Dr. Riadh Hammami

Biography

Dr. Hammami completed in 2004 his Master's degree in Biochemistry at the Institute Pasteur of Tunis, University of Tunis El Manar. He received in 2009 his Doctorate in Molecular and Cellular Biology from the University of Lille1 - Sciences & Technologies (France) in conjunction with the University of Tunis El Manar (Tunisia). He then completed five years post-doctoral training in Food Sciences & Technologies at Université Laval, Canada. He was afterward a research scientist at the Institute of Nutrition and Functional Food (INAF), Université Laval. In 2017, Dr. Hammami joined the school of Nutrition Sciences, Faculty of Health Sciences, at the University of Ottawa as an Assistant Professor in gut microbiology.

Research Interests

Dr. Hammami`s research has focused mainly on the potential application of probiotics and their metabolites to modulate the gut microbiota positively and for food safety. He has conducted multiple studies to investigate the probiotic potential of commensal bacteria, their metabolite production, and stability during transit in the gut, and interaction with gut microbiota in- and ex- vivo. Dr. Hammami`s research centers on gut microbiota physiology, its mechanistic modulation by nutritional and xenobiotic factors, and interplay with the host, and is built with around three themes: I) Gut Neuromicrobiology, 2) Interplay Xenobiotics-Microbiota-Nutrition, and 3) Investigation of new probiotic-prebiotic-postbiotic-symbiotic formulations with positive modulation of the gut microbiota and the host.

Neuromicrobiology: how probiotics influence the gut-brain axis? Our gut is populated by a complex microbial community, known as the gut microbiota, which has been linked to many health disorders, including mental health. Psychobiotics are beneficial bacteria (probiotics) or support for such bacteria (prebiotics) that can positively modulate microbiota–gut–brain interactions. While some studies reported mitigated efficacy, several trials support a role for psychobiotics in the normalization of brain processes related to stress responses and mood improvements. The mechanisms by which psychobiotics modulate the microbiota–gut–brain axis and improve mental health remain uncertain but are likely microbial strain-specific. Gut bacteria produce a range of neurotransmitters, including g-aminobutyric acid (GABA), acetylcholine, dopamine, and serotonin, which, beyond interacting with intestinal physiology, can transit through neural pathways linking the enteric and central nervous systems and influence brain functioning. However, there is limited understanding of the neurochemical mechanisms by which psychobiotics orchestrate the microbiota-gut-brain axis, a prerequisite for developing evidence-based microbiota-targeted interventions. Findings from this research will inform the design and development of next-generation probiotics or functional food products with psychobiotic properties, which will be important for the community at large as they will hold the potential to improve human mental health.

Xenobiotics in the gut – protecting human gut microbiota from psychotropics using probiotics: There is an increasing interest in how therapeutic drugs (xenobiotics) could affect and alter the human gut microbiota composition and function. While some knowledge is accumulating on the detrimental impact of some psychotropics on isolated strains or the gut microbiota of animal models, information about other classes of psychotropics and representative species from the human gut is poorly investigated. The antimicrobial effect of psychotropic drugs is usually neglected as a confounding factor when investigating gut microbiome biomarkers, knowing that patients are generally put in long-term medication. There is an urgent need to clarify the real contribution of the antimicrobial role of psychotropics and the subsequent consequences to gut microbiota structure and metabolism. Our findings provide evidence that psychotropics, through their antimicrobial effect, have the potential to alter the human gut microbiota composition and metabolism, while probiotics can mitigate the related dysbiosis. The present research provides new insights into the existing interplay between psychotropic chemicals and gut microbiota, while further investigations are in progress.

Probiotics, Prebiotics, and Postbiotics for positive modulation of the gut microbiota and the host: At the NuGUT Research Platform, which focuses on nutrition-gut interactions, we employ an ex-vivo continuous fermentation model that simulates the human colon to assess the effect of different dietary formulations on microbiota structure functionality. There is a need to understand the chain of events linking food properties and composition, mainly probiotics and dietary fibers, with their effects on host health via the gut microbiota. Our research also explores extracellular vesicles production as a pathway mechanism by which microbiota interact with the gut–brain axis, as well as it is potential to restore dysbiotic gut microbiota, reach the systemic circulation, and deliver host-modulating metabolites in the brain to promote antidepressant effects. Our funded research also aims to develop an integrated nutritional approach based on the use of bacteriocinogenic bacteria for the positive modulation of the gut microbiota while reducing the vertical incidence of foodborne pathogens (such as Salmonella and Campylobacter) in animals.

Selected Publications

• Ait Chait Y., Mottawea W., Tompkins T.A., Hammami R. (2021) Nutritional and therapeutic approaches for protecting human gut microbiota from psychotropic treatments. Progress in Neuropsychopharmacology & Biological Psychiatry 108:110182.
• Soltani S., Hammami R., Cotter P.D, Gaudreau H., Bédard F., Vimont A., Biron E., Drider D., and Fliss I. (2021) Bacteriocins as a new generation of antimicrobials: Toxicity aspects and regulations. FEMS Microbiology Reviews 45(1):fuaa039.
• Lone A., Mottawea W., Ait Chait Y., Hammami R. (2021) Dual Inhibition of Salmonella enterica and Clostridium perfringens by New Probiotic Candidates Isolated from Chicken Intestinal Mucosa. Microorganisms. 9(1):166.
• Ait Chait Y., Mottawea W., Tompkins T.A., Hammami R. (2020) Unravelling the Antimicrobial side of antidepressants on gut commensal microbes. Scientific reports 10(1):17878.

• Mottawea W., Sultan S., Landau K., Bordenave N., Hammami R. (2020) Evaluation of the prebiotic potential of a commercial synbiotic food ingredient on gut microbiota in an ex vivo model of the human colon. Nutrients 12(9):2669.

• Sultan S., El‐Mowafy M., Elgaml A., El‐Mesery M., Elegezy M., Hammami R., Mottawea W. (2020) Alterations of the treatment-naive gut microbiome in newly diagnosed Hepatitis C Virus Infection. ACS Infectious Diseases; doi: 10.1021/acsinfecdis.0c00432.

• Abdmouleh F.*, El Arbi M., Ben Saad H., Jellali K., Ketata E., Ben Amara I., Pigeon P., Ben Hassen H., Top S., Jaouen G., Hammami R., Ben Ali M., Gupta G.K. (2020). Antimicrobial, antitumor and side effects assessment of a newly synthesized tamoxifen analogue. Current Topics in Medicinal Chemistry; DOI: 10.2174/1568026620666200819145526.

• Behera S.S., El Sheikha A.F., Hammami R., and Kumar A. (2020). Traditionally fermented pickles: How the microbial diversity associated with their nutritional and health benefits? J. Funct Foods. 70, 103971.
• Gerliani N.*, Hammami R., and Aïder M. (2020) Extraction of protein and carbohydrates from soybean meal using acidic and alkaline solutions produced by electro‐activation. Food Sci Nutr.  00:1-14.
• Gerliani N., Hammami R., and Aïder M. (2020) A Comparative study of the functional properties and antioxidant activity of soybean meal extracts obtained by conventional extraction and electro-activated solutions. Food Chemistry 307: 125547.
• Gerliani N., Hammami R., and Aïder M. (2019) Production of functional beverage by using protein-carbohydrate extract obtained from soybean meal by electro-activation. LWT - Food Science and Technology 113: 108259.
• Gerliani N., Hammami R., and Aïder M. (2019) Assessment of the extractability of protein-carbohydrate concentrate from soybean meal under acidic and alkaline conditions. Food Bioscience 28: 116-124.
• Ahmed T.A.E. and Hammami R. (2019) Recent insights into structure-function relationships of antimicrobial peptides. J. Food Biochem. e12546 (invited review).
• Hanchi H., Mottawea W., Sebei K., and Hammami R. (2018) The genus Enterococcus: between probiotic potential and safety concerns – an update. Front. Microbiol. 9:1791.
• Naimi S., Zirah S., Hammami R., Fernandez B., Rebuffat S., Fliss I. (2018) Fate and biological activity of the antimicrobial lasso peptide microcin J25 under gastrointestinal tract conditions. Frontiers in Microbiology 9:1764.
• Bédard F., Hammami R., Zirah S., Rebuffat S., Fliss I., Biron E. (2018) Synthesis, antimicrobial activity and conformational analysis of the class IIa bacteriocin pediocin PA-1 and analogs thereof. Scientific Reports 8:9029.
• Boubezari M.T., Idoui T., Hammami R., Fernandez B., Gomaa A. and Fliss I. (2018) Bacteriocinogenic properties of Escherichia coli P2C isolated from pig gastrointestinal tract: Purification and characterization of microcin V. Archives of Microbiology 200(5):771–782.
• Gomaa A.I., Martinent C., Hammami R., Fliss I., Subirade M. (2017) dual coating of liposomes as encapsulating matrix of antimicrobial peptides: development and characterization, Frontiers in  Chemistry 5:103.
• Vimont A., Fernandez B., Hammami R., Ababsa A., Daba H., and Fliss I. (2017) Bacteriocin-producing Enterococcus faecium LCW 44: a high potential probiotic candidate from raw camel milk. Frontiers in Microbiology 8:865.
• Persico M., Mikhaylin S., Doyen A., Firdaous L., Hammami R., Chevalier M., Flahaut C., Dhulster P., Bazinet L. (2017) Formation of peptide layers and adsorption mechanisms on a negatively charged cation-exchange membrane. Journal of Colloid and Interface Science 508:488-499.
• Liato V., Hammami R., Aïder M. (2017) Influence of electro-activated solutions of weak organic acid salts on microbial quality and overall appearance of blueberries during storage, Food Microbiology 64:56-64.
• Hanchi H., Hammami R., Gingras H., Kourda R., Bergeron M., Ben Hamida J., Ouellette M. and Fliss I. (2017) Inhibition of methicillin-resistant Staphylococcus aureus and of Clostridium difficile by durancin 61A: synergy with bacteriocins and antibiotics. Future Microbiology 12(3):205-212.