Bacteria of the genus Sneathia appear as opportunistic pathogens of the female reproductive tract. Species of the genus Sneathia, previously grouped in the genus Leptotrichia, may be part of the normal microbiome of the male and female urogenital system but are also associated with a variety of clinical conditions, such as bacterial vaginosis, preeclampsia, preterm birth, spontaneous abortions, postpartum bacteremia, and other invasive infections. Sneathia species are also significantly associated with sexually transmitted diseases and cervical cancer. Because Sneathia species are almost impossible to cultivate and identify with typical microbiological cultures, on the one hand very little is known about the physiology or infectivity of these organisms and on the other hand, the only way to test their presence is by using modern molecular biology techniques.
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A recent study, based on phylogenetic and phenotypic analyses, showed that the microorganism formerly known as Leptotrichia sanguinegens must be transferred to a separate genus. Thus, the genus Sneathia was created, and the species was officially named Sneathia sanguinegens. Species of this genus are elongated, Gram-negative, non-motile bacteria that sometimes exhibit bulbous protrusions.
Sneathia species have been associated with severe obstetric complications, including spontaneous abortions and premature birth. While the uterine cavity and amniotic fluid are usually sterile, a bacterial infection can occur that is often associated with premature birth and premature rupture of fetal membranes. Sneathia is one of the most common genera of microbes detected in amniotic fluid and its presence can lead to inflammation, chorioamnionitis and/or amnionitis. Two recent studies have examined the rates of bacterial infection in the amniotic cavity. Amniotic fluid samples were analyzed for the presence of bacteria and samples from women with preeclampsia who were positive for bacteria, 50% contained Sneathia, while in samples from women who gave birth prematurely who were positive for bacteria, 25% contained Sneathia. These findings suggest that Sneathia microbes have the pathogenic ability to invade the uterine cavity and amniotic sac and thus cause complications in pregnancy. Sneathia has also been implicated in postpartum bacteremia in both infants and mothers. More recently, a case of septic arthritis has been reported in a healthy, non-pregnant woman, proving that the bacterium has the potential to cause infections outside the reproductive tract.
Sneathia has also been linked to bacterial vaginosis (BV), the most common vaginal disorder in women of childbearing age worldwide. Bacterial vaginosis is considered a clinically significant disorder because it is associated with an increased risk of preterm birth and an increased rate of transmission of HIV and other sexually transmitted infections (STIs). Bacterial vaginosis is characterized by a decrease in the number of vaginal lactobacilli and an increase in the number of small anaerobic bacteria and cocci. The total bacterial load and the diversity of species are greatly increased in bacterial vaginosis. The etiology of bacterial vaginosis is not always easy to determine so treatment is not always effective and often tends to come back. Modern molecular techniques that can identify all of these microbial species associated with bacterial vaginosis have been used in an effort to better understand its etiology. Although these studies have revealed the link between different cases of bacterial vaginosis and the presence of Sneathia sp., the role of these bacteria in the etiology and pathology of the disease remains under investigation.
A recent study of the male genitourinary system microbiome showed that men can also colonize with Sneathia and that there is a significant association between colonization and other sexually transmitted pathogens, suggesting that Sneathia can be transmitted through sexual contact.
In summary, Sneathia appears to be an important, emerging opportunistic pathogen that can play an important role in vaginal and reproductive health. However, very little is known about this genus. Analysis of vaginal microbiome profiles (vaginal flora) in more than 700 women as part of the Vaginal Human Microbiome Project revealed that Sneathia species and especially S. amnii sp. nov., are usually found in the human vagina.
At Diagnostiki Athinon the test for the presence of Sneathia in the urogenital system is tested individually and in combination with other microorganisms in the following laboratory tests:
