(GBS) vaginal carriage populations in pregnant women. For this purpose, we studied each isolate present in a primary culture of a vaginal swab using a new approach based on Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) locus analysis. To evaluate the CRISPR array composition rapidly, a Restriction Fragment Length Polymorphism (RFLP) analysis was performed. For each different pattern observed, the CRISPR array was sequenced and capsular typing and Multi Locus Sequence Typing (MLST) were performed.A total of 970 isolates from ten women were analyzed by CRISPR-RFLP. Each woman carrying GBS isolates presented one to five specific "personal" patterns. Five women shared isolates with specific and unique restriction patterns, suggesting the carriage of a single GBS clone. Different patterns were observed among isolates from the other five women. For three of these, CRISPR locus sequencing highlighted low internal modifications in the locus backbone, whereas there were high modifications for the last two women, suggesting the carriage of two different clones. These two clones were closely related (same ancestral spacer(s), same capsular type and, in one case, same ST), but shared different antibiotic resistance patterns in pairs.Eight out of 10 women were colonized by a single GBS clone, while two of them were colonized by two strains, leading to a risk of selection of more virulent and/or resistant clones during antibiotic prophylaxis. This CRISPR analysis made it possible to separate isolates belonging to a single capsular type and ST, highlighting the greater discriminating power of this approach.