Efflux pumps (EPs) are relevant elements present in all organisms and represent a group of proteins involved in the transport process. The main feature is their ability to extrude a large variety of substrates in addition to antibiotics. Efflux pumps share a conserved organization both at genetic and structural level. In many pathogenic bacteria multidrug EPs contribute to the intrinsic or acquired resistance to antibiotics. It has been suggested by several studies that multidrug efflux pumps, in addition to antibiotic resistance, contribute to other relevant processes of microbial physiology, such as the interactions with host cells. Pathogenic bacteria present different infection mechanisms and they are able to survive within the host cell. Escherichia coli is not only a harmless commensal of normal intestinal microflora, but different strains cause intestinal and extraintestinal diseases. Our model sistem is the invasive adherent E. coli (AIEC) which represents a group of pathogenic bacteria that have been implicated in Chron's ileal disease. AIEC strains are able to adhere and invade the intestinal epithelium and replicate rapidly in epithelial cells. After that, AIEC can translocate through the intestinal epithelium into the lamina propria, where bacteria interact and survive within macrophages without inducing cell death. The project presented is aimed at analyzing the different multidrug efflux pumps present in LF82 and their expression profile in order to understand which of them are more induced during the invasion of macrophages and epithelial cells and how they are regulated.
Escherichia coli is not only a natural commensal of the intestinal microbiota, but it is the major cause of morbidity and mortality (Kaper et al., 2004; Wirth et al., 2006). Indeed, different strains are associated with inflammatory intestinal and extraintestinal diseases (Croxen and Finlay, 2009; Gomes et al., 2016). Among the intestinal pathogenic bacteria the most recently identified pathotype is the invasive adherent E. coli (AIEC) which is associated with the ileal Chron's diseases. The AIEC stains are able to adhere and invade epithelial cells in the ileum moving then towards to the lamina propria where they infect macrophages without inducing cell death (Glasseer et al., 2001). Furthermore, there are evidence suggesting that AIECs are involved in granulomas formation (Rolhion and Darfeuille-Michaud, 2007). Several strategies have been proposed to slow down or block the natural course of the disease, but the results obtained so far are not fully significant (Hansen and Sartor, 2015). The multidrug efflux pumps are a large group of proteins involved in the transport process and play a crucial role in antibiotic resistance processes. Beside drug resistance EPs are involved in the pathogenic process of some pathogens such as Salmonella, Vibrio Cholera and Shigella (Piddock et al., 2006; Alcade-Rico et al., 2016; Pasqua et al., 2019).
The results we obtained, relating to the expression profile of the efflux pumps in LF82 in epithelial cells and macrophage, help to define which Multidrug efflux pumps are present in AIEC LF82 and which of them are expressed during the intracellular life of this pathogenic bacterium.
While EPs systems have been studied in several pathogenic bacteria, no date are available on these system in adherent-invasive Escherichia coli (AIEC). Based on this knowledge we believe that it might be relevant to understand whether also in AIEC EPs play a role in the interaction with the host cell during the infection processes focusing on those pumps that showed the highest levels of expression in macrophages. The work we are doing therefore offers a new perspective in the studies of the interactions between LF82 AIEC strain and infected cells. In particular, this study highlights how AIEC strains are able to respond to the host's harsh environment they encounter within the fagolysosome by expressing, among other factors, also MDR EP to eliminate toxic compounds.
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