Genetic variability of Streptococcus mutans isolated from low-income families, as shown by RAPD markers

Abstract

The detection of Streptococcus mutans isolates with high genetic variability in different individuals indicates the occurrence of transmissibility. In this context, nine low-income families (40 individuals in total) with similar social conditions were assessed to identify the bioserotypes of S. mutans using both biochemical and RAPD markers and to establish the degree of similarity among the intra-familial isolates. The polymorphism analysis used the coefficient of Jaccard in both a Principal Coordinates Analysis (PCO) and in a UPGMA clustering method. A total of 157 isolates were obtained from salivary samples, using the morphology of colonies recovered using MSB agar as indicators. From those, 64 were characterized biochemically as S. mutans and 10 as S. sombrinus. Genetic variability among isolates based on RAPD markers was not consistent with their intra-familial distribution. In particular, some individuals might have experienced multiple infections given the high genetic variability among their isolates. The occurrence of 4 isolates with 100% genetic similarity is indicative of intra-familial transmission.

Methodological variations in the isolation of genomic DNA from Streptococcus bacteria

“…The advantage of using the physical method as pretreatment without heating or freezing/thawing not even the later use of enzymes, is its simplicity and low cost. In addition, it is useful to standardize these methods for easy and rapid extraction of DNA directly from the isolated colonies of GAS strains and Streptococcus of the Mutans group cultivated in liquid media, facilitating molecular studies (Moreira et al, 2007). The present results supported the assumption that the method using ultrasound with a mixture of silica and celite in CTAB had good reproducibility, was straightforward to execute, and allowed the extraction of high-quality DNA from Gram-positive cells, and, thus, could be used in molecular biology laboratories.…”

Molecular characterization of Streptococcus mutans gtfB gene isolated from families

“…We previously evaluated saliva samples from the 40 individuals, and a total of 157 isolates were obtained. The 64 isolates biochemical characterized as S. mutans had the genetic similarity evaluated by RAPD markers [8]. We identified in this way, sixteen intra-familial isolates that had genetic similarity and came from members of two families: family A consisted of a mother and son, and family B consisted of a mother, father, and five children (Table 1).…”

“…The selection of the families for the study was based on their social and biological risk of developing caries. In addition, isolates of S. mutans from saliva samples from each nuclear family were subjected to molecular characterization by RAPD (random amplification of polymorphic DNA) markers [8] and evaluated by partial sequencing of the gene encoding glucosyltransferase B (gtfB) in order to demonstrate the genetic profile of S. mutans within the family and to detect specific serotypes concerning to the virulence.…”

Using molecular markers to assess Streptococcus mutans variability and the biological risk for caries

“…For the RAPD reactions, the following six oligonucleotide primers were used: OPA 2 (5' TGCCGAGCTG 3'), OPA 3 (5' AGTCAGCCAC 3), OPA 5 (5' AGGGGTCTTG 3'), OPA 8 (5' GTGACGTAGG 3'), OPA 9 (5' GGGTAACGCC 3') and OPA 13 (5' CAGCACCCAC 3'). The PCR was performed using the conditions as described previously 9 . The Streptococcus mutans strains ATCC 25175 and UA159 were included as reference samples during the amplifications, and the strains S. sobrinus ATCC 33478 and S. pyogenes ATCC 13540 were included as external control groups.…”

“…Molecular markers have been used to elucidate the genetic variability among S. mutans isolated from saliva and other sources. RAPD (Random Amplified Polymorphic DNA) markers have been most widely used for this purpose [8][9][10] . In addition, IGS sequencing (e.g., sequencing of intergenic regions between the 16S and 23S rRNA genes) has been used to taxonomy studies, while partial sequencing of the gene gtfB, which encodes the enzyme glucosyltransferase B, has been used to investigate enzymatic activity and virulence [11][12] .…”