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Role of bacterial kinases and phosphatases in Staphylococcus aureus infection

S. aureus is a major human pathogen responsible for nosocomial and community-acquired infections that can affect almost all organs, and is notably implicated in skin and soft tissue infections, necrotising pneumonia and infective endocarditis.
S. aureus has an exceptional ability to survive in adverse conditions, either by adapting to environmental factors or by defending itself against exogenous stresses. In the human host, the bacterium can infect and reside in a wide range of tissues, from superficial surfaces such as the skin to deeper tissues such as the gastrointestinal tract, heart and bone. The main objective of this project is to study the role of bacterial kinases and phosphatases secreted during infection, thereby modifying the overall host response and adaptation of S. aureus. Our research focuses on the bacterial kinases and phosphatases involved in the survival of S. aureus during infection in phagocytic and non-phagocytic host cells.


Role of S. aureus prophages in diabetes-related infections

Diabetes mellitus is a major public health problem. Foot ulcers in these patients are very common, leading to polymicrobial infections and subsequent amputations. We have previously identified the presence of colonising strains of S. aureus in these wounds.
These strains have the particularity of possessing a stable integrated phage (prophage) which significantly reduces the virulence of the strain and increases biofilm formation. We have recently characterised the role of the prophage on the virulence and persistence of S. aureus in infected wounds via cellular and animal infection models; identified a phage gene involved in this process (ssb-P) involving a reduction in the immune response; characterised the host response mechanisms involved via transcriptomics.


Role of the host post-translational response during infection

During infection, pathogenic bacteria exploit several eukaryotic signalling pathways and manipulate the host cell to enable their own replication and propagation and to evade host immune responses.
Post-translational modifications (PTMs) are essential regulatory mechanisms that can rapidly and reversibly affect protein functions. PTMs include phosphorylation, acetylation and methylation, as well as the addition of small polypeptides such as ubiquitin or ubiquitin-like proteins (SUMOylation). While several pathogens are known to use PTMs to their own advantage, only a few bacterial pathogens have been reported to interfere with the SUMOylation process. One of the strategies used by S. aureus to survive inside host cells is to bypass host defences, although very little is known about the signals, sensors and effectors that mediate this adaptation. We have recently demonstrated that S. aureus is able to modify the SUMOylation response in order to persist at long infection times. In addition, we have just demonstrated that the phosphatase PtpA is involved in the host SUMO response.



Identification and molecular characterisation of new anti-staphylococcal bacteriophages

More than a century ago, bacteriophages were proposed as an alternative therapy for bacterial diseases. However, the discovery of antibiotics meant that phage therapy was largely ignored, with the exception of a few Eastern European countries. The increase in antibacterial resistance requires the development of new and/or complementary antibacterial approaches, and the use of specialised and individualised phage mixtures has proved to be an interesting alternative in the fight against multi-resistant bacteria.

Phages are lytic viruses that infect bacteria with a high degree of specificity. Lytic phages are often considered to be the most acceptable treatment for use in humans, as they are effective in killing their host in a short period of time, which considerably minimises the likelihood of bacteria acquiring resistance to phages. We have developed a therapeutic approach based on the use of bacteriophages to effectively combat staphylococcal infections of diabetic foot ulcers. We have now isolated several bacteriophages capable of specifically lysing the clinical strains involved in these infections.

Our collaboration with the GREENPHAGE Company aims to develop an innovative therapeutic approach based on bacteriophages, to effectively combat S. aureus infections. This collaboration will enable us to jointly set up and develop the first in vivo trials to assess the antibacterial activity of bacteriophages in S. aureus infections on the zebrafish animal model.



Development of a diabetic zebrafish model infected with S. aureus

We are developing a zebrafish pathological model mimicking the diabetic foot infected by S. aureus in order to validate in vivo the efficacy of treatment against foot infections. It is essential to develop a predictive model,
close to the pathological conditions in humans, and in particular to reproduce the infectious environment observed in diabetic foot wounds. Our model of bone lesion associated with bacterial infection using zebrafish embryos has made it possible to mimic the pathologies observed following an open wound such as a skin lesion, wound, cut, surgical operation with or without fitting a prosthesis, bedsore, leg ulcer or diabetic foot, in humans under normal or pathological conditions.

Development of a Dictyostelium discoideum model to study membrane trafficking events during S. aureus phagocytosis

Many pathogenic bacteria have developed various mechanisms to evade host cell defences. As part of our long-standing analysis of phagosome maturation processes in cell biology, our projects began by understanding
the membrane trafficking events required for the formation of the ‘Legionella-containing vacuole’ (LCV), a model bacterium for studying these interactions. Using the amoeba D. discoideum, a phagocytic host model for the study of L. pneumophila infection, we recently revealed the role of the GTPase Atlastin (Sey1, a member of the dynamin superfamily) in endoplasmic reticulum recruitment to the LCV. Based on our expertise, we have extended the use of this amoeba to the study of intracellular trafficking events during S. aureus infections. This model is highly complementary to our cell and zebrafish models.

Dr. Virginie MOLLE, PhD

+33 (0)6 08 06 49 03