Listeria pathogenesis and molecular virulence determinants

The gram-positive bacterium Listeria monocytogenes is the causative agent of listeriosis, a highly fatal opportunistic foodborne infection. Pregnant women, neonates, the elderly, and debilitated or immunocompromised patients in general are predominantly affected, although the disease can also develop in normal individuals. Clinical manifestations of invasive listeriosis are usually severe and include abortion, sepsis, and meningoencephalitis. Listeriosis can also manifest as a febrile gastroenteritis syndrome. In addition to humans, L. monocytogenes affects many vertebrate species, including birds. Listeria ivanovii, a second pathogenic species of the genus, is specific for ruminants. Our current view of the pathophysiology of listeriosis derives largely from studies with the mouse infection model. Pathogenic listeriae enter the host primarily through the intestine. The liver is thought to be their first target organ after intestinal translocation. In the liver, listeriae actively multiply until the infection is controlled by a cell-mediated immune response. This initial, subclinical step of listeriosis is thought to be common due to the frequent presence of pathogenic L. monocytogenes in food. In normal indivuals, the continual exposure to listerial antigens probably contributes to the maintenance of anti-Listeria memory T cells. However, in debilitated and immunocompromised patients, the unrestricted proliferation of listeriae in the liver may result in prolonged low-level bacteremia, leading to invasion of the preferred secondary target organs (the brain and the gravid uterus) and to overt clinical disease. L. monocytogenes and L. ivanovii are facultative intracellular parasites able to survive in macrophages and to invade a variety of normally nonphagocytic cells, such as epithelial cells, hepatocytes, and endothelial cells. In all these cell types, pathogenic listeriae go through an intracellular life cycle involving early escape from the phagocytic vacuole, rapid intracytoplasmic multiplication, bacterially induced actin-based motility, and direct spread to neighboring cells, in which they reinitiate the cycle. In this way, listeriae disseminate in host tissues sheltered from the humoral arm of the immune system. Over the last 15 years, a number of virulence factors involved in key steps of this intracellular life cycle have been identified. This review describes in detail the molecular determinants of Listeria virulence and their mechanism of action and summarizes the current knowledge on the pathophysiology of listeriosis and the cell biology and host cell responses to Listeria infection. This article provides an updated perspective of the development of our understanding of Listeria pathogenesis from the first molecular genetic analyses of virulence mechanisms reported in 1985 until the start of the genomic era of Listeria research

Development of Methods for the Determination of PhACs in Soil/Earthworm/Crop System Irrigated with Reclaimed Water

Pharmaceuticals have been becoming a major concern of environmental pollution since the beginning of the century. The ways in which these contaminants are introduced into the environment are very different, but almost always associated with wastewater. In fact, current wastewater treatment plants are not designed for the removal of pharmaceutical products. Indeed, the problem of water scarcity has played an important role in the introduction of pharmaceutical products into the environment, particularly in the agricultural sector. Because of the drought, more and more countries are resorting to the use of treated wastewater to irrigate vegetables for human consumption. Consequently, the reuse of wastewater in agriculture constitutes a continuous introduction of these molecules into the soil. The effects of this practice are not entirely clear. However, the probability that these compounds can enter the food chain directly is high. In fact, through radical absorption, plants could uptake pharmaceuticals from soil and water, leading to the accumulation of drugs in the tissues. The development of analytical methods of solid matrices such as soil or plant tissues requires substantial work due to the great complexity of the matrices and the differences between the physico-chemical properties of analytes of interest. Several multi-class methods have recently been developed to determine a large number of pharmaceutical products in soil or plants using different extraction techniques. This chapter addresses to list all the analytical procedures published so far used for the extraction and analysis of pharmaceutical products from plant tissues and from the soil irrigated with treated wastewater.This study has been financially supported by the EU through the WaterJPI-2015 AWARE project (PCIN-2017-067). This work was supported by the Spanish Ministry of Science and Innovation (Project CEX2018-000794-S). The authors thank the Water Challenges for a Changing World Joint Programming Initiative.Peer reviewe