Evaluation of mouthwash-induced antimicrobial resistance in the oral microbiome: a systematic review

Aim Antimicrobial resistance is an emerging global health challenge, driven largely by the overuse of antimicrobial drugs. However, the extent of mouthwash-induced antimicrobial resistance remains poorly understood. This systematic review aimed to assess the influence of commonly used mouthwashes on antimicrobial resistance, focusing on resistance genes, microbial alterations, and cross-resistance to antibiotics.Methods PubMed, Scopus, Web of Science, and grey literature, including Google Scholar, were searched for studies evaluating mouthwash-induced antimicrobial resistance. The search strategy included terms related to 'oral microbiome', 'mouthwash' and 'antimicrobial resistance', with Boolean operators tailored to each database. Risk of bias was assessed using In Vitro Critical Appraisal Tool for in vitro studies and the Modified Joanna Briggs Institute for ex vivo and in vivo studies, respectively.Results Twelve studies were analysed, comprising seven in vitro, four ex vivo and one in vivo study. A total of 91 patients and 213 bacterial isolates were assessed across various mouthwashes, including chlorhexidine digluconate, cetylpyridinium chloride, hydrogen peroxide and others. Due to heterogeneous outcomes, a meta-analysis was not conducted. The findings consistently revealed increased minimum inhibitory concentrations of oral bacteria and the presence of resistance genes, highlighting a potential rise in antimicrobial resistance.Conclusion This systematic review indicates a possible association between mouthwash use and resistance-related changes in the oral microbiome; however, the limited and heterogeneous evidence base warrants cautious interpretation. Further, longitudinal research is needed to elucidate the underlying mechanisms and inform evidence-based guidelines for mouthwash use.