Antibiotic activity of bacteria associated to the marine sponges Hymeniacidon perlevis and Halichondria panicea: focus on Vagococcus fluvialis isolates

Antibiotic resistance is today an important threat to global health. The misuse and overuse of antibiotics has led to the emergence and spread of antibiotic-resistant pathogens worldwide. There is therefore an urgent need for the discovery and development of new antibiotics. As a result, natural products are re-emerging as a source for new drugs engineered by evolution. In this context, marine sponge-associated bacteria are an important and underused source of bioactive compounds. Indeed, these bacteria produce a large array of secondary metabolites, including antibiotics, as defence mechanisms against the threats to which they are exposed due to the filtration activity of the sponge host.We contributed to this line of investigation by exploring the antibacterial potential of cultivable bacteria associated to the marine sponges Hymeniacidon perlevis and Halichondria panicea. Specimens of these intertidal sponges were sampled in the North Atlantic coast of France. A hundred and fourteen bacterial isolates were recovered from the sponge tissue using commercial and dilute media. Numerous isolates demonstrated antibacterial action against methicillin-resistant Staphylococcus aureus and carbapenem-resistant Acinetobacter baumannii clinical strains. These are two of the antibiotic-resistant pathogens prioritized by the World Health Organization for the development of new antibiotics. In particular, sponge-isolated strains of the genera Lactococcus, Pseudomonas and Vagococcus exhibited antibacterial activity against both pathogens. This activity was characterised as bactericidal through co-cultivation of the sponge bacteria with the target strains.We further focused on the sponge-isolated Vagococcus fluvialis strains, as they exhibited potent bactericidal activity against all clinical strains tested. Moreover, this genus has not been previously reported to produce antibiotic compounds. Traditional and gene-based approaches were applied to characterise the antibacterial factor(s) responsible for the observed activity, ...