Antimicrobial resistance in dental unit waterlines: a scoping review of microbial diversity, resistance patterns, and...

Antimicrobial resistance (AMR) is a growing global health threat, and dental unit waterlines (DUWLs) may contribute to AMR, as DUWLs provide ideal conditions for biofilm development and growth of antimicrobial-resistant microorganisms. However, the microorganisms involved and their resistance patterns in DUWLs remains unclear. This scoping review aimed to map the available evidence on antimicrobial-resistant microorganisms in DUWLs and characterize resistance patterns.

We conducted a systematic literature search across the PubMed, Scopus, and Web of Science databases up to March 2026. Studies that reported the isolation of microorganisms from DUWLs and AMR using phenotypic methods and/or genotypic detection of antimicrobial resistance genes (ARGs) were included. Data were extracted and summarized descriptively.

A total of 18 studies were included. Most studies analyzed DUWL water samples and reported bacterial isolates, particularly Gram-negative organisms such as Pseudomonas spp. Phenotypic antimicrobial susceptibility testing was performed in 16 studies, with β-lactams, aminoglycosides, and fluoroquinolones being the most frequently evaluated classes. Ciprofloxacin and gentamicin were the most commonly tested antibiotics. AMR was reported in 15 studies, with frequent resistance to β-lactams and multidrug resistance. Fungal microorganisms showed reduced susceptibility in biofilms compared to planktonic forms. Genotypic data were limited, and no ARGs were detected in the two studies that assessed them.

DUWLs can become sources of antimicrobial-resistant microorganisms. However, the current evidence remains limited due to methodological variability and insufficient genotypic data. Future research should integrate both phenotypic and genotypic approaches, include biofilm-specific analyses, and evaluate the impact of DUWL management and antimicrobial stewardship strategies within a One Health framework.

Open Science Framework (OSF) https://doi.org/10.17605/OSF.IO/P3X5D.