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Korean J Parasitol > Volume 21(2):1983 > Article

Original Article
Korean J Parasitol. 1983 Dec;21(2):234-240. English.
Published online Mar 20, 1994.  http://dx.doi.org/10.3347/kjp.1983.21.2.234
Copyright © 1983 by The Korean Society for Parasitology
Changes in the pathogenicity of Naegleria fowleri by several brain passage in mice
Deung-Ki Lee,Keun-Tae Lee and Kyung-Il Im*
Department of Parasitology, College of Medicine, Yonsei University, Korea.
*Department of Parasitology, College of Medicine, Hanyang University, Korea.
Abstract

The pathogenicity of free-living amoeba, Naegleria fowleri, is influenced according to the strain, cultural condition and host (Culbertson et al., 1968; Carter, 1970; Wong et al., 1975). Phillips (1973) demonstrated that Entamoeba histolytica became avirulent after more than 2 year maintenance in axenic culture in vitro. This study was carried out to compare the difference in pathogenicity between two strains of N. fowleri, one of a prolonged maintenance in axenic medium and the other one obtained by serial brain passage in mice.

The 0 strain was that N. fowleri had cultivated axenically more than 7 years in CGVS medium. The 2-1 strain was obtained from the brain of mouse inoculated intranasally with a strain, which was from the mouse brain infected with 0 strain, and cultured for 15 weeks until the beginning of this experiment. White male mice weighing 18-22 g were used. Mice were anesthetized by an intraperitoneal injection of about 1 mg secobarbital, and inoculated intranasally with 10 × 104 live N. fowleri trophozoites in a 5 µl cell suspension.

Sluggish behaviour, nervousness, rotation and leg paralysis were developed earlier and more frequently in the 2-1 experimental group than the control 0 group. Pathological changes such as inflammatory and necrotic lesion were observed in the olfactory and anterior portion of brain, and these changes were more extensive in the 2-1 group. The edematous and inflammatory changes in lung were demonstrated in mice died after 13th day post-inoculation. The experimental mice of 2-1 group began to die suddenly from 7th day post-inoculation, and the survival time in 2-1 group mice was shorter than 0 group mice.

The typical primary amoebic meningoencephalitis was developed in the mice inoculated intranasally with N. fowleri. The prolonged maintenance of N. fowleri amoebae in axenic CGVS medium was observed to have lost their original pathogenicity for mice, but their pathogenicity was restored by serial brain passage in mice.

Figures


Fig. 1
Fate of mice infected with Naegleria fowleri intranasally. The experimental group received strain 2-1, while the control group received strain 0.


Fig. 2
Naegleria fowleri trophozoites demonstrated in mouse brain tissue with severe inflammatory cells infiltration. (×500)


Figs. 2-3
Naegleria fowleri trophozoites observed in mouse lung tissue with severe inflammatory cells infiltration (×1,000)


Fig. 4
Naegleria fowleri trophozoites shown in the nasal cavity of mouse. (×500)

Tables


Table 1
Naegleria fowleri used in this study


Table 2
Symptoms observed in each postinfection day

References
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