Department of Pediatric Clinics, Preventive and Social Dentistry, School of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil.
Microbiol Res. 2011 Jan 20;166(1):63-7. doi: 10.1016/j.micres.2010.01.001. Epub 2010 Jan 25.
Due to the major role of Streptococcus mutans and Streptococcus sobrinus in the etiology of dental caries, it is important to use culture media that allow for differentiating these bacterial species. The aim of this study was to evaluate the suitability of a modified SB-20 culture medium (SB-20M) for the isolation and morphological differentiation of S. mutans and S. sobrinus, compared to biochemical identification (biotyping). Saliva samples were collected using the spatula method from 145 children, seeded on plates containing the SB-20M, in which sucrose was replaced by coarse granular cane sugar, and incubated in microaerophilia at 37°C during 72 h. Identification of the microorganisms was performed under stereomicroscopy based on colony morphology of 4904 colonies. The morphological identification was examined by biochemical tests of 94 randomly selected colonies with the macroscopic characteristic of S. mutans and S. sobrinus using sugar fermentation, resistance to bacitracin and production of hydrogen peroxide. There was no statistically significant difference (p>0.05) between morphological identification in the SB-20M medium and biochemical identification (biotyping). Biotyping confirmed that S. mutans and S. sobrinus colonies were correctly characterized in the SB-20M in 95.8% and 95.5% of the cases, respectively. Of the mutans streptococci detected in the children 98% were S. mutans and 2% S. sobrinus. The SB-20M medium is reliable for detection and direct morphological identification of S. mutans and S. sobrinus.
由于变形链球菌和远缘链球菌在龋齿病因学中的重要作用，使用能够区分这些细菌物种的培养基非常重要。本研究旨在评估改良 SB-20 培养基（SB-20M）用于分离和形态分化变形链球菌和远缘链球菌的适用性，与生化鉴定（生物分型）相比。使用匙形法从 145 名儿童中采集唾液样本，将其接种在含有 SB-20M 的平板上，其中蔗糖被粗颗粒甘蔗糖代替，并在微需氧条件下于 37°C 孵育 72 小时。根据 4904 个菌落的菌落形态，在立体显微镜下对微生物进行鉴定。通过对 94 个随机选择的具有变形链球菌和远缘链球菌宏观特征的菌落进行糖发酵、杆菌肽抗性和过氧化氢产生的生化试验，检查形态学鉴定。在 SB-20M 培养基中的形态学鉴定和生化鉴定（生物分型）之间没有统计学差异（p>0.05）。生物分型证实，在 SB-20M 中，95.8%和 95.5%的情况下，变形链球菌和远缘链球菌的菌落得到了正确的特征化。在儿童中检测到的变形链球菌中，98%为变形链球菌，2%为远缘链球菌。SB-20M 培养基可用于检测和直接形态学鉴定变形链球菌和远缘链球菌。
