Clinical and microbiological characteristics in predicting dentine caries progression.

The purpose of this study was to evaluate the clinical aspect of dentine and its microbiota in predicting caries progression. The sample consisted of schoolchildren in the 7 to 14 years age group. Treatment involved cavity preparation trough the clinical criterion of hardness, with the collection of carious and remnants dentine for microbiological analysis. The clinical aspect (color and consistency) of the dentine remmants was recorded and the teeth were restored using silver amalgam and glass ionomer cement as pulpal protector (baseline - BL). After 1 year the restoration was removed and after new clinical and microbiological analyses, the teeth were then restored. Microbiological samples were collected at both time-points and cultivated in sheep blood agar, in anaerobiosis for 48 hours. Bacterial growth was analyzed quantitatively. Semiquantitative and qualitative analysis of the bacteria was performed by hybridization with genomic DNA probes and the checkerboard method. A significant difference was observed between the aspect of dentine remnants at BL and at 1 year (p=0.0078). The amount of bacteria at BL and at 1 year did not differ significantly (p= 0.37) and the microbiota of the carious dentine was predominantly composed of Gram-positive cocci. The removal of carious dentine based on the clinical criterion of hardness, followed by a well-adapted restoration, would determine the non-progression of caries. The few bacteria that still remained in the cavity would be no longer viable.

Clinical and microbiological characteristics in predicting dentine caries progression

The purpose of this study was to evaluate the clinical aspect of dentine and its microbiota in predicting caries progression. The sample consisted of schoolchildren in the 7 to14 years age group. Treatment involved cavity preparation trough the clinical criterion of hardness, with the collection of carious and remnants dentine for microbiological analysis. The clinical aspect (color and consistency) of the dentine remmants was recorded and the teeth were restored using silver amalgam and glass ionomer cement as pulpal protector (baseline - BL). After 1 year the restoration was removed and after new clinical and microbiological analyses, the teeth were then restored. Microbiological samples were collected at both time-points and cultivated in sheep blood agar, in anaerobiosis for 48 hours. Bacterial growth was analyzed quantitatively. Semiquantitative and qualitative analysis of the bacteria was performed by hybridization with genomic DNA probes and the checkerboard method. A significant difference was observed between the aspect of dentine remnants at BL and at 1 year (p=0.0078). The amount of bacteria at BL and at 1 year did not differ significantly (p=0.37) and the microbiota of the carious dentine was predominantly composed of Gram-positive cocci. The removal of carious dentine based on the clinical criterion of hardness, followed by a well-adapted restoration, would determine the non-progression of caries. The few bacteria that still remained in the cavity would be no longer viable.

Este trabalho objetivou avaliar o aspecto clinico da dentina e sua microbiota na predicao da progressao de carie. A amostra foi constituida por individuos na faixa etaria de 7 a 14. O tratamento envolveu a remocao de tecido cariado pelo criterio clinico de dureza, o qual foi coletado analise microbiologica. Apos o mesmo, fez-se analise do aspecto clinico da dentina remanescente, bem como nova coleta microbiologica e restaurou- se os elementos com amalgama de prata, apos forramento com ionomero de vidro. Um ano apos, com a reabertura do dente, outra coleta microbiologica foi feita, bem como analise do aspecto clinico do tecido remanescente. O crescimento bacteriano foi analisado quantitativamente atraves de hibridizacao com sondas de DNA genomico e do metodo Checkerboard. Observou-se diferenca estatisticamente significativa entre o aspecto da dentina na linha base do estudo e um ano apos (p=0.0078). A quantidade de bacterias na linha base, em relacao a um ano depois do preparo, nao diferiu estatisticamente (p=0,37) e a microbiota predominante da dentina cariada foi composta de cocos Gram-positivos. A remocao de dentina cariada pelo criterio clinico de dureza, favorecida pela boa adaptacao da restauracao determinaram a nao progressao de carie. As poucas bacterias que ainda permaneceram na cavidade apos o preparo provavelmente tornaramse inviaveis em promover o avanco do processo carioso.

Association between the cfxA gene and transposon Tn4555 in Bacteroides distasonis strains and other Bacteroides species.

The Bacteroides genus, the most prevalent anaerobic bacteria of the intestinal tract, carries a plethora of the mobile elements, such as plasmids and conjugative and mobilizable transposons, which are probably responsible for the spreading of resistance genes. Production of beta-lactamases is the most important resistance mechanism including cephalosporin resistance to beta-lactam agents in species of the Bacteroides fragilis group. In our previous study, the cfxA gene was detected in B. distasonis species, which encodes a clinically significant broad-spectrum beta-lactamase responsible for widespread resistance to cefoxitin and other beta-lactams. Such gene has been associated with the mobilizable transposon Tn4555. Therefore, the aim of this study was to detect the association between the cfxA gene and the presence of transposon Tn4555 in 53 Bacteroides strains isolated in Rio de Janeiro, Brazil, by PCR assay. The cfxA gene was detected in 11 strains and the Tn4555 in 15. The transposon sequence revealed similarities of approximately 96% with the B. vulgatus sequence which has been deposited in GenBank. Hybridization assay was performed in attempt to detect the cfxA gene in the transposon. It was possible to associate the cfxA gene in 11 of 15 strains that harbored Tn4555. Among such strains, 9 presented the cfxA gene as well as Tn4555, but in 2 strains the cfxA gene was not detected by PCR assay. Our results confirm the involvement of Tn4555 in spreading the cfxA gene in Bacteroides species.