Immobilized Artificial Membrane (lAM)-HPLC for Partition Studies of Neutral and Ionized Acids and Bases in Comparison with the Liposomal Partition System

Purpose. To study the partitioning of model acids ((RS)-warfarin and salicylic acid), and bases (lidocaine, (RS)-propranolol and diazepam), with immobilized artificial membrane (lAM)-HPLC, as compared to partitioning in the standardized phosphatidylcholine liposome/buffer system. Methods. The pH-dependent apparent partition coefficients D were calculated from capacity factors (k′IAM) obtained by IAM-HPLC, using a 11-carboxylundecylphosphocholine column. For lipophilic compounds k′IAM, values were determined with organic modifiers and extrapolation to 100% water phase (k′IAMw) was optimized. Temperature dependence was explored (23 to 45° C), and Gibbs free energy (ΔG), partial molar enthalpy (ΔH) and change in entropy (ΔS) were calculated. Equilibrium dialysis was used for the partitioning studies with the liposome/buffer system. Results. For extrapolation of k′IAMw, linear plots were obtained both with the respective dielectric constants and the mole fractions of the organic modifier. All tested compounds showed a similar pH-D diagram in both systems; however, significant differences were reproducibly found in the pH range of 5 to 8. In all cases, ΔG and ΔH were negative, whereas ΔS values were negative for acids and positive for bases. Conclusions. In both partitioning systems, D values decreased significantly with the change from the neutral to the charged ionization state of the solute. The differences found under physiological conditions, i.e. around pH 7.4, were attributed to nonspecific interactions of the drug with the silica surface of the IAM colum

Immobilized Artificial Membrane (lAM)-HPLC for Partition Studies of Neutral and Ionized Acids and Bases in Comparison with the Liposomal Partition System

ISSN:0724-8741ISSN:1573-904

HCV RNA quantification in capillary dried blood spots with the Xpert® HCV Viral Load test for diagnosing chronic HCV infection, monitoring treatment and detecting reinfection

BACKGROUND: For patients with difficult venous access after long-term intravenous drug use, rapid point-of-care hepatitis C virus (HCV) RNA quantification in capillary whole blood with the Xpert® HCV Viral Load Fingerstick (VL FS) test (60 minutes) is a convenient and reliable method for diagnosing chronic HCV infection, monitoring treatment and detecting reinfection. However, an expensive GeneXpert® system must be available on site. In decentralised settings with a low case-load, dried blood spot (DBS) testing might be an alternative. METHODS: Between December 2019 and January 2021, patients with an indication for HCV RNA quantification and informed consent provided 100 µl capillary whole blood each for on-site Xpert® HCV VL FS testing (reference) and DBS testing in the laboratory. For the latter, 100 µl blood, collected with an EDTA Minivette®, were transferred to a Whatman® 903 filter card. After drying for at least 1 hour, the DBS sample was packed into a sealable plastic bag with desiccant and sent to the central laboratory of our hospital, where it was stored at –20°C. For HCV RNA extraction, the whole DBS was cut out with an 18-mm puncher and transferred into 1.3 ml guanidinium thiocyanate-containing buffer (provided by Cepheid®). After mixing and incubating at room temperature for 2–3 hours, 1 ml supernatant was analysed with the Xpert® HCV VL test (105 minutes) (filter paper absorbs 0.3 ml). RESULTS: Of 109 paired samples from 67 patients, 38 (34.9%) were positive with the Xpert® HCV VL FS test. Sensitivity and specificity of DBS testing were 89.5% (34/38; 95% confidence interval [CI] 75.9–95.8%) and 97.2% (69/71; 95% CI 90.3–99.2%), respectively. The six (5.5%) discordant results (four false negative, two false positive) all were observed in samples with HCV RNA detectable below the limit of quantification after 2–8 weeks of pan-genotypic direct-acting antiviral treatment or 5 weeks after acute hepatitis C in a patient clearing HCV spontaneously. Quantifiable results (n = 30; 16 genotype 1, 7 genotype 3, 4 genotype 4, 1 genotype 1a and 3a, 2 unknown; HCV RNA range: 2.74–6.66 log IU/ml) correlated well (R2 = 0.981). On average, uncorrected DBS test results were 1.30 ± 0.14 log IU/ml lower than Xpert® HCV VL FS test results (~42 μl instead of the expected 1000 μl plasma used). Storage of DBS samples at room temperature for 7 days before freezing reduced HCV RNA by 0.29 ± 0.12 log IU/ml. CONCLUSION: HCV RNA can reliably be quantified with the Xpert® HCV VL test in capillary dried blood spot samples. Thus, access to capillary HCV RNA quantification for diagnosing chronic HCV infection, monitoring treatment and detecting reinfection can be extended to decentralised settings with a low case load

Non-Seasonal Variation of Airborne Aspergillus Spore Concentration in a Hospital Building

Nosocomial fungal infections are gaining increased attention from infectiologists. An adequate investigation into the levels of airborne Aspergillus and other fungal spores in hospital settings, under normal conditions, is largely unknown. We monitored airborne spore contamination in a Swiss hospital building in order to establish a seasonally-dependent base-line level. Air was sampled using an impaction technique, twice weekly, at six different locations over one year. Specimens were seeded in duplicate on Sabouraud agar plates. Grown colonies were identified to genus levels. The airborne Aspergillus spore concentration was constantly low throughout the whole year, at a median level of 2 spores/m3 (inter-quartile range = IQR 1–4), and displayed no seasonal dependency. The median concentration of other fungal spores was higher and showed a distinct seasonal variability with the ambient temperature change during the different seasons: 82 spores/m3 (IQR 26–126) in summer and 9 spores/m3 (IQR 6–15) in winter. The spore concentration varied considerably between the six sampling sites in the building (10 to 26 spores/m3). This variability may explain the variability of study results in the literature

Very Low Hepatitis C Viral Loads in Treatment-naive Persons: Do They Compromise Hepatitis C Virus Antigen Testing?

Hepatitis C virus (HCV) antigen testing is less expensive than quantitative reverse-transcription polymerase chain reaction but has lower sensitivity for very low viral load (VLVL; HCV RNA ≤3000 IU/mL). Currently the benefits of antigen testing for screening are discussed, but data on prevalence and outcomes of persons with VLVL are scarce. We assessed prevalence and predictors of VLVL by logistic regression in treatment-naive participants in the Swiss Hepatitis C Cohort Study. We analyzed if the last viral load after VLVL was low, compared cirrhosis and mortality in persons with and without VLVL, and evaluated the number of samples with VLVL that were reactive by antigen testing. We included 2533 treatment-naive persons with available quantitative HCV RNA testing results. Overall, 133 persons (5.3%) had a VLVL. Age 18-40 years, female sex, and human immunodeficiency virus coinfection were associated with VLVL. Of 72 persons with a viral load available after VLVL, 14% had a VLVL and 17% had spontaneous viral clearance. The prevalence and incidence of cirrhosis and mortality were comparable in persons with and without VLVL; all 24 persons with VLVL and cirrhosis had excessive alcohol consumption or immunosuppression. Overall, 33% of samples with VLVL were reactive by antigen testing. The frequency of VLVL was low. Among the persons who would probably be missed by antigen screening, some had a favorable disease course, but some had immunosuppression and liver cirrhosis. The benefit of HCV antigen testing for screening may be limited by the risk of missing patients with severe liver disease

Tectonic control on the late stage exhumation of the Aar Massif (Switzerland): Constraints from apatite fission track and (U-Th)/He data

We examine the hypothesis that Pliocene exhumation of the external massifs in the central Alps is controlled by climatic change. New thermochronological data from the western Gastern-Aar massif are used to investigate the timing, extent, and reasons for Neogene exhumation. Our data reveal that exhumation was constant with 0.5 km/Ma over the last 10 Ma in the north. In the southern part, exhumation was of the same order until ∼3.5 Ma but then increased gradually toward the south to values of up to 1.2 km/Ma, resulting in overall northward tilting of the western Aar massif. We explain this accelerated exhumation in the south after ∼3.5 Ma mainly by tectonic denudation in the footwall of the Rhône-Simplon fault and discuss changes in deep crustal configuration, which may have triggered south directed normal faulting. We propose that the Rhône river was structurally trapped by the Rhône-Simplon normal fault zone, which additionally enhanced erosion in the southern section of the Aar massif. Climatic forcing may have an impact in the very late stage of exhumation due to Alpine glaciation in the late Pliocene