Prevention and Control of Legionella and Pseudomonas spp. Colonization in Dental Units

Dental Unit Waterlines (DUWLs) have shown to be a source of infection. We report the experience of different dental healthcare settings where a risk management plan was implemented. In a Hospital Odontostomatology Clinic (HOC) and three Private Dental Clinics (PDCs) housing 13 and six dental units (DUs), respectively, an assessment checklist was applied to evaluate staff compliance with guideline recommendations. DUWLs microbial parameters were investigated before and after the application of corrective actions. In the HOC a poor adherence to good practices was demonstrated, whereas protocols were carefully applied in PDCs. sg 2-15 was isolated in 31% (4/13) and 33% (2/6) of DUs in HOC and PDCs, respectively, mainly from handpieces (32%, 6/19) with counts >10 colony-forming units per milliliter (CFU/L), often associated with (68%, 13/19). The shock disinfection with 3% v/v hydrogen peroxide (HP) showed a limited effect, with a recolonization period of about 4 weeks. was eradicated only after 6% v/v HP shock disinfection and filters-installation, whilst after the third shock disinfection with a solution of 4% v/v HP and biodegradable surfactants. Our data demonstrate the presence and persistence of microbial contamination within the DUWLs, which required strict adherence to control measures and the choice of effective disinfectants.