Development of resistance of mutans streptococci and Porphyromonas gingivalis to chlorhexidine digluconate and amine fluoride/stannous fluoride-containing mouthrinses, in vitro

Abstract

The use of chlorhexidine should be limited to short periods of time. The amine fluoride/stannous fluoride-containing mouthrinse appears to have the potential to be used on a long-term basis.

Tolerance and Persister Formation in Oral Streptococci

“…Both streptococcal isolates were tested with 64mg/L CHX and with 128mg/L CHX. As the respective MICs of CHX for these strains are between 0.5mg/L and 4mg/L, these concentrations are well above the MICs [23]. Accordingly, CHX was effective against all isolates and no live bacteria could be detected after 24 h. However, for both isolates and at both concentrations, the respective P20-isolates were more resistant to CHX and it took more time to eliminate their growth.…”

“…Two streptococcal strains were tested, i.e., S. mutans ATCC25175 and S. sobrinus ATCC33402. For both strains, isolates were compared that either had not been passaged on CHX ("P0" isolates) or that had been previously subcultivated for 20 passages in subinhibitory concentrations of CHX ("P20" isolates) [23]. For both streptococcal species, the decrease in bacterial cell counts was faster for the P0-isolates ( Figure 1; Figure 2).…”

“…Additionally, there is evidence that the extensive use of CHX could lead to the selection of strains being not only resistant to CHX but also to multiple antibiotics [19][20][21][22]. In a recent study analyzing the minimal inhibitory concentrations (MIC) of CHX and amine fluoride/stannous fluoride-containing mouthrinses against P. gingivalis and mutans streptococci, slightly elevated MIC values could be detected for CHX after long-term subinhibitory exposure for some of the P. gingivalis isolates only [23].…”

“…However, patients may use mouthrinses containing antimicrobial substances over a longer period with biocide concentrations lower than necessary to inhibit bacterial growth completely. Such long-term use may not only result in bacterial isolates with altered susceptibility profiles [23], but may also lead to the development of tolerant and/or persistent bacteria. Therefore, the aim of this study was to analyze the potential influence of long-term exposure in subinhibitory concentrations of CHX on the emergence of tolerant and/or persistent cells in oral streptococci in an in vitro study.…”

Nanoparticles for controlled delivery and sustained release of chlorhexidine in the oral environment

“…One aspect of this work, which merits further attention, is the potential for the development of CHX resistance among the oral flora. Chlorhexidine resistance has been reported in Porphyromonas gingivalis , where a 2–4× increase in MIC was observed for two of five isolates when exposed to subinhibitory concentrations of CHX for 30 passages (Kulik et al , ). However, it is acknowledged that such resistance is typically transitory, with the bacterial population reverting to its prior MIC when the CHX stimulus is removed (Eick et al , ).…”