That reach the colon Met-Enkephalin manufacturer during treatment, thus reducing alterations in the microbiota to a minimum [40,41]. In spite of clavulanic acid presence which is a beta-lactamase inhibitor, remaining intestinal beta-lactamases from individual microbiota could influence the amount of beta-lactam present in the feces during AMC exposure and explain the resistance to changes of some microbiota. Similarity percentages of TTGE profiles at day 33 and day 64 were 59.6 and 62.3 respectively, showing that microbiota did not return to baseline. Cloning and sequencing were performed to identify bands of interest and to evaluate if the changes of bands corresponded to changes of species or 1676428 of strains within the same species. The same 
identifications were obtained for bands with identical Rf. In agreement with previous studies [7,8,19,42], B. adolescentis (83 ), B. longum (52 ) and the B. pseudocatenulatum/B. catenulatum group (46 ) were the most frequent predominant bifidobacterial species present in adult microbiota followed by B. bifidum (35 ). The mean number of Bifidobacterium species per sample harbored in dominant microbiota is significantly lower at day 5 (1.560.3) compared to reference period (2.360.2) (p,0.05). In another study, the average number of species detected per individual were 2.861.2 in healthy adults [8]. Furthermore, at day 5, significant alterations for some Bifidobacterium species were observed: for example, occurrence of B. adolescentis decreased significantly (39 versus 83 in reference period). In some cases, species not present at day 0 and probably belonging to the subdominant microbiota, became dominant, eg B. longum or B. breve. The occurrence of B. longum remained stable after theantibiotherapy. As enlightened in previous studies, the antimicrobial effect is dose-dependent and amoxicillin showed Licochalcone-A site variable MIC (minimum inhibitory concentration) depending on species or strains tested [13,16]. Generally, B. adolescentis, B. bifidum and B. pseudocatenulatum seemed to be more susceptible in vitro (MIC range #0.06?.5 mg/L) than was B. longum (MIC range #0.06? mg/L) [13,16]. Thus, our results could be explained by MIC values, as well as intestinal beta-lactamases from individual microbiota. Similar results were previously obtained within microbiota of infants treated with a 7day-amoxicillin treatment, but long-term impact was not monitored [29]. Jaccard’s similarity coefficients indicated that differences between TTGE profiles corresponded to species changes and not only to strains changes (Fig. 4). B. bifidum was not entirely recovered at day 33 or day 64 (22 versus 35 during reference period). In a previous study, a molecular monitoring of intestinal Bifidobacterium strains in four adults using RFLP and ribotyping, showed little variations 30 days and 90 days after an AMC exposure [19]. Strains detected at day 0 could be detected at day 90 or be replaced by another strain from the same species displaying a different pattern. The B. bifidum species detected in three of four subjects at day 0, disappeared from two microbiota at day 90 [19]. By changing the intestinal species balance, antibiotic exposure may lead to a homeostatic imbalance through alterations in expression of intestinal epithelial cells tight junction proteins, mucins, antimicrobial peptides, and cytokines [43]. A study has shown that capacity of bifidobacterial species to stimulate immunity is strain specific (TH1, TH2 cytokines, no effect) [44,45,46]. Only some.That reach the colon during treatment, thus reducing alterations in the microbiota to a minimum [40,41]. In spite of clavulanic acid presence which is a beta-lactamase inhibitor, remaining intestinal beta-lactamases from individual microbiota could influence the amount of beta-lactam present in the feces during AMC exposure and explain the resistance to changes of some microbiota. Similarity percentages of TTGE profiles at day 33 and day 64 were 59.6 and 62.3 respectively, showing that microbiota did not return to baseline. Cloning and sequencing were performed to identify bands of interest and to evaluate if the changes of bands corresponded to changes of species or 1676428 of strains within the same species. The same identifications were obtained for bands with identical Rf. In agreement with previous studies [7,8,19,42], B. adolescentis (83 ), B. longum (52 ) and the B. pseudocatenulatum/B. catenulatum group (46 ) were the most frequent predominant bifidobacterial species present in adult microbiota followed by B. bifidum (35 ). The mean number of Bifidobacterium species per sample harbored in dominant microbiota is significantly lower at day 5 (1.560.3) compared to reference period (2.360.2) 
(p,0.05). In another study, the average number of species detected per individual were 2.861.2 in healthy adults [8]. Furthermore, at day 5, significant alterations for some Bifidobacterium species were observed: for example, occurrence of B. adolescentis decreased significantly (39 versus 83 in reference period). In some cases, species not present at day 0 and probably belonging to the subdominant microbiota, became dominant, eg B. longum or B. breve. The occurrence of B. longum remained stable after theantibiotherapy. As enlightened in previous studies, the antimicrobial effect is dose-dependent and amoxicillin showed variable MIC (minimum inhibitory concentration) depending on species or strains tested [13,16]. Generally, B. adolescentis, B. bifidum and B. pseudocatenulatum seemed to be more susceptible in vitro (MIC range #0.06?.5 mg/L) than was B. longum (MIC range #0.06? mg/L) [13,16]. Thus, our results could be explained by MIC values, as well as intestinal beta-lactamases from individual microbiota. Similar results were previously obtained within microbiota of infants treated with a 7day-amoxicillin treatment, but long-term impact was not monitored [29]. Jaccard’s similarity coefficients indicated that differences between TTGE profiles corresponded to species changes and not only to strains changes (Fig. 4). B. bifidum was not entirely recovered at day 33 or day 64 (22 versus 35 during reference period). In a previous study, a molecular monitoring of intestinal Bifidobacterium strains in four adults using RFLP and ribotyping, showed little variations 30 days and 90 days after an AMC exposure [19]. Strains detected at day 0 could be detected at day 90 or be replaced by another strain from the same species displaying a different pattern. The B. bifidum species detected in three of four subjects at day 0, disappeared from two microbiota at day 90 [19]. By changing the intestinal species balance, antibiotic exposure may lead to a homeostatic imbalance through alterations in expression of intestinal epithelial cells tight junction proteins, mucins, antimicrobial peptides, and cytokines [43]. A study has shown that capacity of bifidobacterial species to stimulate immunity is strain specific (TH1, TH2 cytokines, no effect) [44,45,46]. Only some.