Pathogenicity of Candida albicans isolates from bloodstream and mucosal candidiasis assessed in mice and Galleria mellonella.

The working hypothesis of this study was to elucidate a possible association between the pathogenic potential of Candida albicans strains with a clinical entity, systemic versus superficial candidiasis. Specifically, we assessed the pathogenicity of two groups of clinical C. albicans isolates: isolates from bloodstream infection (S) versus isolates from vaginitis patients (M), in two experimental in vivo systems - mice and Galleria melonella, in comparison to a control strain (CBS 562). Mice and G. mellonella larvae were inoculated with CBS 562 and the different S and M isolates, and followed up for survival rate and survival time during 30 and 7 days, respectively. Candida kidney colonization of mice was assessed by histopathology and colony-forming units' enumeration. The results revealed: (1) S and M isolates had different behavior patterns in the two models and varied in different parameters; (2) no statistically significant difference in pathogenicity between S and M isolates as whole groups was noted; (3) S14 was the most virulent isolate and close to the standard strain CBS 562 in both models. This study is distinctive in its outline combining two different groups of C. albicans clinical isolates originating from two different clinical entities that were assessed in vivo concurrently in two models.

Evaluation of antifungal combinations of nystatin-intralipid against Aspergillus terreus using checkerboard and disk diffusion methods.

OBJECTIVE: The objective of this study was to evaluate the efficacy of combinations of nystatin-intralipid, found previously to be more active than nystatin, with antifungals of different mode of activity, against Aspergillus terreus. METHODS: Antifungal activity of combinations of nystatin-intralipid with voriconazole, caspofungin, terbinafine or 5-fluorocytosine were evaluated by the checkerboard and disk diffusion methods. The results were compared to those obtained with nystatin. RESULTS: The combination of nystatin-intralipid with caspofungin exhibited better antifungal activity than each drug alone and resulted in a synergistic interaction in three out of six tested strains of A. terreus. No such effect was obtained with Nystatin and caspofungin. Nystatin-intralipid or nystatin with voriconazole yielded indifferent interactions. When nystatin-intralipid was combined with terbinafine, a strong antagonism was produced in all six A. terreus strains. This effect was observed both by checkerboard and disk diffusion methods. In contrast no interaction or only slight antagonism was observed in the combination of nystatin with terbinafine. Disk diffusion method revealed similar inhibition zones when disks impregnated with 5-fluorocytosine were placed on plain, nystatin-intralipid or nystatin containing agar plates. CONCLUSIONS: Among four tested combinations, only combination of nytatin-intralipid with caspofungin, a representative of the echinocandin class of antifungals, resulted in synergistic interaction. Antagonism obtained by combining nystatin-intralipid with terbinafine can be explained by existence of hydrophobic interaction between these two compounds interfering with their antifungal action. The fact that nystatin-intralipid and nystatin interact differently with other antifungals, may indicate differences in their mechanisms of activity.

Activity of an Intralipid formulation of nystatin in murine systemic candidiasis.

Since nystatin (NYT) is used only topically owing to its toxicity upon systemic administration, a study was initiated aiming to develop a formulation of NYT that could be used systemically against invasive mycoses. The present research is a continuation of previous in vitro investigation of the antifungal effect of nystatin-Intralipid (NYT-IL) against Candida, exploring its in vivo activity. NYT-IL was tested in murine systemic candidiasis induced in naïve as well as cyclophosphamide-immunosuppressed female ICR mice. The infection was assessed by survival rate (SR), mean survival time (MST) and qualitative and quantitative fungal organ colonisation. Mice were treated by intravenous administration of various doses of NYT-IL for 5 consecutive days starting either 24h or 48 h after the initiation of infection. The experiments showed that NYT-IL is therapeutically effective in the murine candidiasis model. NYT-IL was found to be less toxic in vivo than NYT and therefore higher doses of NYT-IL could be used. The efficacy of NYT-IL was expressed in treated naïve and immunosuppressed mice by increased SR, prolonged MST and reduced fungal organ colonisation. Early initiation of treatment increased efficacy. In summary, the Intralipid formulation of NYT can be administered parenterally and is effective against systemic experimental Candida infection.

Nystatin-intralipid preparation: characterization and in vitro activity against yeasts and molds.

The objective of our studies is the development of a novel formulation of nystatin (NYT) that could be administered systemically and might be used for therapy of invasive mycoses. We developed a formulation of nystatin and intralipid (IL), which is a clinically used food supplement, and this report focuses on the characterization of NYT-IL, assessment of its antifungal activity and in vitro toxicity. We characterized physical properties of the NYT-IL preparation and its stability during storage. Susceptibility of Candida, Aspergillus and Fusarium species was determined using a CLSI technique. In vitro toxicity of NYT-IL was assessed using an assay measuring hemolysis of sheep red blood cells (SRBC) and leakage of potassium. It was found that: (1) the particle size in NYT-IL did not differ from that of IL; (2) over 80% of NYT was in association with IL; and (3) these features did not change during storage. All Candida and Aspergillus strains had lower minimal inhibitory concentration (MIC) values for NYT-IL than that for NYT; the MICs of the Fusarium strains were similar for NYT & NYT-IL. Toxicity assays showed that the NYT-IL formulation is less toxic than NYT. In conclusion, we describe a novel, characterized, stable formulation of nystatin, nystatin-intralipid, with in vitro activity against pathogenic Candida and Aspergillus species.