Letter: Primary amoebic meningoencephalitis

Fulminant Disseminating Fatal Granulomatous Amebic Encephalitis: The First Case Report in an Immunocompetent Patient in South Korea

Central nervous system infections caused by free-living amoeba are very rare, but often fatal. The typical image findings of amebic meningoencephalitis are non-specific, showing ring-like enhancement. We report the first case of fulminant disseminating fatal granulomatous amebic encephalitis caused by Balamuthia mandrillaris in an immunocompetent patient in South Korea. Our case exhibited two interesting features: one was the unusual clinical course and the other was additional image findings. Magnetic resonance imaging revealed a rim-enhancing lesion with intralesional blooming dark signal intensity on susceptibility weighted imaging and low signal intensity on diffusion weighted images and on apparent diffusion coefficient maps. Differential diagnosis was started from a tumor or non-tumorous lesion, and diagnosis was difficult due to the rarity of the disease. Following the clinical and diagnostic courses of our case, we recommend inspecting image findings of granulomatous amebic encephalitis for early diagnosis.

Comparison of Naegleria fowleri and Naegleria gruberi cultivated in the same nutrient medium

The human pathogenic amoeboflagellate Naegleria fowleri and the nonpathogenic species N. gruberi can be cultivated axenically but usually in different media. Naegleria fowleri 6088 has been adapted to grow in Balamuth H-4 medium, usually used to propagate N. gruberi nB81, and nB81 has been adapted to grow in supplemented Nelson's medium, usually used to propagate N. fowleri. N. gruberi nB81, grown in either medium, enflagellated 135 to 150 min after subculture to non-nutrient amoeba saline, whereas 6088 required 225 min. Naegleria gruberi nB81 grown in either medium was agglutinated by 100 micrograms concanavalin A/ml, whereas N. fowleri 6088 was not. Naegleria fowleri and N. gruberi grown in Nelson's medium became rounded to a greater extent upon chilling at 5 degrees C and remained rounded longer than Naegleria grown in Balamuth medium. The specificity of the surface antigens was an inherent characteristic of each species and not dependent upon the propagating medium, but Naegleria grown in Nelson's medium was agglutinated more reproducibly and more effectively by antiserum. N. gruberi was somewhat more resistant to acriflavine, actinomycin D, cycloheximide, or tetracycline than N. fowleri, regardless of the culture medium. Naegleria fowleri 6088 grown in Nelson's medium, however, was more resistant to actinomycin D, daunomycin, mithramycin, sulfamethoxazole, or tyrocidine than 6088 grown in Balamuth medium. There are limitations on the validity of comparisons of N. fowleri and N. gruberi based upon cultures grown in different media.

In vitro susceptibility of pathogenic Naegleria and Acanthamoeba speicies to a variety of therapeutic agents

Six pathogenic strains of Naegleria fowleri, two of Acanthamoeba castellanii, and three of Acanthamoeba polyphaga were tested in vitro for susceptibility to a variety of potentially useful therapeutic agents. Minimal motility inhibitory concentrations and minimal inhibitory concentrations were determined by a technique of subculturing pure clones of amoebae in plastic tissue culture chamber slides containing liquid axenic media and serially diluted drug, incubating at 30 degrees C for Acanthamoeba and at 37 degrees C for Naegleria, and observing on an inverted microscope at 6 h for inhibition of motility and at 24 and 48 h for inhibition of growth. Drug concentrations were selected on the basis of fluid levels achievable in humans. Amphotericin B, clotrimazole, and miconazole were the most effective drugs against Naegleria, whereas polymyxin B sulfate and pentamidine isethionate were somewhat effective against pathogenic Acanthamoeba. Our results suggest that amphotericin B is the most effective agent against Naegleria, but few agents are effective against Acanthamoeba.

Topical pharmacology of imidazole antifungals

Four imidazole derivatives have now undergone extensive open and comparative trials as topical agents in dermatomycoses and vaginal candidosis. They are chlormidazole (Chemie Grünenthal), clotrimazole (Bayer), miconazole (Janssen) and econazole (Janssen, Cilag-Chemie); all also have some antibacterial activity. Many other imidazoles have been marketed, usually as antiprotozoal or anthelminthic agents, and some of these have some antimycotic activity as well as other miscellaneous therapeutic properties. The mode of action of imidazole antimycotic agents is discussed; after prolonged topical application to animals and human subjects, systemic absorption is negligible. All four agents which are available as cream, powder, lotion or vaginal tablets have many sucessful studies to their credit, often with clinical and mycological cure rates of over 80% in a variety of dermatomycoses and in vaginal candidosis. The relative value of these topical agents is discussed, and it is suggested that in severe and extensive dermatomycoses consideration should be given to the systemic use of miconazole in support of topical therapy.

In vitro effects of amphotericin B on growth and ultrastructure of the amoeboflagellates Naegleria gruberi and Naegleria fowleri

In vitro effects of the polyene antibiotic amphotericin B (AmB) on growth, viability, and ultrastructure of amoeboflagellates of the genus Naegleria were examined. The strains studied were the nonpathogenic Naegleria gruberi EG(B) and the Carter and TY strains of the pathogenic Naegleria fowleri. AmB was amoebicidal at all concentrations used (0.25, 0.50, and 1.0 mug/ml) when the drug was added to cultures in lag phase, as determined by viability testing, but was mainly inhibitory when added to log-phase cultures. The drug produced ultrastructural modifications at all concentrations (0.05 to 1.0 mug/ml). These changes included distortion of nuclear shape, increase in cytoplasmic membranes (both rough and smooth endoplasmic reticulum), decrease in number of food vacuoles, absence of pseudopod formation, mitochondrial abnormalities, increase in autophagic vacuoles, and blebbing of the plasma membrane. These alterations of amoebic ultrastructure became more pronounced with increased time in AmB and with increase in AmB concentration in the growth medium.

Effect of clotrimazole on Naegleria fowleri

The sensitivity of 18 strains of Naegleria fowleri to clotrimazole (Bay b5097) was tested. They showed minimal inhibitory concentrations in the range 0-03-0-125 mug/ml, and minimal amoebicidal concentrations in the range 0-125-0-25 mug/ml. Mice inoculated with N. fowleri were not protected from infection by doses of 100 mg clotrimazole/kg per day given for five days after inoculation. Mice had serum levels of up to 6 mug/ml in the first 32 hours after inoculation. Therefore clotrimazole appears to be ineffective in protecting against infection with N. fowleri.

Clotrimazole: a review of its antifungal activity and therapeutic efficacy

Clotrimazole 2, a synthetic imidazole derivative, is primarily used locally in the treatment of vaginal and skin infections due to yeasts and dermatophytes. In vitro, it is most active against Candida spp., Trichophyton spp., Microsporum spp. and Malazzesia fuffur (Pityrosporon orbiculare). In addition, it has some in vitro activity against certain Gram-positive bacteria, and at very high concentrations has activity against Trichomonas spp. In the treatment of vaginal candidiasis, clotrimazole vaginal tablets have produced cure rates comparable with those of conventional nystatin vaginal tablets. There have been no published comparisons with nystatin vaginal cream or foaming vaginal tablets - nystatin dosage forms preferred by some clinicians. Cootrimazole has also been successful in patients who had failed to respond to other antifungal agents such as nystatin and amphotericin B. Results in trichomonal vaginitis are not impressive. Skin infections caused by Candida or dermatophytes have been effectively treated with topical application of clotrimazole. In comparative trials, clotrimazole cream has been as effective as Whitfield's ointment and tolnaftate in the treatment of dermatophytoses, and as effective as nystatin in cutaneous candidiasis. Clotrimazole topical preparations are generally well tolerated, but local irritation has necessitated withdrawal of therapy in a few cases. Candidal septicemia and urinary and pulmonary candidiasis have been cured with oral clotrimazole therapy. Results in other types of serious fungal infections, including pulmonary aspergillosis, have been disappointing. A limiting factor in oral clotrimazole therapy is the high incidence of gastro-intestinal disturbances and neurological reactions.