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Evolution of resistance to cationic biocides in Streptococcus mutans and Enterococcus faecalis
Haruaki Kitagawa1, Naomi Izutani2, Ranna Kitagawa2
1Department of Biomaterials Science, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
Journal of Dentistry
|February 25, 2016
Summary
Enterococcus faecalis developed resistance to chlorhexidine (CHX) after repeated exposure, unlike Streptococcus mutans. Alkyl pyridinium compounds like CPC and MDPB showed a lower risk of adaptation in E. faecalis compared to CHX.
Area of Science:
- Microbiology
- Dental Research
- Antimicrobial Resistance
Background:
- * Streptococcus mutans* and *Enterococcus faecalis*
- are key pathogens in dental caries.
- Cationic biocides like chlorhexidine (CHX), cetylpyridinium chloride (CPC), and 12-methacryloyloxydodecylpyridinium bromide (MDPB) are used to control these bacteria.
Purpose of the Study:
- To investigate the development of resistance in *S. mutans* and *E. faecalis* to CHX, CPC, and MDPB.
- To explore potential mechanisms of resistance, including changes in cell-surface hydrophobicity and protein expression.
Main Methods:
- * Minimum inhibitory concentrations* (MICs) were determined after repeated biocide exposure.
- * Bacterial cell-surface hydrophobicity* and protein expression profiles were analyzed.
Main Results:
- * *E. faecalis* developed resistance to CHX* with increasing MICs over 10 passages.
- No significant changes in MICs were observed for CPC or MDPB against *E. faecalis*, or for any biocide against *S. mutans*.
- * CHX-exposed *E. faecalis* showed increased surface hydrophobicity* and altered protein expression, including a novel 19-kDa band.
Conclusions:
- * Repeated CHX exposure can induce resistance in *E. faecalis*, likely due to altered protein composition.*
- * *S. mutans* did not develop resistance to the tested biocides.
- * Alkyl pyridinium compounds (CPC, MDPB) may pose a lower risk for *E. faecalis* adaptation compared to CHX.*
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