Sappinia

The name Sappinia was named after Mister Sappin-Trouffy, who was a mycologist at the Paris Academy of Sciences, where the genus was first discovered.[2]

The genus Sappinia was discovered in 1896 by Pierre Augustin Dangeard at the Paris Academy of Sciences.[2] Dangeard noticed white patches on a desiccated culture of horse dung, and when viewed under the microscope, he observed many amoebae.[2] These amoebae were generally binucleated and resembled the myxamoeba life cycle stage present in some plasmodial slime molds; however, Dangeard never observed the plasmodia stage.[2] This was the first species of Sappinia discovered, Sappinia pedata. The second species discovered, Sappinia diploidea was originally named Amoeba diploidea, and was first found in 1908 by Max Hartmann and Kurt Nägler.[2] It was isolated from the intestinal material of a lizard; however, it was not thought to be parasitic, as it was not found in 20 other lizards sampled, and a very similar strain was isolated from soil.[2] It was named “diploidea” because the organism was only ever seen in the diploid stage.[2] Nägler stated that there is no true haploid stage; however, further studies have not been able to come to this conclusion, as the nuclei become difficult to discern during sexual reproduction.[1][2][3] In 1912 A. diploidea was transferred to the genus Sappinia by Alexis Alexeieff.[2] He classified the genus Sappinia on the basis of being mostly binucleate, with promitotic cell division without the presence of an equatorial plate.[2] Up until very recently these were the only known species of Sappinia, but a new study published in 2015 indicates the discovery of a third species, Sappinia platani, isolated from the bark of a sycamore tree. Sequencing of its small subunit ribosomal RNA (SSU rRNA) confirmed that it is a member of the genus Sappinia, but genetically distinct from S. pedata and S. diploidea.[4] Morphologically, S. platani appears very similar to a typical member of Sappinia, but contains dictyosomes, which had not been reported in this genus previously.[4]

Initially, members of Sappinia were thought to be only coprozoic, as they were first found in animal feces; however, they have now been found in many other habitats, and are considered typical free living amoebae.[2] Sappinia species are found worldwide in soil, plant litter, and standing decaying plants, freshwater ponds, and have also been found in the feces of horses, lizards, bison, elk, buffalo, and dogs.[1][2] They are heterotrophic, and feed mostly on bacteria and smaller amoebae.[6] Sappinia species, like many other free-living amoebae, play an important role in nutrient cycling in soil.[6] Sappinia species and their sister genus Thecamoeba are susceptible to infection by rozellids, that act as endonuclear parasites.[6][7] Sappinia species are not generally susceptible to bacterial infection; but, they have been shown to harbor bacterial endosymbionts.[6] In a recent study, Corsaro et al. (2016), found that all of the Sappinia strains tested harbored distinct species of Flavobacterium and/or Pedobacter, which are not known to be commensals of any other free-living amoebae. When these bacterial endosymbionts were isolated, they were unable to grow them in culture, thus they hypothesize that these bacterial species are obligate endosymbionts specific to the genus Sappinia. Although Sappinia species are generally considered to be non-parasitic, there has been one confirmed case of amoebic encephalitis in a non-immunocompromised 38-year-old male caused by S. pedata.[8]

Amoebic encephalitis is an infection of the brain caused by various different amoebae, for example Naegleria fowleri, Acanthamoeba species, Balamuthia mandrillaris, or Entamoeba histolytica.[5] These infections are rare, and usually lethal.[10] Naegleria fowleri causes primary amoebic encephalitis (PAE), which progresses very rapidly, whereas Acanthamoeba species cause granulomatous amoebic encephalitis (GAE), which is also usually lethal, but develops slower than PAE.[10] Acanthamoeba species and Balamuthia mandrillaris usually only cause disease in immunocompromised patients and Entamoeba histolytica can cause encephalitis after infecting another region in the body.[10] There has been only one documented case of pathogenesis involving Sappinia species, which resulted in granulomatous amoebic encephalitis in a non-immunocompromised 38-year-old male from Texas in 1998.[5] The fact that the patient was non-immunocompromised is surprising because there is only one known amoeba (Naegleria fowleri) that causes disease in healthy individuals. The patient lived on a farm and was in close contact with grazing farm animals, which is likely where he contracted the infection.[5] The Sappinia species was likely in the soil, and was consumed by a grazing animal along with plant matter, and was then expelled in the feces. The patient is thought to have inhaled the Sappinia species while cleaning up the animal dung. As described by Gelman et al. (2003), the patient “presented with a history of loss of consciousness for 45 min and emesis, followed by bifrontal headache, photophobia, and blurry vision for 2 to 3 days” (p. 990). His medical history only consisted of a recent sinus infection, which was probably due to Sappinia, which then spread to the brain.[10] An MRI revealed a 2 cm mass in the left temporal lobe, and when excised, showed necrotizing hemorrhagic inflammation containing trophozoite amoebae.[5] The trophozoites were between 40–60 mm in diameter, and had two closely apposed nuclei with a distinct central flattening.[5] The trophozoites also contained tubular mitochondrial cristae, and a large contractile vacuole.[5] All of these characteristics are distinguishing features of the genus Sappinia. The medical team sent the sample to the CDC, who confirmed that these characteristics do not coincide with any previously known pathogenic amoebae in humans.[5] The patient was treated with several antimicrobials and recovered completely.[5] After 14 months, the CDC diagnosed the causative agent as S. diploidea based on morphological characteristics.[5] In 2009, Qvarnstrom et al. reevaluated this conclusion, as the morphological characteristics present in the scans cannot distinguish between S. diploidea and S. pedata. Qvarnstrom et al. (2009) first used PCR primers and TaqMan probes to detect if the trophozoites did in fact belong to Sappinia, and to rule out other amoeba genera. They found that the DNA was that of Sappinia, and no other amoebae DNA was found.[8] They then had to use species-specific PCR primers for S. diploidea and S. pedata to determine the causative agent.[8] Qvarnstrom et al. (2009) found that the sample tested negative for S. diploidea but had S. pedata-specific priming sites, which then allowed them to conlucde that the causative agent of GAE in this case was S. pedata.

• Sappinia pedata
• Sappinia diploidea
• Sappinia platani