Epithelial Lining Fluid Concentrations Research Articles

Pharmacokinetics of nebulized colistin methanesulfonate in critically ill patients

Optimal dosing for nebulized colistin methanesulfonate (CMS), the prodrug of colistin, is unknown. We describe the pulmonary and systemic pharmacokinetics of CMS and colistin following nebulization of 0.5 million IU (MIU) of CMS in ventilated patients. Twelve critically ill patients received 0.5 MIU of CMS administered every 8 h as 30 min nebulizations. Blood samples were collected immediately before and until 8 h after first nebulization; mini-bronchoalveolar lavage (mini-BAL) was performed at 1 and 5 h or 3 and 8 h (six patients each) post-dose. Pharmacokinetic analysis was performed for CMS and colistin plasma concentrations using a non-compartmental method. ClinicalTrials.gov: NCT01060891. After nebulization, CMS concentrations in epithelial lining fluid (ELF) were much higher (100- to 1000-fold) than those in plasma. Concentrations of colistin in ELF should be considered with caution because when <6 mg/L in BAL, colistin bound to mini-BAL devices. Nevertheless, CMS and colistin concentrations in ELF were much lower than expected from previous results with a 2 MIU dose. From CMS plasma pharmacokinetics it was shown that CMS systemic bioavailability was only slightly decreased for the 0.5 MIU dose compared with 2 MIU. This study shows that CMS concentrations were much higher (100- to 1000-fold) in ELF than in plasma after a 0.5 MIU aerosol of CMS, but much lower (10-fold) than expected from previous results with a 2 MIU dose. Therefore, until new pharmacokinetic and pharmacodynamic assessments of the treatment of ventilator-associated pneumonia with nebulized CMS are performed, the 2 MIU dose should be preferred to the 0.5 MIU dose.

Pharmacological indices and pulmonary distribution of rifampicin after repeated oral administration in healthy foals.

The treatment of equine lung infections by Rhodococcus equi with rifampicin is empirically based because pharmacokinetic/pharmacodynamic (PK/PD) indices and pivotal clinical outcome data are not available. To evaluate the pharmacokinetics and pulmonary distribution of rifampicin into epithelial lining fluid (ELF) and bronchoalveolar lavage cells (BALC) to predict antimicrobial activity in the lung using PK/PD indices. Controlled, randomised, two-period, crossover, repeated-dose study with an initial arm to measure disposition after i.v. administration of rifampicin. Pharmacokinetics and lung distribution were evaluated in six healthy foals treated with 10 mg/kg bwt rifampicin i.v. (initial arm) and with repeated oral doses of rifampicin at 10 mg/kg bwt and 20 mg/kg bwt once per day for 10 days (crossover arms). ELF and BALC were sampled by bronchoalveolar lavage 24 h after the last oral dosing. Rifampicin and 25-O-desacetyl rifampicin were quantified using liquid chromatography tandem-mass spectrometry. Enzyme induction by rifampicin was confirmed by evaluation of plasma 4β-OH-cholesterol:cholesterol ratios. The distribution volume of rifampicin administered i.v. was ~0.85 L/kg. Terminal elimination half-life was ~11 h. Orally given rifampicin was slowly absorbed (Tmax , range: 2.5-8.0 h) and eliminated with apparent half-lives of ~6-8 h. Trough concentrations in ELF and BALC were 1.01 ± 0.20 μg/mL and 1.25 ± 0.29 μg/mL, respectively, after 10 mg/kg bwt rifampicin and 2.71 ± 1.25 μg/mL and 3.09 ± 1.63 μg/mL, respectively, after 20 mg/kg bwt rifampicin. The average ratios of area under the plasma concentration time curve during an administration interval of 24 h (AUC0-24 h ) to minimum inhibitory concentration (MIC) were 145 and 322 h, respectively, for less susceptible strains of R. equi (MIC90 : 0.5 μg/mL). The clearance and bioavailability of rifampicin after repeated oral dosing were not evaluated. Treatment with rifampicin at 10 mg/kg bwt administered once per day is suitable to generate drug concentrations above the MIC90 in the ELF and BALC of foals. Future clinical studies with rifampicin in combination with macrolide antibiotics with low drug interaction potential are required to translate the PK/PD indices into protocols for the treatment of R. equi lung infections.

Bronchopulmonary pharmacokinetics of (R)-salbutamol and (S)-salbutamol enantiomers in pulmonary epithelial lining fluid and lung tissue of horses.

Salbutamol is usually administered as a racemic mixture but little is known about the enantioselectivity of salbutamol pharmacokinetics in the lung. This study was designed to investigate enantiomer concentrations in lung tissue after inhaled dosing. Horses (n=12) received racemic salbutamol 1000 μg via inhalation. Enantioselective ultra performance liquid chromatography-tandem mass spectrometry was used to determine salbutamol concentrations in pulmonary epithelial lining fluid (PELF) sampled 2, 5, 10 and 15min after administration, in central lung (endoscopic bronchial biopsy) and peripheral lung (percutaneous pulmonary biopsy) tissues (at 20 and 25min respectively), and in plasma samples. Mean±95% confidence interval (CI) yield of PELF was 57±10mg. Initial mean±95%CI (R)- and (S)-salbutamol PELF concentrations were 389±189ngg-1 and 378±177ngg-1 respectively, and both reduced approximately 50% by 15min. Mean±95%CI central lung levels of drug were higher than peripheral lung tissue for both (R)-salbutamol (875±945 vs. 49.5±12ngg-1 ) and (S)-salbutamol (877±955 vs. 50.9±12ngg-1 ) respectively. There was no evidence of enantioselectivity in PELF or central lung but minor (~2%) enantioselectivity was observed in the peripheral lung. Enantioselectivity was clearly evident in plasma with (S):(R) ratio of 1.25 and 1.14 for both area under the concentration-time curve (0-25min) and Cmax respectively. PELF sampling in horses offers sufficient yield allowing direct detection of drug and, combined with tissue sampling, is a valuable model to investigate bronchopulmonary pharmacokinetics. Salbutamol did not demonstrate enantioselectivity in PELF or central lung tissue uptake following acute dosing, however, enantioselective plasma concentrations were demonstrated, with minor enantioselectivity in the peripheral lung.

Substantial Targeting Advantage Achieved by Pulmonary Administration of Colistin Methanesulfonate in a Large-Animal Model.

Colistin, administered as its inactive prodrug colistin methanesulfonate (CMS), is often used in multidrug-resistant Gram-negative pulmonary infections. The CMS and colistin pharmacokinetics in plasma and epithelial lining fluid (ELF) following intravenous and pulmonary dosing have not been evaluated in a large-animal model with pulmonary architecture similar to that of humans. Six merino sheep (34 to 43 kg body weight) received an intravenous or pulmonary dose of 4 to 8 mg/kg CMS (sodium) or 2 to 3 mg/kg colistin (sulfate) in a 4-way crossover study. Pulmonary dosing was achieved via jet nebulization through an endotracheal tube cuff. CMS and colistin were quantified in plasma and bronchoalveolar lavage fluid (BALF) samples by high-performance liquid chromatography (HPLC). ELF concentrations were calculated via the urea method. CMS and colistin were comodeled in S-ADAPT. Following intravenous CMS or colistin administration, no concentrations were quantifiable in BALF samples. Elimination clearance was 1.97 liters/h (4% interindividual variability) for CMS (other than conversion to colistin) and 1.08 liters/h (25%) for colistin. On average, 18% of a CMS dose was converted to colistin. Following pulmonary delivery, colistin was not quantifiable in plasma and CMS was detected in only one sheep. Average ELF concentrations (standard deviations [SD]) of formed colistin were 400 (243), 384 (187), and 184 (190) mg/liter at 1, 4, and 24 h after pulmonary CMS administration. The population pharmacokinetic model described well CMS and colistin in plasma and ELF following intravenous and pulmonary administration. Pulmonary dosing provided high ELF and low plasma colistin concentrations, representing a substantial targeting advantage over intravenous administration. Predictions from the pharmacokinetic model indicate that sheep are an advantageous model for translational research.

Pharmacodynamic and pharmacokinetic profiling of delafloxacin in a murine lung model against community-acquired respiratory tract pathogens

Increasing antimicrobial resistance in community-acquired pneumonia (CAP) pathogens has contributed to infection-related morbidity and mortality. Delafloxacin is a novel fluoroquinolone with broad-spectrum activity against Gram-positive and -negative organisms, including Streptococcus pneumoniae and methicillin-resistant Staphylococcus aureus (MRSA). This study aimed to define the pharmacodynamic profile of delafloxacin against CAP pathogens using a neutropenic murine lung infection model. Five S. pneumoniae, 2 methicillin-susceptible S. aureus (MSSA), 2 MRSA and 2 Klebsiella pneumoniae isolates were studied. Delafloxacin doses varied from 0.5 mg/kg/day to 640 mg/kg/day and were given as once-daily to every 3 h regimens over the 24-h treatment period. Efficacy was measured as the change in log10 CFU at 24 h compared with 0-h controls. Plasma and bronchopulmonary pharmacokinetic studies were conducted. Delafloxacin demonstrated potent in vitro and in vivo activity. Delafloxacin demonstrated high penetration into the lung compartment, as epithelial lining fluid concentrations were substantially higher than free drug in plasma. The ratio of the area under the free drug concentration–time curve to the minimum inhibitory concentration of the infecting organism (fAUC/MIC) was the parameter that best correlated with the efficacy of the drug, and the magnitude required to achieve 1 log10 CFU reduction was 31.8, 24.7, 0.4 and 9.6 for S. pneumoniae, MRSA, MSSA and K. pneumoniae, respectively. The observed in vivo efficacy of delafloxacin was supported by the high pulmonary disposition of the compound. The results derived from this pre-clinical lung model support the continued investigation of delafloxacin for the treatment of community-acquired lower respiratory tract infections.

Comparative pharmacokinetics of minocycline in foals and adult horses.

The objective of this study was to compare the pharmacokinetics of minocycline in foals vs. adult horses. Minocycline was administered to six healthy 6-to 9-week-old foals and six adult horses at a dose of 4mg/kg intragastrically (IG) and 2mg/kg intravenously (i.v.) in a cross-over design. Five additional oral doses were administered at 12-h intervals in foals. A microbiologic assay was used to measure minocycline concentration in plasma, urine, synovial fluid, and cerebrospinal fluid (CSF). Liquid chromatography-tandem mass spectrometry was used to measure minocycline concentrations in pulmonary epithelial lining fluid (PELF) and bronchoalveolar (BAL) cells. After i.v. administration to foals, minocycline had a mean (±SD) elimination half-life of 8.5±2.1h, a systemic clearance of 113.3±26.1mL/h/kg, and an apparent volume of distribution of 1.24±0.19L/kg. Pharmacokinetic variables determined after i.v. administration to adult horses were not significantly different from those determined in foals. Bioavailability was significantly higher in foals (57.8±19.3%) than in adult horses (32.0±18.0%). Minocycline concentrations in PELF were higher than in other body fluids. Oral minocycline dosed at 4mg/kg every 12h might be adequate for the treatment of susceptible bacterial infections in foals.

Biopharmaceutical Characterization of Nebulized Antimicrobial Agents in Rats: 5. Oseltamivir Carboxylate.

The aim of this study was to determine the biopharmaceutical characteristics of oseltamivir carboxylate (OC) after pulmonary delivery. After OC bolus and intratracheal nebulization (NEB) in rats, blood was collected and bronchoalveolar lavages (BALs) were performed. Epithelial lining fluid (ELF) concentrations were estimated from BAL fluid. The area under the curve (AUC) ratio for ELF to plasma was 842 times higher after NEB than after intravenous (i.v.) administration, indicating that OC nebulization offers a biopharmaceutical advantage over i.v. administration.

Pharmacokinetics of intravenous peramivir in the airway epithelial lining fluid of healthy volunteers.

Some subtypes of influenza virus, such as H5N1 and H7N9, cause severe viral pneumonia, for which the intraluminal concentration of the anti-influenza agent in the airway is critical. However, the pharmacokinetics of peramivir, the only available injectable neuraminidase inhibitor formulation, in the airway epithelial lining fluid (ELF) remains unclear. In this study, we aimed to determine the time course of peramivir in the pharyngeal ELF, bronchial ELF and plasma of healthy volunteers using bronchoscopic microsampling technique. Six healthy volunteers were studied. After baseline plasma sampling, 0.3 g peramivir was intravenously injected over 0.5 h. ELF was obtained from the upper and lower airways using bronchoscopic microsampling at the end of the infusion (0.5 h) and after 1.0, 1.5, 2.0, 2.5, 3.0, 4.0 and 5.0 h. The concentrations of peramivir in the ELFs and in the plasma were quantified by LC/MS/MS analysis. The mean maximum concentration (Cmax) in pharyngeal ELF, bronchial ELF and plasma was 1.20 ±0.42, 9.60 ±2.30 and 50.52 ±17.51 ng/ml, respectively. The penetration ratio at Cmax in pharyngeal and bronchial ELFs was 2.4 and 19.0, respectively. The ratio of the area under the curve from 0 to infinity in pharyngeal and bronchial ELFs was 4.8 and 39.1 mg•min/l, respectively. The time course of peramivir concentration in the ELFs revealed that concentrations above the 50% inhibitory concentration value of influenza were achieved in the upper and lower airways. Therefore, peramivir could be an important treatment option for influenza viral pneumonia.

Structure-Based Prediction of Anti-infective Drug Concentrations in the Human Lung Epithelial Lining Fluid.

Obtaining pharmacologically relevant exposure levels of antibiotics in the epithelial lining fluid (ELF) is of critical importance to ensure optimal treatment of lung infections. Our objectives were to develop a model for the prediction of the ELF-plasma concentration ratio (EPR) of antibiotics based on their chemical structure descriptors (CSDs). EPR data was obtained by aggregating ELF and plasma concentrations from historical clinical studies investigating antibiotics and associated agents. An elastic net regularized regression model was used to predict EPRs based on a large number of CSDs. The model was tuned using leave-one-drug-out cross validation, and the predictions were further evaluated using a test dataset. EPR data of 56 unique compounds was included. A high degree of variability in EPRs both between- and within drugs was apparent. No trends related to study design or pharmacokinetic factors could be identified. The model predicted 80% of the within-drug variability (R(2) WDV) and 78.6% of drugs were within 3-fold difference from the observations. Key CSDs were related to molecular size and lipophilicity. When predicting EPRs for a test dataset the R(2) WDV was 75%. This model is of relevance to inform dose selection and optimization during antibiotic drug development of agents targeting lung infections.

Biopharmaceutical Characterization of Nebulized Antimicrobial Agents in Rats: 3. Tobramycin.

The aim of this study was to determine the biopharmaceutical characteristics of tobramycin (TOB) after nebulization in rats. TOB was administered by intravenous (i.v.) bolus or intratracheal nebulization (3 mg · kg(-1)), and concentrations were determined in plasma and epithelial lining fluid (ELF) by liquid chromatography-tandem mass spectrometry. The ratio of the TOB concentration in ELF to the plasma area under the curve (AUC) was more than 200 times as high after NEB as after i.v. bolus administration, indicating that TOB nebulization offers a biopharmaceutical advantage over i.v. administration.

Pulmonary delivery of pyrazinamide-loaded large porous particles

We have improved the aerodynamic properties of pyrazinamide loaded large porous particles (PZA-LPPs) designed for pulmonary delivery. To overcome the segregation of the different components occurring during the spray drying process and to obtain homogeneous LPPs, spray drying parameters were modified to decrease the drying speed. As a result, good aerodynamic properties for lung delivery were obtained with a fine particle fraction (FPF) of 40.1±1.0%, an alveolar fraction (AF) of 29.6±3.1%, a mass median aerodynamic diameter (MMADaer) of 4.1±0.2μm and a geometric standard deviation (GSD) of 2.16±0.16. Plasma and epithelial lining fluid (ELF) concentrations of pyrazinamide were evaluated after intratracheal insufflation of PZA-LPPs (4.22mgkg−1) into rats and compared to intravenous administration (iv) of a pyrazinamide solution (5.82mgkg−1). The in vivo pharmacokinetic evaluation of PZA-LPPs in rats reveals that intratracheal insufflation of PZA-LPPs leads to a rapid absorption in plasma with an absolute bioavailability of 66%. This proves that PZA-LPPs dissolve fast upon deposition and that PZA crosses efficiently the lung barrier to reach the systemic circulation. PZA concentrations were 1.28-fold higher in ELF after intratracheal administration than after iv administration and the ratio of ELF concentrations over plasma concentrations was 2-fold greater. Although these improvements are moderate, lung delivery of PZA appears an interesting alternative to oral delivery of the molecule and should now be tested in an infected animal model to evaluate its efficacy against Mycobacterium tuberculosis.

370. F/HN Pseudotyped Lentivirus Generates Therapeutically Relevant and Long-Lasting Alpha-1-Antitrypsin Expression in Mouse Lung

A protease/anti-protease imbalance is a characteristic feature of inflammatory lung diseases such as cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD). However, alpha-1-antitrypsin (AAT) enzyme replacement therapy (ERT) trials have not shown conclusive evidence of a therapeutic benefit. This may be due to inefficient protein delivery to the lung and/or the half-life of the protein. The UK Cystic Fibrosis Gene Therapy Consortium (GTC) has pseudotyped a simian immunodeficiency viral vector with the Sendai virus F and HN proteins (rSIV.F/HN) and selected an internal synthetic promoter/enhancer consisting of the elongation factor 1α promoter and the CMV enhancer (hCEF) for efficient transduction of airway epithelial cells. Here, we assessed whether transduction of murine lungs with rSIV.F/HN with a human AAT transgene generates therapeutic levels of AAT. Mice were transduced with rSIV.F/HN-hCEF-AAT (2e8 TU/mouse) by nasal instillation and culled 10 days after transduction. AAT levels in lung homogenate and broncho-alveolar lavage fluid (BALF) were at least 3 logs above controls (p<0.05). A urea assay was used to determine that lavage diluted the epithelial lining fluid (ELF) by ≈40-fold, which allowed us to calculate the AAT concentration in ELF to be 92±28 mg/ml (= 1.4 μμ). In the context of AAT deficiency, an ELF concentration of 70 mg/ml (1.1 μM) AAT is of therapeutic relevance. For comparison transfection of mouse lung with the cationic lipid GL67A complexed to pCMV-AAT only led to 0.4±0.1 mg/ml (n=6) of AAT in ELF. A neutrophil elastase (NE) activity assay showed that the recombinant AAT successfully neutralised NE activity (p<0.05). In a separate experiment, mice were treated with rSIV.F/HN-hCEF-AAT (4e7 TU/mouse) and quantification of AAT 7 and 90 days post-transduction showed that expression was stable over this period. We also transduced mice with rSIV.F/HN-hCEF carrying a secreted Gaussia luciferase reporter gene (1e7 TU/mouse) and showed that stable expression in lung and BALF persisted for at least 12 months. Here, we also demonstrate for the first time that rSIV.F/HN transduction of lung generates significant (p<0.05) levels of GLux and AAT recombinant proteins in serum. AAT enzyme replacement therapy is currently being assessed for the treatment of a range of diseases including diabetes and graft-vs-host disease, but shortage of human plasma-derived protein, as well as high costs, may limit the application. In conclusion, rSIV.F/HN produces therapeutically relevant and long lasting levels of AAT in murine lung. In addition, we showed that AAT escapes from the lung into the circulation, suggesting that gene therapy may help to overcome some of the current bottlenecks of ERT.

Presence of infection influences the epithelial lining fluid penetration of oral levofloxacin in adult patients

Although epithelial lining fluid (ELF) is the presumed site for pulmonary infections, most antibiotic penetration studies are conducted in uninfected patients or healthy volunteers. Levofloxacin concentrations in plasma and ELF were collected from two previous studies involving 18 infected patients with acute exacerbations of chronic bronchitis and 15 uninfected elderly patients undergoing diagnostic bronchoscopy. Concentration data were population modelled using the BigNPAG algorithm, and a 5000-patient Monte Carlo simulation was conducted to simulate ELF exposure for a dosing regimen 750mg every 24h for five doses in plasma and ELF of infected versus uninfected patients. Mean±S.D. model parameters for plasma in infected patients were similar to uninfected patients (volume of central compartment, 68.4±36.3 vs. 50.2±17.3L; clearance, 6.0±2.5 vs. 6.8±3.3L/h; and absorption rate, 5.4±2.5 vs. 4.7±2.7h−1), resulting in similar simulated AUC in plasma (infected, 140.5±54.8 vs. uninfected, 133.7±61.6μgh/mL). The volume of ELF was 57.2±25.0 and 14.8±9.0L in infected and uninfected patients, respectively, resulting in a lower simulated AUCELF exposure for infected patients (189.1±210.5 vs. 461.0±558.7μgh/mL). Penetration ratios for infected and uninfected patients were, respectively, 1.4±1.8 and 3.5±3.7, with median values of 0.9 and 2.4. ELF penetration in infected patients was approximately one-half that of uninfected adults. These data highlight the importance of confirming exposure in infected patients to further support dosage regimen selection.

Modelled target attainment after meropenem infusion in patients with severe nosocomial pneumonia: the PROMESSE study

The objective of this study was to propose an optimal treatment regimen of meropenem in critically ill patients with severe nosocomial pneumonia. Among 55 patients in intensive care treated with 1 g of meropenem every 8 h for severe nosocomial pneumonia, 30 were assigned to intermittent infusion (II; over 0.5 h) and 25 to extended infusion (EI; over 3 h) groups. Based on plasma and epithelial lining fluid (ELF) concentrations determined at steady-state, pharmacokinetic modelling and Monte Carlo simulations were undertaken to assess the probability of attaining drug concentrations above the MIC for 40%-100% of the time between doses (%T > 1-fold and 4-fold MIC), for 1 or 2 g administered by either method. Penetration ratio, measured by the ELF/plasma ratio of AUCs, was statistically higher in the EI group than in the II group (mean ± SEM: 0.29 ± 0.030 versus 0.20 ± 0.033, P = 0.047). Considering a maximum susceptibility breakpoint of 2 mg/L, all dosages and modes of infusions achieved 40%-100% T > 1-fold MIC in plasma, but none did so in ELF, and only the 2 g dose over EI achieved 40%-100% T > 4-fold MIC in plasma. The optimum regimen to treat severe nosocomial pneumonia was 2 g of meropenem infused over 3 h every 8 h. This regimen achieved the highest pharmacodynamic targets both in plasma and in ELF.

Colistin and anti-Gram-positive bacterial agents against Acinetobacter baumannii.

Acinetobacter baumannii has attained an alarming level of resistance to antibacterial drugs. Clinicians are now considering the use of older agents or unorthodox combinations of licensed drugs against multidrug-resistant strains to bridge the current treatment gap. We investigated the in vitro activities of combination treatments that included colistin with vancomycin, norvancomycin or linezolid against multidrug-resistant Acinetobacter baumannii. The fractional inhibitory concentration index and time-kill assays were used to explore the combined effects of colistin with vancomycin, norvancomycin or linezolid against 40 clinical isolates of multidrug-resistant Acinetobacter baumannii. Transmission electron microscopy was performed to evaluate the interactions in response to the combination of colistin and vancomycin. The minimum inhibitory concentrations (MICs) of vancomycin and norvancomycin for half of the isolates decreased below the susceptibility break point, and the MIC of linezolid for one isolate was decreased to the blood and epithelial lining fluid concentration using the current dosing regimen. When vancomycin or norvancomycin was combined with subinhibitory doses of colistin, the multidrug-resistant Acinetobacter baumannii test samples were eradicated. Transmission electron microscopy revealed that subinhibitory doses of colistin were able to disrupt the outer membrane, facilitating a disruption of the cell wall and leading to cell lysis. Subinhibitory doses of colistin significantly enhanced the antibacterial activity of vancomycin, norvancomycin, and linezolid against multidrug-resistant Acinetobacter baumannii.

Pharmacokinetics of arbekacin in bronchial epithelial lining fluid of healthy volunteers.

Arbekacin is a unique aminoglycoside antibiotic with anti-methicillin-resistant Staphylococcus aureus activity. The efficacy of aminoglycosides is related to their serum maximum concentration. Local concentration of antibiotics in pulmonary epithelial lining fluid, rather than its serum concentration, can help determine its clinical efficacy more precisely for treatment of respiratory infectious disease. The objective of this study was to sequentially measure arbekacin concentration in epithelial lining fluid after infusion of a single clinically available dose. After the initial blood sampling, arbekacin was intravenously infused into 6 healthy volunteers over 1h. Epithelial lining fluid and serum samples were collected by bronchoscopic microsampling 1, 1.5, 2, 2.5, 3, 4, 5, and 6h after the start of 200mg arbekacin infusion. Each probe sampled 10.1±5.2μl bronchial epithelial lining fluid. The sample dilution factor was 266.7±157.1. Drug concentration was successfully measured in all but 2 of the epithelial lining fluid samples. The maximum concentration of arbekacin in epithelial lining fluid and serum was 10.4±1.9μg/ml and 26.0±12.2μg/ml, respectively. The ratio of the maximum drug concentration in the epithelial lining fluid to that in the serum was 0.47±0.19. The maximum concentration of epithelial lining fluid reached levels that would effectively treat most clinical strains of methicillin-resistant S. aureus.

Immunomodulatory effect of linezolid on methicillin-resistant Staphylococcus aureus supernatant-induced MUC5AC overexpression in human airway epithelial cells.

Linezolid is the first member of the oxazolidinones and is active against drug-resistant Gram-positive pathogens, such as methicillin-resistant Staphylococcus aureus (MRSA). Additionally, linezolid shows an immunomodulatory effect, such as inhibition of inflammatory cytokine production. In this study, we examined the effect of linezolid on MRSA-induced MUC5AC overexpression in airway epithelial cells. In this study, an MRSA supernatant was used to avoid the direct effect of linezolid on MRSA. MUC5AC protein production was significantly increased with a 40-fold dilution of MRSA supernatant. At the mRNA level, MUC5AC gene expression was significantly increased 6 and 9 h after stimulation. In an inhibition study, linezolid significantly reduced MRSA-induced MUC5AC protein and mRNA overexpression at concentrations of 5 and 20 μg/ml, which were the same as the trough and peak concentrations in human epithelial lining fluid. In an analysis of cell signaling, among the mitogen-activated protein kinase inhibitors, only the extracellular signal-regulated protein kinase 1/2 (ERK1/2) inhibitor reduced the MUC5AC protein production to the same level as that of the control; on Western blot analysis, only ERK1/2 was phosphorylated by the MRSA supernatant. In addition, the ERK1/2 phosphorylation was inhibited by linezolid. MUC5AC and MUC5B are the major barrier that traps inhaled microbial organisms, particulates, and foreign irritants. However, in patients with chronic respiratory diseases, pathogen-induced MUC5AC overexpression causes many problems, and control of the overexpression is important. Thus, this study revealed that linezolid showed a direct immunomodulatory effect in airway epithelial cells.

Interpretation of Epithelial Lining Fluid Concentrations of Antibiotics against Methicillin Resistant Staphylococcus aureus.

Although antibiotics whose epithelial lining fluid (ELF) concentrations are reported high tend to be preferred in treatment of pneumonia, measurement of ELF concentrations of antibiotics could be misled by contamination from lysis of ELF cells and technical errors of bronchoalveolar lavage (BAL). In this review, ELF concentrations of anti-methicillin resistant Staphylococcus aureus (MRSA) antibiotics were interpreted considering above confounding factors. An equation used to explain antibiotic diffusion into CSF (cerebrospinal fluid) was adopted: ELF/free serum concentration ratio = 0.96 + 0.091 × ln (partition coefficient / molecular weight1/2). Seven anti-MRSA antibiotics with reported ELF concentrations were fitted to this equation to see if their ELF concentrations were explainable by the penetration capacity only. Then, outliers were modeled under the assumption of varying contamination from lysed ELF cells (test range 0-10% of ELF volume). ELF concentrations of oritavancin, telavancin, tigecycline, and vancomycin were well described by the diffusion equation, with or without additional impact from cell lysis. For modestly high ELF/free serum concentration ratio of linezolid, technical errors of BAL should be excluded. Although teicoplanin and iclaprim showed high ELF/free serum ratios also, their protein binding levels need to be cleared for proper interpretation. At the moment, it appears very premature to use ELF concentrations of anti-MRSA antibiotics as a relevant guide for treatment of lung infections by MRSA.

Intrapulmonary concentration of levofloxacin in patients with idiopathic pulmonary fibrosis

Patients with idiopathic pulmonary fibrosis (IPF) have significantly impaired pulmonary diffusion, which may affect the pulmonary concentration of many drugs, including antibiotics. In this study, we compared the difference in pulmonary levofloxacin (LVFX) concentration between patients with normal lung function and IPF. The IPF group included 10 patients with a proven diagnosis of IPF and a diffusing capacity for carbon monoxide ranging from 40% to 70% of predicted values. The control group included 10 patients with normal pulmonary function. Blood and bronchoalveolar lavage fluid (BALF) were taken at 3–3.5 h after fasting. LVFX (500 mg) was administered orally. LVFX concentrations in the serum and BALF were determined using HPLC-MS/MC. The level of LVFX in alveolar epithelial lining fluid (ELF) was calculated using the following formula: LVFX ELF = LVFX BALF × (Urea serum/Urea BALF). No significant differences in age, body weight, height, and calculated creatinine clearance and BALF retrieval rate were observed between groups. LVFX serum concentrations in the IPF and control groups were (5.97 ± 1.28) μg/ml and (6.84 ± 3.43) μg/ml, respectively (P = 0.4727). ELF concentration of LVFX in the control group was (27.81 ± 21.36) μg/ml, while the concentration in the IPF group was (10.17 ± 2.46) μg/ml, less than half of that in the controls (P = 0.0058). The intrapulmonary concentration of LVFX in IPF patients was lower than those with normal lung function. Notably, however, the ELF LVFX concentration following 500 mg once-daily exceeded the MIC90 of common respiratory pathogens. Excellent antibacterial efficacy of LVFX can be expected for IPF patients in the treatment of respiratory tract infections.

Plasma and pulmonary pharmacokinetics of desfuroylceftiofur acetamide after weekly administration of ceftiofur crystalline free acid to adult horses

Current labelling for the use of ceftiofur crystalline free acid (CCFA) in horses states that 2 i.m. doses must be administered 4 days apart to provide 10 days of therapeutic coverage. A 10 day treatment regimen is not sufficient for the long-term treatment of horses with severe lung consolidation or pleuropneumonia. There are currently no data to guide an appropriate dosing interval when a longer treatment regimen is warranted. To determine steady-state plasma and pulmonary epithelial lining fluid (PELF) concentrations of desfuroylceftiofur acetamide (DCA) after weekly i.m. administration of CCFA to adult horses. Experimental study. Seven adult horses received i.m. CCFA at a dose of 6.6 mg/kg bwt on Day 0, Day 4 and every 7 days thereafter for 3 additional doses. Concentrations of DCA in plasma and PELF were measured at various time intervals. After weekly i.m. administration, the mean (± s.d.) steady-state peak DCA concentration in plasma (2.87 ± 1.50 μg/ml) was significantly higher than that in PELF (0.84 ± 0.53 μg/ml). Mean terminal half-lives in plasma (77.5 ± 17.5 h) and PELF (92.8 ± 59.0 h) were not significantly different. Concentrations of DCA in plasma and PELF remained in the therapeutic range for the entire dosing interval. After the initial 2-dose regimen 4 days apart, weekly i.m. administration of CCFA was well tolerated and resulted in plasma and PELF DCA concentrations above the minimal inhibitory concentration that inhibits growth of at least 90% of common lower respiratory tract pathogens of horses. Weekly administration of CCFA would appear appropriate when a treatment regimen longer than 10 days is warranted based on clinical signs and disease severity.