IADR Abstract Archives
Strong biofilm formers of Enterococcus faecalis are resistant to antibiotics
Objectives: Enterococci faecalis is pathogenic bacteria strongly associated with endodontic infections as well as systemic diseases such as bacterial endocarditis, urinary tract infections, and wound infections, among others. E. faecalis is able to adhere to surfaces and forms microbial communities known as biofilms, which is directly associated with therapeutic failure. In the present study, we aimed to comprehensively investigate the biofilm forming ability of E. faecalis clinical isolates in comparison to the laboratory isolates.
Methods: Biofilm formation of eighteen clinical isolates of E. faecalis derived from failed root canal treatment and saliva were compared with the laboratory strains ATCC 29212 and ATCC 51299 using standard methodology. Biofilm formation was evaluated by crystal violet (CV) assay and counting colony forming units (CFU). Next, antibiotic susceptibility of the isolates in the planktonic mode was examined using CLSI standards. Effect of antibiotics on biofilms was evaluated by CV and CFU assays. Scanning electron microscopy and confocal electron microscopy were used to assess the ultrastructure and cellular viability.
Results: Most of the clinical isolates formed comparable biofilms to that of E. faecalis ATCC strains. Interesting a few isolates formed significantly strong biofilms (e.g. mean CV reading of 2.8) and weak biofilms (1.4 in CV assay) compared to ATCC isolates (2.1 in CV assay) (p < 0.05). At the planktonic mode all isolates were susceptible to ampicillin and vancomycin. In general, E. faecalis biofilms had higher minimum inhibitory concentration values (e.g. >256 µg/ml for ampicillin) compared to the planktonic mode (e.g. 0.5 µg/ml for ampicillin). Interestingly, strong biofilm formers exhibited more resistance to antibiotics than weak biofilm formers.
Conclusions: Herein we have demonstrated that strong biofilm formation ability is related to the higher drug resistance in E. faecalis which may be the cause of therapeutic failure in the clinical settings.
Methods: Biofilm formation of eighteen clinical isolates of E. faecalis derived from failed root canal treatment and saliva were compared with the laboratory strains ATCC 29212 and ATCC 51299 using standard methodology. Biofilm formation was evaluated by crystal violet (CV) assay and counting colony forming units (CFU). Next, antibiotic susceptibility of the isolates in the planktonic mode was examined using CLSI standards. Effect of antibiotics on biofilms was evaluated by CV and CFU assays. Scanning electron microscopy and confocal electron microscopy were used to assess the ultrastructure and cellular viability.
Results: Most of the clinical isolates formed comparable biofilms to that of E. faecalis ATCC strains. Interesting a few isolates formed significantly strong biofilms (e.g. mean CV reading of 2.8) and weak biofilms (1.4 in CV assay) compared to ATCC isolates (2.1 in CV assay) (p < 0.05). At the planktonic mode all isolates were susceptible to ampicillin and vancomycin. In general, E. faecalis biofilms had higher minimum inhibitory concentration values (e.g. >256 µg/ml for ampicillin) compared to the planktonic mode (e.g. 0.5 µg/ml for ampicillin). Interestingly, strong biofilm formers exhibited more resistance to antibiotics than weak biofilm formers.
Conclusions: Herein we have demonstrated that strong biofilm formation ability is related to the higher drug resistance in E. faecalis which may be the cause of therapeutic failure in the clinical settings.