The Potential of Phenothiazines against Endodontic Pathogens: A Focus on Enterococcus-Candida Dual-Species Biofilm

Abstract

Persistent apical periodontitis occurs when the endodontic treatment fails to eradicate the intraradicular infection, and is mainly caused by Gram-positive bacteria and yeasts, such as Enterococcus faecalis and Candida albicans, respectively. Phenothiazines have been described as potential antimicrobials against bacteria and fungi. This study aimed to investigate the antimicrobial potential of promethazine (PMZ) and chlorpromazine (CPZ) against E. faecalis and C. albicans dual-species biofilms. The susceptibility of planktonic cells to phenothiazines, chlorhexidine (CHX) and sodium hypochlorite (NaOCl) was initially analyzed by broth microdilution. Interaction between phenothiazines and CHX was examined by chequerboard assay. The effect of NaOCl, PMZ, CPZ, CHX, PMZ + CHX, and CPZ + CHX on biofilms was investigated by susceptibility assays, biochemical and morphological analyses. Results were evaluated through one-way ANOVA and Tukey’s multiple comparison post-test. PMZ, alone or in combination with irrigants, was the most efficient phenothiazine, capable of reducing cell counts, biomass, biovolume, carbohydrate and protein contents of dual-species biofilms. Neither PMZ nor CPZ increased the antimicrobial activity of CHX. Further investigations of the properties of phenothiazines should be performed to encourage their use in endodontic clinical practice.

The effect of root canal preparation tapers on planktonic bacteria and biofilm reduction in the apical third: A correlative microtomography and microbiological laboratory study

“…The literature highlights the polymicrobial nature of endodontic infections (Fiallos et al., 2022). However, Enterococcus species appear to be the most common microorganisms involved in persistent endodontic infections.…”

“…Most in vitro studies have used E . faecalis to evaluate the efficiency of root canal cleaning and shaping (Cardoso et al., 2008; Fiallos et al., 2022; Wang et al., 2012; Zancan et al., 2019). To simulate a clinical situation of secondary or persistent infection, we used a dual‐species biofilm of E .…”

“…faecalis and C . albicans resistant to endodontic treatment (Cardoso et al., 2008; Fiallos et al., 2022). Co‐culture of E .…”

“…faecalis and C . albicans in endodontic studies is primarily motivated by their association with persistent or refractory endodontic infections (Cardoso et al., 2008; Fiallos et al., 2022). Microbial cultures were grown in 10 mL of brain–heart infusion (BHI) broth containing 20% glycerol or peptone mushroom extract (yeast extract, Peptone, Dextrose, 1:2:4) (both from Accumedia Manufacturers, Lansing, USA) for E .…”

“…albicans was added into sterile glass tubes and the specimens were kept in a bacteriological incubator at 37°C for 28 days to allow dual‐species biofilm formation. Every 2 days, 25 μL of the microbial broth was removed from the tube containing the specimen and 25 μL of pure BHI was added to ensure cell nutrition and viability (Cardoso et al., 2008; Fiallos et al., 2022).…”