Sneathia amnii

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Create a resource for other people to appreciate the amazing diversity of the microbial world! Demonstrate your knowledge of your microbe by creating a MicrobeWiki page using the scientific literature and reputable resources. Each section of your page must integrate course Learning Objectives (LO) to demonstrate your understanding of microbiology. Each section must have at least 2 references to the primary peer-reviewed literature and at least 1 reference to a reputable reference book. All references must be cited in the References section. Please remove the LO and the instructions from each section. You only need to put your text in the different sections.

Introduction

Have you ever wondered exactly what microbes are in your normal microbiota? The microorganisms within our normal microbiota live within us and remain with us every day! Bacteria of the genus Sneathia were isolated from blood cultures taken from obstetric patients with post-partum fever, two newborn children and a 100-year-old woman in 1995. The bacteria are Gram stain negative, anaerobic, rod-shaped bacteria are emerging as potential pathogens of the female reproductive tract (Eisenberg et al, 2018). The species Sneathia, which had been a part of the genus Leptotrichia prior to its reclassification, is a part of the normal microbiota of the genitourinary tracts of men and women. Sneathia have a significant role in obstetrics and the health of women’s reproductive systems. This bacteria is of particular concern for women because it most commonly inhabits the human vagina and poses risk, especially for those who are pregnant. Sneathia has been known to cause preterm delivery and is heavily present in the blood of newborn babies, but it doesn’t just stop there. They are also associated with numerous clinical conditions such as bacterial vaginosis, preeclampsia, miscarriages, post-partum bacteremia and some other invasive infections (Harwich et al, 2020). Sneathia species also exhibit a significant correlation with sexually transmitted diseases and cervical cancer. The limited forms of carbohydrates that S. amnii is able to metabolize include glucose, maltose, glycogen and glucosamine (Harwich et al, 2020). Due to the very fixed nutrient requirement of Sneathia, it is difficult to cultivate in the lab. A consequence of this is that very is little known about its biology or its pathogenic capabilities. They are not able to ferment starch, mucin and mannose. In order to learn more about how pathogenic Sneathia are in terms of pelvic inflammatory disease, more studies will need to be done. Pelvic inflammatory disease is an infection of particular concern for women because it effects the reproductive organs and can possibly lead to infertility or chronic pelvic pain.


Electron Micrographs of S. amnii. S. amnii were fixed to either glass cover slips or copper grids, and visualized by SEM (a) or TEM (b), respectively by Harwich Jr et al. (2012) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3535699/


Gram stain of Sneathia amnii by Duployez et al. (2020). Gram stain from colonies on blood agar, image taken at magnification 1000x. Presence of long and short Gram-negative rods. https://reader.elsevier.com/reader/sd/pii/S1075996420301335?token=E22DB79E5100C93C86CD14DBA659C6A7B8C73FD251F2702FCB1FD5A4ADBB24B26E5A134903DB9E32EFA6815BE5CE4DEB

Classification

Higher order taxa

Bacteria; Fusobacteria; Fusobacteriia; Fusobacteriales; Leptotrichiaceae

Species Sneathia amnii, Sneathia sanguinegens NCBI: https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=168808 JGI: https://gold.jgi.doe.gov/project?id=Gp0121048 Genus species

Phylogenetic Relatedness

Phylogenetic Relatedness Researchers set out to isolate a clone from the mid-vaginal sample that was taken from the young African American woman with a goal of better defining the role of novel S. amnii. She was presenting with symptoms of preterm labor after carrying her child for only 26 weeks. The 16S rRNA gene of the clone was completely sequenced and then compared to the 16S rDNAs from various members of the Fusobacteriaceae family. This enabled researchers to assess the phylogenetic relationships between the different bacteria. The alignment showed that the 16S rDNA of the Sneathia amnii isolate is almost 99.8% identical to the 16S rDNA of the Leptotrichia amnii isolate. The 16S rDNA of the Sneathia isolate showed 94.7% overall sameness to S. sanguinegens, but only 84.4% overall sameness to Leptotrichia buccalis, the type species of the genus Leptotrichia.

Presented is the maximum likelihood phylogenetic tree of S. amnii and its related organisms within the family Fusobacteriaceae (Harwich Jr et al., 2012) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3535699/

Ecological Habitat

 Sneathia are most commonly found in the genitourinary tract but are also found as pathogens in the amniotic fluid of pregnant women (Harwich et al., 2012). It plays a large role in vaginal and reproductive health, as it is found in the microbiome of both the male and female urogenital tracts. In women, Sneathia can contribute to serious complications of birth, such as preterm labor or miscarriage, bacterial vaginosis, inflammation, histological amnionitis and amnionitis. It’s very important to remember that Sneathia is not only found in women! In males, the microbe contributed to and was associated with sexually transmitted diseases.

Figure 1: This heat map shows the vaginal microbiota community state types.8 Compared to the other microbes that are present in community state 5, Sneathia are of the most prevalent species, which is denoted by the darker blue color. The bacteria in community state type 5 are the ones that are most microbially similar to bacterial vaginosis. Sneathia are associated with the clinical condition of bacterial vaginosis. Credit: Swidsinski et al., 2017

Figure 2: This picture shows the vaginal epithelium under 1000x magnification from a post-menopausal, which was taken with unstructured biofilm.7 This is where Sneathia is most likely to interact in the vagina and receive their nutrients but are found can be found as a pathogen in the amniotic fluid. Credit: Smith and Ravel, 2017


 Human clinical specimen are the main sources of isolation. The genus is most commonly found in clinical samples from the mid-vaginal wall area or amniotic fluid. In order to identify Sneathia amnii from a sample, the V1-V3 region of the 16s-ribosomal-RNA-endocded gene is amplified (Harwich et al., 2012). The analysis was able to clearly differentiate S. amnii from S. sanguinegens. It turns out that these two species are approximately only 91% to 93% identical to one another; this actually makes them distant. The specific growth requirements of S. amnii makes it a difficult species to culture in the lab with common microbiological techniques.

 Sneathia amnii’s enviornment is one that is very acidic. The normal pH of the vagina is about 4 but ranges from 3.5 to 4.5. The normal pH of amniotic fluid is 6.5 or higher. When Sneathia amnii is present, pH levels will rise and become even more basic (Ray et al., 2017). The temperature is about the same as body temperature, a range of 36 to 37 degrees Celsius. The human body does contain oxygen but S. amnii is an aerotolerant anaerobe that protects itself from reactive oxygen molecules and avoid their use. The area receives little to no amounts of light and is moist. There is lactic acid, urea, estrogen, progesterone, luteinizing hormone and amines, including isobutylamine, phenethylamine, putrescine, cadaverine, and tyramine, found in vaginal secretions (Wolrath et al., 2001).

Significance to the Environment

 S. amnii has very complicated growth requirements. It is able to metabolize few carbohydrates, including glucose, maltose, glycogen and glucosamine. This species, however, lacks the ability to ferment starch, mucin, fructose, sucrose or mannose (Eisenberg et al., 2018). S. amnii’s fermentative style of metabolism leaves lactic acid, formic acid, a small amount of acetic acid and sometimes succinic acids as the waste products after metabolizing glucose. Since the epithelium of the vagina produces a lot of glucose, especially when a woman is at reproductive age, S. amnii is able to use this carbohydrate source despite its reduced metabolic capabilities with other carbohydrates.

 More information about fermentative metabolism of glucose: o https://umaine.edu/carbohydrates/carbohydrate-digestion/fermentation/ (University of Maine, n.d.)

 Sneathia strains tend to be susceptible to and best treated with antimicrobials, such as metronidazole, but can be resistant to erythromycin, kanamycin, vancomycin, aminoglycosides, and fluoroquinolone. We know that S. amnii is one of the anaerobic microbes that plays a role in the development of bacterial vaginosis. The overuse of metronidazole in treatment may have caused the recent relative resistance to it (Eschenbach, 2007). This conclusion comes from a study that showed increase failure rate of a treatment course using metronidazole spanning over two weeks of time.

Ecological Lifestyle and Interactions

 Sneathia amnii is an opportunistic microbe that is emerging as being increasingly pathogenic. It most commonly associates itself with humans, as it is mostly found in the female urogenital tracts. Its presence causes infections, and it has also been found in cultured blood samples and fluid of the joints (Eisenberg et al., 2018). When Sneathia amnii’s genome was sequenced, there were potential cytotoxins revealed that had the ability to kill eukaryotic cells in the test tube or culture dish (Fettweis et al., 2019). Microbes that were phenotypically similar to Sneathia were found in the urine of cows and female sheep; the effect of the microbe on uterine health in these animals is yet to be clearly defined (Eisenberg et al., 2018).

Lewis et al (2017) published a figure in their study showing the sociological framework for the determinants of one’s “normal” vaginal microbiome. All these factors have potential for determining what microbes Sneathia amnii will be interacting with in the vagina. For example, women of European and African descent can have differing profiles for their vaginal microbiome (Fettweis et al., 2019). A woman of African descent is more likely to have an abundance of L. crispatus. Figure Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6743080/#:~:text=Significant%20evidence%20now%20indicates%20that,is%20optimal%20for%20vaginal%20health.&text=Recent%20studies%20have%20shown%20that,the%20absence%20of%20bacterial%20vaginosis

 Sneathia amnii can be associated with other microbes that makeup the normal vaginal microbiome, along with those that contribute to bacterial vaginosis. One of the microbes it’s associated with is the uncultured Bacterial Vaginosis Associated Bacterium (BVAB1), also known as Candidatus Lachnocurva vaginae. This microbe is held responsible for interminable bacterial vaginosis (BV), inflammation of the vagina and harmful childbirths (Holm et al., 2020). Lactobacilli make up most of the microbe population in the vagina of women who are at reproductive age. Lactobacillus crispatus (https://microbewiki.kenyon.edu/index.php/Lactobacillus_crispatus), Lactobacillus iners, Lactobacillus gasseri, and Lactobacillus jensenii are the main species of Lactobacillus in the vagina. S. amnii interact with these species as it fights to carry on its pathogenic processes. Lactobacilli’s ability to inhibit pro-inflammatory cytokines from initiating their performance comes as a threat to Sneathia. Lactobacilli can also keep bacteria from forming attachments to the vaginal epithelium and produce lactic acid to kill other bacteria (Witkin and Linares, 2017). Since BV is associated with a significant reduction of the lactobacilli morphotypes, S. amnii also gets to interact with bacteria that are anaerobic and short rodded and coccoid (Harwich et al., 2012). The anerobic bacteria include Gardnerella vaginalis (https://microbewiki.kenyon.edu/index.php/Gardenerella_vaginalis), Prevotella spp (https://microbewiki.kenyon.edu/index.php/Prevotella), Peptostreptococcus (https://microbewiki.kenyon.edu/index.php/Peptostreptococcus_anaerobius), Bacteroides spp, Mobiluncus spp., Ureaplasma urelyticum (https://microbewiki.kenyon.edu/index.php/Ureaplasma_urealyticum) and Mycoplasma hominis (https://microbewiki.kenyon.edu/index.php/Mycoplasma_hominis).

 The biological interaction between Lactobacilli and Sneathia are very important in the vaginal environment. Bacteria of the Lactobacillus species are able to prevent other bacteria from binding to the vagina’s epithelium, in part with their lactic acid production. It sets out to stop any and all functions of pro-inflammatory cytokines. Secretion of lactic acid allows for Lactobacilli to kill other bacteria or at least put a stop to their growth (Witkin and Linares, 2017). Lactic acid is sometime released with bacteriocins to ensure efficacy. Bacteriocins are just additional antimicrobial factors. Lactic acid can further stimulate transcription of genes and DNA restoration by restricting histone deacetylases. Autophagy is induced when lactic acid is released, causing the harmful cells to degrade themselves and maintain normal functioning and processes. Lactobacilli’s proficiency in preventing infections without having to initiate any inflammation promotes fertility and successful pregnancies in women (Witkin and Linares, 2017).

Significance to Humans

 S. amnii has very complicated growth requirements. It is able to metabolize few carbohydrates, including glucose, maltose, glycogen and glucosamine. This species, however, lacks the ability to ferment starch, mucin, fructose, sucrose or mannose (Eisenberg et al., 2018). S. amnii’s fermentative style of metabolism leaves lactic acid, formic acid, a small amount of acetic acid and sometimes succinic acids as the waste products after metabolizing glucose. Since the epithelium of the vagina produces a lot of glucose, especially when a woman is at reproductive age, S. amnii is able to use this carbohydrate source despite its reduced metabolic capabilities with other carbohydrates.

 More information about fermentative metabolism of glucose: o https://umaine.edu/carbohydrates/carbohydrate-digestion/fermentation/ (University of Maine, n.d.)

 Sneathia strains tend to be susceptible to and best treated with antimicrobials, such as metronidazole, but can be resistant to erythromycin, kanamycin, vancomycin, aminoglycosides, and fluoroquinolone. We know that S. amnii is one of the anaerobic microbes that plays a role in the development of bacterial vaginosis. The overuse of metronidazole in treatment may have caused the recent relative resistance to it (Eschenbach, 2007). This conclusion comes from a study that showed increase failure rate of a treatment course using metronidazole spanning over two weeks of time.

Cell Structure

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.

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References

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Example references: Vancouver citation

Journal

Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500. https://doi.org/10.1099/00207713-50-2-489

Book

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Books with Editors

Beers MH, Porter RS, Jones TV, Kaplan JL, Berkwits M, editors. The Merck manual of diagnosis and therapy. 18th ed. Whitehouse Station (NJ): Merck Research Laboratories; 2006.

Authored chapter in edited publication;;

Glennon RA, Dukat M. Serotonin receptors and drugs affecting serotonergic neurotransmission. In: Williams DA, Lemke TL, editors. Foye's principles of medicinal chemistry. 5th ed. Philadelphia: Lippincott Williams & Wilkins; 2002.

Electronic

World Health Organization (WHO). Mortality country fact sheet 2006 [internet]. Geneva: WHO; 2006. Available from: www.who.int/whosis/mort_emro_pak_pakistan.pdf


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