The influence of laterally inhomogeneous corrosion on electrical and optical calcium moisture barrier characterization

The reaction of calcium thin films with water - monitored optically or electrically - is widely used for evaluating ultrahigh barrier foils for the encapsulation of organic electronic devices. We studied the common optical and the electrical method and compared them with in situ atomic force microscope topography scans. All three methods were applied at the same sample in parallel in a typical test design containing a gas volume for water distribution next to the calcium layer of 60 and 1000 nm thickness, respectively. The common assumption for the interpretation of such measurement data is laterally homogeneous calcium consumption of the layer from top to bottom. In contrast, we observed a significant ratio of laterally inhomogeneous corrosion of the calcium on the micro-scale for both thicknesses. Some areas were strongly or completely corroded through the whole layer while others exhibited less or no corrosion. Furthermore, those corroded spots grew in lateral direction. As a consequence of lateral inhomogeneous calcium corrosion the electrical calcium measurement method underestimates the amount of calcium left; according to our results this does not affect the water vapor transmission rate (WVTR). Optical data evaluated by Lambert-Beer law underestimate the amount of calcium left as well and also underestimate the WVTR. If the data are evaluated, using a linear relationship between transmission and amount of calcium left, the both values are more precise. The scope of this study is to call attention to the existence of lateral inhomogeneity in calcium corrosion and its impact on the calcium permeation measurements. While more investigations would be needed to quantify the effect of this inhomogeneity on the electrical and optical method in general, the discussion sheds light on the way, calcium test data are influenced by lateral inhomogeneous calcium corrosion. Our observations highlight the need for careful interpretation of calcium test results, but also demonstrate its capabilities for precise ultrahigh barrier measurements.

Volatile compound profiling for the identification of Gram-negative bacteria by ion-molecule reaction-mass spectrometry

AIMS

Fast and reliable methods for the early detection and identification of micro-organism are of high interest. In addition to established methods, direct mass spectrometry-based analysis of volatile compounds (VCs) emitted by micro-organisms has recently been shown to allow species differentiation. Thus, a large number of pathogenic Gram-negative bacteria, which comprised Acinetobacter baumannii, Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca, Pseudomonas aeruginosa, Proteus vulgaris and Serratia marcescens, were subjected to headspace VC composition analysis using direct mass spectrometry in a low sample volume that allows for automation.

METHODS AND RESULTS

Ion-molecule reaction-mass spectrometry (IMR-MS) was applied to headspace analysis of the above bacterial samples incubated at 37°C starting with 10(2) CFU ml(-1) . Measurements of sample VC composition were performed at 4, 8 and 24 h. Microbial growth was detected in all samples after 8 h. After 24 h, species-specific mass spectra were obtained allowing differentiation between bacterial species.

CONCLUSIONS

IMR-MS provided rapid growth detection and identification of micro-organisms using a cumulative end-point model with a short analysis time of 3 min per sample.

SIGNIFICANCE AND IMPACT OF THE STUDY

Following further validation, the presented method of bacterial sample headspace VC analysis has the potential to be used for bacteria differentiation.

Staphylococcus aureus infection following nasal colonization: an approach to rapid risk stratification in a university healthcare system

Staphylococcus aureus carriage increases the risk of infection. Demographic and microbiological data from adult patients with nasal S. aureus carriage were analysed in order to define effect modifiers of this association. Predictors for growth of S. aureus from clinical cultures were identified in a case-control study using bivariate and multi-variate logistic regression analysis. Between 1 January 2005 and 1 April 2009, 645 patients with nasal S. aureus colonization and documented follow-up of ≥90 days were identified; 159 (25%) patients were found to carry meticillin-resistant S. aureus (MRSA). The median age of patients was 58 years, and 421 (65%) were male. During the subsequent 90 days, one or more clinical cultures were positive for S. aureus in 131 patients (20%). Multi-variate analysis identified a prior history of any S. aureus positive culture [adjusted odds ratio (aOR) 2.4, 95% confidence interval (CI) 1.5-3.8; P=0.0005) as an independent predictor of subsequent S. aureus infection. MRSA colonization was a predictor of infection in patients aged >40 years (aOR 2.5, 95% CI 1.4-4.1; P=0.0004), and even more so in patients aged ≤40 years (aOR 12.4, 95% CI 3.0-51; P=0.0005). Age >40 years was an additional independent risk factor for meticillin-susceptible S. aureus carriers (aOR 3.0, 95% CI 1.2-7.8; P=0.02) but not for MRSA carriers. Preferential screening of patients at high risk for MRSA carriage and subsequent infection, as well as the absence of a universal policy for the use of decolonization regimens, may partly explain the relatively high risk of S. aureus infection in the patient population. MRSA carriers and older patients with recurrent S. aureus positive cultures may gain the greatest benefit from routine decolonization measures.

Electrical calcium test for moisture barrier evaluation for organic devices

We discuss the electrical calcium test--a method to measure very small rates of water vapor permeation through barrier films with high throughput. The sensitivity range for our design is found to be 10(-5) to 15 g/(m(2) d). Moreover, a closer look at the importance of electrodes series resistance is taken: We show that permeation rates are underestimated if it is neglected. Taking this series resistance and Fickian diffusion into account not only the steady, but also the transient state of the permeation curve can be fitted. Using this approach, permeation barriers with different permeabilities are evaluated leading to water vapor transmission rates well comparable to coulometric measurements. The calcium layer morphology is investigated by atomic force microscopy measurements indicating microscopical inhomogeneities during degradation. Variations of electrode material and calcium layer thickness are carried out to examine their influence on the measured permeation. Additionally, optical and electrical calcium tests are compared. Small differences in the time dependence are observed and discussed.

Proliferation signal inhibitors and post-transplant malignancies in heart transplantation: practical clinical management questions

Although malignancy is a major threat to long-term survival of heart transplant (HT) recipients, clear strategies to manage immunosuppression in these patients are lacking. Several lines of evidences support the hypothesis of an anticancer effect of proliferation signal inhibitors (PSIs: mammalian target of rapamycin [mTOR] inhibitors) in HT recipients. This property may arise from PSI's ability to replace immunosuppressive therapies that promote cancer progression, such as calcineurin inhibitors or azathioprine, and/or through their direct biological actions in preventing tumor development and progression. Given the lack of randomized studies specifically exploring these issues in the transplant setting, a collaborative group reviewed current literature and personal clinical experience to reach a consensus aimed to provide practical guidance for the clinical conduct in HT recipients with malignancy, or at high risk of malignancy, with a special focus on advice relevant to potential role of PSIs.

In-vitro activities of tetracyclines, macrolides, fluoroquinolones and clindamycin against Mycoplasma hominis and Ureaplasma ssp. isolated in Germany over 20 years

Antimicrobial resistance in genital mycoplasmas is increasing and shows global variation. We determined the susceptibilities of 469 mycoplamas, comprising 290 Mycoplasma hominis and 179 ureaplasma isolates collected during 1983 and 1989-2004, to eleven antibacterials by agar dilution. Additionally, we analyzed the results of routine E-testing during 2005-2008. Doxycycline was the most active tetracycline with (MIC₉₀ of 1 and 8 mg/L for ureaplasmas and M. hominis, respectively. Significantly more M. hominis isolates (approximately 10-13%) than ureaplasmas (approximately 1-3%) were resistant to tetracyclines. Ofloxacin was effective against both species (>95% susceptibility). Ciprofloxacin was moderately active against M. hominis and less active against ureaplasmas (70.3% and 35.2% susceptibility, respectively). Clarithromycin and josamycin were the most potent macrolides (MIC₉₀ of 0.5 mg/L) against ureaplasmas. Erythromycin had the lowest activity (MIC₉₀ of 8 mg/L) against ureaplasmas like clindamycin which was the most potent agent against M. hominis. Cross-resistance was found between tetracyclines (53-93%), macrolides and erythromycin (70-100%), and between erythromycin and ciprofloxacin (43-55%). M. hominis became more resistant to tetracyclines and fluoroquinolones between 1989 and 2004, although there was little change during 2005-2008. Ureaplasmas became more resistant to cipfloxacin during 1997 – 2004 and showed high resistance rates to erythromycin during 1989-2008. Doxycycline is still the drug of first-choice for the treatment of ureaplasmal infections and may be used for co-infection with M. hominis.

A novel ex vivo set-up for dynamic long-term characterization of processes on mucosal interfaces by confocal imaging and simultaneous cytokine measurements

We present a novel organ-explant imaging system for easy and cost-effective extended-time observation of host-pathogen interactions at mucosal interfaces. Data are complemented by parallel cytokine measurements at high temporal resolution. The set-up is based on a custom-built reusable organ chamber compatible with standard microscopes. Luminal and basal side of the explanted mucosa are connected to separate channels for optimized incubation and cytokine measurements, oxygen is provided via membrane oxygenation. Dynamic imaging with confocal microscopy permits a detailed analysis of the dynamics of pathogen-host cell interactions at the mucosal interface and the neighbouring tissue at high resolution. The system can be applied to various hollow organs with few modifications. Here we present first applications to study representative infections such as uropathogenic Escherichia coli (UPEC) infections in the urinary bladder or amoebiasis of the colon by using mouse organs. We show (i) intracellular bacteria in UPEC infections, (ii) phagocytic events on tissue during infection, as well as (iii) tissue invasion of virulent protozoans into epithelia. The versatility of this system and its higher degree of control in comparison with both traditional explant microscopy and in vivo two photon imaging solutions make it a valuable and easy-to-use addition to other current imaging techniques.