In vitro bactericidal activity of retainer/denture-cleaning formulations against planktonic populations of Pseudomonas aeruginosa and other common bacterial pathogens in cystic fibrosis.

INTRODUCTION: Life expectancy has risen significantly in people with cystic fibrosis (PwCF) with the introduction of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) modulators. This has resulted in new infection challenges for PwCF, including the increasing employment of dentures, which have been shown to harbour CF-related bacterial pathogens. HYPOTHESIS/GAP STATEMENT: To date, there is no evidence-based infection prevention and control (IPC) guidance, specific to the CF community, on how to optimally clean and disinfect dentures in PwCF, including the efficacy of denture cleaning formulations against CF pathogens. AIM: To examine the in vitro bactericidal activity of two leading brands of denture cleaning formulations against planktonic suspensions of CF-related bacterial pathogens. METHODOLOGY: CF and bronchiectasis-related bacterial pathogens were employed in this study, including Pseudomonas aeruginosa, methicillin-sensitive Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), Burkholderia multivorans, Burkholderia cenocepacia and Stenotrophomonas maltophilia. Planktonic suspensions of each organism was exposed to denture cleaning fluid for 20 min and recovery of surviving cells attempted through direct plating and enhanced enrichment methods. RESULTS: Pseudomonas aeruginosa was able to survive for the suggested manufacturers' exposure time (3 min). All bacteria were unable to be recovered following 20 min exposure to each of the denture cleaning formulations, as well as following enrichment in nutrient broth at both 24 h and 48 h, indicating that both formulations were completely bactericidal to all organisms tested, after exposure for 20 min. CONCLUSION: This study indicates that the five clinically important species of CF bacterial pathogens tested were not able to remain culturable for 20 min in planktonic form, in commonly used retainer/denture-cleaning formulations widely available on the UK High Street. Survival of Pseudomonas aeruginosa was possible if exposed for the 3 min, as indicated with the instructions of these products. Employment of successful evidence-based cleaning and disinfection regimens of retainers/dentures in people with CF will help break the chain of transmission of CF pathogens, which is especially important during eradication treatments for first isolates, thereby avoiding re-infection. Clinically, the findings of this study are important to the small number of younger individuals with CF who wear dentures, and to CF adolescents and young people with CF who wear retainers, as well as providing data for an emerging aging CF population, where dentures will become more common. Further work is however required to establish the most effective retainer/denture cleaning regimen, as well as to examine the more complex survival dynamics of these organisms on naturally derived retainer/denture biofilm, associated with dental plaque.