Detection of viable oral bacteria of the patient on the surgical mask of dentists.

Introduction and aim: Bioaerosols contaminate the personal protective equipment (PPE), especially masks. The PPE harbors microorganisms from various sources. However, no previous studies have investigated the specific sources of bacteria found on used masks and their correlation with those from the treated patient.

Setting, design, material and methods: Intraoral samples from the patient were collected prior to dental aerosol-producing treatments using a nylon flock fiber swab. After treatment, the practitioner's mask was imprinted onto agar plates.

Main outcome methods: Following cultivation, colony forming units were counted and identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). After the samples were analyzed, the intraoral samples as well as the mask samples were assessed for the presence of identical species, which were subsequently quantified.

Results: 126 treatments were included. One species match occurred most frequently (26.2%), followed by two (11.9%%) and three or more (3.97%). In the intraoral samples, Neisseria subflava occurred most often, within mask samples Staphylococcus epidermidis were detected most. Staphylococcus aureus could be cultivated three times more often in intraoral samples than on the mask.

Discussion and conclusion: Oral microorganisms originating from the patient's oral cavity can be found on the outside of masks. When using PPE during treatments, it should therefore always be in mind that potentially pathogenic microorganisms may land on the mask becoming a source of for itself.