Bacillus cereus Biovar Anthracis Causing Anthrax in Sub-Saharan Africa—Chromosomal Monophyly and Broad Geographic Distribution

Through full genome analyses of four atypical Bacillus cereus isolates, designated B. cereus biovar anthracis, we describe a distinct clade within the B. cereus group that presents with anthrax-like disease, carrying virulence plasmids similar to those of classic Bacillus anthracis. We have isolated members of this clade from different mammals (wild chimpanzees, gorillas, an elephant and goats) in West and Central Africa (Côte d’Ivoire, Cameroon, Central African Republic and Democratic Republic of Congo). The isolates shared several phenotypic features of both B. anthracis and B. cereus, but differed amongst each other in motility and their resistance or sensitivity to penicillin. They all possessed the same mutation in the regulator gene plcR, different from the one found in B. anthracis, and in addition, carry genes which enable them to produce a second capsule composed of hyaluronic acid. Our findings show the existence of a discrete clade of the B. cereus group capable of causing anthrax-like disease, found in areas of high biodiversity, which are possibly also the origin of the worldwide distributed B. anthracis. Establishing the impact of these pathogenic bacteria on threatened wildlife species will require systematic investigation. Furthermore, the consumption of wildlife found dead by the local population and presence in a domestic animal reveal potential sources of exposure to humans

Persistent anthrax as a major driver of wildlife mortality in a tropical rainforest

Anthrax is a globally important animal disease and zoonosis. Despite this, our current knowledge of anthrax ecology is largely limited to arid ecosystems, where outbreaks are most commonly reported. Here we show that the dynamics of an anthrax-causing agent, Bacillus cereus biovar anthracis, in a tropical rainforest have severe consequences for local wildlife communities. Using data and samples collected over three decades, we show that rainforest anthrax is a persistent and widespread cause of death for a broad range of mammalian hosts. We predict that this pathogen will accelerate the decline and possibly result in the extirpation of local chimpanzee (Pan troglodytes verus) populations. We present the epidemiology of a cryptic pathogen and show that its presence has important implications for conservation

Investigating the zoonotic origin of the West African Ebola epidemic

The severe Ebola virus disease epidemic occurring in West Africa stems from a single zoonotic transmission event to a 2‐year‐old boy in Meliandou, Guinea. We investigated the zoonotic origins of the epidemic using wildlife surveys, interviews, and molecular analyses of bat and environmental samples. We found no evidence for a concurrent outbreak in larger wildlife. Exposure to fruit bats is common in the region, but the index case may have been infected by playing in a hollow tree housing a colony of insectivorous free‐tailed bats (Mops condylurus). Bats in this family have previously been discussed as potential sources for Ebola virus outbreaks, and experimental data have shown that this species can survive experimental infection. These analyses expand the range of possible Ebola virus sources to include insectivorous bats and reiterate the importance of broader sampling efforts for understanding Ebola virus ecology

Persistent anthrax as a major driver of wildlife mortality in a tropical rainforest

Anthrax is a globally important animal disease and zoonosis. Despite this, our current knowledge of anthrax ecology is largely limited to arid ecosystems, where outbreaks are most commonly reported. Here we show that the dynamics of an anthrax-causing agent, Bacillus cereus biovar anthracis, in a tropical rainforest have severe consequences for local wildlife communities. Using data and samples collected over three decades, we show that rainforest anthrax is a persistent and widespread cause of death for a broad range of mammalian hosts. We predict that this pathogen will accelerate the decline and possibly result in the extirpation of local chimpanzee (Pan troglodytes verus) populations. We present the epidemiology of a cryptic pathogen and show that its presence has important implications for conservation

A quantitative systems pharmacology approach, incorporating a novel liver model, for predicting pharmacokinetic drug-drug interactions

All pharmaceutical companies are required to assess pharmacokinetic drug-drug interactions (DDIs) of new chemical entities (NCEs) and mathematical prediction helps to select the best NCE candidate with regard to adverse effects resulting from a DDI before any costly clinical studies. Most current models assume that the liver is a homogeneous organ where the majority of the metabolism occurs. However, the circulatory system of the liver has a complex hierarchical geometry which distributes xenobiotics throughout the organ. Nevertheless, the lobule (liver unit), located at the end of each branch, is composed of many sinusoids where the blood flow can vary and therefore creates heterogeneity (e.g. drug concentration, enzyme level). A liver model was constructed by describing the geometry of a lobule, where the blood velocity increases toward the central vein, and by modeling the exchange mechanisms between the blood and hepatocytes. Moreover, the three major DDI mechanisms of metabolic enzymes; competitive inhibition, mechanism based inhibition and induction, were accounted for with an undefined number of drugs and/or enzymes. The liver model was incorporated into a physiological-based pharmacokinetic (PBPK) model and simulations produced, that in turn were compared to ten clinical results. The liver model generated a hierarchy of 5 sinusoidal levels and estimated a blood volume of 283 mL and a cell density of 193 × 106 cells/g in the liver. The overall PBPK model predicted the pharmacokinetics of midazolam and the magnitude of the clinical DDI with perpetrator drug(s) including spatial and temporal enzyme levels changes. The model presented herein may reduce costs and the use of laboratory animals and give the opportunity to explore different clinical scenarios, which reduce the risk of adverse events, prior to costly human clinical studies

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Epidemiologie und Ökologie von Bacillus cereus biovar anthracis im Taï Nationalpark, Elfenbeinküste

Sudden death was observed in chimpanzees and gorillas in Côte d’Ivoire (Taï National Park) and Cameroon (Dja Reserve) in 2001 and 2004 and the causative agent was identified as a before unknown Bacillus anthracis-like bacterium designated Bacillus cereus biovar anthracis (Bcbva) (1, 2). Bcbva combines the chromosomal background of B. cereus with the virulence plasmids of B. anthracis and was shown to be as virulent as B. anthracis in small animal models (3). As part of an ongoing long-term study in Taï National Park (TNP), autopsies on all available deceased wildlife were performed and environmental samples were collected. Bcbva positive samples dated back up to 1991 and Bcbva was identified as a continuous cause of death for a number of large mammal species (4). The aim of the present study was to investigate the epidemiology and ecology of Bcbva in its natural rainforest habitat in TNP using a broad array of phylogenetic and serological methods. Bacterial isolates could be retrieved from various sample types (tissue samples, bones, carrion flies) and 178 whole Bcbva genomes were derived covering a period from 1996 to 2014. SNP-based phylogenomic analysis in a Bayesian statistical framework revealed that Bcbva chromosomes had measurably evolved over this time span. This allowed us to determine that the median time to their most recent common ancestor (tMRCA) was 146 years (95 % highest posterior density (HPD): 70-237) and that 0.2 new mutations are introduced in average per Bcbva chromosome/year. Bayesian Markov Chain Monte Carlo (BMCMC) analyses were run under several demographic models. No model outperformed a constant population size model, suggesting Bcbva population size did not vary much over this period. To further inform the latter, in vitro experiments were performed determining the whole genome mutation rate of Bcbva, which was shown to be comparable to the in vitro mutation rate of B. anthracis. Comparison of Bcbva evolutionary rate and in vitro mutation rate approximated hypothetical Bcbva activity to be in average 102 generations/year, pointing against a significant extra mammalian lifecycle of Bcbva.The whole genome sequencing data provided evidence for multiple co-existing transmission chains that appear to be localized within different areas of the park. Genomic and geographic distances were correlated, particularly when genomic distances were low, reflecting the carcass-mediated dynamics of the disease. To reveal further possible transmission pathways, carrion flies were trapped in the rainforest canopy and we were able to isolate Bcbva from flies caught up to 25m high. While we observe constant substantial pressure by Bcbva on the TNP fauna, only two monkeys were found to have significant amounts of antibodies against the disease in a serological study in five different wildlife species (n=59), indicating that Bcbva-infections in these species are likely often lethal. Combining data from TNP with sequence data from other sites of Bcbva occurrence revealed that Bcbva has been present in sub-Saharan Africa for millennia.Der plötzliche Tod von Schimpansen in Côte d’Ivoire (Taï National Park) und Gorillas in Kamerun (Dja Reservat) in den Jahren 2001 und 2004 wurde von einem unbekannten Bacillus anthracis-ähnlichen Erreger verursacht, der später als Bacillus cereus biovar anthracis (Bcbva) bezeichnet wurde. Bcbva kombiniert den chromosomalen Hintergrund von Bacillus cereus mit den Virulenzplasmiden von Bacillus anthracis. In Tierversuchen wurde gezeigt, dass die Virulenz von B. cereus und B. anthracis vergleichbar ist. Im Rahmen einer Langzeitstudie im Taï National Park (TNP) wurden alle gefundenen Wildtierkadaver autopsiert und Umweltproben gesammelt. Bcbva positive Proben reichen zurück bis 1991 und es konnte gezeigt werden, dass Bcbva kontinuierlich Todesfälle bei mehreren Säugetierarten verursacht. Das Ziel dieser Dissertation war es, unter Anwendung phylogenetischer und serologischer Methoden die Epidemiologie und Ökologie von Bcbva im Taï Nationalpark, dem natürlichen Regenwaldhabitat des Erregers, zu untersuchen. Bcbva konnte aus verschiedenen Probenmaterialien kultiviert werden (Gewebe, Knochen, Aasfliegen) und 178 Bcbva Vollgenome wurden sequenzanalysiert. Diese decken den Zeitraum von 1996 bis 2014 ab. SNP-basierte phylogenetische Analysen unter Anwendung bayesischer statistischer Methoden zeigten eine messbare Evolution des Erregers über diesen Zeitraum. Die Zeit bis zum letzten gemeinsamen Vorfahren der Isolate (tMRCA) beträgt 146 Jahre (95% Konfidenzintervall: 70-237 Jahre) und pro Bcbva Chromosom und Jahr enstehen im Durchschnitt 0.2 neue Mutationen. In bayesischen Monte-Carlo-Sampling-Verfahren (BMCMC) unter Annahme verschiedener demografischer Szenarien war kein Modell wahrscheinlicher als die Annahme einer konstanten Bakterienpopulation. Dies deutet darauf hin, dass die Größe der Bakterienpopulation über diesen Zeitraum nicht bedeutend variiert hat. Um diese Ergebnisse besser einordnen zu können, wurde die Mutationsrate des Bcbva Gesamtgenoms in in vitro Experimenten bestimmt. Diese ist vergleichbar mit der Mutationsrate von B. anthracis. Der Vergleich der Evolutions- und der Mutationsrate von Bcbva deutet darauf hin, dass der Erreger im TNP im Durschnitt pro Jahr nur 102 Generationen durchläuft. Dies spricht gegen eine bedeutende Vermehrung des Erregers außerhalb von Säugetierwirten. Weiterhin deckten die Sequenzdaten mehrere parallele Infektionsketten in unterschiedlichen Teilen des Parks auf. Für kleine genomische Distanzen sind genomische und geographische Distanz der Isolate korreliert, eine typische Folge der Ansteckung an eingegrenzten Quellen, z.B. Kadavern. Um weitere mögliche Übetragungswege aufzudecken, wurden Aasfliegen auch im Blätterdach des Regenwaldes gefangen. Bcbva konnte aus Fliegen aus einer Höhe von bis zu 25m kultiviert werden. Trotz des großflächigen, konstanten Drucks von Bcbva auf die TNP Fauna zeigten in einer serologischen Studie in fünf Wildtierspezies (n=59) nur zwei Affen eine eindeutige Antikörperantwort gegen Milzbrand. Dies ist ein Hinweis dafür, dass Bcbva-Infektionen in den getesteten Spezies oft tödlich enden. Abschließend führte eine Kombination unserer im TNP erhobenen Daten mit Bcbva Sequenzdaten aus anderen Ländern zu der Einschätzung, dass Bcbva schon seit mehreren tausend Jahren im Afrika südlich der Sahara existiert