Phialophora richardsiae isolated from infected human bone: morphological, physiological and antifungal susceptibility studies.

A dematiaceous fungus, Phialophora richardsiae (Nannf.) Conant, was isolated from human bone. In culture the fungus produced no yeast forms and was less pigmented than two other P. richardsiae isolates. While growth rates were similar, colonial forms differed. Phialides were of two kinds. While both had broad bases and tapered at the tips, only one terminated with a cupulate or rarely a saucer-shaped collarette. Most phialides were hyaline with a few lightly pigmented ones in older cultures. Broth dilution susceptibility testing of the isolates against amphotericin B, miconazole, ketoconazole, clotrimazole, and 5-fluorocytosine showed the fungus was susceptible to miconazole, ketoconazole and amphotericin B at achievable serum levels and resistant to 5-fluorocytosine and clotrimazole. The other isolates were reported to differ in their resistance to miconazole and amphotericin B. Enzyme and salinity studies showed minor difference among the isolates.

In vitro susceptibilities of human and wild-type isolates of Basidiobolus and Conidiobolus species.

The in vitro activities of amphotericin B, miconazole, ketoconazole, 5-fluorocytosine, and potassium iodide (KI) were studied on human and wild-type isolates of Basidiobolus and Conidiobolus species. Of the antifungal agents tested, the imidazole derivatives, especially ketoconazole, were the most active against the agents of entomophthoromycosis. Transmission electron microscopy showed severe morphological alteration of Basidiobolus sp. exposed to 0.78 micrograms of ketoconazole per ml. The MIC and minimal fungicidal concentration of ketoconazole was often lowered in the presence of 10% fetal calf serum or antibiotic medium no. 3. Half of the Basidiobolus isolates and all Conidiobolus isolates were inhibited by amphotericin B at 0.39 micrograms/ml. None of the strains tested were inhibited or killed at maximum concentrations of 5-fluorocytosine and KI. The in vitro resistance of these fungi to KI at high concentrations suggests that the reported favorable treatment with KI may not be due to its direct effect on these fungi but rather to other, undefined factors in combination with KI. These data suggest that ketoconazole may be of use in the treatment of entomophthoromycosis, particularly in cases which are not responsive to KI.

Effect of aponin, a substance from a green alga Nannochloris species, on the spore germination of two fungi.

Fungistasis which occurs in soil has also been reported to exist in seawater. Nannochloris sp. (Chlorophyta) found along the west coast of Florida, has been shown to elaborate a compound which is cytolytic towards Ptychodiscus brevis, the Florida red tide organism. Aponin, a chloroform extract containing the cytolytic compound or compounds, was tested on the spore germination of two fungi, Dendryphiella salina, a facultative marine organism and Curvularia sp. a terrestrial one. Aponin was stimulatory towards D. salina at all concentrations tested, while Curvularia sp. was stimulated at the highest concentration used but inhibited at the lower concentrations. The culture age of the two fungi did not alter the relative sensitivity of both fungi towards aponin but the germination percentage of Curvularia sp. was affected by the culture age. An aqueous extract of Nannochloris sp. was also tested on the two fungi and was shown to be inhibitory to both. The results seem to indicate that more than one compound from Nannochloris sp. is capable of affecting spore germination indicating that this alga might be playing a role in the reported fungistasis in seawater. Gulf seawater was tested and found to have little if any fungistatic activity.

A Basidiobolus sp. and its association with reptiles and amphibians in southern Florida.

To provide information about the distribution of a Basidiobolus sp., an occasional pathogen in the subtropics and tropics, 95 reptiles and amphibians, comprising eight different species, were trapped from the beaches and inland habitats of Tampa and Miami, Florida. Five of the eight animal species were infested with Basidiobolus sp. Approximately 50% of the animals collected carried this zygomycete. Under laboratory conditions, it remained in the digestive tracts of some starved anoles for up to 3 weeks. Some animals, whose digestive tract was fungus-free, could be colonized with the Basidiobolus sp. by feeding them mealworms contaminated with propagules of this fungus. This finding alters, in a minor way, the present concept of the life history of the fungus.