Participants were enrolled in a cross-sectional study described previously [5
]. In brief, the 392 participants were predominantly white (88%), the median age was 28 years, and the median numbers of lifetime male and female sex partners reported were 7 and 6, respectively. Most (58%) reported having had only 1 female partner during the past 6 months. Almost all reported having received and performed oral-vaginal and digital-vaginal sex with female partners during the past year, and many reported having engaged in oral-anal and digital-anal sex during the past year (34% and 63%, respectively). Overall, 36.8% had abnormal vaginal flora (25.3% had BV, and 11.5% had intermediate flora as defined by the Nugent score).
Of 356 women who had rectal and vaginal specimens cultured, 262 (72%) had lactobacilli recovered from either site. Of these 262 women, 237 (91%) had viable lactobacilli for species-level identification. These 237 participants did not differ from the entire group of 392 participants with respect to factors such as age, race, and sexual history, but they were less likely to have BV. This difference was expected—the 237 women were selected because they had lactobacilli recovered from genital specimens.
The distribution of Lactobacillus species by anatomic site is depicted in . L. crispatus was most common, followed by Lactobacillus gasseri and L. jensenii. For women colonized with L. crispatus, rectal colonization alone was uncommon; most women had either vaginal colonization only or both vaginal and rectal colonization. The overall prevalence of rectal colonization did not differ between L. crispatus and L. gasseri. However, relative to L. crispatus, the rectum was more commonly the sole site of L. gasseri colonization (P < .001). Relatively few women with L. jensenii had this organism recovered from the rectum. Of women who had any vaginal lactobacilli detected, 57 (24%) had >1 species type. L. jensenii was rarely detected as the single Lactobacillus species in either the vagina or the rectum; this occurred in only 4 of 26 women with L. jensenii colonization.
Distribution of Lactobacillus strains among 237 women for whom cultures of vaginal and rectal specimens were performed.
Relative to women without L. gasseri, women with L. gasseri reported a shorter median interval since they last had receptive digital-vaginal sex (3 days vs. 21 days; P = .03) and were more likely to have abnormal vaginal flora, defined as a Nugent score of >4 (37.2% vs. 13.1%; OR, 3.9; 95% CI, 1.9–8.3; P = .001) or BV (14.0% vs. 3.7%; OR, 4.3; 95% CI, 1.4 –13.4; P = .02).
Both members from 72 monogamous partnerships were enrolled. In 40 couples (56%), lactobacilli were detected in cultures of vaginal or rectal specimens for both women. In 16 couples (22%), lactobacilli were detected by cultures of vaginal or rectal specimens for only 1 partner. No lactobacilli were isolated by culture for either partner in 15 couples (21%). Culture was not performed for 1 woman in the remaining couple. Of the 40 couples with both partners colonized by lactobacilli, 31 had strains available for rep-PCR. Isolates were not available for the remaining 9 couples because they were enrolled before initiation of the protocol for saving lactobacilli isolates. When both partners in a couple were colonized by lactobacilli, L. crispatus colonization of both was the most common outcome (74%). Nonetheless, of 31 couples with strains available for rep-PCR, identical strains were recovered from both women in 23 (74%). Of these 23 couples, partners in 18 shared the same L. crispatus strain, partners in 5 shared the same L. gasseri strain, and partners in 1 shared the same L. jensenii strain. Women in one of these couples shared an L. crispatus strain and an L. gasseri strain.
The gels in depict rep-PCR findings for 18 women: 6 case couples (A through F) and 6 matched control women (AA through FF). Unique patterns are seen for each couple, and no similarity was seen for control subjects. Both partners of couple A were vaginally colonized by 2 different L. crispatus strains. Two different strains both vaginally and rectally colonized partner 1 of couple B. One strain colonized both the rectum and vagina of partner 1 of couple C and was only isolated from the vagina of partner 2. The same strain was detected from the vagina of both partners of couple D. Vaginal and rectal colonization by the same strain was found in both partners of couple E. Partners of couple F did not have a strain in common. However, partner 1 was colonized rectally and vaginally by the same strain. Rep-PCR findings were available for 46 other women in the study. Overall, at least half of the women (51% [60 of 118]) had >1 strain with a distinct rep-PCR pattern.
Figure 1 Representative gels of repetitive element sequence– based PCR DNA fingerprints of Lactobacillus crispatus isolates from 18 subjects, of whom 12 were from 6 monogamous couples (A through F) and 6 were from matched control women who were unpartnered (more ...)
Couples who shared identical Lactobacillus strains reported having had fewer female partners in the prior year (P = .03) and a longer median relationship duration (16 vs. 9.8 months; P = .6). The likelihood of sharing identical lactobacilli was not related to the mean age of the couple, the median number of lifetime male sex partners, or the practice, frequency, or timing of other types of sexual behaviors, including oral or anal sexual practices; one exception was reported use of shared vaginal sex toys, for which there was a trend toward an association with sharing identical lactobacilli strains (OR, 1.6; 95% CI, 0.94 –2.7; P = .2).