Short-term effects of Chlorhexidine mouthwash and Listerine on oral microbiome in hospitalized patients

Chlorhexidine (CHX) and essential oil (EO) containing mouthwashes maintain oral hygiene via suppressing oral microbes. In hospitalized patients, CHX mouthwash was associated with increased mortality, which could be related to nitrate-reducing bacteria. Currently no study determines oral bacteria targeted by EO mouthwash in hospitalized patients using a metagenomic approach. We recruited 87 hospitalized patients, who were randomly assigned to three mouthwash groups: CHX, Listerine® (an EO mouthwash), and normal saline (control). Before and after gargling the mouthwash twice a day for 5-7 days, oral bacteria were examined using a 16S rDNA approach. Alpha diversities at the genus level decreased significantly only for the CHX and Listerine groups. Only for the two groups, oral microbiota before and after gargling were significantly different, but not clearly distinct. Paired analysis eliminated the substantial individual differences and revealed eight bacterial genera (including Prevotella, Fusobacterium, and Selenomonas) with a decreased relative abundance, while Rothia increased after gargling CHX mouthwash. After gargling Listerine, seven genera (including Parvimonas, Eubacterium, and Selenomonas) showed a decreased relative abundance, and the magnitudes were smaller compared to the CHX group. In summary, short-term gargling of CHX mouthwash and Listerine altered oral microbiota in our hospitalized patients. The bacterial genera targeted by CHX mouthwash and Listerine were largely different and the magnitudes of changes were smaller using Listerine. Fewer bacteria targeted by Listerine were reported to be nitrate-reducing compared to CHX mouthwash. These findings provide guidance for oral care of hospitalized patients. Contact: chenghan Lin [e-mail]. This submission was powered by METAGENOTE (https://metagenote.niaid.nih.gov).