The cultivable microbiota of primary and secondary infected root canals, their susceptibility to antibiotics and association with the signs and symptoms of infection.

AIM: To examine the presence of microbial species in primary and secondary infections and identify the signs and symptoms associated with them. METHODOLOGY: A total number of 37 root canals from 33 patients undergoing root canal treatment were selected. Samples were taken using a sterile paper point following chemomechanical canal instrumentation. Microbiological identification was performed by macromorphological, micromorphological and commercial biochemical tests (ATB system). The antibiotic susceptibility profile of isolated Enterococcus, Streptococcus and Propionibacterium spp. was evaluated. RESULTS: A total number of 54 species were isolated. The most common was E. faecalis followed by Propionibacterium acnes and Streptococcus spp. Five multidrug-resistant enterococcal strains were isolated. However, resistance to linezolid or glycopeptides was not found. Radiolucency was observed significantly more often in symptomatic infections (P = 0.0061) caused by Actinomyces spp. than in asymptomatic ones. CONCLUSIONS: Enterococci and streptococci were the most commonly isolated bacteria from root canals. The resistance of enterococci to many antimicrobials may pose a problem in their eradication.