The human gut microbiota enhances the host’s resistance to enteric pathogens via colonisation resistance, a phenomenon that is driven by multiple mechanisms, such as production of antimicrobial metabolites and activation of host immune responses. However, there is limited information on how individual gut bacterial species, particularly many of the dominant anaerobes, might impact the host’s defence.

This study investigated the potential of specific human gut isolates to bolster the host’s resistance to infection. First, by antagonising the opportunistic fungal pathogen Candida albicans, and secondly, by modulating the killing capacity of human-isolated macrophages .

Co-culturing with faecal microbiota from different healthy individuals revealed varying levels of fungal inhibition. assays with a panel of representative human gut anaerobes confirmed that culture supernatants from certain bacterial isolates, in particular of , significantly inhibited growth. Mechanistic studies revealed that microbial fermentation acids including acetate and lactate, in combination with the associated decrease in pH, were strong drivers of this inhibitory activity.

In the second assay, human-isolated macrophages were exposed to bacterial supernatants, and subsequently tested for their capacity to eliminate adherent-invasive . Among the gut anaerobes tested, was revealed to exert the strongest immunostimulatory and killing effect when compared to the unstimulated macrophages control.

is known to be stimulated by dietary consumption of resistant starch andmay therefore represent an attractive target for the development of probiotic and prebiotic interventions tailored to enhancethe host’s natural defences against infection.

  • This is an open-access article distributed under the terms of the Creative Commons Attribution License.

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