OECD validation study to assess intra- and inter-laboratory reproducibility of the zebrafish embryo toxicity test for acute aquatic toxicity testing

The OECD validation study of the zebrafish embryo acute toxicity test (ZFET) for acute aquatic toxicity testing evaluated the ZFET reproducibility by testing 20 chemicals at 5 different concentrations in 3 independent runs in at least 3 laboratories. Stock solutions and test concentrations were analytically confirmed for 11 chemicals. Newly fertilised zebrafish eggs (20/concentration and control) were exposed for 96 h to chemicals. Four apical endpoints were recorded daily as indicators of acute lethality: coagulation of the embryo, lack of somite formation, non-detachment of the tail bud from the yolk sac and lack of heartbeat. Results (LC50 values for 48/96 h exposure) show that the ZFET is a robust method with a good intra- and inter-laboratory reproducibility (CV 30%) for some very toxic or volatile chemicals, and chemicals tested close to their limit of solubility. The ZFET is now available as OECD Test Guideline 236. Considering the high predictive capacity of the ZFET demonstrated by Belanger et al. (2013) in their retrospective analysis of acute fish toxicity and fish embryo acute toxicity data, the ZFET is ready to be considered for acute fish toxicity for regulatory purposes

An RND-Type Efflux System in Borrelia burgdorferi Is Involved in Virulence and Resistance to Antimicrobial Compounds

Borrelia burgdorferi is remarkable for its ability to thrive in widely different environments due to its ability to infect various organisms. In comparison to enteric Gram-negative bacteria, these spirochetes have only a few transmembrane proteins some of which are thought to play a role in solute and nutrient uptake and excretion of toxic substances. Here, we have identified an outer membrane protein, BesC, which is part of a putative export system comprising the components BesA, BesB and BesC. We show that BesC, a TolC homolog, forms channels in planar lipid bilayers and is involved in antibiotic resistance. A besC knockout was unable to establish infection in mice, signifying the importance of this outer membrane channel in the mammalian host. The biophysical properties of BesC could be explained by a model based on the channel-tunnel structure. We have also generated a structural model of the efflux apparatus showing the putative spatial orientation of BesC with respect to the AcrAB homologs BesAB. We believe that our findings will be helpful in unraveling the pathogenic mechanisms of borreliae as well as in developing novel therapeutic agents aiming to block the function of this secretion apparatus

The CPCAT as a novel tool to overcome the shortcomings of NOEC/LOEC statistics in ecotoxicology: a simulation study to evaluate the statistical power

Abstract Species reproduction is an important determinant of population dynamics. As such, this is an important parameter in environmental risk assessment. The closure principle computational approach test (CPCAT) was recently proposed as a method to derive a NOEC/LOEC for reproduction count data such as the number of juvenile Daphnia. The Poisson distribution used by CPCAT can be too restrictive as a model of the data-generating process. In practice, the generalized Poisson distribution could be more appropriate, as it allows for inequality of the population mean $$\mu$$ μ and the population variance $$\sigma ^2$$ σ2 . It is of fundamental interest to explore the statistical power of CPCAT and the probability of determining a regulatory relevant effect correctly. Using a simulation, we varied between Poisson distribution ($$\mu =\sigma ^2$$ μ=σ2 ) and generalized Poisson distribution allowing for over-dispersion ($$\mu \sigma ^2$$ μ>σ2 ). The results indicated that the probability of detecting the LOEC/NOEC correctly was $$\ge 0.8$$ ≥0.8 provided the effect was at least 20% above or below the mean level of the control group and mean reproduction of the control was at least 50 individuals while over-dispersion was missing. Specifically, under-dispersion increased, whereas over-dispersion reduced the statistical power of the CPCAT. Using the well-known Hampel identifier, we propose a simple and straight forward method to assess whether the data-generating process of real data could be over- or under-dispersed

Vor-Ort-Nachweis bioterroristisch relevanter Agenzien

In Europa besteht eine abstrakte Gefährdungslage nicht nur für konventionell durchgeführte Anschläge mit Waffen oder Sprengstoffen, sondern auch für Anschläge, bei denen biologische Agenzien eingesetzt werden. Zur Gefahrenabwehr werden daher kontinuierlich schnelle und zuverlässige Nachweisverfahren entwickelt und erprobt. Für die Anwendung im stationären Labor wurde für bioterroristisch relevante Agenzien bereits ein umfassendes Spektrum an Nachweismethoden etabliert. Für eine Vor-Ort-Detektion aus Umweltproben werden darüber hinaus von den Einsatzkräften zunehmend vergleichbar verlässliche mobile Nachweissysteme zur ersten Lagebewertung gewünscht. Basierend auf den Funktionsprinzipien können generische, immunologische und nukleinsäurebasierte Vor-Ort-Detektionsverfahren unterschieden werden. Diese sollten einfach durchzuführen, schnell, sensitiv und spezifisch sein. Kommerziell erhältliche Vor-Ort-Detektionssysteme haben systembedingt häufig eine eingeschränkte Sensitivität und sind zumeist nicht von unabhängiger Seite validiert. Darüber hinaus stellt die Vielfalt an potenziell nachzuweisenden Agenzien in komplexen Umweltproben eine besondere Herausforderung dar. Daher ist detailliertes Wissen über Einsatzbereiche und Limitation der verwendeten Testsysteme zwingend erforderlich, um erhaltene Ergebnisse zielführend bewerten und Handlungsempfehlungen ableiten zu können. Ziel dieses Artikels ist es, einen Überblick über die Messprinzipien von Vor-Ort-Detektionssystemen für bioterroristisch relevante Viren, Bakterien und Toxine sowie Vor- und Nachteile der Testsysteme zu geben. Trotz vielversprechender Entwicklungen sind derzeit erhältliche Testsysteme zur Vor-Ort-Detektion noch beschränkt aussagekräftig. Deshalb sind Expertenlabore zur gesicherten Befundung von Umweltproben weiterhin einzubeziehen