Epithelial Lining Fluid Concentrations Research Articles

1379. Determination of the Arbekacin Exposure Required to Prevent Amplification of Resistant Subpopulations Using Patient Pharmacokinetics Simulated in a Hollow-Fiber Infection Model (HFIM)

BackgroundME1100 (arbekacin inhalational solution) is an aminoglycoside in clinical development for the treatment of patients with hospital-acquired and ventilator-associated bacterial pneumonia (HABP and VABP, respectively). Due to the increase in resistance of Staphylococcus aureus and Pseudomonas aeruginosa to many antimicrobial agents, it is important to understand the relationships between amplification of drug resistance and each of drug exposure and therapy duration. The objective of the studies described herein was to utilize the HFIM to determine the arbekacin exposure after ME1100 administration required to prevent the emergence of drug-resistant subpopulations.MethodsDuplicate 10-day HFIM assays were completed in which arbekacin total-drug epithelial lining fluid (ELF) concentration–time profiles following inhalational administration of ME1100 every 12 hours were simulated. Four isolates, two methicillin-resistant S. aureus (Arbekacin MIC = 1 mg/L), and two P. aeruginosa (Arbekacin MIC = 4 mg/L), were exposed to total-drug ELF area under the concentration–time curve (AUC) values ranging from 217 to 25,053 mg hour/L, which were simulated using two different half-lives, 1 hour (α) and 6.93 hours (β). The initial bacterial burden was 1.0 × 108 CFU/mL. Samples were collected for enumeration of both the total and drug-resistant bacterial burdens and evaluation of pharmacokinetic samples using LC/MS–MS.ResultsTotal-drug ELF AUC:MIC ratios required to prevent amplification of MRSA and P. aeruginosa resistance in the HFIM over 10 days were 1,512 and 2,942, respectively. The higher AUC:MIC ratio required to prevent resistance for P. aeruginosa was most likely due to the presence of a small colony variant population. The relationship between total-drug ELF AUC:MIC ratio and change in log10 CFU from baseline of the drug-resistant sub-populations found on agar plates on Day 10 took the form of an inverted-U for three pathogens and a step-function for one (Figure 1).ConclusionThese data, which address the goal of considering arbekacin exposures that prevent the development of on-therapy resistance in a clinical setting, will help to provide guidance for future ME1100 dose selection for the treatment of patients with HABP/VABP.Disclosures B. D. VanScoy, Meiji Seika Pharma Co. Ltd.: Research Contractor, Research support. E. A. Lakota, Meiji Seika Pharma Co. Ltd.: Research Contractor, Research support. S. M. Bhavnani, Meiji Seika Pharma Co. Ltd.: Research Contractor, Research support. G. Giesel, Meiji Seika Pharma Co. Ltd.: Research Contractor, Research support. A. I. Carranco, Meiji Seika Pharma Co. Ltd.: Research Contractor, Research support. Y. Nagira, Meiji Seika Pharma Co. Ltd.: Employee, Salary. S. Ouchi, Meiji Seika Pharma Co. Ltd.: Employee, Salary. K. Kondo, Meiji Seika Pharma Co. Ltd.: Employee, Salary. P. G. Ambrose, Meiji Seika Pharma Co. Ltd.: Research Contractor, Research support.

1398. β-Lactam Probability of Target Attainment (PTA) and Penetration into Epithelial Lining Fluid (ELF) Based on Multiple Bronchoalveolar Lavage (BAL) Sampling Time Points in a Swine Pneumonia Model

BackgroundDefining ELF concentrations is desired for antibiotics developed for pneumonia. For ethical reasons, BAL sampling in humans is routinely done at a single time point, thereby creating ambiguity in the precise ELF profile. It is unknown if additional sampling of the ELF would lead to more accurate estimates of exposure. The swine pneumonia model was used to characterize the full ELF profiles (5-BAL) of two β-lactams for comparison with models employing 1-BAL (1B) and 2-BAL (2B) sampling time points only.MethodsSixteen ventilated swine were infected with Pseudomonas aeruginosa to establish pneumonia and then treated for 72 hours with ceftolozane/tazobactam (C/T) 50 mg/kg q8h (n = 8) or piperacillin/tazobactam (TZP) 200 mg/kg q8h (n = 8). Plasma and BAL concentrations were measured in each swine at 1, 2, 4, 6, and 8 hours after the first dose. Urea correction was used to calculate ELF values. Ceftolozane and piperacillin plasma and ELF data were fitted to a two compartment model using the nonparametric adaptive grid program in Pmetrics. Hypothetical models were refitted after randomly selecting either 1B or 2B sampling time points from each swine. A 5,000 subject Monte-Carlo simulation was performed for each model to define PTA (60% free time above the MIC) and ELF penetration [area under the curve in ELF (AUCELF) vs. free AUCplasma]. The KS-test was used to analyze distribution differences, reporting maximum vertical deviation (D) as percent difference; D < 20% was defined as negligible.ResultsThirty-two C/T and 34 TZP plasma samples and 29 and 32 BAL samples were available for the full model, respectively; 1B and 2B sampling models used eight and 16 BAL samples. All models adequately fitted the data. C/T PTA at 4 mg/L was 94.8, 96.1, and 98.0%, for the full, 1B and 2B models. TZP PTA at 16 mg/L was 55.8, 46.8, and 46.7%, respectively. C/T median [interquartile range] penetration differences were negligible between the full (65% [25––109]) and 1B (72% [45––125], D = 15%) or 2B models (62% [32––111], D = 6%). TZP penetration differences were also minimal between the full (32% [9––67]) and 1B (17% [5––49], D = 18%) or 2B models (27% [9––44], D = 15%).ConclusionThese data suggest that antibiotic ELF models constructed from a single BAL time point result in similar exposure estimates to full ELF profiles.Disclosures G. Li Bassi, MSD: Grant Investigator, Grant recipient. A. Torres, MSD: Grant Investigator, Grant recipient.

Biopharmaceutical Characterization of Nebulized Antimicrobial Agents in Rats: 6. Aminoglycosides.

Amikacin and gentamicin pharmacokinetic behaviors after nebulization were determined by comparing plasma and pulmonary epithelial lining fluid (ELF) concentrations in rats after intratracheal and intravenous administrations. ELF areas under concentration-time curve were 874 and 162 times higher after nebulization than after intravenous administration for amikacin and gentamicin, respectively. Even if both molecules appear to be good candidates for nebulization, these results demonstrate a much higher targeting advantage of nebulization for amikacin than for gentamicin.

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 (AUC0-8) for plasma, ELF, and AM using mean and median concentrations at each BAL sampling time. The plasma maximum concentration of drug (Cmax) and AUC values of cefepime and zidebactam increased by 8% to 9% after the seventh versus the first dose of WCK 5222. The respective AUC0-8 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 AUC0-8 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.

Anti-Proteases and Alpha-1 Antitrypsin Augmentation Therapy.

Alpha-1 antitrypsin deficiency is a genetic disease that first highlighted the importance of protease balance in normal lung homeostasis. Proteases such as neutrophil elastase are important in many pulmonary diseases. However, the first commercially licensed anti-protease therapy was used for emphysema in alpha-1 antitrypsin deficiency. The 4 commercial alpha-1 protease inhibitor preparations in the United States are currently given intravenously to augment the serum and alveolar epithelial lining fluid concentrations of alpha-1 antitrypsin. Since the discovery of alpha-1 antitrypsin deficiency in 1963, many genetic polymorphisms of the SERPINA1 gene have been discovered. Because neutrophilic inflammation is the hallmark of usual COPD, anti-protease therapy also has been explored in this disease. Further trials with different dosing schema, inhaled therapy, and in different disease states are all ongoing. These studies would be facilitated by having COPD outcomes that are independent of measurement of air flow and achievable in smaller populations over a short period of time.

Pharmacodynamics of inhaled amikacin (BAY 41-6551) studied in an in vitro pharmacokinetic model of infection

The pharmacodynamics of inhaled antimicrobials are poorly studied. Amikacin is being developed for inhalational therapy as BAY 41-6551. We employed an in vitro pharmacokinetic model to study the pharmacokinetics/pharmacodynamics of amikacin. A dose-ranging design was used to establish fAUC/MIC and fCmax/MIC targets for static, -1 log drop and -2 log drop effects for strains of Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. We then modelled epithelial lining fluid (ELF) concentration associated with inhaled amikacin (400 mg every 12 h), over 5 days using mean human concentrations. The 24 h static effect fAUC/MIC targets and -1 log drop targets were 51.0 ± 26.7 and 71.6 ± 27.6 for all species of aerobic Gram-negative bacilli. fAUC/MIC targets for static effect, -1 log drop or -2 log drop were smaller than the 24 h values at 12 h and larger at 48 h. Emergence of resistance occurred maximally with E. coli in the fAUC/MIC range 12-60; K. pneumoniae 0-60 (48 h) and P. aeruginosa 12-80. When human ELF concentrations were modelled for strains with MIC ≤8 mg/L, there was rapid clearance and no regrowth. For strains with MIC ≥32 mg/L, there was initial clearance followed by regrowth. If MIC values were related to bacterial clearance then at least a static effect or -1 log drop in count would be expected for bacterial strains with MICs of ≤180 mg/L (static effect) or ≤148 mg/L (-1 log drop effect). An fAUC/MIC amikacin target of 50-80 is appropriate for aerobic Gram-negative bacilli and mean ELF concentrations of BAY 41-6551 would produce a static to -1 log clearance with strains up to 128 mg/L.

Salmeterol undergoes enantioselective bronchopulmonary distribution with receptor localisation a likely determinant of duration of action

BackgroundSalmeterol (a long acting beta2-agonist) is a chiral molecule. (RR)-salmeterol is responsible for pharmacological effect, but basic knowledge of enantioselective pulmonary pharmacodynamics and pharmacokinetics of salmeterol remains unknown. There are safety concerns with (S)-enantiomers of beta2-agonists, with suggestions that these enantiomers may increase bronchial hyperresponsivneness in asthma patients. MethodologyHorses (n = 12) received racemic (rac-) salmeterol 250 μg via inhalation. Enantioselective UPLC–MS/MS was used to determine (R)- and (S)-salmeterol concentrations in pulmonary epithelial lining fluid (PELF) sampled 2, 5, 10 and 15 min after administration, in central lung (endoscopic bronchial biopsy) and peripheral lung (percutaneous pulmonary biopsy) tissues (at 20 and 25 min respectively), and in plasma samples. ResultsPhysiologically relevant tissue concentrations were found for both enantiomers, with median levels greater in central than peripheral lung (equivalent to 32 and 5 mM (R)-salmeterol for central and peripheral lung respectively). Levels in PELF decreased around 50% over 15 min and enantioselective distribution was observed in the central lung with levels of (R)-salmeterol around 30% higher than (S)-salmeterol. ConclusionSalmeterol distribution is enantioselective in the central lung. This suggests duration of action is more likely associated with specific B2ADR localisation effects rather than non-specific physiochemical factors which would not be enantioselective.

New aerosol formulation to control ciprofloxacin pulmonary concentration

Ciprofloxacin (CIP) apparent permeability across a pulmonary epithelium model can be controlled by the affinity of its complex with a metal cation. The higher the complex affinity, the larger is the reduction in CIP apparent permeability. The aim of this study was to evaluate if the control of the CIP apparent permeability observed in vitro could be transposed in vivo to control the CIP lung-to-blood absorption rate and CIP concentrations in the lung epithelial lining fluid (ELF) after intratracheal (IT) administration. Two types of innovative inhalable microparticles loaded with the low-affinity CIP-calcium complex (CIP-Ca) or with the high-affinity CIP-copper complex (CIP-Cu) were formulated and characterized. Then, ELF and plasma pharmacokinetics of CIP were studied in rats after IT administration of these two types of microparticles and of a CIP solution (2.5mg/kg). The presence of Cu2+ had little effect on the microparticle properties and the dry powder had aerodynamic properties which allowed it to reach the lungs. CIP concentrations in ELF were much higher after CIP-Cu microparticles IT administration compared to the other two formulations, with mean AUCELF to AUCu,plasma ratios equal to 1069, 203 and 9.8 after CIP-Cu microparticles, CIP-Ca microparticles and CIP solution pulmonary administration, respectively. No significant modification of lung toxicity markers was found (lactate dehydrogenase and total protein). CIP complexation with Cu2+ seems to be an interesting approach to obtain high CIP concentrations in the ELF of lungs after dry powder IT administration.

Intrapulmonary Pharmacokinetics of Laninamivir, a Neuraminidase Inhibitor, after a Single Nebulized Administration of Laninamivir Octanoate in Healthy Japanese Subjects.

A single dose of laninamivir octanoate (LO) inhaled using a dry powder inhaler (DPI) is effective for the treatment and prophylaxis of influenza. Nebulizers are an option for pediatric and elderly patients who may have difficulty in using a DPI. A single-center, open-label study was conducted to evaluate the plasma and intrapulmonary pharmacokinetics (PK) of laninamivir after a single nebulized administration of LO in healthy male Japanese subjects for identifying a safe and effective dosage regimen for a nebulizer. A single dose of LO (40 to 320 mg) was administered using a nebulizer, and plasma concentrations of LO and laninamivir were analyzed up to 168 h after inhalation by validated liquid chromatography-tandem mass spectrometry methods. Subgroups of 6 subjects each underwent bronchoalveolar lavage at specified time intervals over 4 to 168 h following a single nebulized administration of LO (160 mg), and the concentrations in epithelial lining fluid (ELF) were calculated by the urea diffusion method. PK parameters were determined by noncompartment analysis. Inhaled nebulized LO was found to be safe and well tolerated up to the highest dose evaluated (320 mg). Plasma laninamivir concentrations increased almost dose proportionally. Laninamivir concentrations in ELF exceeded the 50% inhibitory concentrations for viral neuraminidase up to 168 h after the nebulized inhalation of 160 mg LO. Thus, similarly to the DPI, ELF concentration profiles of laninamivir after a single nebulized administration support its long-lasting effect against influenza virus infection. This study has been registered at JAPIC Clinical Trials Information (http://www.clinicaltrials.jp/) under registration no. JAPIC CTI-152996.

Dilution Factor of Quantitative Bacterial Cultures Obtained by Bronchoalveolar Lavage in Patients with Ventilator-Associated Bacterial Pneumonia.

Ventilator-associated bacterial pneumonia (VABP) is a difficult therapeutic problem. Considerable controversy exists regarding the optimal chemotherapy for this entity. The recent guidelines of the Infectious Diseases Society of America and the American Thoracic Society recommend a 7-day therapeutic course for VABP based on the balance of no negative impact on all-cause mortality, less resistance emergence, and fewer antibiotic treatment days, counterbalanced with a higher relapse rate for patients whose pathogen is a nonfermenter. The bacterial burden causing an infection has a substantial impact on treatment outcome and resistance selection. We describe the baseline bronchoalveolar lavage (BAL) fluid burden of organisms in suspected VABP patients screened for inclusion in a clinical trial. We measured the urea concentrations in plasma and BAL fluid to provide an index of the dilution of the bacterial and drug concentrations in the lung epithelial lining fluid introduced by the BAL procedure. We were then able to calculate the true bacterial burden as the diluted colony count times the dilution factor. The median dilution factor was 28.7, with the interquartile range (IQR) being 11.9 to 53.2. Median dilution factor-corrected colony counts were 6.18 log10(CFU/ml) [IQR, 5.43 to 6.46 log10(CFU/ml)]. In a subset of patients, repeat BAL on day 5 showed a good stability of the dilution factor. We previously showed that large bacterial burdens reduce or stop bacterial killing by granulocytes. (This study has been registered at ClinicalTrials.gov under registration no. NCT01570192.).

Development of an Adult Physiologically Based Pharmacokinetic Model of Solithromycin in Plasma and Epithelial Lining Fluid.

Solithromycin is a fluoroketolide antibiotic under investigation for community‐acquired bacterial pneumonia (CABP). We developed a whole‐body physiologically based pharmacokinetic (PBPK) model for solithromycin in adults using PK‐Sim and MoBi version 6.2, which incorporated time‐dependent CYP3A4 auto‐inhibition. The model was developed and evaluated using plasma and epithelial lining fluid (ELF) concentration data from 100 healthy subjects and 22 patients with CABP (1,966 plasma, 30 ELF samples). We performed population simulations and calculated the number of observations falling outside the 90% prediction interval. For the oral regimen (800 mg on day 1 and 400 mg daily on days 2–5) that was evaluated in phase III studies, 11% and 23% of observations from healthy adults fell outside the 90% prediction interval for plasma and ELF, respectively. This regimen should be effective because ≥97% of simulated adults achieved area under the concentration vs. time curve (AUC) to minimum inhibitory concentration ratios associated with a log10 colony forming unit reduction in ELF.

Pulmonary Pharmacokinetics of Colistin following Administration of Dry Powder Aerosols in Rats.

Colistin has been administered via nebulization for the treatment of respiratory tract infections. Recently, dry powder inhalation (DPI) has attracted increasing attention. The current study aimed to investigate the pharmacokinetics (PK) of colistin in epithelial lining fluid (ELF) and plasma following DPI and intravenous (i.v.) administration in healthy Sprague-Dawley rats. Rats were given colistin as DPI intratracheally (0.66 and 1.32 mg base/kg of body weight) or i.v. injection (0.66 mg base/kg). Histopathological examination of lung tissue was performed at 24 h. Colistin concentrations in both ELF and plasma were quantified, and a population PK model was developed and compared to a previously published PK model of nebulized colistin in rats. A two-compartment structural model was developed to describe the PK of colistin in both ELF and plasma following pulmonary or i.v. administration. The model-estimated clearance from the central plasma compartment was 0.271 liter/h/kg (standard error [SE] = 2.51%). The transfer of colistin from the ELF compartment to the plasma compartment was best described by a first-order rate constant (clearance of colistin from the ELF compartment to the plasma compartment = 4.03 × 10-4 liter/h/kg, SE = 15%). DPI appeared to have a higher rate of absorption (time to the maximum concentration in plasma after administration of colistin by DPI, ≤10 min) than nebulization (time to the maximum concentration in plasma after administration of colistin by nebulization, 20 to 30 min), but the systemic bioavailabilities by the two routes of administration were similar (∼46.5%, SE = 8.43%). Histopathological examination revealed no significant differences in inflammation in lung tissues between the two treatments. Our findings suggest that colistin DPI is a promising alternative to nebulization considering the similar PK and safety profiles of the two forms of administration. The PK and histopathological information obtained is critical for the development of optimal aerosolized colistin regimens with activity against lung infections caused by Gram-negative bacteria.

Serum and Lung Pharmacokinetics of ASN100, a Monoclonal Antibody Combination for the Prevention and Treatment of Staphylococcus aureus Pneumonia

BackgroundMonoclonal antibodies (mAbs) are well-suited for the prevention and treatment of acute bacterial infections. ASN100 is a combination of two fully human IgG1 mAbs, ASN-1 and ASN-2 that together neutralize six Staphylococcus aureus cytotoxins, alpha-hemolysin (Hla) and five leukocidins (HlgAB, HlgCB, LukED, LukSF [PVL] and LukGH) that are important in the pathogenesis of S. Aureus pneumonia. We aimed to characterize the pharmacokinetics (PK) of ASN100 in both serum and lung epithelial lining fluid (ELF) in male and female healthy volunteers.MethodsThe safety, tolerability, and serum and lung PK of single intravenous infusion of ASN100 was evaluated in a Phase 1 study. Eight subjects (3:1 randomization) in two double-blind cohorts received ASN100 (doses of 3600 mg or 8000 mg) or placebo. ASN-1 and ASN-2 were administered in a fixed dose 1:1 ratio. Twelve subjects received ASN100 open-label at doses of 3600 mg or 8000 mg and each underwent two bronchoalveolar lavage (BAL) fluid collections either on days 1 and 30 or on days 2 and 8 post-dosing. ASN-1 and ASN-2 concentrations were determined by ELISA. The ELF concentrations were normalized based on urea concentrations in serum and BAL fluid.ResultsNo dose limiting toxicity was observed. Adverse events (AEs) showed no association of increased incidence with higher dose. All AEs were mild or moderate in severity, with 83.3% of subjects receiving ASN100 reporting at least one AE vs. 100% of placebo subjects. A dose proportional increase in serum peak and exposure (AUC) of ASN-1 and ASN-2 was observed and the serum PK of ASN-1 and ASN-2 were comparable (approximate half-life of each antibody was 3 weeks). Penetration of ASN-1 and ASN-2 into the ELF of the lung was observed at the first post-dose time point of 24 hours, peak concentrations were observed after day 2 and the mAbs remained detectable at day 30.ConclusionASN100 was safe and well tolerated at doses up to 8000 mg (4000 mg ASN-1 and 4000 mg ASN-2). The PK profiles of ASN-1 and ASN-2 were comparable following simultaneous administration. Significant lung concentrations of each mAb were demonstrated between day 1 and 30 post-dosing. These data support continued clinical development of ASN100 for the prevention and treatment of S. Aureus pneumonia.Disclosures Z. Magyarics, Arsanis Biosciences GmbH: Employee, Salary. Arsanis, Inc.: Shareholder, Share options. F. Leslie, Arsanis., Inc.: Employee and Shareholder, Salary. S. A. Luperchio, Arsanis Inc.: Employee and Shareholder, Salary. B. Jilma, Arsanis Biosciences GmbH: Investigator, Investigator fee. C. Stevens, Arsanis Inc.: Employee and Shareholder, Salary.E. Nagy, Arsanis: Employee and Shareholder, Salary.

Dexamethasone palmitate large porous particles: A controlled release formulation for lung delivery of corticosteroids

We have optimized a formulation of a prodrug of dexamethasone (DXM), dexamethasone palmitate (DXP) for pulmonary delivery as a dry powder. Formulations were prepared by spray drying DXP with 1,2-Dipalmitoyl-sn-Glycero-3-Phosphocholine (DPPC) and Hyaluronic Acid (HA) as excipients. Large porous particles around 13 μm were produced with a tap density of 0.05g/cm3 and a Fine particle fraction around 40%. The palmitate moiety favors DXP insertion into DPPC bilayers therefore limiting its in vitro release as shown by differential scanning calorimetry. After administering DXP powder intratracheally to rats by insufflation, bronchoalveolar lavage fluid (BALF) and blood samples were collected up to 24h and DXP and DXM concentrations were determined by HPLC analysis after extraction. PK parameters were evaluated according to a non-compartmental model. We observe that DXP remains for up to 6h in the epithelial lining fluid (ELF) of the lungs at very high concentration. In addition, DXP concentration decreases according to two characteristic times. Consequently, DXM can be detected at rather important concentration in ELF up to 24h. The passage of DXP from the lungs to the bloodstream is very poor whereas DXM seems to be absorbed in the blood more easily. These results suggest that once administered DXP undergoes two different processes: hydrolysis into DXM due to the presence of esterases in the lungs and distribution in the lung tissue. This formulation appears promising to reduce systemic exposure and prolong the effect of the drug locally.

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

ABSTRACTThe 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 (AUC0–24) (based on mean concentrations) in ELF and the ratio of the ELF to total plasma omadacycline concentration based on AUC0–24 values were 17.23 mg · h/liter and 1.47, respectively. The AUC0–24 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 (AUC0–12) 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 AUC0–12 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.

Antibacterial activity of human simulated epithelial lining fluid concentrations of amikacin inhale alone and in combination with meropenem against Acinetobacter baumannii

Background: Acinetobacter baumannii(ACBN) is a MDR organism causing pneumonia in ventilated patients. High MICs often result in insufficient lung exposures, thus poor outcomes have been observed with parenteral antimicrobials. Amikacin Inhale(AMK-I), is a drug–device combination of amikacin and a Pulmonary Drug Delivery System device. We aimed to describe the pharmacodynamic profile of human simulated epithelial lining fluid(ELF) exposures of AMK-I and intravenous meropenem alone and in combination against ACBN with variable susceptibility profiles.Methods: AMK-I ELF exposures and the ELF profile of meropenem achieved after intravenous administration were evaluated in an in vitro pharmacodynamic model. Nine ACBN with amikacin/meropenem MICs of 2–512/2 to >64 mg/L were utilized. MICs were repeated post exposure to assess the development of resistance.Results: AMK-I monotherapy rapidly achieved and sustained bactericidal activity for isolates with amikacin MIC ≤128 mg/L. For isolates with MICs of 256 and 512 mg/L initial reductions in bacterial density were observed followed by regrowth. The combination produced similar bactericidal activity against ACBN with amikacin MICs of ≤128. While the combination regimen produced initial reductions and prolonged the duration of activity against organisms with MICs of 256 and 512 mg/L, regrowth and MIC elevations were noted during the 72-h exposure period.Conclusion: The combination achieved rapid and sustained efficacy when amikacin MICs were ≤128 mg/L and prolonged the duration of activity compared to monotherapy for organisms with MICs 256 mg/L and 512 mg/L. These data support the utility of AMK-I as an adjunct for the treatment of pneumonia caused by A. baumannii with MICs above current susceptibility break-points.

Tedizolid inhibits MUC5AC production induced by methicillin-resistant Staphylococcus aureus in human airway epithelial cells.

The innate immune system plays an important role in early immunity against respiratory tract infection. Although airway epithelial cells produce mucus to eliminate pathogens and irritants, hypersecretion of mucus is harmful for the host as it may cause airway obstruction and inhibit influx of antimicrobial agents. It has been reported that several antimicrobial agents have an immunomodulatory effect invitro and invivo, but little is known about whether tedizolid, a novel oxazolidinone, can modulate immune responses. In this study, we evaluated whether tedizolid can suppress MUC5AC production in human airway epithelial cells stimulated by methicillin-resistant Staphylococcus aureus (MRSA). Compared with the control, tedizolid significantly inhibited MUC5AC protein production and mRNA overexpression at concentrations of both 2 and 10μg/mL (representative of trough and peak concentrations in human epithelial lining fluid). Among the mitogen-activated protein kinase inhibitors tested, only extracellular signal-regulated protein kinase 1/2 (ERK1/2) phosphorylation was inhibited by tedizolid as indicated by western blot analysis. These results indicate that tedizolid inhibits the overproduction of MUC5AC protein by inhibiting phosphorylation of ERK1/2. This study revealed that tedizolid suppresses excessive mucin production in human airway epithelial cells. The immunomodulatory effect of tedizolid may improve outcomes in patients with severe respiratory infectious diseases caused by MRSA.

Bronchial microdialysis monitoring of inflammatory response in open abdominal aortic aneurysm repair; an observational study.

Aortic surgery results in ischemia–reperfusion injury that induces an inflammatory response and frequent complications. The magnitude of the inflammatory response in blood and bronchi may be associated with the risk of immediate complications. The purpose of the study was to evaluate bronchial microdialysis as a continuous monitoring of cytokines in bronchial epithelial lining fluid (ELF) and to determine whether bronchial ELF cytokine levels reflect the ischemia–reperfusion injury and risk for complications during open abdominal aortic aneurysm (AAA) repair. We measured cytokines in venous blood using microdialysis and in serum for comparison. Sixteen patients scheduled for elective open AAA repair were included in a prospective observational study. Microdialysis catheters were introduced into a bronchi and a cubital vein. Eighteen cytokines were measured using a Bio‐Plex Magnetic Human Cytokine Panel. Samples were collected before and during cross‐clamping of the aorta as well as from 0 to 60 min and from 60 to 120 min of reperfusion. The ELF levels of several cytokines changed significantly during reperfusion. In particular, IL‐6 increased more than 10‐fold and IL‐13 more than 5‐fold during ischemia and reperfusion. Also, the venous levels of several inflammatory and anti‐inflammatory cytokines increased and exhibited their highest concentration during reperfusion. Both bronchial and venous cytokine levels correlated with duration of the procedure, intensive care days, and preoperative kidney disease. Three patients suffered organ failure as a direct consequence of the procedure, and in these patients the bronchial ELF concentrations of 17 of 18 cytokines differed significantly from patients without such complications. Bronchial microdialysis is suited for continuous monitoring of inflammation during open AAA repair. The bronchial ELF cytokine levels may be useful in predicting immediate complications such as organ failure in patients undergoing vascular surgery.

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.