Paravahlkampfia francinae n. sp. Masquerading as an Agent of Primary Amoebic Meningoencephalitis

Abstract

Paravahlkampfia francinae n. sp., a new species of the free-living amoeba genus Paravahlkampfia, designated as CDC:V595, was isolated from the cerebrospinal fluid of a patient with headache, sore throat, and vomiting, typical symptoms of primary amoebic meningoencephalitis (PAM) caused by Naegleria fowleri. The isolate grew at 33 degrees C, 37 degrees C, 40 degrees C, and 42 degrees C and destroyed mammalian cell cultures. However, it did not kill young mice upon intranasal inoculation. P. francinae does not produce flagellates and does not grow on agar plates coated with Gram-negative bacteria such as Escherichia coli, the usual food source of Paravahlkampfia ustiana, the type species of the genus. The trophozoite at light microscopy exhibited eruptive locomotion and possessed a single vesicular nucleus. Ultrastructurally, the trophozoites had numerous mitochondria with discoidal cristae but did not have a Golgi apparatus. The trophozoites differentiated into cysts after consuming most of the monolayer. The cyst had an inner well-differentiated endocyst and an outer thin, wrinkled, and wavy ectocyst with no pores. During excystation trophozoites ruptured the cyst wall and emerged from the cysts. A unique feature seen in the cysts was the presence of bacterial endosymbionts, both in the endoplasm and within the cyst wall. Full-length sequencing analysis of the 18S and 5.8S RNA genes of P. francinae showed that they were distinct from those of other Paravahlkampfia species. The patient recovered within a few days indicating that some of the previously reported cases of PAM that survived may have been due to P. francinae.

Diversity of Heterolobosea

“…In addition to N. fowleri, pathogenicity was suggested also for N. australiensis and N. italica on the basis of tests on mice (De Jonckheere, 2002). There is a single report on PAM-like disease caused by Paravahlkampfia francinae (Visvesvara et al, 2009). In contrast to PAM caused by N. fowleri, the affected patient recovered within a few days.…”

“…The surface of the cyst is wrinkled, rough or smooth, and can be sticky (e.g., in Paravahlkampfia). Most heterolobosean cysts have no pores and presumably excyst by a wall rupture as in representatives of Paravahlkampfia (Visvesvara et al, 2009). The cyst of genera Tulamoeba and Monopylocystis has a single pore that penetrates the wall and is sealed with a mucoid plug (Park et al, 2009).…”

“…Few heteroloboseans are facultative endobionts of both vertebrates and invertebrates. Naegleria fowleri and Paravahlkampfia francinae are even able to parasitize humans (Visvesvara et al, 2007(Visvesvara et al, , 2009). The genus Stephanopogon, whose members are multiflagellate, was once considered to be a primitive ciliate and was affiliated with Heterolobosea only on the basis of cell structure and phylogenetic position.…”

Molecular Diagnostics in the Diagnosis of Parasitic Infection

“…This infection is not fatal, but can be recalcitrant to treatment and lead to significant morbidity including blindness. Finally, Sappinia pedata (previously thought to be Sappinia diploidea) and Paravahlkampfia francinae have been recognised as rare causes of amoebic CNS infection (Qvarnstrom, da Silva, Schuster, Gelman, & Visvesvara, 2009;Visvesvara et al, 2009).…”

Free-living amoebae isolated in the Central African Republic: epidemiological and molecular aspects

“…Some free-living amphizoic amoebae can, however, accidentally infect humans and cause neurological, ocular and cutaneous infections [2, 3]. The main organisms involved are Naegleria, Acanthamoeba, Balamuthia , several amoebae of the genus Sappinia (S. diploidea, S. pedata) and a species of the genus Paravahlkampfia, P. francina , which was recently incriminated in cases of encephalitis [4–6]. Some of the cases of encephalitis were opportunistic infections in immunodepressed individuals and consisted of granulomatous encephalitis due to Acanthamoeba and Balamuthia , which evolves chronically and is usually fatal.…”