The vaginal microbiome is a complex environment that consists of many microorganisms, some commensal, others symbiotic and some pathogens. The main genus that constitutes the vaginal microbiota is Lactobacillus sp, which contribute to vaginal health in several ways, including maintaining a low pH (3.5-4.5) through the production of lactic, producing bacteriocins, biosurfactants and H2O2, inhibiting the growth of pathogenic bacteria and competing for adhesion to the vaginal epithelia. The most common species is Lactobacillus crispatus. One of the most important pathogens that can commensally inhabit the vaginal microbiome is Group B Streptococcus (GBS). Streptococcus agalactiae, or GBS, is the major cause of newborn sepsis worldwide. In this project we explore the ability of L. crispatus (LC), one of the most abundant Lactobacilli of the vaginal microbiota, to inhibit GBS growth or stunt its capacity to colonize the vaginal epithelia. We obtained six GBS strains from vaginal swabs of pregnant women, LC strains were acquired commercially. GBS strains were characterized according to capsular serotype, virulence factors, resistance to antibiotics, Restriction Fragment Length Polymorphism (RFLP) and Multi-Locus Sequence Types (MLST). We also built an 8h-growth-curve for each GBS strain. The interaction between GBS and LC was evaluated with co-culture assays, where both growth and biofilm formation were measured. GBS and LC interactions when in human cell culture (HeLa) was also observed. Our results showed that LC can interfere with GBS growth, biofilm formation and other mechanisms. However, that effect depends on GBS strain, regardless of capsular serotypes.