Microorganisms from canals of root-filled teeth with periapical lesions and the antimicrobial susceptibility to different antibiotics of enterococcus faecalis isolates

O presente estudo teve por objetivos: identificar a microbiota de canais radiculares de dentes com insucesso do tratamento endodôntico, e testar, in vitro, a suscetibilidade de cepas de Enterococcus faecalis a diferentes antibióticos. Sessenta dentes tratados endodonticamente com lesões periapicais persistentes foram selecionados para esse estudo. Durante o retratamento endodôntico, o material obturador foi removido e foi realizada a coleta microbiológica dos canais radiculares. Foram utilizados meios de transporte, cultura e incubação que propiciam o crescimento de bactérias anaeróbias estritas. Vinte e uma cepas de Enterococcus faecalis foram testadas quanto à suscetibilidade aos seguintes antimicrobianos: benzilpenicilina, amoxicilina, amoxicilina + ácido clavulânico, clindamicina, eritromicina, azitromicina, vancomicina, cloranfenicol, tetraciclina, doxiciclina, ciprofloxacino e moxifloxacino. As concentrações inibitórias mínimas (CIMs) dos agentes antimicrobianos foram determinadas pelo método do E-test. As cepas também foram testadas quanto à produção de beta-lactamase utilizando nitrocefin. Microrganismos foram isolados em 51 casos. A maioria dos canais apresentava somente 1 ou 2 espécies bacterianas. Do total de espécies bacterianas isoladas, 57,4% eram bactérias anaeróbias facultativas e 83,3% Gram-positivas. Enterococcus faecalis foi a espécie bacteriana mais freqüentemente isolada. Bactérias anaeróbias estritas representavam 42,6% das espécies e, entre eles, Peptostreptococcus spp. foram os mais isolados. Associações significantes foram encontradas entre dor ou história de dor e infecções anaeróbias e polimicrobianas (p<0,05). Todas as cepas de Enterococcus faecalis foram sensíveis, in vitro, às penicilinas, entretanto as CIMs de amoxicilina e amoxicilina + ácido clavulânico (CIM90= 0,75 µg/ml) foram menores do que as de benzilpenicilina (CIM90= 3.0 µg/ml). Todas as cepas também foram sensíveis a vancomicina e moxifloxacino, enquanto 95,2% foram sensíveis a cloranfenicol. Entre os isolados, 85,7% foram sensíveis a tetraciclina e doxiciclina, e 80,9% a ciprofloxacino. As CIMs de eritromicina variaram de 0,38 a >256 µg/ml, com apenas 28,5% das cepas sensíveis (CIM ?0.5 µg/ml). Suscetibilidade limitada também foi verificada com azitromicina, que foi ativa contra somente 14,2% dos isolados. Nenhuma cepa produziu beta-lactamase. Concluímos que a microbiota dos canais de dentes tratados endodonticamente é composta por um número limitado de espécies microbianas, predominantemente Gram-positivas. Anaeróbios facultativos, especialmente Enterococcus faecalis, são os microrganismos mais comumente isolados, entretanto, infecções polimicrobianas e anaeróbios estritos são freqüentemente encontrados em canais de dentes tratados endodonticamente com sintomatologia clínica. As cepas de Enterococcus faecalis foram sensíveis, in vitro, a amoxicilina, amoxicilina associada ao ácido clavulânico, vancomicina e moxifloxacino. A maioria dos isolados foi sensível aos antibióticos: cloranfenicol, tetraciclina, doxiciclina, ou ciprofloxacino. Eritromicina e azitromicina foram menos eficazesThe objectives of the present study were to identify the microbial flora within root canals of teeth with failed root canal treatment, and to test, in vitro, the susceptibility of Enterococcus faecalis isolates. Sixty root-filled teeth with persisting periapical lesions were selected for this study. During nonsurgical endodontic re-treatment, the root-filling material was removed and the canals were sampled. Microbial sampling, isolation and species determination were performed using advanced microbiologic techniques for anaerobic species. Additionally, 21 Enterococcus faecalis isolates were tested for their antibiotic susceptibilities to benzylpenicillin, amoxicillin, amoxicillin-clavulanic acid, erythromycin, azithromycin, vancomycin, chloramphenicol, tetracycline, doxycycline, ciprofloxacin and moxifloxacin. Minimal inhibitory concentrations (MICs) for the antimicrobial agents were determined using the E-test System. The strains were also tested for ?-lactamase production with nitrocefin. Microorganisms were recovered from 51 teeth. In most cases, one or two strains per canal were found. Of the microbial species isolated, 57.4% were facultative anaerobic species and 83.3% Gram-positive microorganisms. Enterococcus faecalis was the bacterial species most frequently recovered. Obligate anaerobes accounted for 42.6% of the species and the most frequently isolated genera was Peptostreptococcus. Significant associations were observed between pain or history of pain and polymicrobial infections or anaerobes (p<0.05). All Enterococcus faecalis strains were susceptible to penicillins in vitro, however, the MICs of amoxicillin and amoxicillinclavulanic acid (MIC90= 0.75 µg/ml) were lower than for benzylpenicillin (MIC90= 3.0 µg/ml). All strains studied were also susceptible to vancomycin and moxifloxacin, while 95.2% were susceptible to chloramphenicol. Among the isolates, 85.7% were susceptible to tetracycline and doxycycline, and 80.9% to ciprofloxacin. The MIC of erythromycin ranged from 0.38 to >256 µg/ml; only 28.5% of the strains were susceptible (MIC ?0.5 µg/ml). Limited susceptibility was also observed with azithromycin which was active against only 14.2% of isolates. No strains produced ?-lactamase. Therefore, it was concluded that the microbial flora in canals after failure of root canal treatment were limited to a small number of predominantly Gram-positive microbial species. Facultative anaerobes, especially Enterococcus faecalis, were the most commonly isolated microorganisms, however, polymicrobial infections and obligate anaerobes were frequently found in canals of symptomatic root-filled teeth. Enterococcus faecalis isolates were completely susceptible, in vitro, to amoxicillin, amoxicillin-clavulanic acid, vancomycin, and moxifloxacin. Most isolates were susceptible to chloramphenicol, tetracycline, doxycycline, or ciprofloxacin. Erythromycin and azithromycin were least effectiv