Evaluation of the automated cartridge-based ARIES SARS-CoV-2 Assay (RUO) against automated Cepheid Xpert Xpress SARS-CoV-2 PCR as gold standard.

INTRODUCTION: To evaluate the automated cartridge-based PCR approach ARIES SARS-CoV-2 Assay targeting the ORF-sequence and the N-gene of SARS-CoV-2. METHODS: In line with the suggestions by Rabenau and colleagues, the automated ARIES SARS-CoV-2 Assay was challenged with strongly positive samples, weakly positive samples and negative samples. Further, intra-assay and inter-assay precision as well as the limit-of-detection (lod) were defined with quantified target RNA and DNA. The Cepheid Xpert Xpress SARS-Cov-2 Assay was used as gold standard. RESULTS: Concordance between the ARIES assay and the Cepheid assay was 100% for strongly positive samples and for negative samples, respectively. For weakly positive samples as confirmed applying the Cepheid assay, a relevant minority of 4 out of 15 samples (26.7%) went undetected by the ARIES assay. Intra- and inter-assay precision were satisfactory, while the lod was in the 103 DNA copies/reaction-range, in the 103 virus copies/reaction-range, or in the 103-104 free RNA copies/reaction-range in our hands. CONCLUSIONS: The automated ARIES assay shows comparable test characteristics as the Cepheid assay focusing on strongly positive and negative samples but a slightly reduced sensitivity with weakly positive samples. Decisions on diagnostic use should include considerations on the lod.

Ductile sliding between mineral crystals followed by rupture of collagen crosslinks: experimentally supported micromechanical explanation of bone strength.

There is an ongoing discussion on how bone strength could be explained from its internal structure and composition. Reviewing recent experimental and molecular dynamics studies, we here propose a new vision on bone material failure: mutual ductile sliding of hydroxyapatite mineral crystals along layered water films is followed by rupture of collagen crosslinks. In order to cast this vision into a mathematical form, a multiscale continuum micromechanics theory for upscaling of elastoplastic properties is developed, based on the concept of concentration and influence tensors for eigenstressed microheterogeneous materials. The model reflects bone's hierarchical organization, in terms of representative volume elements for cortical bone, for extravascular and extracellular bone material, for mineralized fibrils and the extrafibrillar space, and for wet collagen. In order to get access to the stress states at the interfaces between crystals, the extrafibrillar mineral is resolved into an infinite amount of cylindrical material phases oriented in all directions in space. The multiscale micromechanics model is shown to be able to satisfactorily predict the strength characteristics of different bones from different species, on the basis of their mineral/collagen content, their intercrystalline, intermolecular, lacunar, and vascular porosities, and the elastic and strength properties of hydroxyapatite and (molecular) collagen.

Microbiological screenings for infection control in unaccompanied minor refugees: the German Armed Forces Medical Service's experience.

BACKGROUND: The German Military Medical Service contributed to the medical screening of unaccompanied minor refugees (UMRs) coming to Germany in 2014 and 2015. In this study, a broad range of diagnostic procedures was applied to identify microorganisms with clinical or public health significance. Previously, those tests had only been used to screen soldiers returning from tropical deployments. This instance is the first time the approach has been studied in a humanitarian context. METHODS: The offered screenings included blood cell counts, hepatitis B serology and microscopy of the stool to look for protozoa and worm eggs as well as PCR from stool samples targeting pathogenic bacteria, protozoa and helminths. If individuals refused certain assessments, their decision to do so was accepted. A total of 219 apparently healthy male UMRs coming from Afghanistan, Egypt, Somalia, Eritrea, Syria, Ghana, Guinea, Iran, Algeria, Iraq, Benin, Gambia, Libya, Morocco, Pakistan, and Palestine were assessed. All UMRs who were examined at the study department were included in the assessment. RESULTS: We detected decreasing frequencies of pathogens that included diarrhoea-associated bacteria [Campylobacter (C.) jejuni, enteropathogenic Escherichia (E.) coli (EPEC), enterotoxic E. coli (ETEC), enteroaggregative E. coli (EAEC), enteroinvasive E. coli (EIEC)/Shigella spp.), Giardia (G.) duodenalis, helminths (comprising Schistosoma spp., Hymenolepis (H.) nana, Strongyloides (S.) stercoralis] as well as hepatitis B virus. Pathogenic microorganisms dominated the samples by far. While G. duodenalis was detected in 11.4% of the assessed UMRs, the incidence of newly identified cases in the German population was 4.5 cases per 100,000 inhabitants. CONCLUSIONS: We conclude that the applied in-house PCR screening systems, which have proven to be useful for screening military returnees from tropical deployments, can also be used for health assessment of immigrants from the respective sites. Apparently healthy UMRs may be enterically colonized with a broad variety of pathogenic and apathogenic microorganisms. Increased colonization rates, as shown for G. duodenalis, can pose a hygiene problem in centralized homes for asylum seekers.

Experimental poromechanics of trabecular bone strength: role of Terzaghi's effective stress and of tissue level stress fluctuations.

In the 1920s and 1930s, Terzaghi and coworkers realized that the failure of various porous geomaterials under internal pore pressure is given through evaluating the failure function for the same materials at zero pressure, with 'total stress plus pore pressure' instead of 'total stress alone' as argument. As to check, probably for the first time, the relevance of this ('Terzaghi's') failure criterion for trabecular bone, a series of poromechanical and ultrasonic tests was conducted on bovine and human trabecular bone samples. Evaluation of respective experimental results within the theoretical framework of microporomechanics showed that (i) Terzaghi's effective stress indeed governs trabecular bone failure, (ii) deviatoric stress states at the level of the solid bone matrix (also called tissue level) are primary candidates for initiating bone failure, and (iii) the high heterogeneity of these deviatoric tissue stresses, which increases with increasing intertrabecular porosity, governs the overall failure of trabecular bone. Result (i) lets us use the widely documented experimental results for strength values of bone samples without pore pressure, as to predict failure of the same bone samples under internal pore pressure. Result (ii) suggests a favorable mode for strength modeling of solid bone matrix. Finally, result (iii) underlines the suitability of microfinite element simulations for trabecular bone microstructures.

Impact of lymph node metastases on serum level of melanoma inhibitory activity in stage III melanoma patients.

Melanoma patients in stage III have a considerable recurrence rate. The 10-year survival in this stage depends on the number and size of affected nodes. Currently, there is no optimal serum marker for early detection of relapse available. The goal of the study was to assess the utility of melanoma inhibitory activity (MIA) serum marker in the follow up and primary diagnosis of stage III melanoma patients. One hundred and thirty-eight melanoma patients in stage III at time of primary diagnosis were analyzed at time of primary diagnosis and during periodical routine follow up both for serum MIA using an enzyme-linked immunosorbent assay and for serum lactate dehydrogenase (LDH). Results were correlated with the positivity of the sentinel lymph node (SLN) and the number of lymph node metastases in the completion lymph node dissection at time of primary diagnosis. During follow up, the overall survival time was assessed using the Kaplan-Meier method in terms of elevated MIA (>12 ng/mL) values. Regarding SLN status, significant differences of MIA values (P = 0.024) and LDH (P = 0.007) were found, both within the normal cut-off. Having lymph node metastases in the completion lymph node dissection, significantly higher MIA values (12.55 ng/mL [±0.48], P < 0.0001) were found. In patients with three or more tumor-positive nodes, MIA values were significantly higher when compared to patients with one or two affected nodes (P = 0.024). In the routine follow-up, stage III patients with an MIA value of more than 12 ng/mL had a five times higher risk for developing recurrences (P < 0.0001). Patients with relapsing disease had a significantly (P < 0.0001) higher mean MIA value (13.76 ng/mL) compared to patients without relapse (7.52 ng/mL). The MIA serum marker can be helpful in patients undergoing lymph node dissection. Furthermore, during follow up, patients showing relapsing diseases can have an elevated MIA value.

The role of disc-type crystal shape for micromechanical predictions of elasticity and strength of hydroxyapatite biomaterials.

The successful design of ceramic bone biomaterials is challenged by two competing requirements: on the one hand, such materials need to be stiff and strong, which would suggest a low porosity (of pore sizes in the 10-100 microm range) to be targeted; on the other hand, bone biomaterials need to be bioactive (in particular vascularized), which suggests a high porosity of such materials. Conclusively, reliable information on how porosity drives the stiffness and strength properties of ceramic bone biomaterials (tissue engineering scaffolds) is of great interest. In this context, mathematical models are increasingly being introduced into the field. Recently, self-consistent continuum micromechanics formulations have turned out as expressedly efficient and reliable tools to predict hydroxyapatite biomaterials' stiffness and strength, as a function of the biomaterial-specific porosity, and of the 'universal' properties of the individual hydroxyapatite crystals: their stiffness, strength and shape. However, the precise crystal shape can be suitably approximated by specific ellipsoidal shapes: while it was shown earlier that spherical shapes do not lead to satisfactory results, and that acicular shapes are an appropriate choice, we here concentrate on disc-type crystal shape as, besides needles, plates are often reported in micrographs of hydroxyapatite biomaterials. Disc-based model predictions of a substantial set of experimental data on stiffness and strength of hydroxyapatite biomaterials almost attain the quality of the very satisfactory needle-based models. This suggests that, as long as the crystal shape is clearly non-spherical, its precise shape is of secondary importance if stiffness and strength of hydroxyapatite biomaterials are predicted on the basis of continuum micromechanics, from their micromorphology and porosity.

Mechanical behavior of hydroxyapatite biomaterials: an experimentally validated micromechanical model for elasticity and strength.

Hydroxyapatite (HA) biomaterials production has been a major field in biomaterials science and biomechanical engineering. As concerns prediction of their stiffness and strength, we propose to go beyond statistical correlations with porosity or empirical structure-property relationships, as to resolve the material-immanent microstructures governing the overall mechanical behavior. The macroscopic mechanical properties are estimated from the microstructures of the materials and their composition, in a homogenization process based on continuum micromechanics. Thereby, biomaterials are envisioned as porous polycrystals consisting of HA needles and spherical pores. Validation of respective micromechanical models relies on two independent experimental sets: biomaterial-specific macroscopic (homogenized) stiffness and uniaxial (tensile and compressive) strength predicted from biomaterial-specific porosities, on the basis of biomaterial-independent ("universal") elastic and strength properties of HA, are compared with corresponding biomaterial-specific experimentally determined (acoustic and mechanical) stiffness and strength values. The good agreement between model predictions and the corresponding experiments underlines the potential of micromechanical modeling in improving biomaterial design, through optimization of key parameters such as porosities or geometries of microstructures, in order to reach the desired values for biomaterial stiffness or strength.

'Universal' microstructural patterns in cortical and trabecular, extracellular and extravascular bone materials: micromechanics-based prediction of anisotropic elasticity.

Bone materials are characterized by an astonishing variability and diversity. Still, because of 'architectural constraints' due to once chosen material constituents and their physical interaction, the fundamental hierarchical organization or basic building plans of bone materials remain largely unchanged during biological evolution. Such universal patterns of microstructural organization govern the mechanical interaction of the elementary components of bone (hydroxyapatite, collagen, water; with directly measurable tissue-independent elastic properties), which are here quantified through a multiscale homogenization scheme delivering effective elastic properties of bone materials: at a scale of 10nm, long cylindrical collagen molecules, attached to each other at their ends by approximately 1.5nm long crosslinks and hosting intermolecular water inbetween, form a contiguous matrix called wet collagen. At a scale of several hundred nanometers, wet collagen and mineral crystal agglomerations interpenetrate each other, forming the mineralized fibril. At a scale of 5-10microm, the extracellular solid bone matrix is represented as collagen fibril inclusions embedded in a foam of largely disordered (extrafibrillar) mineral crystals. At a scale above the ultrastructure, where lacunae are embedded in extracellular bone matrix, the extravascular bone material is observed. Model estimates predicted from tissue-specific composition data gained from a multitude of chemical and physical tests agree remarkably well with corresponding acoustic stiffness experiments across a variety of cortical and trabecular, extracellular and extravascular materials. Besides from reconciling the well-documented, seemingly opposed concepts of 'mineral-reinforced collagen matrix' and 'collagen-reinforced mineral matrix' for bone ultrastructure, this approach opens new possibilities in the exploitation of computer tomographic data for nano-to-macro mechanics of bone organs.