Intrapulmonary and Systemic Pharmacokinetics of Colistin Following Nebulization of Low-Dose Colistimethate Sodium in Patients with Ventilator-Associated Pneumonia Caused by Carbapenem-Resistant Acinetobacter baumannii

Colistimethate sodium (CMS) nebulization is associated with reduced systemic toxicity compared to intravenous injection, with potentially enhanced clinical efficacy. This study aimed to assess the pharmacokinetic (PK) properties of colistin during low-dose CMS nebulization in patients with ventilator-associated pneumonia (VAP) caused by carbapenem-resistant Acinetobacter baumannii. A nonlinear mixed-effects modeling approach was applied to develop population PK models for colistin in both epithelial lining fluid (ELF) and plasma. Twenty patients participated, and 80 ELF and 100 plasma samples were used for model development. Median colistin concentrations measured in ELF were 614-fold, 408-fold, and 250-fold higher than in plasma at 1, 3, and 5 h, respectively. Time courses in both ELF and plasma were best described by a one-compartment model with a Weibull absorption process. When the final model was simulated, the maximum free concentration and area under the free colistin concentration-time curve at steady state over 24 h in the plasma were approximately 1/90 and 1/50 of the corresponding values in ELF at steady state, respectively. For an A. baumannii MIC of 1 mg/L, inhaling 75 mg of CMS at 6 h intervals was deemed appropriate, with dose adjustments needed for MICs exceeding 2 mg/L. Using a nebulizer for CMS resulted in a notably higher exposure of colistin in the ELF than plasma, indicating the potential of nebulization to reduce systemic toxicity while effectively treating VAP.

The development, validation, and in vivo testing of a high-precision bronchial epithelial lining fluid sampling device

Introduction

Analysis of respiratory biomarkers or pharmaceutical drug concentrations in bronchial epithelial lining fluid (bELF) using a high-precision sampling method is crucial for effective clinical respiratory diagnostics and research. Here, we utilized a cellulose matrix as an absorptive probe for bELF sampling, subsequently testing the design of a device and sampling technique in vivo.

Methods

The absorptive matrix [Whatman® qualitative filter paper (Grade CF-12)] was first tested through tissue-contact experiments on porcine airway tissue. The absorption and elution capacity of the matrix, as well as the laboratory processing and analysis method, was validated with a range of Interleukin-8 (CXCL8) and C-Reactive protein (CRP) stock solutions. Subsequently, the device's design was optimized for universal in-house production and both, safe and efficient sampling. The airway sampling method was then tested in a group of 10 patients with Chronic Obstructive Pulmonary Disease (COPD). For each patient, a bELF sample was obtained using the newly developed bELF probe, as well as a reference 20 mL saline bronchial wash sample. Supernatants were assessed, using an immunoassay, for levels of the pro-inflammatory markers CXCL8, Myeloperoxidase (MPO), and CRP. The bELF samples were compared to bronchial wash.

Results

The Whatman® qualitative filter paper (Grade CF-12) bELF probes adhered to porcine airway tissue, softening slightly upon wetting. The material maintained architectural integrity following the removal of the probes, leaving no residual fibers on the porcine airway mucosa. The bELF probe design was optimized for bronchoscopic delivery and in-house production. On average, a fully saturated bELF probe carried 32 μL of protein-rich fluid. The mean return of CXCL8 and CRP from samples collected from a serial dilution series (1, 5, 10, 20 ng/mL) was 69% (range 48%-87%). The bELF probe detected, on average, 7 (MPO), 14 (CRP), and 59 (CXCL8) times higher equivalent inflammatory protein concentrations in the collected bELF probe samples compared to the bronchial wash.

Conclusion

The bELF probe is an effective absorptive technology for high-precision bELF sampling without dilution. With a simple in-house production procedure and bronchoscopic sampling technique, this method can be introduced in any bronchoscopic center for a consistent sampling of bELF.

Pharmacokinetics of SPR206 in Plasma, Pulmonary Epithelial Lining Fluid, and Alveolar Macrophages following Intravenous Administration to Healthy Adult Subjects

SPR206 is a next-generation polymyxin being developed for the treatment of multidrug-resistant (MDR) Gram-negative infections. This Phase 1 bronchoalveolar lavage (BAL) study was conducted to evaluate SPR206's safety and pharmacokinetics in plasma, pulmonary epithelial lining fluid (ELF), and alveolar macrophages (AM) in healthy volunteers. Subjects received a 100 mg intravenous (IV) dose of SPR206 infused over 1 h every 8 h for 3 consecutive doses. Each subject underwent 1 bronchoscopy with BAL at 2, 3, 4, 6, or 8 h after the start of the third IV infusion. SPR206 concentrations in plasma, BAL, and cell pellet were measured with a validated LC-MS/MS assay. Thirty-four subjects completed the study and 30 completed bronchoscopies. Mean SPR206 peak concentrations (Cmax) in plasma, ELF, and AM were 4395.0, 735.5, and 860.6 ng/mL, respectively. Mean area under the concentration-time curve (AUC0-8) for SPR206 in plasma, ELF, and AM was 20120.7, 4859.8, and 6026.4 ng*h/mL, respectively. The mean ELF to unbound plasma concentration ratio was 0.264, and mean AM to unbound plasma concentration ratio was 0.328. Mean SPR206 concentrations in ELF achieved lung exposures above the MIC for target Gram-negative pathogens for the entire 8-h dosing interval. Overall, SPR206 was well tolerated; 22 subjects (64.7%) reported at least 1 treatment-emergent adverse event (TEAE). Of the 40 reported TEAEs, 34 (85.0%) were reported as mild in severity. The most frequent TEAEs were oral paresthesia (10 subjects [29.4%]) and nausea (2 subjects [5.9%]). This study demonstrates pulmonary penetration of SPR206 and supports further development of SPR206 for the treatment of patients with serious infections caused by MDR Gram-negative pathogens.

Stratification of asthma by lipidomic profiling of induced sputum supernatant

BACKGROUND

Asthma is a chronic respiratory disease with significant heterogeneity in its clinical presentation and pathobiology. There is need for improved understanding of respiratory lipid metabolism in asthma patients and its relation to observable clinical features.

OBJECTIVE

We performed a comprehensive, prospective, cross-sectional analysis of the lipid composition of induced sputum supernatant obtained from asthma patients with a range of disease severities, as well as from healthy controls.

METHODS

Induced sputum supernatant was collected from 211 adults with asthma and 41 healthy individuals enrolled onto the U-BIOPRED (Unbiased Biomarkers for the Prediction of Respiratory Disease Outcomes) study. Sputum lipidomes were characterized by semiquantitative shotgun mass spectrometry and clustered using topologic data analysis to identify lipid phenotypes.

RESULTS

Shotgun lipidomics of induced sputum supernatant revealed a spectrum of 9 molecular phenotypes, highlighting not just significant differences between the sputum lipidomes of asthma patients and healthy controls, but also within the asthma patient population. Matching clinical, pathobiologic, proteomic, and transcriptomic data helped inform the underlying disease processes. Sputum lipid phenotypes with higher levels of nonendogenous, cell-derived lipids were associated with significantly worse asthma severity, worse lung function, and elevated granulocyte counts.

CONCLUSION

We propose a novel mechanism of increased lipid loading in the epithelial lining fluid of asthma patients resulting from the secretion of extracellular vesicles by granulocytic inflammatory cells, which could reduce the ability of pulmonary surfactant to lower surface tension in asthmatic small airways, as well as compromise its role as an immune regulator.

Estimating Unbound Drug Concentrations in Simulated Human Lung Fluid: Relevance to Lung Antibiotic PKPD

The use of unbound drug concentrations is crucial for the prediction of efficacious doses. Hence, dose predictions for antibiotics targeting respiratory pathogens should be based on free, rather than the currently used, total drug concentrations in epithelial lining fluid (ELF). In this work, we describe an assay to estimate the percent unbound of drugs in ELF using simulated epithelial lining fluid (sELF) containing the most abundant components of ELF in healthy humans. A diverse set of 85 compounds showed a broad range of unbound values ranging from <0.01 to 100%. Binding in sELF was influenced by ionization, with basic compounds typically resulting in a stronger binding than neutral and acidic compounds (median percent unbound values 17, 50, and 62%, respectively). A permanent positive charge further increased binding (median percent unbound 11%), while zwitterions showed a lower binding (median percent unbound 69%). In lipid-free sELF, the binding of basic compounds was less pronounced, while compounds of other ionization classes were less impacted, indicating that lipids are involved in the binding of bases. A reasonable correlation was found between binding in sELF and human plasma (R² = 0.75); however, plasma binding poorly predicted sELF binding for basic compounds (R² = 0.50). Bases are an important compound class for antibacterial drug development since positive charges affect permeability into Gram-negative bacteria, which are important in terms of bacterial pneumonia. To evaluate in vivo activity, we selected two bases, for which strong sELF binding was observed (percent unbound <1 and 7%) and conducted an analysis of antibacterial efficacy in the neutropenic murine lung efficacy model and total vs free ELF drug concentrations. In both cases, the total ELF resulted in an overprediction of expected efficacy, while the corrected free ELF explained the observed in vivo efficacy. This supports that free, and not total, ELF concentrations should be used for the efficacious dose prediction for pneumonia and highlights the importance of determining binding in this matrix.

Ceftolozane/Tazobactam Probability of Target Attainment in Patients With Hospital-Acquired or Ventilator-Associated Bacterial Pneumonia

Probability of target attainment (PTA) analyses were conducted to support the recommended ceftolozane/tazobactam dosing regimens, adjusted for renal function, in patients with hospital-acquired/ventilator-associated bacterial pneumonia (HABP/VABP). Previously published population pharmacokinetic models describing the disposition of ceftolozane and tazobactam in plasma and epithelial lining fluid (ELF) in patients with HABP/VABP were used to simulate ceftolozane and tazobactam concentration-time profiles in plasma and ELF over the course of 14 days. The simulations were conducted for patients with normal renal function and for patients receiving adjusted doses for mild, moderate, and severe renal impairment. PTA was calculated using established pharmacokinetic/pharmacodynamic targets for ceftolozane and tazobactam. Across renal function groups, plasma PTA was 100% for ceftolozane and >99% for tazobactam; ELF PTA was >99% for ceftolozane and >87% for tazobactam. These results provided support for the currently recommended ceftolozane/tazobactam dosing regimens for HABP/VABP, which were efficacious and well tolerated in the Ceftolozane-Tazobactam Versus Meropenem for Treatment of Nosocomial Pneumonia (ASPECT-NP) trial.

Probability of Target Attainment Analyses to Inform Ceftolozane/Tazobactam Dosing Regimens for Patients With Hospital-Acquired or Ventilator-Associated Bacterial Pneumonia and End-Stage Renal Disease Receiving Intermittent Hemodialysis

ASPECT-NP, a phase 3 trial of ceftolozane/tazobactam in hospital-acquired/ventilator-associated bacterial pneumonia (HABP/VABP), excluded patients with end-stage renal disease (ESRD). A modeling/simulation approach was undertaken to inform optimal dosing in this population, using previously developed ceftolozane and tazobactam population pharmacokinetic models informed by data from 16 clinical studies. Stochastic simulations were performed using NONMEM to support dose justification. Probability of target attainment (PTA) simulations in plasma and epithelial lining fluid were conducted using a 14-day treatment, with hemodialysis every other weekday for a high-dose (4X), middle-dose (3X), or low-dose (2X) regimen, where X was the recommended dose in patients with complicated intra-abdominal infection/complicated urinary tract infection and ESRD (500 mg/250 mg ceftolozane/tazobactam loading dose and 100 mg/50 mg ceftolozane/tazobactam maintenance dose administered by 1-hour infusion every 8 hours). PTA was determined using established pharmacokinetic/pharmacodynamic targets: ceftolozane, 30% of the interdose interval (8 hours) in which free ceftolozane concentration exceeded the minimum inhibitory concentration value of 4 µg/mL; tazobactam, 20% of the interdose interval in which free tazobactam concentration exceeded 1 µg/mL. Plasma PTA was >90% for both agents for all 3 regimens. Plasma ceftolozane exposures at the high-dose regimen exceeded those from phase 3 study experience. Epithelial lining fluid PTA was >90% for high- and middle-dose regimens but was <80% for tazobactam on dialysis days at the low-dose regimen. For patients with HABP/VABP and ESRD requiring intermittent hemodialysis, the middle-dose regimen of 1.5 g/0.75 g ceftolozane/tazobactam loading + 300 mg/150 mg maintenance every 8 hours by 1-hour infusion is recommended.

Superoxide Release by Macrophages through NADPH Oxidase Activation Dominating Chemistry by Isoprene Secondary Organic Aerosols and Quinones to Cause Oxidative Damage on Membranes

Oxidative stress mediated by reactive oxygen species (ROS) is a key process for adverse aerosol health effects. Secondary organic aerosols (SOA) account for a major fraction of fine particulate matter, and their inhalation and deposition into the respiratory tract causes the formation of ROS by chemical and cellular processes, but their relative contributions are hardly quantified and their link to oxidative stress remains uncertain. Here, we quantified cellular and chemical superoxide generation by 9,10-phenanthrenequinone (PQN) and isoprene SOA using a chemiluminescence assay combined with electron paramagnetic resonance spectroscopy as well as kinetic modeling. We also applied cellular imaging techniques to study the cellular mechanism of superoxide release and oxidative damage on cell membranes. We show that PQN and isoprene SOA activate NADPH oxidase in macrophages to release massive amounts of superoxide, overwhelming the superoxide formation by aqueous chemical reactions in the epithelial lining fluid. The activation dose for PQN is 2 orders of magnitude lower than that of isoprene SOA, suggesting that quinones are more toxic. While higher exposures trigger cellular antioxidant response elements, the released ROS induce oxidative damage to the cell membrane through lipid peroxidation. Such mechanistic and quantitative understandings provide a basis for further elucidation of adverse health effects and oxidative stress by fine particulate matter.

Activity of Delafloxacin and Levofloxacin against Stenotrophomonas maltophilia at Simulated Plasma and Intrapulmonary pH Values

Fluoroquinolones have become a popular treatment option for Stenotrophomonas maltophilia infections. Although levofloxacin is most commonly used, delafloxacin demonstrates comparable in vitro activity when evaluated under standard susceptibility testing conditions at neutral pH. At acidic pH, the activity of the anionic delafloxacin is improved, while the activity of the zwitterionic levofloxacin is reduced. Because the human respiratory tract has a pH of ~6.6 and is the most common site of S. maltophilia infection, it is vital to understand the activity of these agents in this environment. Therefore, levofloxacin and delafloxacin were tested against clinical S. maltophilia isolates via broth microdilution testing (n = 37) and time-kill analysis (n = 5) in neutral cation-adjusted Mueller-Hinton broth (CAMHB) (pH 7.3) and acidic CAMHB (aCAMHB) (pH 6.5). In CAMHB, MIC50 values were similar between levofloxacin and delafloxacin (8 mg/L versus 8 mg/L). In aCAMHB, levofloxacin MICs did not change, while delafloxacin MICs decreased by a median of 4 log2 dilutions (MIC50 values of 8 mg/L versus 0.25 mg/L). In time-kill analyses, levofloxacin and delafloxacin at the maximum drug concentration for the free drug (fCmax) were bactericidal against 3 and 2 isolates in CAMHB, respectively. In aCAMHB, levofloxacin was not bactericidal against any isolate, while delafloxacin was bactericidal against the same 2 isolates. Relative to CAMHB, levofloxacin activity was reduced by 2.5 log10 CFU/mL in aCAMHB, whereas delafloxacin activity was increased 2.7 log10 CFU/mL. Although the bactericidal activity of levofloxacin against S. maltophilia was attenuated in an acidic environment in this study, the increased potency of delafloxacin at pH 6.5 did not translate into improved bactericidal activity in time-kill analyses, compared to pH 7.3. IMPORTANCE Stenotrophomonas maltophilia most often infects the lungs, where the physiologic environment is naturally slightly acidic (pH ~6.6), compared to most parts of the body (such as the bloodstream), which have neutral pH values (~7.4). Pneumonia due to S. maltophilia is often treated with the antibiotic levofloxacin, despite the activity of levofloxacin being known to be impaired at acidic pH. Unfortunately, currently available methods for susceptibility testing of levofloxacin against S. maltophilia are performed at a neutral pH and therefore may not accurately represent the activity of levofloxacin at the site of infection in the lungs. A similar but newer antibiotic in the same class as levofloxacin, namely, delafloxacin, is not affected by being in an acidic environment and may actually work better at lower pH values. Therefore, the purpose of this study was to investigate whether one drug might be better than the other in this setting by testing each agent's ability to kill S. maltophilia at pH 7.3 and pH 6.5. These findings could then be used to design confirmatory studies that may ultimately impact which drug is given to patients with lung infections due to S. maltophilia.

Plasma and Intrapulmonary Concentrations of Tebipenem following Oral Administration of Tebipenem Pivoxil Hydrobromide to Healthy Adult Subjects

Tebipenem pivoxil hydrobromide (TBP-PI-HBr) is an oral carbapenem prodrug being developed for the treatment of serious bacterial infections. The active moiety, tebipenem, has broad-spectrum activity against common Enterobacterales pathogens, including extended-spectrum-β-lactamase (ESBL)-producing multidrug-resistant strains. This study evaluated the intrapulmonary pharmacokinetics (PK) and epithelial lining fluid (ELF) and alveolar macrophage (AM) concentrations of tebipenem relative to plasma levels in nonsmoking, healthy adult subjects. Thirty subjects received oral TBP-PI-HBr at 600 mg every 8 h for five doses. Serial blood samples were collected following the last dose. Each subject underwent one standardized bronchoscopy with bronchoalveolar lavage (BAL) 1, 2, 4, 6, or 8 h after the fifth dose of TBP-PI-HBr. The tebipenem area under the concentration-time curve for the 8-h dosing interval (AUC_0-8) values in plasma, ELF, and AMs were calculated using the mean concentration at each BAL sampling time. Ratios of AUC_0-8 values for total ELF and AMs to those for unbound plasma were determined, using a plasma protein binding value of 42%. Mean values ± standard deviations (SD) of tebipenem maximum (C_max) and minimum (C_min) total plasma concentrations were 11.37 ± 3.87 mg/L and 0.043 ± 0.039 mg/L, respectively. Peak tebipenem concentrations in plasma, ELF, and AMs occurred at 1 h and then decreased over 8 h. Ratios of tebipenem AUC_0-8 values for ELF and AMs to those for unbound plasma were 0.191 and 0.047, respectively. Four (13.3%) subjects experienced adverse events (diarrhea, fatigue, papule, and coronavirus disease 2019 [COVID-19]); all resolved, and none were severe or serious. Tebipenem is distributed into the lungs of healthy adults, which supports the further evaluation of TBP-PI-HBr for the treatment of lower respiratory tract bacterial infections caused by susceptible pathogens. (This study has been registered at ClinicalTrials.gov under identifier NCT04710407.).

Target Site Pharmacokinetics of Meropenem: Measurement in Human Explanted Lung Tissue by Bronchoalveolar Lavage, Microdialysis, and Homogenized Lung Tissue

Pneumonia is one of the most common infections in intensive care patients, and it is often treated with beta-lactam antibiotics. Even if therapeutic drug monitoring in blood is available, it is unclear whether sufficient concentrations are reached at the target site: the lung. The present study was initiated to fill this knowledge gap. Various compartments from 10 patients' explanted lungs were subjected to laboratory analysis. Meropenem was quantified in serum, bronchoalveolar lavage (BAL) fluid, microdialysate, and homogenized lung tissue with isotope dilution liquid chromatography tandem mass spectrometry (ID-LC-MS/MS). BAL fluid represents diluted epithelial lining fluid (ELF), and microdialysate represents interstitial fluid (IF). Differences between target site and blood concentrations were investigated. The median meropenem concentration in blood, ELF, IF, and tissue were 26.8, 18.0, 12.1, and 9.1 mg/liter, respectively. A total of 37.5% of the target site ELF and IF meropenem concentrations were below the clinical EUCAST breakpoint of 8 mg/liter. The median ELF/serum quotient was 61.8% (interquartile range [IQR], 24.8% to 87.6%), the median IF/serum quotient was 35.4% (IQR, 23.8% to 54.3%), and the median tissue/serum quotient was 34.2% (IQR, 28.3% to 38.2%). We observed a substantial interindividual variability between the blood and the compartments (ELF and IF), whereas the intraindividual variability was relatively low. Target site measurement in different lung compartments was feasible and successfully applied in a clinical setting. A relevant amount of 37.5% of the target site concentrations were below the clinical EUCAST breakpoint, indicating subtherapeutic dosing in high-risk patients receiving perioperative antibiotic prophylaxis in lung transplantation. (This study has been registered at ClinicalTrials.gov under identifier NCT03970265.).

Hydroxyl Radical Production by Air Pollutants in Epithelial Lining Fluid Governed by Interconversion and Scavenging of Reactive Oxygen Species

Air pollution is a major risk factor for human health. Chemical reactions in the epithelial lining fluid (ELF) of the human respiratory tract result in the formation of reactive oxygen species (ROS), which can lead to oxidative stress and adverse health effects. We use kinetic modeling to quantify the effects of fine particulate matter (PM2.5), ozone (O₃), and nitrogen dioxide (NO₂) on ROS formation, interconversion, and reactivity, and discuss different chemical metrics for oxidative stress, such as cumulative production of ROS and hydrogen peroxide (H₂O₂) to hydroxyl radical (OH) conversion. All three air pollutants produce ROS that accumulate in the ELF as H₂O₂, which serves as reservoir for radical species. At low PM2.5 concentrations (<10 μg m^-3), we find that less than 4% of all produced H₂O₂ is converted into highly reactive OH, while the rest is intercepted by antioxidants and enzymes that serve as ROS buffering agents. At elevated PM2.5 concentrations (>10 μg m^-3), however, Fenton chemistry overwhelms the ROS buffering effect and leads to a tipping point in H₂O₂ fate, causing a strong nonlinear increase in OH production. This shift in ROS chemistry and the enhanced OH production provide a tentative mechanistic explanation for how the inhalation of PM2.5 induces oxidative stress and adverse health effects.

Lung macrophages: current understanding of their roles in Ozone-induced lung diseases

Through the National Ambient Air Quality Standards (NAAQS), the Clean Air Act of the United States outlines acceptable levels of six different air pollutants considered harmful to humans and the environment. Included in this list is ozone (O₃), a highly reactive oxidant gas, respiratory health hazard, and common environmental air pollutant at ground level. The respiratory health effects due to O₃ exposure are often associated with molecular and cellular perturbations in the respiratory tract. Periodic review of NAAQS requires comprehensive scientific evaluation of the public health effects of these pollutants, which is formulated through integrated science assessment (ISA) of the most policy-relevant scientific literature. This review focuses on the protective and pathogenic effects of macrophages in the O₃-exposed respiratory tract, with emphasis on mouse model-based toxicological studies. Critical findings from 39 studies containing the words O₃, macrophage, mice, and lung within the full text were assessed. While some of these studies highlight the presence of disease-relevant pathogenic macrophages in the airspaces, others emphasize a protective role for macrophages in O₃-induced lung diseases. Moreover, a comprehensive list of currently known macrophage-specific roles in O₃-induced lung diseases is included in this review and the significant knowledge gaps that still exist in the field are outlined. In conclusion, there is a vital need in this field for additional policy-relevant scientific information, including mechanistic studies to further define the role of macrophages in response to O₃.

Pharmacodynamics of Cefepime Combined with the Novel Extended-Spectrum-β-Lactamase (ESBL) Inhibitor Enmetazobactam for Murine Pneumonia Caused by ESBL-Producing Klebsiella pneumoniae

Klebsiella pneumoniae strains that produce extended-spectrum beta lactamases (ESBLs) are a persistent public health threat. There are relatively few therapeutic options, and there is undue reliance on carbapenems. Alternative therapeutic options are urgently required. A combination of cefepime and the novel beta lactamase inhibitor enmetazobactam is being developed for the treatment of serious infections caused by ESBL-producing organisms. The pharmacokinetics-pharmacodynamics (PK-PD) of cefepime-enmetazobactam against ESBL-producing K. pneumoniae was studied in a neutropenic murine pneumonia model. Dose-ranging studies were performed. Dose fractionation studies were performed to define the relevant PD index for the inhibitor. The partitioning of cefepime and enmetazobactam into the lung was determined by comparing the area under the concentration-time curve (AUC) in plasma and epithelial lining fluid. The magnitude of drug exposure for cefepime-enmetazobactam required for logarithmic killing in the lung was defined using 3 ESBL-producing strains. Cefepime, given as 100 mg/kg of body weight every 8 h intravenously (q8h i.v.), had minimal antimicrobial effect. When this background regimen of cefepime was combined with enmetazobactam, a half-maximal effect was induced with enmetazobactam at 4.71 mg/kg q8h i.v. The dose fractionation study suggested both fT > threshold and fAUC:MIC are relevant PD indices. The AUC_ELF:AUC_plasma ratio for cefepime and enmetazobactam was 73.4% and 61.5%, respectively. A ≥2-log kill in the lung was achieved with a plasma and ELF cefepime fT > MIC of ≥20% and enmetazobactam fT > 2 mg/liter of ≥20% of the dosing interval. These data and analyses provide the underpinning evidence for the combined use of cefepime and enmetazobactam for nosocomial pneumonia.

Pharmacokinetics and Penetration of Sitafloxacin into Alveolar Epithelial Lining Fluid in Critically Ill Thai Patients with Pneumonia

Sitafloxacin showed potent activity against various respiratory pathogens. Blood and bronchoalveolar lavage (BAL) fluid samples were obtained from 12 subjects after a single oral dose of sitafloxacin 200 mg. The mean ± SD (median) maximum ratio of epithelial lining fluid (ELF) to unbound plasma concentration was 1.02 ± 0.58 (1.33). The penetration ratios based on the mean and median area under the curve from 0 to 8 h (AUC_0-8) were 0.85 and 0.79 μg · h/ml, respectively. Sitafloxacin penetrates well into ELF in critically ill Thai patients with pneumonia. (This study has been registered in the Thai Clinical Trials Registry [TCTR] under registration no. TCTR20170222001.).

Meropenem Combined with Ciprofloxacin Combats Hypermutable Pseudomonas aeruginosa from Respiratory Infections of Cystic Fibrosis Patients

Hypermutable Pseudomonas aeruginosa organisms are prevalent in chronic respiratory infections and have been associated with reduced lung function in cystic fibrosis (CF); these isolates can become resistant to all antibiotics in monotherapy. This study aimed to evaluate the time course of bacterial killing and resistance of meropenem and ciprofloxacin in combination against hypermutable and nonhypermutable P. aeruginosa Static concentration time-kill experiments over 72 h assessed meropenem and ciprofloxacin in mono- and combination therapies against PAO1 (nonhypermutable), PAOΔmutS (hypermutable), and hypermutable isolates CW8, CW35, and CW44 obtained from CF patients with chronic respiratory infections. Meropenem (1 or 2 g every 8 h [q8h] as 3-h infusions and 3 g/day as a continuous infusion) and ciprofloxacin (400 mg q8h as 1-h infusions) in monotherapies and combinations were further evaluated in an 8-day hollow-fiber infection model study (HFIM) against CW44. Concentration-time profiles in lung epithelial lining fluid reflecting the pharmacokinetics in CF patients were simulated and counts of total and resistant bacteria determined. All data were analyzed by mechanism-based modeling (MBM). In the HFIM, all monotherapies resulted in rapid regrowth with resistance at 48 h. The maximum daily doses of 6 g meropenem (T_>MIC of 80% to 88%) and 1.2 g ciprofloxacin (area under the concentration-time curve over 24 h in the steady state divided by the MIC [AUC/MIC], 176), both given intermittently, in monotherapy failed to suppress regrowth and resulted in substantial emergence of resistance (≥7.6 log₁₀ CFU/ml resistant populations). The combination of these regimens achieved synergistic killing and suppressed resistance. MBM with subpopulation and mechanistic synergy yielded unbiased and precise curve fits. Thus, the combination of 6 g/day meropenem plus ciprofloxacin holds promise for future clinical evaluation against infections by susceptible hypermutable P. aeruginosa.

Plasma and Intrapulmonary Concentrations of ETX2514 and Sulbactam following Intravenous Administration of ETX2514SUL to Healthy Adult Subjects

ETX2514 is a novel β-lactamase inhibitor that broadly inhibits Ambler class A, C, and D β-lactamases. ETX2514 combined with sulbactam (SUL) in vitro restores sulbactam activity against Acinetobacter baumannii ETX2514-sulbactam (ETX2514SUL) is under development for the treatment of A. baumannii infections. The objective of this study was to determine and compare plasma, epithelial lining fluid (ELF), and alveolar macrophage (AM) concentrations following intravenous (i.v.) ETX2514 and sulbactam. Plasma, ELF, and AM concentrations of ETX2514 and sulbactam were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in 30 healthy adult subjects following repeated dosing (ETX2514 [1 g] and sulbactam [1 g] every 6 h [q6h], as a 3-h i.v. infusion, for a total of 3 doses). A bronchoalveolar lavage (BAL) was performed once in each subject at either 1, 2.5, 3.25, 4, or 6 h after the start of the last infusion. Penetration ratios were calculated from area under the concentration-time curve from 0 to 6 h (AUC_0-6) values for total plasma and ELF using mean and median concentrations at the BAL fluid sampling times. Respective ELF AUC_0-6 values, based on mean and median concentrations, were 40.1 and 39.4 mg · h/liter for ETX2514 and 34.7 and 34.5 mg · h/liter for sulbactam. Respective penetration ratios of ELF to total/unbound plasma concentrations, based on mean and median AUC_0-6 values, of ETX2514 were 0.37/0.41 and 0.36/0.40, whereas these same ratio values were 0.50/0.81 and 0.50/0.80 for sulbactam. ETX2514 and sulbactam concentrations in AM were measurable and fairly constant throughout the dosing interval (median values of 1.31 and 1.01 mg/liter, respectively). These data support further study of ETX2514SUL for the treatment of pneumonia caused by multidrug-resistant A. baumannii (This study has been registered at ClinicalTrials.gov under identifier NCT03303924.).

Oxidative stress-linked biomarkers in idiopathic pulmonary fibrosis: a systematic review and meta-analysis

AIM

The aim of this meta-analysis was to investigate associations between idiopathic pulmonary fibrosis (IPF) and markers of oxidative stress (OS) measured in different biological samples.

METHODS

A systematic search of publications listed in PubMed, Web of Science, Scopus and Google Scholar from inception to December 2017 was conducted.

RESULTS

Significant differences between IPF patients and controls were observed for all biomarkers (thiobarbituric acid reactive substances, hydroperoxides and glutathione), barring systemic isoprostanes.

CONCLUSION

This meta-analysis showed a consistent increase in the concentrations of OS markers or a reduction in antioxidant markers, in patients with IPF, independent of the type of biological sample. Pending the results of further studies, OS biomarkers might be useful for the diagnosis and monitoring of IPF.

Plasma and Intrapulmonary Concentrations of Cefepime and Zidebactam following Intravenous Administration of WCK 5222 to Healthy Adult Subjects

WCK 5222 is a combination of cefepime and the novel β-lactam enhancer zidebactam being developed for the treatment of serious Gram-negative bacterial infections. The objective of this study was to compare plasma (total), epithelial lining fluid (ELF), and alveolar macrophage (AM) concentrations of cefepime and zidebactam in healthy adult subjects. The WCK 5222 dosing regimen was 2 g cefepime/1 g zidebactam administered as a 1-h intravenous infusion every 8 h for a total of 7 doses. Subjects were assigned to one bronchoalveolar lavage (BAL) sampling time at 0.5, 1.25, 3, 6, 8, or 10 h after the seventh dose. Noncompartmental pharmacokinetic parameters were determined from serial plasma concentrations collected over 8-hour and 10-hour intervals following the first and seventh doses, respectively. Penetration ratios were calculated from the area under the plasma concentration-time curve from 0 to 8 h (AUC_0-8) for plasma, ELF, and AM using mean and median concentrations at each BAL sampling time. The plasma maximum concentration of drug (C_max) and AUC values of cefepime and zidebactam increased by 8% to 9% after the seventh versus the first dose of WCK 5222. The respective AUC_0-8 values based on mean concentrations of cefepime and zidebactam in ELF were 127.9 and 52.0 mg · h/liter, and 87.9 and 13.2 mg · h/liter in AM. The ELF to total plasma penetration ratios of cefepime and zidebactam based on mean AUC_0-8 values were 0.39 and 0.38, respectively. The AM to total plasma ratios were 0.27 and 0.10, respectively. The observed plasma, ELF, and AM concentrations of cefepime and zidebactam support studies of WCK 5222 for treatment of pneumonia caused by susceptible pathogens.

Intrapulmonary Pharmacokinetics of Levonadifloxacin following Oral Administration of Alalevonadifloxacin to Healthy Adult Subjects

Alalevonadifloxacin (WCK 2349) is a novel l-alanine ester prodrug of levonadifloxacin that is being developed as an oral fluoroquinolone antibiotic. The primary objective of this study was to determine and compare plasma, epithelial lining fluid (ELF), and alveolar macrophage (AM) concentrations of levonadifloxacin following oral administration of alalevonadifloxacin to healthy adult subjects. Levonadifloxacin concentrations in plasma, ELF, and AM samples from 30 healthy subjects were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) following oral dosing of alalevonadifloxacin (1,000 mg twice daily for 5 days). Six subjects were assigned to each bronchoalveolar lavage (BAL) fluid sampling time, i.e., 2, 4, 6, 8, or 12 h after the ninth oral dose. Noncompartmental pharmacokinetic (PK) parameters were determined from serial total plasma concentrations collected over a 12-h interval following the first and ninth oral doses. Penetration ratios were calculated from the areas under the concentration-time curves from 0 to 12 h (AUC_0-12) for plasma, ELF, and AM by using mean (and median) concentrations at each BAL sampling time. Unbound plasma concentrations (∼85% plasma protein binding) were used to determine site-to-plasma penetration ratios. Plasma PK parameter values for levonadifloxacin were similar after the first and ninth doses. The respective AUC_0-12 values based on mean ELF and AM concentrations were 172.6 and 35.3 mg · h/liter, respectively. The penetration ratios for ELF and AM levonadifloxacin concentrations to unbound plasma levonadifloxacin concentrations were 7.66 and 1.58, respectively. Similar penetration ratios were observed with median concentrations. The observed plasma, ELF, and AM concentrations of levonadifloxacin support further studies of alalevonadifloxacin for treatment of lower respiratory tract bacterial infections caused by susceptible pathogens. (This study has been registered at ClinicalTrials.gov under identifier NCT02253342.).

Comparison of Omadacycline and Tigecycline Pharmacokinetics in the Plasma, Epithelial Lining Fluid, and Alveolar Cells of Healthy Adult Subjects

The steady-state concentrations of omadacycline and tigecycline in the plasma, epithelial lining fluid (ELF), and alveolar cells (AC) of 58 healthy adult subjects were obtained. Subjects were administered either omadacycline at 100 mg intravenously (i.v.) every 12 h for two doses followed by 100 mg i.v. every 24 h for three doses or tigecycline at an initial dose of 100 mg i.v. followed by 50 mg i.v. every 12 h for six doses. A bronchoscopy and bronchoalveolar lavage were performed once in each subject following the start of the fifth dose of omadacycline at 0.5, 1, 2, 4, 8, 12, or 24 h and after the start of the seventh dose of tigecycline at 2, 4, 6, or 12 h. The value of the area under the concentration-time curve (AUC) from time zero to 24 h postdosing (AUC_0–24) (based on mean concentrations) in ELF and the ratio of the ELF to total plasma omadacycline concentration based on AUC_0–24 values were 17.23 mg · h/liter and 1.47, respectively. The AUC_0–24 value in AC was 302.46 mg · h/liter, and the ratio of the AC to total plasma omadacycline concentration was 25.8. In comparison, the values of the AUC from time zero to 12 h postdosing (AUC_0–12) based on the mean concentrations of tigecycline in ELF and AC were 3.16 and 38.50 mg · h/liter, respectively. The ratio of the ELF and AC to total plasma concentrations of tigecycline based on AUC_0–12 values were 1.71 and 20.8, respectively. The pharmacokinetic advantages of higher and sustained concentrations of omadacycline compared to those of tigecycline in plasma, ELF, and AC suggest that omadacycline is a promising antibacterial agent for the treatment of lower respiratory tract bacterial infections caused by susceptible pathogens.

Comparison of Plasma and Intrapulmonary Concentrations of Nafithromycin (WCK 4873) in Healthy Adult Subjects

The nafithromycin concentrations in the plasma, epithelial lining fluid (ELF), and alveolar macrophages (AM) of 37 healthy adult subjects were measured following repeated dosing of oral nafithromycin at 800 mg once daily for 3 days. The values of noncompartmental pharmacokinetic (PK) parameters were determined from serial plasma samples collected over a 24-h interval following the first and third oral doses. Each subject underwent one standardized bronchoscopy with bronchoalveolar lavage (BAL) at 3, 6, 9, 12, 24, or 48 h after the third dose of nafithromycin. The mean ± standard deviation values of the plasma PK parameters after the first and third doses included maximum plasma concentrations (C_max) of 1.02 ± 0.31 μg/ml and 1.39 ± 0.36 μg/ml, respectively; times to C_max of 3.97 ± 1.30 h and 3.69 ± 1.28 h, respectively; clearances of 67.3 ± 21.3 liters/h and 52.4 ± 18.5 liters/h, respectively, and elimination half-lives of 7.7 ± 1.1 h and 9.1 ± 1.7 h, respectively. The values of the area under the plasma concentration-time curve (AUC) from time zero to 24 h postdosing (AUC_0-24) for nafithromycin based on the mean or median total plasma concentrations at BAL fluid sampling times were 16.2 μg · h/ml. For ELF, the respective AUC_0-24 values based on the mean and median concentrations were 224.1 and 176.3 μg · h/ml, whereas for AM, the respective AUC_0-24 values were 8,538 and 5,894 μg · h/ml. Penetration ratios based on ELF and total plasma AUC_0-24 values based on the mean and median concentrations were 13.8 and 10.9, respectively, whereas the ratios of the AM to total plasma concentrations based on the mean and median concentrations were 527 and 364, respectively. The sustained ELF and AM concentrations for 48 h after the third dose suggest that nafithromycin has the potential to be a useful agent for the treatment of lower respiratory tract infections. (This study has been registered at ClinicalTrials.gov under registration no. NCT02453529.).

Comparative Pharmacodynamics of Telavancin and Vancomycin in the Neutropenic Murine Thigh and Lung Infection Models against Staphylococcus aureus

The pharmacodynamics of telavancin and vancomycin were compared using neutropenic murine thigh and lung infection models. Four Staphylococcus aureus strains were included. The telavancin MIC ranged from 0.06 to 0.25 mg/liter, and the vancomycin MIC ranged from 1 to 4 mg/liter. The plasma pharmacokinetics of escalating doses (1.25, 5, 20, and 80 mg/kg of body weight) of telavancin and vancomycin were linear over the dose range. Epithelial lining fluid (ELF) pharmacokinetics for each drug revealed that penetration into the ELF mirrored the percentage of the free fraction (the fraction not protein bound) in plasma for each drug. Telavancin (0.3125 to 80 mg/kg/6 h) and vancomycin (0.3125 to 1,280 mg/kg/6 h) were administered by the subcutaneous route in treatment studies. Dose-dependent bactericidal activity against all four strains was observed in both models. A sigmoid maximum-effect model was used to determine the area under the concentration-time curve (AUC)/MIC exposure associated with net stasis and 1-log₁₀ kill relative to the burden at the start of therapy. The 24-h plasma free drug AUC (fAUC)/MIC values associated with stasis and 1-log kill were remarkably congruent. Net stasis for telavancin was noted at fAUC/MIC values of 83 and 40.4 in the thigh and lung, respectively, and 1-log kill was noted at fAUC/MIC values of 215 and 76.4, respectively. For vancomycin, the fAUC/MIC values for stasis were 77.9 and 45.3, respectively, and those for 1-log kill were 282 and 113, respectively. The 24-h ELF total drug AUC/MIC targets in the lung model were very similar to the 24-h plasma free drug AUC/MIC targets for each drug. Integration of human pharmacokinetic data for telavancin, the results of the MIC distribution studies, and the pharmacodynamic targets identified in this study suggests that the current dosing regimen of telavancin is optimized to obtain drug exposures sufficient to treat S. aureus infections.

Penetration of Ciprofloxacin and Amikacin into the Alveolar Epithelial Lining Fluid of Rats with Pulmonary Fibrosis

We determined the concentration-time profiles of ciprofloxacin and amikacin in serum and alveolar epithelial lining fluid (ELF) of rats with or without pulmonary fibrosis and investigated the effect of pulmonary fibrosis on the capacity for penetration of antimicrobials into the ELF of rats. Pulmonary fibrosis was induced in rats with a single intratracheal instillation of bleomycin. After intravenous injection of ciprofloxacin or amikacin, blood and bronchoalveolar lavage fluid samples were collected. Urea concentrations in serum and lavage fluid were determined using an enzymatic assay. Ciprofloxacin and amikacin concentrations were determined by high-performance liquid chromatography and liquid chromatography-tandem mass spectrometry, respectively. The mean ratio of ELF to plasma concentrations of ciprofloxacin at each time point in the normal group did not significantly differ from that in the pulmonary fibrosis group. However, the ratio of the ciprofloxacin area under the concentration-time curve from 0 to 24 h (AUC_0-24) in ELF to the AUC_0-24 in plasma was 1.02 in the normal group and 0.76 in the pulmonary fibrosis group. The mean ELF-to-plasma concentration ratios of amikacin at each time point in the normal group were higher than those in the pulmonary fibrosis group, reaching a statistically significant difference at 1, 2, and 4 h. The ratio of the AUC_0-24 in ELF to the AUC_0-24 in plasma was 0.49 in the normal group and 0.27 in the pulmonary fibrosis group. In conclusion, pulmonary fibrosis can influence the penetration of antimicrobials into the ELF of rats and may have a marked effect on the penetration of amikacin than that of ciprofloxacin.

Novel applications for a noninvasive sampling method of the nasal mucosa

Reliable methods for sampling the nasal mucosa provide clinical researchers with key information regarding respiratory biomarkers of exposure and disease. For quick and noninvasive sampling of the nasal mucosa, nasal lavage (NL) collection has been widely used as a clinical tool; however, limitations including volume variability, sample dilution, and storage prevent NL collection from being used in nonlaboratory settings and analysis of low abundance biomarkers. In this study, we optimize and validate a novel methodology using absorbent Leukosorb paper cut to fit the nasal passage to extract epithelial lining fluid (ELF) from the nasal mucosa. The ELF sampling method limits the dilution of soluble mediators, allowing quantification of both high- and low-abundance soluble biomarkers such as IL-1β, IL-8, IL-6, interferon gamma-induced protein 10 (IP-10), and neutrophil elastase. Additionally, we demonstrate that this method can successfully detect the presence of respiratory pathogens such as influenza virus and markers of antibiotic-resistant bacteria in the nasal mucosa. Efficacy of ELF collection by this method is not diminished in consecutive-day sampling, and percent recovery of both recombinant IL-8 and soluble mediators are not changed despite freezing or room temperature storage for 24 h. Our results indicate that ELF collection using Leukosorb paper sampling of ELF provides a sensitive, easy-to-use, and reproducible methodology to collect concentrated amounts of soluble biomarkers from the nasal mucosa. Moreover, the methodology described herein improves upon the standard NL collection method and provides researchers with a novel tool to assess changes in nasal mucosal host defense status.

Pooled population pharmacokinetic model of imipenem in plasma and the lung epithelial lining fluid

AIMS

Several clinical trials have confirmed the therapeutic benefit of imipenem for treatment of lung infections. There is however no knowledge of the penetration of imipenem into the lung epithelial lining fluid (ELF), the site of action relevant for lung infections. Furthermore, although the plasma pharmacokinetics (PK) of imipenem has been widely studied, most studies have been based on selected patient groups. The aim of this analysis was to characterize imipenem plasma PK across populations and to quantify imipenem ELF penetration.

METHODS

A population model for imipenem plasma PK was developed using data obtained from healthy volunteers, elderly subjects and subjects with renal impairment, in order to identify predictors for inter-individual variability (IIV) of imipenem PK. Subsequently, a clinical study which measured plasma and ELF concentrations of imipenem was included in order to quantify lung penetration.

RESULTS

A two compartmental model best described the plasma PK of imipenem. Creatinine clearance and body weight were included as subject characteristics predictive for IIV on clearance. Typical estimates for clearance, central and peripheral volume, and inter-compartmental clearance were 11.5 l h(-1) , 9.37 l, 6.41 l, 13.7 l h(-1) , respectively (relative standard error (RSE) <8%). The distribution of imipenem into ELF was described using a time-independent penetration coefficient of 0.44 (RSE 14%).

CONCLUSION

The identified lung penetration coefficient confirms the clinical relevance of imipenem for treatment of lung infections, while the population PK model provided insights into predictors of IIV for imipenem PK and may be of relevance to support dose optimization in various subject groups.

Ceftolozane/tazobactam pharmacokinetic/pharmacodynamic-derived dose justification for phase 3 studies in patients with nosocomial pneumonia

Ceftolozane/tazobactam is an antipseudomonal antibacterial approved for the treatment of complicated urinary tract infections (cUTIs) and complicated intra‐abdominal infections (cIAIs) and in phase 3 clinical development for treatment of nosocomial pneumonia. A population pharmacokinetic (PK) model with the plasma‐to‐epithelial lining fluid (ELF) kinetics of ceftolozane/tazobactam was used to justify dosing regimens for patients with nosocomial pneumonia in phase 3 studies. Monte Carlo simulations were performed to determine ceftolozane/tazobactam dosing regimens with a >90% probability of target attainment (PTA) for a range of pharmacokinetic/pharmacodynamic targets at relevant minimum inhibitory concentrations (MICs) for key pathogens in nosocomial pneumonia. With a plasma‐to‐ELF penetration ratio of approximately 50%, as observed from an ELF PK study, a doubling of the current dose regimens for different renal functions that are approved for cUTIs and cIAIs is needed to achieve >90% PTA for nosocomial pneumonia. For example, a 3‐g dose of ceftolozane/tazobactam for nosocomial pneumonia patients with normal renal function is needed to achieve a >90% PTA (actual 98%) for the 1‐log kill target against pathogens with an MIC of ≤8 mg/L in ELF, compared with the 1.5‐g dose approved for cIAIs and cUTIs.

Desferrioxamine inhibits protein tyrosine nitration: mechanisms and implications

Tissues are exposed to exogenous and endogenous nitrogen dioxide ((·)NO(2)), which is the terminal agent in protein tyrosine nitration. Besides iron chelation, the hydroxamic acid (HA) desferrioxamine (DFO) shows multiple functionalities including nitration inhibition. To investigate mechanisms whereby DFO affects 3-nitrotyrosine (3-NT) formation, we utilized gas-phase (·)NO(2) exposures, to limit introduction of other reactive species, and a lung surface model wherein red cell membranes (RCM) were immobilized under a defined aqueous film. When RCM were exposed to ()NO(2) covered by +/- DFO: (i) DFO inhibited 3-NT formation more effectively than other HA and non-HA chelators; (ii) 3-NT inhibition occurred at very low[DFO] for prolonged times; and (iii) 3-NT formation was iron independent but inhibition required DFO present. DFO poorly reacted with (·)NO(2) compared to ascorbate, assessed via (·)NO(2) reactive absorption and aqueous-phase oxidation rates, yet limited 3-NT formation at far lower concentrations. DFO also inhibited nitration under aqueous bulk-phase conditions, and inhibited 3-NT generated by active myeloperoxidase "bound" to RCM. Per the above and kinetic analyses suggesting preferential DFO versus (·)NO(2) reaction within membranes, we conclude that DFO inhibits 3-NT formation predominantly by facile repair of the tyrosyl radical intermediate, which prevents (·)NO(2) addition, and thus nitration, and potentially influences biochemical functionalities.

Possible impact of salivary influence on cytokine analysis in exhaled breath condensate

BACKGROUND

Exhaled breath condensate (EBC) is thought to contain substances of the lower airway epithelial lining fluid (ELF) aerosolized by turbulent flow. However, contamination by saliva may affect the EBC when collected orally.

OBJECTIVE

The purpose of this study was to compare the cytokine expression levels in EBC with those in saliva, and to clarify the influence of saliva on cytokine measurements of EBC.

METHODS

EBC and saliva samples were obtained from 10 adult subjects with stable asthma. To estimate differences in the contents of substances between EBC and saliva, the total protein concentration of each sample was measured. Further, we also measured the total protein concentration of ELF obtained from another patient group with suspected lung cancer using a micro sampling probe during bronchoscopic examination and roughly estimated the dilution of EBC by comparing the total protein concentration of EBC and ELF from those two patient groups. The cytokine expression levels of EBC and saliva from asthmatic group were assessed by a cytokine protein array.

RESULTS

The mean total protein concentrations in EBC, saliva and ELF were 4.6 microg/ml, 2,398 microg/ml and 14,111 microg/ml, respectively. The dilution of EBC could be estimated as 1:3000. Forty cytokines were analyzed by a cytokine protein array and each cytokine expression level of EBC was found to be different from that of saliva. Corrected by the total protein concentration, all cytokine expression levels of EBC were significantly higher than those of saliva.

CONCLUSION

These results suggest that the salivary influence on the cytokine assessment in EBC may be negligible.