Highlights from the APDW 2021

Pr. Fergus Shanahan (University College Cork, APC Microbiome Ireland) introduced the concept of the “social microbiome” which includes the factors promoting transmission and sharing of microbes within human social networks [1]. He emphasised that the consequences of social influences on the microbiome are likely to be most evident in the elderly. Aloneness, life indoors, institutional care and loss of human contact – all of which were increased during Covid-19 – are among the factors leading to a deterioration in the health of the microbiome with age. Emphasising the need for more research on the lifestyle and environmental influences on the microbiome, he observed that most of the variance in the human microbiome remains unaccounted for.

Pr. Martin Blaser (Rutgers University, NJ, USA) then outlined the known influences on the composition of the human microbiome, and illustrated his ground-breaking research on the adverse effects of antibiotics. Progressive loss of ancestral microbes has occurred since the introduction of antibiotics [2]. This has been associated with the increased frequency of non-communicable chronic diseases, including immune and metabolic disorders. While the causal nature of these associations is unproven, Pr. Blaser reviewed his own experimental work which provides clear evidence for permanent, long-term and even trans-generational adverse effects of antibiotics on the microbiome and host health.

Pr. Francisco Guarner (Vall d’Hebron Research Institute, Barcelona, Spain) showed how gut microbes shape mucosal and systemic immune responses and particularly how a healthy gut microbiome promotes tolerogenic rather than immunogenic host responses. He pointed out that the clinical significance of this is shown by the impact of the microbiota on responses to immunotherapy in patients with cancer and how antibiotics may alter immunity to vaccines [3]. Pr. Guarner also showed the influence of certain probiotics on host immune responses.

In discussion, the speakers highlighted the clinical importance of retaining biodiversity within the gut. In addition to limiting injudicious use of broad-spectrum antibiotics, the role of dietary diversity as a simple personal measure for maintaining gut microbial diversity, was emphasised. There was a consensus that therapeutic modulation of the microbiota is a realistic prospect. While the promises of microbiome science are extensive, many gaps in knowledge persist [4]. Unknowns such as the long-term consequences of social distancing represent opportunities to explore the importance of the microbiome on health and disease in all sectors of society.