Gut Microbiome and Intestinal Colonization with Multidrug-Resistant Strains of Enterobacterales: An Interplay Between Microbial Communities.

Background: The intestinal tract is a host to a high number of diverse bacteria, and the presence of multidrug-resistant (MDR) Enterobacterales strains acts as a reservoir and a source of infection. The interactions between the intestinal microbiome and colonizer Enterobacterales strains influence long-lasting colonization. Aims: In this narrative review, we summarize available data about the intestinal colonization of MDR Enterobacterales strains and correlations between colonization and the intestinal microbiome. Results: Several endogenous and exogenous factors influence the intestinal colonization of MDR Enterobacterales strains. On the gut microbiome level, the intestinal microbial community is composed of the Lachnospiraceae family (e.g., Lachnoclostridium, Agathobacter, Roseburia, Tyzzerella), which indicates a protective role against colonizer MDR Enterobacterales strains; by contrast, a high abundance of Enterobacterales correlates with the colonization of MDR Enterobacterales strains. In specific patient groups, striking differences in microbiome composition can be detected. Among hematopoietic stem-cell-transplanted patients colonized by extended-spectrum beta-lactamase (ESBL)-producing Enterobacterales, a greater abundance of Bifidobacterium, Blautia, Clostridium, Coprococcus, L-Ruminococcus, Mogibacteriaceae, Peptostreptococceae and Oscillospira was observed compared to patients not colonized by ESBL-producing strains, who had a greater abundance of Actinomycetales. In liver transplant patients, a reduction in the alpha-diversity of the intestinal microbiome in fecal samples correlates with the carriage of MDR Enterobacterales. Conclusions: Intestinal colonization with MDR Enterobacterales is a multifactorial process that involves the MDR strain (e.g., its plasmids, fimbria), host and mucosal factors (e.g., IgA and defensin) and exogenous factors (e.g., use of antibiotics, hospitalization). On the gut microbiome level, the Lachnospiraceae family is dominant among intestines not colonized by MDR strains, but a high abundance of Enterobacterales was correlated with colonization with MDR Enterobacterales strains.