including age, race, and region of facility. A current diagnosis of chronic respiratory disease (46% vs 42%) and diagnosis of pneumonia in the year before the MRSA pneumonia admission (37% vs 32%) were both more common in the clinical success group. Despite these significant differences, only 2 predictors of clinical success were identified in our study: previous complication of an implant or graft, including mechanical complications and infections, in the year before the MRSA pneumonia admission (adjusted OR, 1.55 [95% CI, 1.17-2.06]) and treatment with linezolid (adjusted OR, 1.53 [95% CI, 1.12-2.10]). Predictors of nonsuccess (adjusted OR [95% CI) included diagnosis of concomitant urinary tract infection (0.82 [0.70-0.96]), intravenous line (0.76 [0.66-0.89]), previous coagulopathy (0.74 [0.56-0.96]), previous amputation procedure (0.72 [0.53-0.98]), current coagulopathy diagnosis (0.71 [0.53-0.96]), dialysis (0.54 [0.38-0.76]), multiple inpatient procedures (0.53 [0.45-0.62]), inpatient surgery (0.48 [0.41-0.57]), and previous endocarditis (0.24 [0.07-0.81]).

CONCLUSIONS

MRSA pneumonia tends to affect patients with complex care, and identification of the predictors of clinical success is useful when considering different therapeutic approaches. In this national cohort of VA patients with MRSA pneumonia, treatment was the only modifiable variable predicting clinical success.

Linezolid compared with vancomycin for the prevention of methicillin-resistant Staphylococcus aureus or Staphylococcus epidermidis vascular graft infection in rats: A randomized, controlled, experimental study

BACKGROUND

Graft infections are severe complications of vascular surgery that may result in amputation or mortality. Staphylococci are the most frequent cause of vascular graft infections.

OBJECTIVE

In this study we assessed the prophylactic efficacy of linezolid in comparison with vancomycin in preventing prosthetic vascular graft infection due to methicillin-resistant Staphylococcus aureus (MRSA) or methicillin-resistant Staphylococcus epidermidis (MRSE).

METHODS

This randomized, controlled, experimental study using healthy adult (aged >5 months) male Wistar rats was conducted in the research laboratory of the Pamukkale University, Denizli, Turkey. The study consisted of an uncontaminated control group and 3 groups for both staphylococcal strains: a contaminated group that did not receive any antibiotic prophylaxis; a contaminated group that received preoperative intraperitoneal (IP) prophylaxis with vancomycin; and a contaminated group that received preoperative IP prophylaxis with linezolid. All rats received a vascular Dacron graft placed inside a subcutaneous pocket created on the right side of the median line. Sterile saline solution (1 mL), to which MRSA or MRSE at a concentration of 2 × 10(7) colony-forming units per milliliter had been added, was inoculated onto the graft surface using a tuberculin syringe to fill the pocket. The grafts were explanted 7 days after implantation and assessed by quantitative culture.

RESULTS

Seventy rats (mean [SD]weight, 323.7 [17.9]g; mean [SD]age, 5.98 [0.64] months) were evenly divided between the 7 groups. Statistical analysis of the quantitative graft culture suggested that both vancomycin and linezolid were effective in significantly inhibiting bacterial growth when compared with the untreated contaminated groups (all, P < 0.001). However, a statistically significant difference was not observed between the bacteria count in the vancomycin and linezolid prophylaxis groups. When a comparison was made between the bacterial growth in the contaminated control groups, MRSA had significantly greater affinity to the Dacron prostheses than MRSE (all, P < 0.001).

CONCLUSION

Our study found that linezolid was as effective as vancomycin in suppressing colony counts in MRSA- or MRSE-infected vascular Dacron grafts in rats.

Lymphocutaneous nocardiosis caused by Nocardia otitidiscaviarum: A case report and review of literature

Nocardia otitidiscaviarum is a rare clinical isolate of primary cutaneous infections. This report describes a case of lymphocutaneous nocardiosis caused by N. otitidiscaviarum. Analysis of 16S ribosomal RNA gene of the isolate and the type strain of N. otitidiscaviarum DSM 43242 showed 100% similarity. The partial gene sequence of 1439 bp was submitted to GenBank. (EU031786). The isolate was susceptible only to amikacin, minocycline, linezolid and resistant to remaining other routine anti-nocardial drugs. The patient was free of nocardiosis after 12 weeks of treatment with amikacin and linezolid. We reviewed four other cases of lymphocutaneous nocardiosis caused by N. otitidiscaviarum.

Risk factors for thrombocytopenia in adult chinese patients receiving linezolid therapy

BACKGROUND

Linezolid (LZD), an oxazolidinone antibiotic agent, has excellent activity and bioavailability against most methicillin-sensitive and methicillin-resistant gram-positive bacteria. Although LZD is generally well tolerated, several studies have found adverse hematologic effects, of which thrombocytopenia is of most concern.

OBJECTIVE

To investigate the risk factors for thrombocytopenia in patients who received oral or parenteral LZD therapy between February 1 and November 30, 2010.

METHODS

Data were extracted retrospectively from the electronic medical records in our hospital information system. Thrombocytopenia was defined as either a final platelet count of <100 × 10(9)/L (criterion 1) or a 25% reduction from the baseline platelet count (criterion 2). Risk factors were determined using logistic regression analysis, and clinical features were predicted using receiver operating characteristic curves.

RESULTS

The study included 254 patients, with mean (SD) age of 59 (17.66) years. The duration of LZD therapy was 9.43 (5.63) days. Thrombocytopenia developed in 69 patients (27.2%), as defined by criterion 1, and in 127 patients (50%), as defined by criterion 2. At univariate analysis, age, weight, creatinine clearance, serum albumin concentration, baseline platelet count, daily dosage, and concomitant use of caspofungin, levofloxacin, and meropenem were significant risk factors for thrombocytopenia. At multivariate analysis and using ROC curves, daily dose ≥18.75 mg/kg, baseline platelet count ≤181 × 10(9)/L, duration of LZD therapy ≥10 days, and concomitant use of caspofungin and levofloxacin were independent risk factors for thrombocytopenia as defined by criterion 1, whereas creatinine clearance ≤88.39 mL/min/1.73 m(2), serum albumin concentration ≤33.5 g/L, daily dose ≥18.46 mg/kg, and caspofungin were independent risk factors for thrombocytopenia as defined by criterion 2.

CONCLUSIONS

The incidence of LZD-related thrombocytopenia in the Chinese population is much higher than that suggested by the drug instructions. Low pretreatment platelet count, low body weight, low serum albumin concentration, long-term drug administration, advanced age, renal insufficiency, and concomitant use of caspofungin, levofloxacin, and meropenem have been identified as risk factors. Although predictors have been proposed for use in clinical practice to screen for patients at high risk who require intensified monitoring, further research on the dosage-based pharmacokinetics and pharmacodynamics of LZD are urgently needed.

Pasteurella multocida infected total knee arthroplasty: a case report and review of the literature

Pasteurella multocida is a rare cause of prosthetic joint infection. This infection generally follows significant animal contact, usually licks and scratches. We report a case of P multocida infection that was treated with linezolid with salvage of the implant. Linezolid is generally active against Gram-positive organisms only with the exception of Pasteurella, which is Gram-negative. We extensively review the previous reported cases of implant infection with P multocida.

A cfr-positive clinical staphylococcal isolate from India with multiple mechanisms of linezolid-resistance

BACKGROUND & OBJECTIVES

Linezolid, a member of the oxazolidinone class of antibiotics, has been an effective therapeutic option to treat severe infections caused by multidrug resistant Gram positive bacteria. Emergence of linezolid resistant clinical strains is a serious issue in the healthcare settings worldwide. We report here the molecular characterization of a linezolid resistant clinical isolate of Staphylococcus haemolyticus from India.

METHODS

The species of the clinical isolate was identified by 16S rRNA gene sequencing. The minimum inhibitory concentrations (MICs) of linezolid, clindamycin, chloramphenicol and oxacillin were determined by E-test method. To elucidate the mechanism of linezolid-resistance, presence of cfr gene (chloramphenicol florfenicol resistance) and mutations in 23S rRNA and ribosomal proteins (L3, L4 and L22) were investigated. Staphylococcal Cassette Chromosome mec (SCCmec) typing was performed by multiplex PCR.

RESULTS

The study documented a rare clinical S. haemolyticus strain with three independent mechanisms of linezolid-resistance. The strain carried cfr gene, the only known transmissible mechanism of linezolid-resistance. The strain also possessed resistance-conferring mutations such as G 2576 T in domain V of 23S rRNA gene and Met 156 Thr in L3 ribosomal protein. The other ribosomal proteins (L4 and L22) did not exhibit mutations accountable for linezolid-resistance. Restriction digestion by NheI revealed that all the alleles of 23S rRNA gene were mutated. The isolate showed elevated MIC values (>256 μg ml -[1] of linezolid, clindamycin, chloramphenicol and oxacillin. Methicillin resistance was conferred by type I SCCmec element. The strain also harboured lsa(B) gene which encodes an ABC transporter that can efflux clindamycin.

INTERPRETATION & CONCLUSIONS

The present study reports the first clinical strain from India with transmissible and multiple mechanisms of linezolid-resistance. Judicious use of linezolid in clinical practice and proper surveillance of cfr-positive strains are of utmost importance to safeguard the efficacy of linezolid.

Comparative effectiveness of linezolid and vancomycin among a national veterans affairs cohort with methicillin-resistant Staphylococcus aureus pneumonia

STUDY OBJECTIVE

As variability in vancomycin dosing, susceptibility, and tolerability has driven the need to compare newer agents with vancomycin in real-world clinical settings, we sought to quantify the effectiveness of linezolid compared with vancomycin on clinical outcomes for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) pneumonia.

DESIGN

Retrospective cohort study.

DATA SOURCE

Veterans Health Administration national databases.

PATIENTS

Adults admitted to Veterans Affairs hospitals between January 2002 and September 2010 with diagnosis codes for MRSA and pneumonia, plus initiation and receipt of at least 3 days of continuous intravenous vancomycin therapy (4943 patients) or intravenous or oral linezolid therapy (328 patients) while in the hospital.

MEASUREMENTS AND MAIN RESULTS

Propensity score-adjusted Cox proportional hazards regression models quantified the effect of linezolid compared with vancomycin on time to 30-day mortality (primary outcome), therapy change, hospital discharge, discharge from intensive care, intubation, 30-day readmission, and 30-day MRSA reinfection. In addition, a composite outcome of clinical success was defined as discharge from the hospital or intensive care unit by day 14 after treatment initiation, in the absence of death, therapy change, or intubation by day 14. Subgroup analyses were performed in a validated microbiology-confirmed MRSA subgroup and clinical subgroup meeting clinical criteria for infection. Although a number of baseline variables differed significantly between the vancomycin and linezolid treatment groups, balance was achieved within propensity score quintiles. A significantly lower rate of therapy change was observed in the linezolid group (adjusted hazard ratio [HR] 0.68, 95% confidence interval [CI] 0.48-0.96). The clinical success rate was significantly higher among patients treated with linezolid (adjusted HR 1.25, 95% CI 1.07-1.47). Comparable findings were observed in the subgroup analyses.

CONCLUSION

Individual clinical outcomes were similar among patients treated for MRSA pneumonia with linezolid compared with vancomycin. A significantly higher rate of the composite outcome of clinical success was observed, however, among patients treated with linezolid compared with vancomycin.

Comparative cost-effectiveness of alternative empiric antimicrobial treatment options for suspected enterococcal bacteremia

OBJECTIVES

Enterococcus species are the fourth leading cause of bacteremia. Resistance rates are rising and delays in appropriate initial antimicrobial therapy have been associated with increased mortality. Empiric treatment of patients with suspected enterococcal bacteremia varies and significant cost differences exist between alternatives. The objective of this study was to determine the cost-effectiveness of various empiric treatments for patients with suspected enterococcal bacteremia.

METHODS

A decision-analytic model was constructed from the hospital perspective to assess the cost-effectiveness of alternative empiric treatment options for enterococcal bacteremia, including antimicrobials active against vancomycin-resistant enterococcus (VRE). The model was populated from available literature sources and included resistance patterns, associated mortality with early versus delayed effective treatment, and the cost of treatment. Univariate sensitivity analyses tested the robustness of the model to determine the degree to which model uncertainties influenced outcomes. We also undertook a probabilistic sensitivity analysis varying parameters in 10,000 Monte Carlo simulations.

MAIN RESULTS

The incremental cost-effectiveness ratio was $791 and $749/quality-adjusted-life-year utilizing empiric daptomycin and linezolid, respectively. The model also predicted an incremental cost/life saved of $11,703 by utilizing empiric daptomycin and $11,084 with linezolid utilization. Ampicillin was dominated (i.e., less effective and associated with increased costs) by both VRE-active agents and vancomycin. A probabilistic Monte Carlo sensitivity analysis showed that an agent with VRE activity had a 100% chance of being cost-effective at traditionally used willingness-to-pay thresholds. The decision-analytic model was sensitive to variations in E. faecium mortality and short-term postdischarge survival rates.

CONCLUSION

Results of our model showed that empiric utilization of an antimicrobial with activity against VRE may be a cost-effective option for the treatment of suspected enterococcal bacteremia when compared with vancomycin or β-lactam therapy.

Effects of vitamin b6 therapy for sepsis patients with linezolid-associated cytopenias: a retrospective study

Background

The common adverse effects of linezolid for treating septic patients with gram-positive cocci is anemia and thrombocytopenia, which limit its clinical application.

Objectives

We determined the effects of vitamin B6 adjunctive therapy on linezolid-associated cytopenias, and retrospectively studied 75 septic patients who received at least 7 days of linezolid treatment.

Methods

Patients were divided into a linezolid treatment group (LTG; n = 41) that received linezolid only and a combination treatment group (CTG; n = 34) that received both linezolid and vitamin B6. Each group was further subdivided into those with sepsis and those with severe sepsis. Each patient had red blood cell (RBC), hemoglobin (Hb), hematocrit (Hct), and platelet (PLT) measurements at baseline (day 0) and every other day for 2 weeks during treatment; these parameters were compared between the groups and assessed for time-dependent trends.

Results

For patients in the LTG, RBC, Hb, and Hct values showed statistically significant reductions over time, and these values were lower compared with the values in the CTG. The CTG also showed downward trends, except on the first day of treatment. The PLT count also decreased in both groups. Patients with severe sepsis had lower PLT counts in both treatment groups compared with the septic patients.

Conclusions

Septic patients who received a combination treatment of linezolid and vitamin B6 might show positive effects for linezolid-associated reductions in some hematologic parameters (RBC, Hb, and Hct). This combined treatment might also slow PLT reduction, which was more evident in patients with severe sepsis. ClinicalTrials.gov identifier: NCT01295801.

Comparative evaluation of thrombocytopenia in adult patients receiving linezolid or glycopeptides in a respiratory intensive care unit

Linezolid is an oxazolidinone antibiotic agent, active against gram-positive bacteria that are resistant to traditional antibiotics, including glycopeptides. Linezolid is generally well tolerated, but has been associated with hematologic adverse effects such as thrombocytopenia. The primary objective of this study was to compare the incidence of thrombocytopenia between patients receiving linezolid or glycopeptides in different age groups. The secondary objective was to assess the association between the time-to-event and occurrence of thrombocytopenia. This retrospective study reviewed the medical records of patients who were treated with linezolid or glycopeptides (vancomycin or teicoplanin) between January 2010 and June 2013 in a respiratory intensive care unit. Data were extracted from the patients' electronic medical records, which were obtained from a central database in the hospital, and multivariate analyses were performed. In total, the study included 225 patients who received linezolid or glycopeptides. The cumulative probability of thrombocytopenia was higher in the patients receiving linezolid than in those receiving glycopeptides (P<0.05), however the cumulative probability of thrombocytopenia did not differ significantly between patients receiving linezolid or glycopeptides in the subgroup whose age was <65 years (P>0.05). With a treatment duration of ≥7 days, the incidence of thrombocytopenia and the mean platelet count reduction in the patients receiving linezolid was significantly higher than in those receiving glycopeptides (P<0.05). No significant difference was identified in the mean platelet counts between the patients receiving linezolid and those receiving glycopeptides. In conclusion, it was identified that patients in a respiratory intensive care unit, aged ≥65 years or with a treatment duration of ≥7 days who were treated with linezolid were more likely to develop thrombocytopenia than patients of the same subgroup who were treated with glycopeptides.

Population pharmacokinetic analysis of linezolid in low body weight patients with renal dysfunction

Linezolid has antibacterial activity against aerobic Gram-positive cocci, including methicillin-resistant Staphylococcus aureus (MRSA). Adjustment of the dose of linezolid has been proposed to be unnecessary in patients with reduced renal function. However, platelet counts and hemoglobin levels were shown to be significantly lower in such patients than in patients with normal renal function. The population pharmacokinetic (PPK) of linezolid was investigated in MRSA infected patients with renal dysfunction. Linezolid concentrations in serum were measured by high-performance liquid chromatography. PPK analysis was performed in the nonlinear mixed effects model (NONMEM) computer program. In the final PPK model, total body weight (TBW), estimated glomerular filtration rate (eGFR), hemoglobin (HB), and alanine amino transferase (ALT) were influential covariates on total body clearance (CL), and the volume of distribution (Vd) was affected by TBW, which was expressed as CL (L/h) = 0.00327 × TBW × eGFR(0.428) × HB(0.502) × 0.283 (ALT ≥ 100 IU/L) and CL (L/h) = 0.00327 × TBW × eGFR(0.428) × HB(0.502) (ALT < 100 IU/L), Vd (L) = 1.310 × TBW. The PPK parameters of linezolid obtained here are useful for the optimal use of linezolid with similar patient population characteristics.

Linezolid-induced near-fatal serotonin syndrome during escitalopram therapy: case report and review of literature

Linezolid is a synthetic antimicrobial agent of the oxazolidinone class with weak, nonspecific inhibitor of monoamine oxidase enzymes. Concomitant therapy with an adrenergic or serotonergic agent or consuming tyramine (>100 mg/day) may induce serotonin syndrome (SS). We present a case report of near-fatal adverse interaction between linezolid and escitalopram inducing SS in a 65-year-old woman with sepsis, under empirical antibiotic treatment. This report also summarizes the current relevant literature as identified via PubMed, EMBASE, and PsycINFO, supplemented with a manual search of cross references.

Phenotypic & genotypic characterization of vancomycin resistant Enterococcus isolates from clinical specimens

BACKGROUND & OBJECTIVES

Enterococci have emerged as important nosocomial pathogens and emergence of resistance to many of the antimicrobials used for Gram-positive organisms has made the management of infections due to Enterococcus species difficult. Resistance to glycopeptide antibiotics, especially vancomycin is of special concern. This study was undertaken to perform a phenotypic and genotypic characterization of vancomycin resistant Enterococcus (VRE) isolates obtained from clinical samples in a tertiary care hospital in southern India.

METHODS

Susceptibility testing was performed for Enterococcus isolates collected over a period of one year (November 2008-October 2009). Minimum inhibitory concentrations (MIC) of vancomycin and teicoplanin were determined for the isolates by the agar dilution method. Genotypic characterization of VRE isolates was done by performing multiplex polymerase chain reaction (PCR) for detecting the various vancomycin resistance genes.

RESULTS

Of the 367 isolates of Enterococcus species isolated, 32 were found to be resistant to vancomycin after MIC testing. VanA was the commonest phenotype of vancomycin resistance and the commonest genotype was vanA. Among the other important findings of the study was the presence of heterogeneity in isolates of VRE with the vanA gene cluster with regards to resistance to teicoplanin and the coexistence of vanA and vanC1 gene clusters in an isolate of E. gallinarum which conferred high level glycopeptide resistance to the isolate.

INTERPRETATION & CONCLUSIONS

Enterococcus species have emerged as important nosocomial pathogens in our patients with a capacity to cause a variety of infections. The vancomycin resistance among Enterococcus isolates was 8.7 per cent in our study which was high compared to other Indian studies. VanA was the commonest phenotype of glycopeptide resistance and vanA was the commonest vancomycin resistance gene. The study also demonstrates phenotypic as well as genotypic heterogeneity among isolates of VRE from clinical specimens.