Which trial do we need? Combination antimicrobial therapy for hospital-acquired bacterial pneumonia caused by Pseudomonas aeruginosa

Meropenem therapy will be open-label, while tobramycin or placebo will be administered in a double-blind fashion. The primary trial endpoint will be a composite hierarchical outcome of 1) 28-day all-cause mortality, 2) ventilator-free days, and 3) modified time to clinical stability, evaluated using a win ratio methodology (see below). Secondary trial outcomes will include frequency of safety events (acute kidney injury), resolution of circulatory shock, recurrent HABP, and emergence of meropenem resistance both during treatment and in cases of recurrent infection. Using simulation studies to inform sample size calculations, we estimate that recruitment of 130 patients per treatment arm would provide at least 80% power to detect a win ratio of 1.50 while preserving a two-sided type 1 error rate of 0.05.

Management of pneumonia in the critically ill

Pneumonias continue to be major public health issues and are commonly encountered in the intensive care setting. The most common types of pneumonia leading to critical illness include severe community acquired pneumonia, hospital acquired pneumonia, and ventilator associated pneumonia. Early evaluation, diagnosis, and escalation to appropriate levels of care are imperative to improving survival. Treatment remains challenging with the need to balance antibiotic stewardship and minimizing patient harm. As evidenced in the most recent society guidelines, the identification of risk factors for severe disease and the causative pathogens are crucial in guiding the most appropriate therapy.

Risk Factors and Algorithms for the Empirical Treatment of Hospital-Acquired Pneumonia and Ventilator-Associated Pneumonia

Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) continue to be major concerns for morbidity and mortality, especially in patients treated in the intensive care unit. With the rise in multidrug-resistant organisms, HAP and VAP treatment is challenged by the need for early appropriate treatment, with broad-spectrum agents, while still being aware of the principles of antibiotic stewardship. The two major society guidelines proposed a series of risk factors in their most recent guidelines to help identify patients who can most benefit from narrow- or broad-spectrum initial empiric antibiotic therapy. The guidelines reveal differences in the proposed risk factors and treatment approaches, as well as major similarities.

Comparative Efficacy and Safety of Vancomycin, Linezolid, Tedizolid, and Daptomycin in Treating Patients with Suspected or Proven Complicated Skin and Soft Tissue Infections: An Updated Network Meta-Analysis

Introduction

Skin and soft structure infections (SSTIs) caused by methicillin-resistant Staphylococcus aureus (MRSA) pose serious health risks and cause significant cost burdens, and a conclusive recommendation about antibiotics has not yet been generated. Therefore, we performed this updated network meta-analysis to determine the preferred drug for the treatment of MRSA-caused SSTIs.

Methods

We searched PubMed, Embase, and Cochrane Library to identify any potentially eligible randomized controlled trials (RCTs) investigating the comparative efficacy and safety of any two of vancomycin, linezolid, tedizolid, and daptomycin in MRSA-caused SSTIs. All statistical analyses were conducted with RevMan, ADDIS, and STATA software.

Results

Twenty eligible RCTs involving 7804 patients were included for the final analysis. Direct meta-analysis suggested that linezolid was superior to vancomycin in improving clinical (odds ratio [OR], 1.46; 95% confidence interval [CI], 1.07–1.99; P = 0.02) and microbiological (OR, 1.89; 95% CI, 1.24–2.86; P = 0.003) success, which were all confirmed by network meta-analyses. No statistical differences were identified regarding other comparisons. Meanwhile, there were no significant differences between any two antibiotics related to safety. Moreover, ranking probabilities indicated that linezolid had the highest probability of being ranked best in terms of clinical and microbiological success.

Conclusion

Based on the limited evidence, linezolid may be a preferred antibiotic for the treatment of MRSA-caused SSTIs because it showed superiority in clinical and microbiological success without difference regarding safety.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-021-00456-0.

Meta-analysis of vancomycin versus linezolid in pneumonia with proven methicillin-resistant Staphylococcus aureus

OBJECTIVE

American Thoracic Society/Infectious Diseases Society of America (ATS/IDSA) guidelines suggest that linezolid (LZD) is preferred over vancomycin (VCM) for treating methicillin-resistant Staphylococcus aureus (MRSA) pneumonia. We conducted a systematic review and comparative meta-analysis to compare VCM and LZD efficacy against proven MRSA pneumonia.

METHODS

We searched EMBASE, CINAHL, Cochrane Central Register of Controlled Trials (CENTRAL), and PubMed up to November 2019. The outcomes of the meta-analysis were mortality, clinical cure, microbiological evaluation, and adverse events.

RESULTS

Seven randomized controlled trials (RCTs) with a total of 1239 patients and eight retrospective cohort or case-control studies (CSs) with a total 6125 patients were identified. Clinical cure and microbiological eradication rates were significantly increased in patients treated with LZD in RCTs (clinical cure: risk ratio (RR) = 0.81, 95% confidential interval (CI) = 0.71-0.92; microbiological eradication: RR = 0.71, 95% CI = 0.62-0.81) and CSs (clinical cure: odds ratio (OR) = 0.35, 95% CI = 0.18-0.69). However, mortality was comparable between patients treated with VCM and LZD in RCTs (RR = 1.08, 95% CI = 0.88-1.32) and CSs (OR = 1.20, 95% CI = 0.94-1.53). Likewise, there was no significant difference in adverse events between VCM and LZD in CSs (thrombocytopenia: OR = 0.95, 95% CI = 0.50-1.82; nephrotoxicity: OR = 1.72, 95% CI = 0.85-3.45).

CONCLUSIONS

According to our meta-analysis of RCTs and CSs conducted worldwide, we found robust evidence to corroborate the IDSA guidelines for the treatment of proven MRSA pneumonia.

Efficacy of Telavancin in Comparison to Linezolid in a Porcine Model of Severe Methicillin-Resistant Staphylococcus aureus Pneumonia

Current guidelines recommend vancomycin and linezolid as first-line agents against methicillin-resistant Staphylococcus aureus (MRSA) nosocomial pneumonia. Telavancin is a potential new therapeutic alternative, specifically in monomicrobial MRSA pneumonia. This study compared the efficacies of telavancin versus linezolid in a porcine model of severe MRSA pneumonia. In 18 mechanically ventilated pigs (32.11 ± 1.18 kg), 75 ml of 10⁶ CFU/ml of MRSA was administered into each pulmonary lobe. After the onset of pneumonia, pigs were randomized into three groups: a control group, a group receiving 22.5 mg/kg of body weight every 24 h (q24h) of telavancin, and a group receiving 10 mg/kg q12h of linezolid intravenously. Tracheal aspirate and bronchoalveolar lavage (BAL) fluids were cultured every 24 h. After 48 h of treatment, tissue samples were collected from the ventral and dorsal sections of each lobe. Microbiological and histopathological analyses were performed. Lung tissue concentrations differed among the groups (P = 0.019), with the lowest MRSA lung burden in the telavancin group (P < 0.05 versus the control). MRSA was detected in 46.7%, 40.0%, and 21.7% of the lung tissue samples from the control, linezolid, and telavancin groups, respectively (P < 0.001). MRSA concentrations differed among the groups in tracheal aspirate fluid (P = 0.011) but not in BAL fluid. Furthermore, there was no increased risk of kidney injury during telavancin use. Thus, telavancin has higher bactericidal efficacy than linezolid during the first 48 h of treatment in a porcine model of severe MRSA pneumonia. However, studies are needed to confirm the benefits of telavancin in treating MRSA nosocomial pneumonia.

Contrasting effects of linezolid on healthy and dysfunctional human neutrophils: reducing C5a-induced injury

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of ventilator-associated pneumonia (VAP). Patients with VAP have poorly functioning neutrophils, related to increased levels of the complement fragment C5a. The antibiotic linezolid has been useful in controlling MRSA-related VAP infections; however clinical benefit does not always correlate with antimicrobial effect, suggesting the possibility of immunomodulatory properties. Here the effects of linezolid on healthy and dysfunctional neutrophils (modelled by C5a-induced injury) was investigated. Functional assays (killing, phagocytosis, transmigration, and respiratory burst) were used to assess the effects of pre-, co- and post-incubating linezolid (0.4-40 mg/L) with healthy neutrophils relative to those with C5a-induced injury. C5a decreased neutrophil killing, and phagocytosis of MRSA. Furthermore, C5a significantly decreased neutrophil transmigration to IL-8, but did not affect respiratory burst. Co-incubation of linezolid significantly improved killing of MRSA by dysfunctional neutrophils, which was supported by concomitant increases in phagocytosis. Conversely linezolid impaired killing responses in healthy neutrophils. Pre- or post-incubation of linezolid prior or following C5a induced injury had no effect on neutrophil function. This study suggests that linezolid has immunomodulatory properties that protect human neutrophils from injury and provides insight into its mode of action beyond a basic antibiotic.

Calculated parenteral initial treatment of bacterial infections: Respiratory infections

This is the fifth chapter of the guideline "Calculated initial parenteral treatment of bacterial infections in adults - update 2018" in the 2nd updated version. The German guideline by the Paul-Ehrlich-Gesellschaft für Chemotherapie e.V. (PEG) has been translated to address an international audience. It provides recommendations for the empirical and targeted antimicrobial treatment of lower respiratory tract infections, with a special emphasis on the treatment of acute exacerbation of COPD, community-acquired pneumonia and hospital-acquired pneumonia.

Linezolid: a promising option in the treatment of Gram-positives

Linezolid, an oxazolidinone antimicrobial agent that acts by inhibiting protein synthesis in a unique fashion, is used in the treatment of community-acquired pneumonia, skin and soft-tissue infections and other infections caused by Gram-positive bacteria including VRE and methicillin-resistant staphylococci. Currently, linezolid resistance among these pathogens remains low, commonly <1.0%, although the prevalence of antibiotic resistance is increasing in many countries. Therefore, the development of resistance by clinical isolates should prompt increased attention of clinical laboratories to routinely perform linezolid susceptibility testing for this important agent and should be taken into account when considering its therapeutic use. Considering the importance of linezolid in the treatment of infections caused by Gram-positive bacteria, this review was undertaken to optimize the clinical use of this antibiotic.

Management of Adults With Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society

It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.These guidelines are intended for use by healthcare professionals who care for patients at risk for hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP), including specialists in infectious diseases, pulmonary diseases, critical care, and surgeons, anesthesiologists, hospitalists, and any clinicians and healthcare providers caring for hospitalized patients with nosocomial pneumonia. The panel's recommendations for the diagnosis and treatment of HAP and VAP are based upon evidence derived from topic-specific systematic literature reviews.

Methicillin-resistant Staphylococcus aureus nosocomial pneumonia: role of linezolid in the People's Republic of China

The burden of methicillin-resistant Staphylococcus aureus (MRSA) nosocomial pneumonia in the People’s Republic of China is high, with methicillin-resistance rates greater than 80% reported for patients with S. aureus pneumonia treated in intensive care units. Historically, vancomycin was the treatment of choice for patients with hospital-acquired MRSA infections. Recent evidence suggests that the minimum inhibitory concentration for vancomycin is increasing. Additionally, patients treated with vancomycin require monitoring of vancomycin trough concentrations and can develop nephrotoxicity. Linezolid is a treatment option for patients with hospital-acquired MRSA infections that can be administered either intravenously or orally. Analysis of data from a worldwide linezolid surveillance program initiated in the year 2004 shows no evidence of increasing linezolid minimum inhibitory concentrations. The clinical efficacy of linezolid for patients with gram-positive, including MRSA, nosocomial pneumonia, was evaluated in numerous studies. In general, results from these studies show higher or similar clinical success with no mortality difference for linezolid compared to vancomycin treated patients. Results from a Phase IV study enrolling patients with MRSA-confirmed nosocomial pneumonia suggest higher clinical cure rates for linezolid compared to vancomycin treated patients. Although acquisition costs are higher for linezolid compared to vancomycin therapy, evidence suggests similar overall medical costs. Cost-analysis results from a Chinese perspective show that linezolid dominated vancomycin therapy for MRSA nosocomial pneumonia in ∼35% of bootstrap simulations whereas vancomycin dominated linezolid in less than 2% of bootstrap simulations. In summary, results from both clinical and economic studies, including studies conducted from a Chinese perspective, support the use of linezolid for the treatment of patients with MRSA nosocomial pneumonia.

MRSA in Croatia: prevalence and management

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are associated with increased morbidity, mortality and length of hospital stay. MRSA is a major pathogen in hospitals and an important pathogen in community infections with few severe and fatal cases. However, MRSA causes the majority of skin and soft tissue infections in the US. The burden of community MRSA is much smaller in Europe, but there are reports of livestock-associated MRSA (LA-MRSA) isolated from pigs and cattle causing significant infections in the people who are connected to these farms. MRSA has been present in Croatia for more than 45 years, and it exerts a different impact on health-care infections. A remarkable increase in MRSA percentage was noted in primarily sterile samples in 2002 (37%) in comparison to 2001 (31%). This percentage remained quite high until 2008, when the first signs of a reduced trend were observed. The lowest percentage was 22% in 2012.

What is the best therapeutic approach to methicillin-resistant Staphylococcus aureus pneumonia?

PURPOSE OF REVIEW

The purpose of this review is to define what the best therapeutic approach is for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) pneumonia.

RECENT FINDINGS

Although two meta-analyses reported conflicting findings, recent retrospective studies reported higher success rates in patients with MRSA pneumonia treated with linezolid when compared to vancomycin. Only registration trials are available for some anti-MRSA antibiotics, such as telavancin, ceftaroline, and ceftobiprole. Scarce information is available regarding the best therapeutic approach for MRSA community-acquired pneumonia.

SUMMARY

Linezolid seems to be a better choice than vancomycin for the treatment of MRSA ventilator-associated pneumonia. It is still unclear whether this affirmation holds for other forms of MRSA pneumonia. Further research is needed to define whether newer antibiotics are better alternatives than currently recommended agents.

Comparative-effectiveness of vancomycin and linezolid as part of guideline-recommended empiric therapy for healthcare-associated pneumonia

BACKGROUND

Linezolid has been directly compared to vancomycin in pneumonia; however, most clinical trials have not compared outcomes specifically in the healthcare-associated pneumonia (HCAP) population. The objective of this study was to compare the effectiveness of vancomycin and linezolid in a national cohort of hospitalized veterans with HCAP.

METHODS

This was a retrospective cohort study of Veterans Health Administration patients admitted to >150 hospitals across the United States between 2002 and 2007. Patients were included if they were at least 65 years old, had an ICD-9-CM code for pneumonia, had one or more HCAP risk factors, and received guideline-concordant antibiotic therapy with linezolid or vancomycin within 48 h of admission. Critically ill patients were excluded. Multivariable logistic regression models and propensity scores were used to examine the association between linezolid or vancomycin therapy and 30-day mortality.

RESULTS

A total of 1211 patients met study criteria; 946 received vancomycin and 265 received linezolid. Thirty-day mortality was higher in patients treated with vancomycin (n = 243; 25.7 %) as compared to linezolid (n = 33; 12.5 %) (adjusted OR 2.56; 95 % CI 1.67-4.04). Vancomycin use (n = 945) was also predictive of 30-day mortality compared to linezolid use (n = 264) in the propensity score analysis (adjusted OR 2.55; 95 % CI 1.66-4.02).

CONCLUSION

Linezolid was associated with decreased patient mortality compared to vancomycin in a national cohort of non-critically ill, hospitalized veterans with HCAP.

A 2015 Update on Ventilator-Associated Pneumonia: New Insights on Its Prevention, Diagnosis, and Treatment

Ventilator-associated pneumonia (VAP), an infection of the lower respiratory tract which occurs in association with mechanical ventilation, is one of the most common causes of nosocomial infection in the intensive care unit (ICU). VAP causes significant morbidity and mortality in critically ill patients including increased duration of mechanical ventilation, ICU stay and hospitalization. Current knowledge for its prevention, diagnosis and management is therefore important clinically and is the basis for this review. We discuss recent changes in VAP surveillance nomenclature incorporating ventilator-associated conditions and ventilator-associated events, terms recently proposed by the Centers for Disease Control. To the extent possible, we rely predominantly on data from randomized control trials (RCTs) and meta-analyses.

Participation of elderly adults in randomized controlled trials addressing antibiotic treatment of pneumonia

OBJECTIVES

To examine how relevant current evidence on antibiotic treatment of pneumonia is for elderly adults.

DESIGN

Systematic review.

SETTING

Randomized controlled trials (RCTs; N = 43) comparing different antibiotics and prospective observational studies (N = 182) published since 2005.

PARTICIPANTS

Adults with community-acquired (CAP), healthcare-associated (HCAP), hospital-acquired (HAP), or ventilator-associated (VAP) pneumonia.

MEASUREMENTS

Exclusion criteria that could preferentially limit participation of elderly adults were examined, subgroup or other adjusted analyses were searched for according to age, and treatment effects in participants younger than 65 in RCTs were compared with those in participants aged 65 and older. Mean participant ages in RCTs and observational studies were compared. Risk ratios (RRs) with 95% confidence intervals (CIs) for differences between older and younger adults were pooled using a fixed effect metaanalysis.

RESULTS

No RCT reported exclusion based on an upper age limit; 100% of community CAP trials, 90% of hospitalized CAP trials, and 76% of HAP and VAP trials excluded individuals based on comorbidities. None of the RCTs reported a subgroup analysis for mortality according to age. The RR for the pooled difference in treatment failure rates between participants younger than 65 and those aged 65 and older was 1.25 (95% CI = 0.94-1.65, 12 RCTs) and between participants younger than 75 and aged 75 and older was 1.43 (95% CI = 0.98-2.09, 7 RCTs). RCT participants were significantly younger (54.0 ± 9.6) than those in observational studies of CAP (66.2 ± 8.1, P < .001). Age differences were not significant for HCAP, HAP, and VAP.

CONCLUSION

Elderly adults are often excluded from RCTs of bacterial pneumonia. No data were found on the comparative efficacy of antibiotic treatment in elderly adults and the general population.

α-Hemolysin activity of methicillin-susceptible Staphylococcus aureus predicts ventilator-associated pneumonia

RATIONALE

Colonization of lower airways by Staphylococcus aureus is a risk factor for the development of ventilator-associated tracheobronchitis (VAT) and ventilator-associated pneumonia (VAP). However, little is known about the virulence factors of methicillin-sensitive and -resistant S. aureus (MSSA and MRSA) that may influence host colonization and progression to VAT and VAP.

OBJECTIVES

We evaluated MRSA and MSSA endotracheal aspirates (ETA) for genotype and α-hemolysin activity in relation to the development of VAT and VAP.

METHODS

Serial S. aureus ETA isolates from ventilated patients were analyzed for methicillin resistance, molecular type by Multi-Locus Sequence Typing and spa-typing, and α-hemolysin activity by semiquantitative analysis of hemolysis on sheep blood agar and quantitative measurement of cytolysis of human lung epithelial cells. The virulence of selected strains was assessed in mice by intranasal challenge.

MEASUREMENTS AND MAIN RESULTS

We detected S. aureus from ETA samples in a quarter of the 231 ventilated patients analyzed; one-third of them developed VAP. VAP patients (n = 15) were mainly infected by MSSA strains (87%), whereas colonized individuals (n = 18) not progressing to disease mainly carried MRSA strains (68%). MSSA isolates from colonized or VAT patients exhibited significantly lower α-hemolysin activity than those from VAP cases; however, no such relationship was found with MRSA strains. α-Hemolysin activity of S. aureus isolates was predictive for virulence in mouse pneumonia model.

CONCLUSIONS

MSSA strains with strong blood agar hemolysis and high α-hemolysin activity are markers for VAP, but not VAT, and might be considered in differential diagnosis and initiation of therapy.

Linezolid versus vancomycin for the treatment of suspected methicillin-resistant Staphylococcus aureus nosocomial pneumonia: a systematic review employing meta-analysis

PURPOSE

The optimal therapy involving linezolid or vancomycin for suspected methicillin-resistant Staphylococcus aureus (MRSA) nosocomial pneumonia (NP) remains controversial. This study compared the efficacy and safety of linezolid and vancomycin therapies in patients with NP.

METHODS

A systematic review of randomized controlled trials with meta-analyses performed by searching PubMed, EMBASE, MEDLINE, and the Cochrane Central Register of Controlled Trials. We screened for relevant randomized controlled studies in which patients with NP were enrolled and linezolid and vancomycin therapies were compared.

RESULTS

Nine trials involving 2618 pneumonia patients were reviewed. Linezolid was not found to be superior to vancomycin for clinical cure when categories of pathogen were not considered and in a subgroup of NP patients with MRSA infection [relative risk (RR)=1.16, 95 % confidence interval (CI)=0.95-1.43, P=0.15]. Compared with vancomycin, linezolid has no difference in the overall microbiological eradication rate (RR=1.12, 95 % CI=0.96-1.30, P=0.15) and specific MRSA eradication rate (RR=1.16, 95 % CI=0.93-1.45, P=0.19) in NP patients. In addition, nephrotoxicity was more frequent with vancomycin (RR=0.50, 95 % CI=0.31-0.81, P=0.005), but no differences between the treatments were found for all-cause mortality, thrombocytopenia, gastrointestinal effects, and drug discontinuation due to adverse events.

CONCLUSION

These results suggest that linezolid is not superior to vancomycin with respect to both clinical and microbiological cure rates in patients with MRSA NP.

Modeling the economic impact of linezolid versus vancomycin in confirmed nosocomial pneumonia caused by methicillin-resistant Staphylococcus aureus

Introduction

We compared the economic impacts of linezolid and vancomycin for the treatment of hospitalized patients with methicillin-resistant Staphylococcus aureus (MRSA)–confirmed nosocomial pneumonia.

Methods

We used a 4-week decision tree model incorporating published data and expert opinion on clinical parameters, resource use and costs (in 2012 US dollars), such as efficacy, mortality, serious adverse events, treatment duration and length of hospital stay. The results presented are from a US payer perspective. The base case first-line treatment duration for patients with MRSA-confirmed nosocomial pneumonia was 10 days. Clinical treatment success (used for the cost-effectiveness ratio) and failure due to lack of efficacy, serious adverse events or mortality were possible clinical outcomes that could impact costs. Cost of treatment and incremental cost-effectiveness per successfully treated patient were calculated for linezolid versus vancomycin. Univariate (one-way) and probabilistic sensitivity analyses were conducted.

Results

The model allowed us to calculate the total base case inpatient costs as $46,168 (linezolid) and $46,992 (vancomycin). The incremental cost-effectiveness ratio favored linezolid (versus vancomycin), with lower costs ($824 less) and greater efficacy (+2.7% absolute difference in the proportion of patients successfully treated for MRSA nosocomial pneumonia). Approximately 80% of the total treatment costs were attributed to hospital stay (primarily in the intensive care unit). The results of our probabilistic sensitivity analysis indicated that linezolid is the cost-effective alternative under varying willingness to pay thresholds.

Conclusion

These model results show that linezolid has a favorable incremental cost-effectiveness ratio compared to vancomycin for MRSA-confirmed nosocomial pneumonia, largely attributable to the higher clinical trial response rate of patients treated with linezolid. The higher drug acquisition cost of linezolid was offset by lower treatment failure–related costs and fewer days of hospitalization.

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.

Assessment of bias in outcomes reported in trials on pneumonia: a systematic review

Subjective outcomes may exaggerate intervention effects compared to objectively measured outcomes. We compared effect estimates for clinical failure and all-cause mortality clinical trials of antibiotic treatment for pneumonia. A systematic review of randomized controlled trials assessing adults with pneumonia, comparing different antibiotics, published between 2005 and 2012 was undertaken. We compared the intervention to the control arm. The all-cause mortality in the intention-to-treat population and clinical failure as defined by the study investigators for the primary analyzed population were the primary outcomes examined. Risk ratios (RRs) with 95 % confidence intervals (CIs) were pooled, using a fixed effect model. Meta-regression was used to examine the impact of clinical failure on the mortality effect size. Thirty-six trials were included, of which 30 were industry-sponsored and 30 were non-inferiority trials. There was no difference between the effect on mortality for intervention versus control (RR 1.02, 95 % CI 0.91-1.16) and clinical failure (RR 1.01, 95 % CI 0.93-1.10), without significant heterogeneity in both analyses. In double-blind trials with adequate sequence generation and concealment, there was a significant advantage to the intervention for clinical failure (RR 0.86, 95 % CI 0.76-0.98), but not for mortality (RR 0.96, 95 % CI 0.76-1.21). RRs for clinical failure did not explain the variability in the RRs for mortality significantly, with a meta-regression coefficient of 0.32 (95 % CI -0.21-0.85). In non-inferiority trials of antibiotic treatment for pneumonia, we did not find evidence for bias induced by the use of a subjective outcome overall. The small number of trials without sponsorship precludes an adequate assessment of sponsorship effects.

Treatment of hospital-acquired pneumonia with linezolid or vancomycin: a systematic review and meta-analysis

OBJECTIVE

Hospital-acquired pneumonia remains the most lethal and expensive nosocomial infection worldwide. Optimal therapy remains controversial. We aimed to compare mortality and clinical response outcomes in patients treated with either linezolid or vancomycin.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed, EMBASE, Cochrane Library, American College of Physicians Journal Club, Evidence-based Medicine BMJ and abstracts from infectious diseases and critical care meetings were searched through April 2013.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

All randomised clinical trials comparing linezolid to vancomycin for hospital-acquired pneumonia.

DATA EXTRACTION

Preferred reporting items for systematic reviews and meta-analyses guidelines were followed. One author extracted the data and two authors rechecked and verified all data.

RESULTS

Nine randomised trials with a total of 4026 patients were included. The adjusted absolute mortality risk difference (RD) between linezolid and vancomycin was 0.01% (95% CI -2.1% to 2.1%; p=0.992; I(2)=13.5%. The adjusted absolute clinical response difference was 0.9% (95% CI -1.2% to 3.1%; p=0.409; I(2)=0%. The risk of both microbiological (RD=5.6%, 95% CI -2.2% to 13.3%; p=0.159; I(2)=0%) and methicillin-resistant Staphylococcus aureus (RD=6.4%, 95% CI -4.1% to 16.9%; p=0.230; I(2)=0%) eradication were not different between linezolid and vancomycin. Gastrointestinal side effects were more frequent with linezolid (RD=0.8% (95% CI 0% to 1.5%; p=0.05), but no differences were found with renal failure, thrombocytopenia and drug discontinuation due to adverse events. Our sample size provided 99.9% statistical power to detect differences between drugs regarding clinical response and mortality.

CONCLUSIONS

Linezolid and vancomycin have similar efficacy and safety profiles. The high statistical power and the near-zero efficacy difference between both antibiotics demonstrates that no drug is superior for the treatment of hospital-acquired pneumonia.

A cluster of fulminant, fatal necrotizing community-associated methicillin-resistant Staphylococcus aureus pneumonias

Community-associated methicillin-resistant Staphylococcus aureus is a frequent cause of skin and soft-tissue infections and is increasingly identified as a cause of pneumonia in immunocompetent patients. Panton-Valentine leukocidin, one of several leukocytotoxic peptides secreted by these cocci, is associated with increased virulence. A cluster of 3 unrelated patients with fatal pneumonia presumably caused by community-associated methicillin-resistant S aureus positive for Panton-Valentine leukocidin were treated in a 3-week period. Despite aggressive care and appropriate, timely administration of antibiotics, all 3 patients died. This article reviews the clinical and laboratory features suggestive of this lethal isolate, including unique findings on Gram stains of sputum.

Linezolid versus vancomycin or teicoplanin for nosocomial pneumonia: meta-analysis of randomised controlled trials

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of nosocomial pneumonia. Compared with glycopeptide antibiotics, linezolid achieves higher lung epithelial lining fluid concentrations, which may have an advantage in treating nosocomial pneumonia patients. The objective of this study was to evaluate the efficacy and safety of linezolid versus vancomycin or teicoplanin for the treatment of nosocomial pneumonia. Data were obtained from the Cochrane Central Register of Controlled Trials and the EMBASE and MEDLINE databases. Randomised controlled studies involving the use of linezolid versus vancomycin or teicoplanin in nosocomial pneumonia patients were included in the study. Twelve linezolid trials were included. There was no statistically significant difference between the two groups in the treatment of nosocomial pneumonia regarding the clinical cure rate [relative risk (RR) = 1.08, 95 % confidence interval (CI) = 1.00-1.17, p = 0.06]. Linezolid was associated with better microbiological eradication rate in nosocomial pneumonia patients compared with glycopeptide antibiotics (RR = 1.16, 95 % CI = 1.03-1.31, p = 0.01). There were no differences in the all-cause mortality (RR = 0.95, 95 % CI = 0.83-1.09, p = 0.46) between the two groups. However, the risks of rash (RR = 0.41, 95 % CI = 0.24-0.71, p = 0.001) and renal dysfunction (RR = 0.41, 95 % CI = 0.27-0.64, p < 0.0001) were higher with glycopeptide antibiotics. Although linezolid was more effective in eradicating microbiology than glycopeptide antibiotics for nosocomial pneumonia patients, it did not demonstrate superiority in clinical cure. The incidences of renal dysfunction and rash are higher in the glycopeptide antibiotics group.

The efficacy and safety of linezolid and glycopeptides in the treatment of Staphylococcus aureus infections

To assess the effectiveness and safety of linezolid in comparison with glycopeptides (vancomycin and teicoplanin) for the treatment of Staphylococcus aureus infections, we conducted a meta-analysis of relevant randomized controlled trials. A thorough search of Pubmed and other databases was performed. Thirteen trials on 3863 clinically assessed patients were included. Linezolid was slightly more effective than glycopeptides in the intent-to-treat population (odds ratio [OR], 1.05; 95% confidence interval [CI], 1.01–1.10), was more effective in clinically assessed patients (OR 95% CI: 1.38, 1.17–1.64) and in all microbiologically assessed patients (OR 95% CI: 1.38, 1.15–1.65). Linezolid was associated with better treatment in skin and soft-tissue infections (SSTIs) patients (OR 95% CI: 1.61, 1.22–2.12), but not in bacteraemia (OR 95% CI: 1.24, 0.78–1.97) or pneumonia (OR 95% CI: 1.25, 0.97–1.60) patients. No difference of mortality between linezolid and glycopeptides was seen in the pooled trials (OR 95% CI: 0.98, 0.83–1.15). While linezolid was associated with more haematological (OR 95% CI: 2.23, 1.07–4.65) and gastrointestinal events (OR 95% CI: 2.34, 1.53–3.59), a significantly fewer events of skin adverse effects (OR 95% CI: 0.27, 0.16–0.46) and nephrotoxicity (OR 95% CI: 0.45, 0.28–0.72) were recorded in linezolid. Based on the analysis of the pooled data of randomized control trials, linezolid should be a better choice for treatment of patients with S. aureus infections, especially in SSTIs patients than glycopeptides. However, when physicians choose to use linezolid, risk of haematological and gastrointestinal events should be taken into account according to the characteristics of the specific patient populations.

Clinical and economic outcomes of a prospective antimicrobial stewardship program

PURPOSE

A pre-post analysis of an antimicrobial stewardship program (ASP) involving the use of data-mining software to prospectively identify cases for ASP intervention was conducted.

METHODS

The investigators evaluated clinical outcomes and cost metrics before and after implementation of the ASP, which entailed daily physician review of summary reports on all adult inpatients receiving antimicrobial therapy. The primary outcome measures were annual antimicrobial expenditures and rates of infections due to common nosocomial pathogens; secondary outcome measures included patient survival and length of stay (LOS) in cases involving the indicator diagnoses of pneumonia and abdominal sepsis.

RESULTS

Antimicrobial expenditures, which had increased by an average of 14.4% annually in the years preceding ASP implementation, decreased by 9.75% in the first year of the program and remained relatively stable in subsequent years, with overall cumulative cost savings estimated at $1.7 million. Rates of nosocomial infections involving Clostridium difficile, methicillin-resistant Staphylococcus aureus, and vancomycin-resistant enterococci all decreased after ASP implementation. A pre-post comparison of survival and LOS in patients with pneumonia (n = 2186) or abdominal sepsis (n = 225) showed no significant differences in those outcomes in either patient group, possibly due to the hospital's initiation of other, concurrent infection-control programs during the study period.

CONCLUSION

A prospective collaborative ASP employed automated reports to efficiently identify key data for ASP review. After ASP implementation, antimicrobial expenditures and rates of nosocomial infections caused by resistant pathogens dropped without significant changes in patient survival, LOS, and readmissions for the two studied illness categories.

A trial of discontinuation of empiric vancomycin therapy in patients with suspected methicillin-resistant Staphylococcus aureus health care-associated pneumonia

Healthcare-associated pneumonia (HCAP) guidelines recommend de-escalating initial antibiotic therapy based on results from lower-respiratory-tract cultures. In the absence of adequate lower respiratory cultures, physicians are sometimes reluctant to discontinue empirical vancomycin, which is given for suspected methicillin-resistant Staphylococcus aureus (MRSA) HCAP. We evaluated a strategy of discontinuing vancomycin if both nasal and throat cultures were negative for MRSA when lower-respiratory-tract cultures were not available. An antimicrobial stewardship team identified patients receiving empirical vancomycin for suspected or proven HCAP but for whom adequate lower-respiratory-tract cultures were not available. Nasal and throat swab specimens were obtained and plated on MRSA selective media. If both nasal and throat MRSA cultures were negative, the stewardship team recommended discontinuation of empirical vancomycin. Demographic and clinical aspects, a clinical pulmonary infection score (CPIS) on the day of the stewardship recommendation, and mortality of patients for whom vancomycin was discontinued were obtained by retrospective chart review. A convenience sample of 91 patients with nasal and throat cultures negative for MRSA in the absence of adequate respiratory cultures had empirical vancomycin therapy discontinued. A retrospective review revealed that 88 (97%) patients had a CPIS of ≤6 on the day of the stewardship recommendation. In-hospital mortality (7.7%) was similar to that of a previous study of de-escalation of antibiotics in pneumonia patients without adequate cultures. In the absence of adequate lower-respiratory-tract cultures, it is reasonable to discontinue empirical vancomycin HCAP therapy in patients with negative MRSA nasal and throat cultures and a CPIS of <6.

How important is methicillin-resistant Staphylococcus aureus as a cause of community-acquired pneumonia and what is best antimicrobial therapy?

The emergence of methicillin-resistant strains of Staphylococcus aureus has raised issues regarding the importance of methicillin-resistant S aureus (MRSA) in community-acquired pneumonia (CAP) and its optimal treatment. Community-acquired MRSA (CA-MRSA) is an important cause of CAP because of the high mortality if not suspected early, and its occurrence in young patients with long life expectancy. Certain clinical features can increase the probability of CA-MRSA as a cause of CAP. The consistent trend toward better outcomes for documented MRSA pneumonia suggests that linezolid be considered the drug of choice for documented MRSA CAP, especially for CA-MRSA.

An evidence-based review of linezolid for the treatment of methicillin-resistant Staphylococcus aureus (MRSA): place in therapy

Methicillin-resistant Staphylococcus aureus (MRSA), including community-associated and hospital-associated strains, is a major cause of human morbidity and mortality. Treatment options have become limited due to the emergence of MRSA strains with decreased sensitivity to vancomycin, which has long been the first-line therapy for serious infections. This has prompted the search for novel antibiotics that are efficacious against MRSA. Linezolid, an oxazolidinone class of antibiotic, was approved by the Food and Drug Administration in 2000 for treatment of MRSA infections. Since then, there have been a multitude of clinical trials and research studies evaluating the effectiveness of linezolid against serious infections, including pneumonia (both community- and hospital-acquired), skin and soft-tissue infections such as diabetic foot ulcers, endocarditis, osteomyelitis, prosthetic devices, and others. The primary aim of this review is to provide an up-to-date evaluation of the clinical evidence for using linezolid to treat MRSA infections, with a focus on recently published studies, including those on nosocomial pneumonia. Other objectives are to analyze the cost-effectiveness of linezolid compared to other agents, and to review the pharmokinetics and pharmacodynamics of linezolid, emphasizing the most current concepts.

Predicting risk for death from MRSA bacteremia

Methicillin-resistant Staphylococcus aureus (MRSA) bacteremia is often fatal. To determine predictors of risk for death, we conducted a retrospective cohort study. We examined 699 episodes of MRSA bacteremia involving 603 patients admitted to an academic medical center in New York City during 2002-2007. Data came from chart reviews, hospital databases, and recultured frozen MRSA specimens. Among the 699 episodes, 55 were caused by vancomycin-intermediate resistant S. aureus strains, 55 by heteroresistant vancomycin-intermediate S. aureus strains, and 589 by non-vancomycin-resistant strains; 190 (31.5%) patients died. We used regression risk analysis to quantify the association between clinical correlates and death. We found that older age, residence in a nursing home, severe bacteremia, and organ impairment were independently associated with increased risk for death; consultation with an infectious disease specialist was associated with lower risk for death; and MRSA strain types were not associated with risk for death.

Comparative in vivo efficacies of epithelial lining fluid exposures of tedizolid, linezolid, and vancomycin for methicillin-resistant Staphylococcus aureus in a mouse pneumonia model

The antibacterial efficacies of tedizolid phosphate (TZD), linezolid, and vancomycin regimens simulating human exposures at the infection site against methicillin-resistant Staphylococcus aureus (MRSA) were compared in an in vivo mouse pneumonia model. Immunocompetent BALB/c mice were orally inoculated with one of three strains of MRSA and subsequently administered 20 mg/kg TZD every 24 hours (q24h), 120 mg/kg linezolid q12h, or 25 mg/kg vancomycin q12h over 24 h. These regimens produced epithelial lining fluid exposures comparable to human exposures observed following intravenous regimens of 200 mg TZD q24h, 600 mg linezolid q12h, and 1 g vancomycin q12h. The differences in CFU after 24 h of treatment were compared between control and treatment groups. Vehicle-dosed control groups increased in bacterial density an average of 1.1 logs. All treatments reduced the bacterial density at 24 h with an average of 1.2, 1.6, and 0.1 logs for TZD, linezolid, and vancomycin, respectively. The efficacy of TZD versus linezolid regimens against the three MRSA isolates was not statistically different (P > 0.05), although both treatments were significantly different from controls. In contrast, the vancomycin regimen was significantly different from TZD against one MRSA isolate and from linezolid against all isolates. The vancomycin regimen was less protective than either the TZD or linezolid regimens, with overall survival of 61.1% versus 94.7% or 89.5%, respectively. At human simulated exposures to epithelial lining fluid, vancomycin resulted in minimal reductions in bacterial counts and higher mortality compared to those of either TZD or linezolid. TZD and linezolid showed similar efficacies in this MRSA pneumonia model.

New therapy options for MRSA with respiratory infection/pneumonia

PURPOSE OF REVIEW

Methicillin-resistant Staphylococcus aureus (MRSA) is a frequent causative agent of nosocomial pneumonia. Because of important clinical consequences of inappropriate treatment, a current review of the potential modifications undergone by S. aureus and adaptation to new treatment options is necessary.

RECENT FINDINGS

Vancomycin has been considered the treatment of choice for pneumonia due to MRSA. However, detection of a progressive increase in the minimum inhibitory concentration for this antibiotic, its limited access to the lung parenchyma, and its considerable adverse effects have called into question its position. Linezolid has been shown to have a better pharmacokinetic and safety profiles. The prior uncertainty regarding the clinical superiority of linezolid appears to have been resolved with the publication of a recent trial. Linezolid achieved a higher clinical and microbiological response rate (the latter was not statistically significant), together with a lower incidence of all types of renal adverse effects in patients with nosocomial pneumonia, compared with vancomycin. Tigecycline, teicoplanin and quinupristin/dalfopristin were inferior to the compared drug in their respective clinical trials. The clinical efficacy of telavancin was similar to that of vancomycin. The renal adverse effects of telavancin have to be clarified. Other drugs are efficacious against MRSA but their profile should be evaluated in nosocomial pneumonia.

SUMMARY

Current therapeutic alternatives for nosocomial pneumonia due to MRSA appear to be limited to vancomycin and linezolid. However, vancomycin pitfalls, together with the apparent clinical superiority of linezolid, appear to restrict its indication. Telavancin could be a good alternative in patients without basal renal failure.

Meta-analysis of randomized controlled trials of vancomycin for the treatment of patients with gram-positive infections: focus on the study design

OBJECTIVE

To study the effectiveness and safety of vancomycin compared with that of other antibiotics for the treatment of gram-positive infections.

METHODS

Major electronic databases were searched. Data from published randomized controlled trials (January 1, 1950, to September 15, 2011) were pooled using a meta-analytic method.

RESULTS

Fifty-three trials comparing vancomycin with linezolid, daptomycin, quinupristin-dalfopristin, tigecycline, ceftaroline, ceftobiprole, telavancin, teicoplanin, iclaprim, and dalbavancin were included in the meta-analysis. Individual antibiotics were as effective as vancomycin, except for linezolid, which was more effective than vancomycin for the treatment of skin and soft tissue infections (odds ratio [OR], 1.61; 95% confidence interval [CI], 1.07-2.43). Comparators were as effective as vancomycin in the intent-to-treat population (OR, 1.08; 95% CI, 0.98-1.18) but were more effective in the clinically evaluable population (OR, 1.14; 95% CI, 1.02-1.27) when all infections were pooled. When available data from all trials were pooled, no differences were noted when patients with febrile neutropenia (OR, 1.07; 95% CI, 0.82-1.39), pneumonia (OR, 1.10; 95% CI, 0.87-1.37), bacteremia (OR, 1.05; 95% CI, 0.76-1.45), and skin and soft tissue infections (OR, 1.11; 95% CI, 0.89-1.39) were studied. Comparators were more effective in open-label (OR, 1.28; 95% CI, 1.08-1.50) but not in double-blind trials (OR, 1.04; 95% CI, 0.90-1.20). Total adverse events attributed to studied antibiotics (OR, 1.07; 95% CI, 0.90-1.28) and patients withdrawn from trials (OR, 0.86; 95% CI, 0.68-1.09) were similar in the compared groups. Mortality was not different between vancomycin and comparator antibiotics when all trials were included in the analysis (OR, 1.09; 95% CI, 0.96-1.23). Comparators were associated with higher mortality in open-label (OR, 1.27; 95% CI, 1.05-1.54) but not double-blind trials (OR, 0.96; 95% CI, 0.80-1.14).

CONCLUSION

On the basis mainly of data from open-label trials, vancomycin is a treatment choice that is as effective as other available antibiotics for patients with gram-positive infections. Study design seems to make a major contribution to the outcome.

Potential protective role of linezolid against Clostridium difficile infection

Clostridium difficile infection (CDI) is one of the main causes of diarrhoea associated with antimicrobial therapy. Antibiotics with good 'in vitro' activity against C. difficile could protect patients from developing CDI. In this study, the potential of linezolid to protect patients with ventilator-associated pneumonia (VAP) from developing CDI was assessed. Over a 4-year period, a cohort of patients who developed VAP following major heart surgery (MHS) in Gregorio Marañón General Hospital (Madrid, Spain) was retrospectively analysed. Patients were divided into those who developed CDI in the post-operative period and those who did not. Variables associated with the development of CDI were analysed, including the role of antimicrobial therapy. Overall, 1934 patients underwent MHS; 90 patients were excluded due to intra-operative or early post-operative (first 48h) death, leaving a study population of 1844 patients, of which 105 cases had VAP. Complete clinical data were available in 91 cases. CDI occurred in 22 patients (24.2%). When comparing VAP cases with and without CDI, EuroSCORE and overall antibiotics prescribed were not significantly different. Patients with chronic renal failure (CRF) were more prone to develop CDI than those without CRF (32% vs. 13%; P=0.04), and patients without [corrected] CDI received more doses of linezolid than those with [corrected] CDI [12.4±9.7 defined daily doses (DDDs) vs. 6.7±4.0 DDDs; P=0.007]. Multivariate analysis confirmed that receiving more DDDs of linezolid protects from developing CDI (hazard ratio=0.908, 95% confidence interval 0.83-0.99; P=0.04). This work is retrospective and addresses a very particular population, but it is the first to suggest the potential impact of linezolid against CDI.

Current review of antimicrobial treatment of nosocomial pneumonia caused by multidrug-resistant pathogens

Nosocomial pneumonia (including ventilator-associated pneumonia; VAP), a consistently difficult-to-treat entity, is frequently caused by multidrug-resistant (MDR) or pandrug-resistant (PDR) bacteria. Given the high mortality rates caused by drug-resistant bacteria and the difficulty of developing new potent antibiotics to target the problematic pathogens, combination regimens are under ardent evaluation as new strategies to overcome increasing drug resistance. Adjustment of the administration method of certain β-lactams (meropenem, or imipenem/cilastatin), or combination of tigecycline with some agents, may show promise with regard to successful management of MDR or PDR Acinetobacter baumannii pneumonia. Additionally, vancomycin plus rifampicin is an effective regimen against nosocomial pneumonia caused by methicillin-resistant Staphylococcus aureus (MRSA) responding poorly to vancomycin monotherapy. The clinical appropriateness of parenteral colistin against pneumonia caused by MDR A. baumannii has been established in a clinical trial. Facing the decline of clinical vancomycin efficacy after initial use, linezolid might be the drug of choice with regard to the treatment of MRSA-VAP. The role of tigecycline monotherapy for the management of nosocomial pneumonia caused by MRSA and extended-spectrum β-lactamase-producing Enterobacteriaceae needs to be cautiously evaluated.

A comparative evaluation of adverse platelet outcomes among Veterans' Affairs patients receiving linezolid or vancomycin

OBJECTIVES

The primary objectives were to compare the incidences of severe thrombocytopenia, critical thrombocytopenia and a relative decline in platelets from baseline (≥50% decline) between patients receiving linezolid and those receiving vancomycin. The secondary objective was to assess the relationship between vancomycin trough concentration and adverse platelet outcomes.

METHODS

A matched cohort study was performed at the Upstate New York Veterans' Affairs Healthcare Network from January 2005 until February 2008. Eligibility criteria were: (i) receipt of linezolid or vancomycin therapy for ≥48 h; (ii) initiation of therapy as an inpatient; and (iii) baseline platelets available for evaluation. Patients who received linezolid were matched 1:1 to patients who received vancomycin. Cumulative incidences and times to event for (i) platelet count ≤50,000 cells/mm(3), (ii) platelet count ≤20,000 cells/mm(3) and (iii) ≥50% decline in platelets from baseline were evaluated. Multivariate analyses were performed.

RESULTS

The study included 502 patients (251 matched pairs). The occurrences of platelet counts ≤50,000 cells/mm(3) and ≤20,000 cells/mm(3) did not differ significantly between linezolid and vancomycin patients. A ≥50% decline in platelets from baseline was observed in 78 (31.1%) patients receiving vancomycin and 43 (17.1%) patients receiving linezolid (risk ratio 0.55; 95% CI 0.40-0.77). A clear exposure-response relationship was observed between vancomycin trough concentration and ≥50% decline in platelets from baseline.

CONCLUSIONS

The incidence of thrombocytopenia was low and did not differ significantly among vancomycin and linezolid patients.

Does linezolid modulate lung innate immunity in a murine model of methicillin-resistant Staphylococcus aureus pneumonia?

OBJECTIVES

Methicillin-resistant Staphylococcus aureus is an important cause of mortality among nosocomial infections. Recent investigations suggest that linezolid is superior to vancomycin in achieving clinical cure in patients with nosocomial pneumonia. We hypothesized that linezolid may exhibit anti-inflammatory properties in vivo model of pneumonia.

DESIGN

Prospective interventional study.

SETTING

University affiliated laboratory.

SUBJECTS

BALB/c mice.

INTERVENTIONS

Three groups of BALB/c mice were inoculated with methicillin-resistant S. aureus American Type Culture Collection 33,591 to induce pneumonia. Each group (n = 6) underwent bronchoalveolar lavage at 24 hrs, 48 hrs, and 72 hrs after inoculation after treatment with vancomycin, linezolid, or no antibiotic. Bronchoalveolar lavage fluid levels of monocyte chemotactic protein-5 and interleukin-6 were quantified using cytometric bead array. Metalloproteinase-9 was detected by enzyme-linked immunosorbent assay and gelatin zymography. Neutrophil apoptosis in bronchoalveolar lavage was assessed by annexin V and 7-aminoactinomycin D staining. Neutrophil activity was determined by myeloperoxidase enzyme activity. Phagocytosis of apoptotic neutrophils by linezolid- vs. vancomycin treated-alveolar macrophages was examined in vitro.

MEASUREMENTS AND MAIN RESULTS

Infected mice had a significant reduction in lung bacterial titers compared with controls (p < .05) after treatment with linezolid or vancomycin. There was no difference in bronchoalveolar lavage levels of monocyte chemotactic protein-5 or interleukin-6 between vancomycin- and linezolid-treated groups. Both antimicrobials were comparable in modulating the expression of matrix metalloproteinase-9 in bronchoalveolar lavage. Neutrophil apoptosis was comparable in both vancomycin- and linezolid-treated groups at all three time points. Vancomycin showed lower myeloperoxidase activity compared with linezolid in the first 24 hrs after inoculation (p = .03), but the difference was undetectable at 48 hrs and 72 hrs. Neither compound had an impact on the process of removal of apoptotic neutrophils by alveolar macrophages.

CONCLUSIONS

Linezolid did not display an advantage over vancomycin in modulating pulmonary innate immune response in a murine model of methicillin-resistant S. aureus pneumonia.

Penetration of vancomycin into epithelial lining fluid in healthy volunteers

Although vancomycin is often regarded as an agent that concentrates poorly in the lower respiratory tract, as determined from concentrations in epithelial lining fluid (ELF), few data are available. This study sought to determine the profile of vancomycin exposure in the ELF relative to plasma. Population modeling and Monte Carlo simulation were employed to estimate the penetration of vancomycin into ELF. Plasma and ELF pharmacokinetic (PK) data were obtained from 10 healthy volunteers. Concentration-time profiles in plasma and ELF were simultaneously modeled using a three-compartment model with zero-order infusion and first-order elimination and transfer using the big nonparametric adaptive grid (BigNPAG) program. Monte Carlo simulation with 9,999 subjects was performed to calculate the ELF/plasma penetration ratios by estimating the area under the concentration-time curve (AUC) in ELF (AUC(ELF)) and plasma (AUC(plasma)) after a single simulated 1,000-mg dose. The mean (standard deviation) AUC(ELF)/AUC(plasma) penetration ratio was 0.675 (0.677), and the 25th, 50th, and 75th percentile penetration ratios were 0.265, 0.474, and 0.842, respectively. Our results indicate that vancomycin penetrates ELF at approximately 50% of plasma levels. To properly judge the adequacy of current doses and schedules employed in practice, future studies are needed to delineate the PK/PD (pharmacodynamics) target for vancomycin in ELF. If the PK/PD target in ELF is found to be consistent with the currently proposed target of an AUC/MIC of ≥400, suboptimal probability of target attainment would be expected when vancomycin is utilized for pneumonias due to MRSA (methicillin-resistant Staphylococcus aureus) with MICs in excess of 1 mg/liter.