Our research aims at understanding bacterial intracellular lifestyles for the development/optimization of antimicrobial therapies
Below is a summary of the main research lines of the group.
Identification and characterization of microRNAs regulating infection by bacterial pathogens
MicroRNAs, due to their instrumental role as post-transcriptional regulators of gene expression, are emerging as important players in the interaction between mammalian hosts and bacterial pathogens. We have pioneered the application of high-content microscopy screenings coupled with genome-wide libraries for modulation of microRNA levels, to identify microRNAs controlling infection by important bacterial pathogens – Salmonella Typhimurium, Shigella flexneri, Campylobacter jejuni, and Staphylococcus aureus.
The identification and characterization of downstream microRNA targets are also leading to the discovery of novel molecular players and pathways relevant to the host-pathogen interplay. Among others, we have identified and characterized the host cell cycle as a major player in Salmonella infection, and shown that microRNAs play a critical role in the regulation of Shigella capture by host filopodia, as well as in the control of bacterial actin-based motility for intra- and inter-cellular spreading. Our work highlights the diverse nature of microRNA regulation in bacterial infections, showcasing its role either in the host response to the infection or as a strategy employed by bacteria to alter the host environment to promote pathogenesis.
Investigation of the molecular mechanisms of microRNA regulation by bacterial pathogens
The impact of bacterial infection on the host miRNome expression and the underlying molecular mechanisms are also crucial to understand bacterial pathogenesis. To address this issue, we have been performing RNA-sequencing analysis of the small RNA population of epithelial cells infected with various bacterial pathogens, analyzing both infected and bystander cells. We discovered, for example, that Salmonella infection of epithelial cells leads to a dramatic downregulation of microRNA expression (ca. 50% of the total detected microRNAs), which occurs both in host cells with internalized bacteria, as well as in bystander cells. These changes are dependent, to a large extent, on the transcription factor E2F1.
Bystander cell activation is increasingly recognized as a crucial event in bacterial pathogen-host interactions, mostly as part of the host immune response. Along this line, we have recently discovered that regulation of microRNA expression renders bystander cells more permissive to Salmonella infection. This demonstrates that, in contrast to the established paradigm that bystander cell reprogramming serves solely an anti-infective purpose, bacterial pathogens are able to subvert bystander cell functions in order to stimulate bacterial replication and dissemination.
Deciphering intracellular lifestyles of Staphylococcus aureus to optimize antimicrobial therapies
Staphylococcus aureus is an important human pathogen responsible for a broad spectrum of life-threatening nosocomial and community-acquired infections, and one of the leading pathogens responsible for deaths associated with antimicrobial resistance. S. aureus was initially considered an extracellular pathogen, though cumulating evidence indicates that it is a facultative intracellular pathogen.
To understand the relevance and prevalence of S. aureus intracellular lifestyle, we have applied fluorescence microscopy-based infection assays and automated image analysis to profile the interaction of 191 S. aureus isolates from patients with bone/joint infections, bacteremia, and infective endocarditis, with four host cell types (epithelial and endothelial cells, osteoblasts, and macrophages), at five times post-infection. This study established S. aureus intracellular lifestyle as a prevalent feature and identified a great diversity of intracellular fates of the clinical isolates, with relevance to pathogenicity.