Isolation of a ThermotolerantParavahlkampfiasp. from Lizard Intestine: Biology and Molecular Identification

ABSTRACT. An amoeba was isolated from the intestines of several moribund pink‐tongued skinks (lizards), Hemisphaeriodon ger‐rardi Unusual features of this isolate were its ability to grow at temperatures of ≥ 37 °C, and its inability to use Escherichia coli as a food source or to grow axenically on a variety of enriched culture media suitable for other soil amoeba isolates. Growth was abundant, however, on tissue culture cells, with amoebae clearing cell monolayers in ∼48 h at 37 °C. Trophozoites had a vahlkampfiid‐like morphology, moving by means of an anterior eruptive pseudopod. Cysts, round to slightly ovoid and lacking exit pores, were formed in culture. Tests for enflagellation of trophic amoebae were negative. Indirect immunofluorescence staining was negative for Naegleria fowleri and Willaertia sp. The isolate was sensitive to azithromycin, but not to amphotericin B, pentamidine isethionate, fluconazole, 5‐fluorocytosine, and sulfadiazine. Phylogenetic analysis based on the PCR‐amplified small subunit ribosomal DNA, identified the organism as Paravahlkampfia ustiana , an amoeba not previously isolated from either poikilothermic or homeothermic hosts. No evidence of pathology was seen in stained sections of lizard intestine, suggesting that the ameba was part of the normal fauna of the lizard gut. Its diet in the lizard intestine is unknown and the organism may have unusual growth requirements. Thus, P. ustiana joins other soil amoebae that have been isolated from mammals, amphibia, fish, and reptiles, which have the potential of becoming opportunistic pathogens.