Qualitative and quantitative molecular analysis of bacteria in root canals of primary teeth with pulp necrosis

Abstract Information about bacterial diversity, such as the number of each species in the root canals of primary teeth, contributes to improving our effective management of infections of endodontic origin in primary teeth. This study made a qualitative and quantitative assessment of the bacteria in the root canals of primary teeth with necrotic pulp, using the fluorescence in situ hybridization (FISH) technique. Thirty-one primary teeth with pulp necrosis from 31 children were evaluated using the FISH technique, to detect the presence and density of Aggregatibacter actinomycetemcomitans, Campylobacter rectus, Enterococcus faecalis, Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, Streptococcus, Streptococcus mutans, Streptococcus sobrinus, Tannerella forsythia and Treponema denticola. Descriptive measures explained the data related to density, and Student’s t-test assessed the differences among the densities of each bacterium, according to signs and symptoms. The bacterial density was paired and correlated. All bacteria tested were detected and identified in all the samples. The average number of bacterial individuals from each species ranged from 1.9 x 108 cells/mL (S. mutans) to 3.1 x 108 cells/mL (F. nucleatum) (p > 0.05). The sum of the mean counts of each bacterium represented almost 80% of the entire microbial community. Patients with pain had significantly more T. denticola, and those with edema showed a greater density of Streptococcus and P. nigrescens (p < 0.05). This study revealed that all 12 bacteria evaluated were found in all primary teeth with pulp necrosis. There was no predominance among the species studied; all species had a similar number of individuals.

摘要：关于细菌多样性的相关信息——例如乳牙根管内各菌种的数量——有助于提升我们对乳牙牙髓源性感染的临床诊疗效能。本研究采用荧光原位杂交（fluorescence in situ hybridization, FISH）技术，对牙髓坏死的乳牙根管内细菌开展定性与定量分析。研究纳入31名儿童的31颗牙髓坏死乳牙，通过FISH技术检测伴放线聚集杆菌（Aggregatibacter actinomycetemcomitans）、直形弯曲杆菌（Campylobacter rectus）、粪肠球菌（Enterococcus faecalis）、具核梭杆菌（Fusobacterium nucleatum）、牙龈卟啉单胞菌（Porphyromonas gingivalis）、中间普雷沃菌（Prevotella intermedia）、变黑普雷沃菌（Prevotella nigrescens）、链球菌属（Streptococcus）、变形链球菌（Streptococcus mutans）、远缘链球菌（Streptococcus sobrinus）、福赛斯坦纳菌（Tannerella forsythia）及齿垢密螺旋体（Treponema denticola）的存在情况与密度。本研究采用描述性统计方法阐释细菌密度相关数据，并通过Student t检验（Student’s t-test）依据临床体征与症状分析各菌种密度间的差异，同时对细菌密度进行配对相关性分析。所有受试菌种均在全部样本中被检出并鉴定。各菌种的平均细菌数量范围为1.9×10^8 细胞/mL（变形链球菌，S. mutans）至3.1×10^8 细胞/mL（具核梭杆菌，F. nucleatum），组间差异无统计学意义（p > 0.05）。各菌种平均计数之和约占整个微生物群落总丰度的80%。伴有疼痛症状的患儿体内齿垢密螺旋体（T. denticola）的载量显著更高，而伴有水肿症状的患儿则表现出更高的链球菌属与变黑普雷沃菌密度（p < 0.05）。本研究表明，本次评估的12种细菌均存在于所有牙髓坏死乳牙样本中，受试菌种间无明显优势菌群，各菌种的个体数量均处于相近水平。