Background The normal microbial flora of the vagina plays an important role in preventing genital and urinary tract infections in women. Thus an accurate understanding of the composition and ecology of the ecosystem is important to understanding the etiology of these diseases. This study aimed to compare the characteristics of main lactobacillus species between healthy women and women with bacterial vaginosis （BV） by quantitative culture and PCR methods. Main lactobacillus species include L. crispatus , L. gasseri, L. jensenii and L. iners.Methods A total of 150 Women attending Gynecology Outpatient Clinic of Beijing Friendship Hospital, were diagnosed as having BV because three or more of the following criteria were met （standard of Amsel＇s composite criteria）： homogeneous discharge, elevated vaginal pH （pH 〉4.5）, production of amines, and presence of ＂clue＂ cells. Those with less than three of the criteria were considered as healthy. Simultaneously, smears were made of vaginal fluid and Gram stained, then were assessed qualitatively as normal （grade Ⅰ）, intermediate （grade Ⅱ）, or consistent with BV （grade Ⅲ）. Gardnerella vaginalis were identified by using Vitek 2 Compact and PCR methods. Lactobacillus species were identified by PCR methods. Gardnerella vaginalis and lactobacilli colony counts were determined by calculating the most number of colonies of each species in the appropriate plates （colonies between 10 and 300）, corrected by the dilution of the sample in the plates, and multiplied by 10 （to account for plating 100 μl）, in order to get colony forming units per milliliter of vaginal secretion.Results BV was diagnosed in 31% （46/150） patients using the composite criteria, the remainder being regarded as healthy. The majority of patients with BV had a smear assessed as grade Ⅲ （91%, 42/46） and minority of them had a smear assessed as grade Ⅱ（9%, 4/46）. The majority of healthy women had a smear assessed as grade Ⅰ （64%, 67/104）. Smears
