Objective: The aim of the present study was to investigate the microbial flora of root filled teeth with apical periodontitis and to determine the prevalence of β-lactamase producing strains in isolated bacteria in Latvian patients.
Materials and methods: 33 root filled teeth with asymptomatic persisting periapical lesions were selected for the present study. During nonsurgical endodontic retreatment, the root filling material was removed and canals were sampled. Determination of microbial species was based on series of biochemical tests using identification kits. All strains of bacteria were tested for β-lactamase production by using chromogenic nitrocefin-impregnated slides.
Results: Bacteria were found in 32 (97%) of initial specimens from the teeth. The number of isolated microbial strains in the specimens ranged from one to six (mean 2.7). 79% of the isolated microbial species were Gram-positive bacteria. The most common isolates were Streptococcus (27%), Actinomyces (27%), Staphylococcus (18%), Enterococcus (18%) and Lactobacillus (18%) spp. Yeasts were found as four isolates in 3 cases (9%). β-lactamase-producing bacterial strains were detected in 12 specimens, 36% of the patients. The most common enzyme-producing bacteria belonged to Actinomyces and Staphylococcus spp.
Conclusions: The microbial flora in previously treated root canals with apical periodontitis is limited to a small number of predominantly Gram-positive microbial species. The most common isolates are Streptococcus, Actinomyces, Staphylococcus, Enterococcus and Lactobacillus spp. A moderately high prevalence of β-lactamase producing bacterial strains was detected in patients with root filled teeth with apical periodontitis.