Short- and long-term impact of aseptic bathing strategies on the skin microbiome in ICU patients.

Bathing strategies with antiseptic agents, such as Chlorhexidine and Octenidine, have been widely adopted to mitigate infection risks in intensive care units (ICU). However, concerns exist regarding their long-term effects on skin microbiome structures and potential unintended consequences, including antibiotic cross-resistance. This longitudinal study characterized the compositional changes of the skin microbiome of ICU patients upon these two antiseptic bathing strategies when compared to standard water and soap bathing. Samples were collected in a three-armed cluster randomized decolonization trial (registration number DRKS00010475). Skin swabs from 5 different sites and three time points were analyzed by culture-based methods, 16S rRNA-gene amplicon sequencing and multiplex Taq-Man assays for detection of antimicrobial resistance genes (ARG). Our results show that Chlorhexidine bathing led to a sustained reduction of the bacterial biomass on different skin sites, as measured by both molecular and culture-based methods. Thereby, the microbial structures remained largely unaltered both in their diversity and their taxonomic composition. However, the loss of microbiome site-specificity observed on the skin of ICU patients remained unchanged independently from the bathing strategy applied and persisted even after discharge. None of the antiseptic bathing strategies led to an increase or accumulation of antibiotic-resistance determinants on any of the skin sites investigated in this study. Thus, this study suggests that daily patient bathing with 2% Chlorhexidine impregnated cloths or 0.08% Octenidine wash mitts does not impact skin microbiome structures and antibiotic resistance gene accumulation in ICU patients when compared to non-antiseptic water and soap bathing routine.