Lactobacillus crispatus is a species of bacteria naturally present in the human body, particularly within the vaginal microbiome. As a probiotic microbe, it is a beneficial microorganism belonging to the Lactobacillus genus, which is known for producing lactic acid. Its presence is considered a marker of a healthy microbial balance, and its characteristics make it a subject of ongoing scientific research into its contributions to human health.
The Role in Vaginal Health
Lactobacillus crispatus plays a part in maintaining the ecological balance of the vaginal microbiome. One of its primary functions is the production of lactic acid through the fermentation of glycogen, a sugar derivative found in the vagina. This process results in an acidic environment with a pH level of 4.5 or lower, which is inhospitable to many pathogenic bacteria, fungi, and viruses, limiting their ability to cause infections.
Beyond creating an acidic environment, this bacterium employs other protective mechanisms. It produces antimicrobial compounds, including hydrogen peroxide and specialized proteins called bacteriocins, which can directly inhibit or kill harmful microbes. The production of these compounds varies between different strains of L. crispatus, suggesting that some may offer more potent protection than others.
L. crispatus also contributes to a healthy vaginal environment by physically occupying space. It adheres to the epithelial cells that line the vaginal wall, forming a protective barrier. This colonization prevents pathogenic organisms from attaching to host tissues by outcompeting them for nutrients and attachment sites, a process known as competitive exclusion. This bacterium also modulates the local immune response, helping to reduce inflammation.
Connection to Common Health Conditions
A reduction in the population of Lactobacillus crispatus can disrupt the balance of the vaginal microbiome, increasing susceptibility to various health conditions. One of the most common issues linked to a deficiency of this bacterium is bacterial vaginosis (BV). BV is characterized by a shift in vaginal flora, where beneficial lactobacilli decrease and opportunistic bacteria like Gardnerella vaginalis overgrow, leading to symptoms like a thin, grayish discharge and a distinct fishy odor.
The presence of L. crispatus is inversely correlated with the abundance of G. vaginalis, as studies show it actively suppresses the pathogen’s growth. It achieves this by blocking the pathogen’s ability to adhere to vaginal epithelial cells and by reducing the expression of its virulence factors, such as vaginolysin. When L. crispatus levels are low, this protective pressure is removed, allowing G. vaginalis and other bacteria to flourish and form biofilms, which are more resistant to treatment.
In addition to BV, a diminished L. crispatus population is also associated with a higher incidence of vulvovaginal candidiasis, known as a yeast infection. The protective qualities of L. crispatus help keep Candida populations in check. A similar protective role is observed concerning urinary tract infections (UTIs), as a healthy vaginal microbiome can prevent pathogens from ascending into the urinary tract.
Influence on Fertility and Pregnancy
A vaginal microbiome dominated by Lactobacillus crispatus is increasingly associated with positive reproductive outcomes. Research suggests that the presence of L. crispatus may improve the chances of successful conception, both naturally and through assisted reproductive technologies like in vitro fertilization (IVF). A stable, acidic environment maintained by this microbe is thought to be more supportive for sperm survival and function.
Studies have shown a strong correlation between a high relative abundance of L. crispatus at the time of embryo transfer and higher rates of implantation, pregnancy, and live births in women undergoing IVF. Conversely, a vaginal environment not dominated by lactobacilli, often referred to as dysbiosis, is linked to recurrent implantation failure. The composition of the vaginal microbiota appears to influence the uterine environment, suggesting a connection between vaginal health and endometrial receptivity.
During pregnancy, the role of L. crispatus continues. A microbiome rich in this bacterium is associated with a reduced risk of complications such as preterm birth. Its protective functions, like preventing infections and modulating inflammation, contribute to maintaining a stable gestational environment. An overgrowth of pathogenic bacteria associated with conditions like BV has been linked to an increased risk of premature delivery.
Sources and Supplementation
For individuals looking to support their vaginal microbiome, probiotic supplements containing Lactobacillus crispatus are a direct option. They are available in different forms, primarily as oral capsules or vaginal suppositories.
Oral probiotics are designed to survive the passage through the gastrointestinal system and eventually colonize the vaginal area. This route is convenient, and studies show that oral administration can lead to improvements in vaginal health by reducing symptoms of conditions like BV and yeast infections. Vaginal suppositories, on the other hand, deliver the probiotics directly to the target site, which can result in a more rapid increase in local lactobacilli counts.
While some fermented foods, such as yogurt and kefir, are sources of other Lactobacillus species, they are not reliable sources of L. crispatus. The strains present in these foods are often different from those native to the vaginal environment. For those seeking targeted vaginal health benefits, a focused probiotic supplement is a more effective approach.