The D isoforms of lactic acid produced by L. crispatus, L. jensenii and L. gasseri were negatively correlated with the levels of vaginal extracellular matrix metalloproteinase-inducer (EMMPRIN) and matrix metalloproteinase-8 (MMP-8), which are known to alter the tight junctions in the endocervical epithelium, making the female genital tract susceptible to infection. This evidence concerns the gene MMP8 and infection.