Changes in the Virulence of Naegleria fowleri Maintained In vitro

In Vitro Susceptibilities of Naegleria fowleri Strain HB-1 to Selected Antimicrobial Agents, Singly and in Combination

“…Testing anti-Naegleria drugs in a tissue culture system appears to have advantages over other in vitro methods. Most highly virulent isolates of N. fowleri that have been tested cause destruction oftissue culture monolayers through undefined cytotoxic mechanisms (7,20,22). For the HB-1 and Carter-66 strains of N. fowleri the ability to damage MKC cultures has been demonstrated to be associated with pathogenicity for experimental animal hosts (23).…”

Primary Amebic Meningoencephalitis and the Biology of Naegleria Fowleri

“…Wong et al (142) observed differences in cytolytic enzyme synthesis be tween highly virulent and low-virulent strains of N. fowleri; for example, highly virulent strains produced a magnitude more catalase than low-viru lent strains. Cursons et al (33) found that N. fowleri produced a greater amount of phospholipase A than did nonpathogenic N. gruheri.…”

“…Axenic cultivation gradually de creases the virulence of N. fowleri. However, virulence can be enhanced and perhaps restored to original levels by passage of amebae in mammalian cell culture and by serial mouse passage (43,142).…”

“…A delayed hypersensitivity reaction has been described for guinea pigs sensitized by the soluble antigens of fr eeze-thawed N. fowleri (4 6) and by freeze-thawed amebae plus complete Freund adjuvant (142). Macrophage inhibition by the lymphokine macrophage inhibition factor has been described for N. fowleri (36).…”

PCR-Based Diagnosis of Naegleria sp. Infection in Formalin-Fixed and Paraffin-Embedded Brain Sections

“…In order to increase the virulence of this strain for infection in the mouse model, the trophozoites were exposed to the murine fibroblast cell line L-929 (ATCC, Rockville, MD) by coculture on a monocellular layer of L-929 cells until the majority of the murine cells were lysed (11,28). Upon cocultivation, 5 ϫ 10 5 trophozoites were intranasally inoculated into 6-week-old C57BL/6 mice (purchased from Charles River GmbH, Germany; the mice were kept at biosafety level 3, according to the Swiss regulations for animal experiments), as described previously (6).…”