The oral microbiome in oral lichen planus during a 1-year randomized clinical trial

Background Several recent studies have investigated the oral bacteriome in oral lichen planus (OLP), but longitudinal changes in microbiome have not been investigated. Objective To study the bacteriome and mycobiome in OLP over a 1-year period and the impact of topical treatment. Material and methods Samples from 22 symptomatic OLP patients from a double-blinded, randomized intervention study were collected over a 1-year course at five visits. Bacterial and fungal abundances were investigated through lesional cytobrush (CB) and full mouthwash (MW). Initially, all patients received conventional (antimycotic or steroid) and probiotic or placebo treatment. Results The microbial composition differed between the MW and CB samples. During the study period, the microbial composition was individual, with pronounced variability between visits. Patients grouped according to initial conventional treatment. During the study period, unidirectional change in the bacteriome was seen in the antimycotic group, whereas the mycobiome was stable. Malassezia restricta was the most abundant fungus. Conclusions The microbial composition of MW and CB differs in OLP. CB composition is less influenced by conventional and probiotic intervention. Initial antimycotic treatment influenced the bacteriome during the 1-year period. How the oral microbiome in health and disease is influenced by individual variability of fungi and bacteria, and Malassezia needs further investigation.