For example, multiple isolates of L. acidophilus were found to possess identical RAPD fingerprints (using primer 272) to the type strain for the species, LMG 9433T (Fig. 3, panel A). These included 4 additional reference isolates that had originally been recovered from diverse sources such as from rat and human faeces, as well as 4 isolates used in the commercial probiotic products (Table 2). All L. acidophilus isolates were genotypically indistinguishable even

when examined with additional RAPD primers 277 and 287. These data suggested there was little selleck genetic heterogeneity among isolates of L. acidophilus examined in this study. In addition they show that isolates genotypically identical to the L. acidophilus Type strain have been widely adopted for commercial use (Fig. 3, panel A; Table 2). Of the remaining 8 LAB reference isolates examined, 8 distinct RAPD strain types were found that corresponded to each LAB species (Table 2). Figure 3 Discrimination of LAB by RAPD typing. The ability of PCR fingerprinting (with primer 272) to cluster identical isolates learn more (Panel A) and differentiate distinct isolates within the L. casei group (Panel B) is shown. Strains shown in each lane are as follows: Panel A; 1, L. acidophilus LMG 9433T; lanes 2 to 6, matching L. acidophilus isolates LMG 11428, LMG 11430, C21, C46 and NCIMB 30211, respectively;

Panel B; lanes 7 to 11, L. paracasei subsp paracasei isolates C48, C65, C83, C79 and LMG 7955, respectively; 12, L. casei LMG 6904 T; and 13, L. rhamnosus

MW. Molecular size markers were run in lane M and the size of relevant bands is indicated; panel A and B represent composite lanes taken from a single gel in each case. RAPD fingerprinting was also able to differentiate genetically Calpain unique strain types within very closely related species such as those within the L. casei group (Fig. 2); these included L. casei, L. paracasei and L. rhamnosus (Fig. 3, panel B). From this closely related complex of species (Fig. 2), a total of 9 distinct RAPD types (10, 11, 12, 16, 17, 18, 20, 21, and 27; Table 2) were identified. Two commercially marketed probiotics were found to contain the same strain of L. rhamnosus (isolates FMD T2 and MW, RAPD type 10; Table 2). Another commercial probiotic formulation contained an L. casei strain, designated BF T1, that was identical by RAPD to the L. casei Type strain LMG 6904T (Table 2). Overall, the RAPD fingerprinting method was highly effective, working on all 38 LAB isolates examined irrespective of their species and reproducibly defining 26 RAPD types within this diverse collection (Table 2). Application of RAPD fingerprinting to single colonies To facilitate high throughput typing that could be applied to screening LAB isolates cultivated directly from human faeces, we evaluated if the PCR-fingerprinting method could be adapted for use on single bacteria colonies.