Colonisation resistance against multidrug-resistant bacteria: a narrative review.

Abstract

Colonisation resistance by gut microbiota is a fundamental phenomenon in infection prevention and control. Hospitalised patients may be exposed to multidrug-resistant bacteria when hand hygiene compliance among healthcare workers is not adequate. An additional layer of defence is provided by the healthy gut microbiota, which helps clear the exogenous bacteria and acts as a safety net when hand hygiene procedures are not followed. This narrative review focuses on the gut microbiota s role in colonisation resistance against multidrug-resistant bacteria and its implications for infection control. We discuss the underlying mechanisms of colonisation resistance (direct or indirect), the concept of gut microbiota resilience, the link between the antimicrobial spectrum and gut dysbiosis, and possible therapeutic strategies. Antimicrobial stewardship is crucial to maximising the effects of colonisation resistance. Avoiding unnecessary antimicrobial therapy, shortening the antimicrobial duration as much as possible, and favouring antibiotics with low anti-anaerobe activity may decrease multidrug-resistant bacteria acquisition and expansion. Even after antimicrobial therapy, the resilience of the gut microbiota often occurs spontaneously. Spontaneous resilience explains the existence of a window of opportunity for multidrug-resistant bacteria colonisation during or just after antimicrobial therapy. Strategies favouring gut microbiota resilience, such as high-fibre diets or precision probiotics, should be evaluated.