Antimicrobial activity of different concentrations of NaOCl and chlorhexidine using a contact test

The purpose of this study was to analyze the in vitro antimicrobial activity of sodium hypochlorite (1% and 5%) and chlorhexidine (0.12%, 0.5% and 1%). Bacterial samples (ATCC) of Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Porphyromonas gingivalis and Fusobacterium nucleatum were submitted to a contact test. Solutions were evaluated at different time intervals: immediately, 5 min, 15 min, and 30 min after contact and repeated 10 times. The results of the contact test showed that 0.12% chlorhexidine did not eliminate E. faecalis at any time interval, while 0.5% and 1% chlorhexidine and 1% and 5% sodium hypochlorite did. These results permit us to conclude that to obtain better antimicrobial activity, chlorhexidine in a concentration greater than 0.12% should be used

Antimicrobial resistance and virulence traits of Enterococcus faecalis from primary endodontic infections

Objectives To determine the phenotypic and molecular characteristics of Enterococcus faecalis recovered from primary endodontic infections in Brazilian patients. Methods Twenty isolates of E. faecalis recovered from 43 Brazilian patients with primary endodontic infections were identified by biochemical profiling (API20Strep) and 16S rDNA sequencing. Antimicrobial susceptibility was ascertained by agar dilution, using the recommended protocol of the Clinical and Laboratory Standards Institute (CLSI). PCR with validated primers was used to detect genes associated with antibiotic resistance and specific virulence factors. Results All isolates were deemed susceptible to penicillin G, erythromycin and vancomycin. However, nine isolates had a minimum inhibitory concentration of 4μg/mL to vancomycin (the resistance breakpoint). Fourteen isolates (70% of isolates) were also resistant to tetracycline with MICs of >64μg/mL. PCR products for tetracycline resistance genes were detected in test isolates, while erythromycin and vancomycin resistance genes were not evident. Gelatinase, aggregation substance and enteroccocal surface protein genes were detected in 20, 18 and 12 isolates, respectively. Conclusions Endodontic E. faecalis isolates exhibit high level of resistance to tetracycline, an antibiotic that has use in local treatment of dental infections. This opens up a much-needed debate on the role and efficacy of this antibiotic for oral infections. Furthermore, these isolates were shown to possess genes that could contribute to pathogenicity in the pulp cavity