Richard Schwameis

Effect of pulmonary surfactant on antimicrobial activity in-vitro

ABSTRACT Time-kill curve experiments were performed with linezolid, doripenem, tigecycline, moxifloxacin, and daptomycin against Staphylococcus aureus and with colistin, moxifloxacin, and doripenem against Pseudomonas aeruginosa to evaluate the effect of porcine pulmonary surfactant on antimicrobial activity. Pulmonary surfactant significantly impaired the activities of moxifloxacin and colistin. When antibiotics are being developed for respiratory tract infections, the method described here might be used to preliminarily quantify the effect of pulmonary surfactant on antimicrobial activity.

Simultaneous assessment of the pharmacokinetics of a pleuromutilin, lefamulin, in plasma, soft tissues and pulmonary epithelial lining fluid.

BACKGROUND Lefamulin is a pleuromutilin antibiotic under evaluation for the treatment of bacterial infections, including respiratory tract infections. Currently, there are no high-quality pharmacokinetic data on drug tissue concentrations of lefamulin available. METHODS A single dose of intravenous lefamulin (150 mg) was given to 12 healthy men. The registered EudraCT number for this study was 2010-021938-54. Lefamulin concentrations were simultaneously measured in plasma, skeletal muscle tissue, subcutaneous adipose tissue and epithelial lining fluid (ELF) over 24 h, and corresponding pharmacokinetic parameters were calculated. Microdialysis was used to measure unbound lefamulin concentrations in skeletal muscle tissue and subcutaneous adipose tissue, which were similar to unbound lefamulin concentrations in plasma. Bronchoalveolar lavage was performed 1, 2, 4 and 8 h post-dose to determine lefamulin concentrations in ELF. RESULTS Unbound lefamulin levels showed a 5.7-fold higher exposure in ELF compared with that in plasma, demonstrating good penetration to the target site. CONCLUSIONS Lefamulin may be an addition to the therapeutic armamentarium for the treatment of infections. Simultaneous measurements of unbound drug concentration can guide target attainment for future therapeutic trials.

A FIM study to assess safety and exposure of inhaled single doses of AP301-A specific ENaC channel activator for the treatment of acute lung injury.

AP301 is an activator of ENaC‐mediated Na+ uptake for the treatment of pulmonary permeability edema in acute respiratory distress syndrome (ARDS). The purpose of this “first‐in‐man” study was to examine local and systemic safety and systemic exposure of ascending single doses of AP301, when inhaled by healthy male subjects. In a double‐blind, placebo‐controlled study, 48 healthy male subjects were randomized to 6 ascending dose groups (single doses up to 120 mg) of 8 subjects each (3:1 randomization of AP301: placebo). Serial assessments included spirometry, exhaled nitric oxide (eNO), vital signs, ECG, safety laboratory, adverse events (AE), and blood samples for the quantification of AP301 in plasma. Descriptive statistics was applied. All 48 subjects received treatment, and completed the study as per protocol. No serious, local (e.g., hoarseness, cough, bronchospasm), or dose‐limiting AEs were noted. None of the assessments indicated notable dose or time‐related alterations of safety outcomes. Observed AP301 systemic exposure levels were very low, with mean Cmax values of <2.5 ng/mL in the highest dose groups. Inhaled AP301 single doses up to 120 mg were safe and well tolerated by healthy male subjects. Distribution of inhaled AP301 was largely confined to the lung, as indicated by very low AP301 systemic exposure levels.

Cerebrospinal fluid impairs antimicrobial activity of fosfomycin in vitro

OBJECTIVES Fosfomycin penetrates well into cerebrospinal fluid (CSF) and is considered for treatment of infections of the central nervous system (CNS). This study evaluated the influence of human CSF on the antimicrobial activity of fosfomycin. METHODS Time-kill curves were performed in Mueller-Hinton broth (MHB) and in pooled human CSF using fosfomycin concentrations ranging from 0.25x to 8x MIC for a clinical Staphylococcus aureus isolate. To estimate the activity of fosfomycin at the target site, the concentration-time curve measured in CSF of a patient at steady state was simulated in vitro in human CSF using two S. aureus isolates. RESULTS In CSF a higher fosfomycin concentration (8x MIC) was required to achieve sustained bacterial killing than in MHB (1x MIC). In vitro simulation of the pharmacokinetic profile measured in CSF of the selected patient showed initial killing, but terminal re-growth of both test strains. CONCLUSIONS The antibacterial activity of fosfomycin is lower in CSF than in MHB, and drug concentrations slightly exceeding the MIC may not be sufficient to achieve bactericidal effects in the CNS.

Antimicrobial activity of cefepime and rifampicin in cerebrospinal fluid in vitro

OBJECTIVES Though used for infections of the central nervous system, the pharmacodynamics of antimicrobial agents is commonly evaluated only in commercially available bacterial growth media. In the present study, the effects of cerebrospinal fluid (CSF) on bacterial killing by cefepime and rifampicin were investigated. METHODS CSF was collected from patients who did not receive antibiotics. Time-kill curves were performed over 24 h using drug concentrations of 0.25-, 0.5-, 1-, 2-, 4- and 8-fold the respective MIC for the Staphylococcus aureus test strain. Killing curves were performed in Mueller-Hinton broth (MHB), in CSF incubated in ambient air (CSF(AIR)) and in CSF in air with 5% CO(2) (CSF(CO(2))). CO(2) served to adjust the pH of CSF to physiological values. RESULTS Sustained bacterial killing was achieved by cefepime at lower drug concentrations in CSF(CO(2)) than in MHB. In contrast, rifampicin concentrations above the MIC were required to exert sustained killing in CSF(CO(2)). Both drugs were least effective in CSF(AIR). CONCLUSIONS Standard susceptibility tests may lead to over- or underestimation of the activity of distinct antibiotics in CSF. Evaluation of the antimicrobial activity in pH-adjusted CSF can provide useful information on drugs considered for the treatment of bacterial infections residing in CSF.

Methods to measure target site penetration of antibiotics in critically ill patients.

While several tools are necessary to repair a car, the engineer knows exactly which instrument he has to utilize at different parts of the broken machine. Likewise, depending on the information we are interested in, we have to choose different tools to investigate and consecutively understand the multiple aspects that are involved in pharmacokinetics of antimicrobial agents in critically ill patients. Some techniques, like blood sampling, microdialysis or positrons emission tomography (PET) will allow for obtaining continues concentration time profiles while others like bronchoalveolar lavage (BAL), biopsy or surgical tissue samples can only be used a limited number of times per subject. PET and methods based on tissue homogenization will deliver an average of the actual concentrations in intra - and extracellular compartments while investigations in isolated blood cells or microdialysis allow for more distinguished allocation of a concentration to a defined compartment. The present review aims at discussing the advantages and disadvantages of the various methods used for assessing pharmacokinetics in critically ill patients with regard to specific aspects of pharmacokinetic research and further reviews data of selected antibiotics as examples for applications of the individual techniques.

The Prognostic Value of C-Reactive Protein Serum Levels in Patients with Uterine Leiomyosarcoma

Objective C-reactive protein (CRP) has previously been shown to serve as a prognostic parameter in women with gynecologic malignancies. Due to the lack of valid prognostic markers for uterine leiomyosarcoma (ULMS) this study set out to investigate the value of pre-treatment CRP serum levels as prognostic parameter. Methods Data of women with ULMS were extracted from databases of three Austrian centres for gynaecologic oncology. Pre-treatment CRP serum levels were measured and correlated with clinico-pathological parameters. Univariate and multivariable survival analyses were performed. Results In total, 53 patients with ULMS were included into the analysis. Mean (SD) CRP serum level was 3.46 mg/dL (3.96). Solely, an association between pre-treatment CRP serum levels and tumor size (p = 0.04) but no other clinic-pathologic parameter such as tumor stage (p = 0.16), or histological grade (p = 0.07), was observed. Univariate and multivariable survival analyses revealed that CRP serum levels (HR 2.7 [1.1–7.2], p = 0.037) and tumor stage (HR 6.1 [1.9–19.5], p = 0.002) were the only independent prognostic factors for overall survival (OS) in patients with ULMS. Patients with high pre-treatment CRP serum levels showed impaired OS compared to women with low levels (5-year-OS rates: 22.6% and 52.3%, p = 0.007). Conclusion High pre-treatment CRP serum levels were independently associated with impaired prognosis in women with ULMS and might serve as a prognostic parameter in these patients.

A double-blind, randomized clinical study to determine the efficacy of benzocaine 10% on histamine-induced pruritus and UVB-light induced slight sunburn pain.

Abstract Introduction: This study aims to explore the efficacy of the topical application of 10% benzocaine for treating pruritus and pain as compared to vehicle ointment. Methods: Twenty male subjects were treated in a randomized double-blind fashion with the investigational medicinal product (IMPD) and vehicle. Immediately after the injection of 100 µg histamine on both arms, subjects received topical treatment and pruritus was subsequently assessed with visual analogue scale (VASpruritus) and Eppendorfer questionnaire. Ultraviolet B radiation (UVB) was administered on the back to induce slight sunburn. Twelve hours after UVB application again the IMPD was applied on the right or left upper back and vehicle on the other side and pain related to sunburn was measured with VASpain and pressure algometry. Results: A trend towards better reduction of pruritus was shown for benzocaine in VASpruritus. For the VASpain significant differences in group comparison (p = 0.02) were observed. Algometer measurements showed onset of pain reduction in the verum group after 20 min whereas in the vehicle-treated area pain relief occurred only after 60 min after application. Conclusions: The topically administered ointment containing 10% benzocaine was found superior over vehicle for treating pain, but not pruritus.

Enhanced activity of linezolid against Staphylococcus aureus in cerebrospinal fluid.

Linezolid is considered for treatment of central nervous system (CNS) infections caused by multidrug-resistant Gram-positive bacteria. Therefore, the influence of cerebrospinal fluid (CSF) on the antimicrobial activity of linezolid was evaluated in vitro. Time-kill curves were conducted in CSF and Mueller-Hinton broth (MHB) using Staphylococcus aureus (ATCC 29213) and Staphylococcus epidermidis (ATCC 12228) strains. In CSF lower linezolid concentrations were needed against S. aureus (1× MIC) and S. epidermidis (0.5× MIC) to achieve bacteriostasis than in MHB (4× MIC for both strains). Good activity of linezolid in CSF supports performance of clinical trials evaluating its potential for treatment of CNS infections.

Prognostic value of lymph node ratio and number of positive inguinal nodes in patients with vulvar cancer

OBJECTIVE To estimate the prognostic significance of lymph node ratio and number of positive nodes in vulvar cancer patients. METHODS This international multicenter retrospective study included patients diagnosed with vulvar cancer treated with inguinal lymphadenectomy. Lymph node ratio (LNR) is the ratio of the number of positive lymph nodes (LN) to the number of removed LN. Patients were stratified into risk groups according to LNR. LNR was correlated with clinical-pathological parameters. Survival analyses were performed. RESULTS This analysis included 745 patients. In total, 292 (39.2%) patients had positive inguinal LN. The mean (SD) number of resected and positive LN was 14.1 (7.6) and 3.0 (2.9), respectively. High LNR was associated with larger tumor size and higher tumor grade. Patients with LNRs 0% (N0), >0<20%, and >20% had 5-year overall survival (OS) rates of 90.9%, 70.7%, and 61.8%, respectively (P<0.001). LNR was associated with both local and distant recurrence-free survival (P<0.001). Patients with 0, 1, 2, 3 or >3 positive lymph nodes had 5-year OS rates of 90.9%, 70.8%, 67.8%, 70.8% and 63.4% respectively (P<0.001). In multivariate analysis, LNR (P=0.01) and FIGO stage (P<0.001), were associated with OS, whereas the number of positive nodes (P=0.8), age (P=0.2), and tumor grade (P=0.7), were not. In high-risk patients, adjuvant radiotherapy was associated with improved survival. CONCLUSIONS LNR provides useful prognostic information in vulvar cancer patients with inguinal LN resection in vulvar cancer. LNR allows for more accurate prognostic stratification of patients than number of positive nodes. LNR seems useful to select appropriate candidates for adjuvant radiation.