Screening for multidrug-resistant organism: clinical benefit or unquestioned routine

Current strategies for multidrug-resistant organism (MDRO) screening are primarily intended to support infection prevention programs. However, accumulating evidence indicates that intestinal colonization also provides clinically relevant information for antimicrobial stewardship. This review examines the biological basis and clinical utility of mucosal screening for optimizing empirical antibiotic therapy and proposes a new conceptual framework linking intestinal pathobiont burden with endogenous bloodstream infection.

Recent studies consistently show that the absence of MDRO carriage is associated with a very low risk of subsequent infection, supporting well tolerated antimicrobial de-escalation in patients with negative clinical cultures. Emerging evidence further indicates that prolonged exposure to antianaerobic antibiotics promotes expansion of intestinal pathobionts, whereas preservation or restoration of the gut microbiota limits this process. Experimental and clinical observations suggest that the abundance of pathobionts, rather than simple carriage status, determines the probability of bacterial translocation and invasive infection.

We propose that physiological bacterial translocation from the intestinal microbiota is a common phenomenon and may represent one of the mechanisms of bloodstream infection in critically ill and immunocompromised patients. In this model, progression to invasive infection depends on intestinal pathobiont burden exceeding the capacity of host immune clearance. If validated, this concept would support a transition from qualitative MDRO screening to quantitative assessment of intestinal pathobiont burden to guide antimicrobial stewardship and targeted preventive strategies.