The aim of the current study was to identify oral strains of Lactobacillusrhamnosus and L. acidophilus by PCR species-specific and other Lactobacilli by a biochemical test (API 50CH) from Mexican and French children with and without dental decay and to compare them using a RAPD-PCR analysis. Saliva samples were collected from Mexican and French children who were 6 to 12 years old. Children were either caries free or harboring carious lesions. Microorganisms were cultured in MRS media and Lactobacilli (L. rhamnosus and L. acidophilus) were identified by PCR species-specific. Other Lactobacilli strains were identified by a biochemical test (API 50CH). All Lactobacilli strains isolated in this study were compared using a molecular biology technique (RAPD-PCR). One hundred and sixty-three strains were isolated. The predominant species in French children with caries was L. rhamnosus, while L. rhamnosus, L. acidophilus and L. brevis were prevalent among the Mexican children. In children without caries, L. acidophiluswas the predominant species identified among the Mexican population, whereas no Lactobacilli species were isolated from French children without caries. The RAPD-PCR results showed the same patterns of amplification between the type strain L. rhamnosus ATCC 9595 and wild strains isolated in this study, meanwhileL. acidophilus showed differences in the pattern of bands between the L. acidophilus ATCC 4656 strain and the wild strains isolated from the saliva of children with and without caries. Similar results were found with the API 50CH test. Even though this study does not investigate it, our results suggest that L. rhamnosus could be involved in both French and Mexican populations as a potential cariogenic agent.
Key words: Lactobacillus rhamnosus, Lactobacillus acidophilus, PCR.
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