rhamnosus A+7-5a; 2, A+28-3b*; 3, E. sanguinicola G0-2a*; 4, G0-2b; 5, G+21-1a; 6, E. faecalis Q0-1a; 7, Q0-1b; Selleckchem AZD8931 8, Q+28-1a, 9, Q+28-1b; 10, L. rhamnosus T0-2a; 11, T+23-1a; 12, T+28-1b (systematic identification for the latter strains shown in Table 2). Molecular size markers are shown in lane M (size in bp indicated) and the figure is a composite of lanes drawn from 8 gels. All the volunteers were colonised with persistent LAB strains (specific to each individual) that represented greater than 1% of their viable faecal growth; at least one of these strains was identified to the species level for each volunteer except J (Table 3). Apart from sharing of the L. salivarius NCIMB
30211 and L. acidophilus NCIMB 30156 strains present within the administered feeding capsule, only one other strain was detected in two volunteers, the L. rhamnosus RAPD type 41 strain (Table 2). This L. rhamnosus strain was shared by individuals P and T (Table 2 and Table 3). Overall, these results demonstrate the ability of the fingerprinting strategy to detect and track the population biology of cultivable faecal
strains representative of a broad range of LAB species. Discussion We successfully developed a rapid, colony-based strain typing strategy that was able to track two Lactobacillus strains from feeding via a capsule through to faecal discharge in human volunteers. The RAPD typing system was capable of genotyping a wide variety of LAB species and its efficacy on single colonies provided a means to rapidly discriminate LAB isolates cultivated from human faeces. Evidence for survival and growth of the L. salivarius Dinaciclib strain was most convincing as it was not detected in any of volunteers prior to the feeding study (Table 3). In contrast, the L. acidophilus strain used in the capsule represented a very common genotype used in commercial applications (Table 2). Hence the appearance of L. acidophilus
isolates which matched the feeding strain NCIMB 30156 may have been less attributable to consumption of the capsule. However, statistical analysis demonstrated that the distribution of L. acidophilus NCIMB 30156 after the feeding trial was significant in terms of the number of positive volunteers PLEKHB2 and in the majority of these positive individuals it was the dominant cultivable LAB strain in faeces. As far as we are aware, previous studies evaluating the dynamics of LAB consumption by humans have not examined the cultivable faecal diversity at the strain level. Several studies have used cultivation-independent methods such as real-time PCR to quantify the DNA from probiotic strains present in faeces by extrapolating this amplification data to estimate of the numbers of bacteria. Bartosch et al.  used real-time PCR to estimate the total numbers of Bifidobacterium species present in the faeces of elderly people taking a probiotic containing two Bifidobacterium strains and an inulin-based prebiotic.