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

Benedetta Tuvo,Sara Profeti,Beatrice Casini,Michele Totaro,David Di Cave,Maria Luisa Cristina,Anna Maria Spagnolo,Gaetano Privitera,Angelo Baggiani

doi:10.3390/pathogens9040305

Benedetta Tuvo, Sara Profeti + Show 7 more

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https://doi.org/10.3390/pathogens9040305

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Abstract

Introduction: Dental Unit Waterlines (DUWLs) have shown to be a source of Legionella infection. We report the experience of different dental healthcare settings where a risk management plan was implemented. Materials and methods: 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. Results: In the HOC a poor adherence to good practices was demonstrated, whereas protocols were carefully applied in PDCs. L. pneumophila 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 >102 colony-forming units per milliliter (CFU/L), often associated with P. aeruginosa (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. Legionella was eradicated only after 6% v/v HP shock disinfection and filters-installation, whilst P. aeruginosa after the third shock disinfection with a solution of 4% v/v HP and biodegradable surfactants. Conclusions: 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.

Highlights

Dental Unit Waterlines (DUWLs) have shown to be a source of Legionella infection
Using the checklist allowed us to verify that a water safety plan was in place in the hospital and a maintenance and control program was constantly applied to the water of the buildings and to the aeration systems. This should ensure a good quality of municipal water that can feed the DUWL when the switching is applied if the sterile water in the bottle runs out
Pseudomonas aeruginosa and coliform bacteria were not isolated despite the fact that the total microbial counts at 22 ◦ C and 37 ◦ C were higher than the values recommended by Italian regulations

Summary

Introduction

Dental Unit Waterlines (DUWLs) have shown to be a source of Legionella infection. We report the experience of different dental healthcare settings where a risk management plan was implemented. Several studies have demonstrated that water output from Dental Unit Waterlines (DUWLs) is often contaminated with high densities of microorganisms [1,2], ranging from 102 to 106 colony-forming units per milliliter (CFU/mL) [3,4,5,6,7,8,9,10]. The biofilm remains fixed to the tubing wall, but microbes keep spreading from the biofilm into the water as it flows through. For this reason, high microbial levels have been found in output water from handpieces and air/water syringes [11,12]. DUWLs are equipped with a dual water supply system that permits the Pathogens 2020, 9, 305; doi:10.3390/pathogens9040305 www.mdpi.com/journal/pathogens

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