Iron chelation therapy as a treatment for Pythium insidiosum in an animal model.

OBJECTIVES: Iron plays an important role in the pathogenesis of Pythium insidiosum. Human pythiosis frequently occurs in iron-overloaded thalassaemic patients and experimentally infected animals develop iron deficiency anaemia. Therefore, we sought to determine the in vitro and in vivo activities of the iron chelator deferasirox against P. insidiosum. METHODS: In vitro, the MIC and minimum fungicidal concentration (MFC) values of deferasirox for 17 strains of P. insidiosum were determined in accordance with CLSI document M38-A2. In vivo studies were carried out in 20 inoculated rabbits divided into four groups: placebo, immunotherapy obtained from vortexed P. insidiosum cultures (14 day intervals), deferasirox (15 mg/kg/day) and a combination of immunotherapy and deferasirox. Five non-infected animals were used as controls. RESULTS: The MIC and MFC values of deferasirox for P. insidiosum ranged from 12.5 to 50 mg/L and from 50 to 100 mg/L, respectively. Treatment with deferasirox alone ameliorated anaemia and normalized the serum iron levels and hepatic iron concentration in the animals. However, the mean lesion size, although decreased, did not differ significantly from that in the placebo group. The results of immunotherapy plus iron chelation therapy were worse than those of immunotherapy alone. Moreover, the disease spread to the lung tissue in 5 out of 10 deferasirox-treated animals. CONCLUSIONS: Despite its limited in vitro and in vivo activity, deferasirox improved iron deficiency anaemia in P. insidiosum-infected rabbits. Further studies are needed to investigate the immunomodulatory properties observed in this study and the benefits and drawbacks of using iron-chelating drugs as an adjuvant therapy in pythiosis.

Effects of antifungal interventions on the outcome of experimental infections with phenotypic switch variants of Cryptococcus neoformans.

In cryptococcal infection, phenotypic switching from a smooth to a mucoid variant can occur in vivo, producing variants with enhanced virulence that are subsequently selected and affect the outcome of infection. Here, we demonstrate that antifungal treatment of the chronically infected host can promote this phenomenon. Amphotericin B treatment reduces fungal burden less effectively in mucoid variant-infected than in smooth variant-infected mice. Consequently, amphotericin B treatment resulted in a more pronounced prolongation of survival in smooth variant-infected than in mucoid variant-infected mice (20 versus 42 days; P < 0.05). Administration of anticapsular monoclonal antibody mediated better protection in smooth variant-infected than in mucoid variant-infected mice, although a protective effect was not consistently observed at all doses. Most interestingly, both antifungal drug therapy and administration of anticapsular monoclonal antibody promoted the selection of mucoid variants in smooth variant-infected mice, a phenomenon manifested by a statistically higher percentage of mucoid colonies in smooth variant-infected mice than in nontreated control mice. This finding suggests that both chemotherapeutic and immunological antifungal interventions may promote the selection of the more virulent mucoid variant, which could affect the outcome of infection in chronically infected hosts.

Investigación fitoquímica de plantas con actividad antibacteriana y antimicótica

La investigación fitoquimica fue llevada a cabo paralelamente con la investigación microbiologica, tomado en cuenta la actividad antibacteriana y antimicótica de cada una de las plantas medicinales. Los resultados obtenidos del Screening Fitoquímico Preliminar de las 63 plantas medicinales investigadas, pertenecientes a 28 familias, 49 géneros y 63 especies, son los siguientes: Alcaloides en 20, esteroles en 46, Flavonoides en 23, taninos en 35 Saponinas en 24, Artraquinonas en 18, Heterósidos Cardiotónicos en 8, Sesquiterpenolactonas en 5 y Cumarinas en 9. Se seleccionó cuatro plantas: Monina obtusifolia, Heisteria acuminata, Schinus molle, Baccharis tiendalensis, cuyos extractos totales presentaron una actividad antibacteriana y/o antimicótica excelente para continuar con el fraccionamiento y purificación de metabolitos bioactivos. De aquellas fracciones que tienen actividad antibacteriana y/o antifúngica excelente, se aisló, purificó, y caracterizó metabolitos secundarios que mantienen esta actividad biológica: Bifénilos y Xantonas en Monina obtusifolia y sesquiferpenos y triterpenos en Schinus molle.

Effect of attachment of anticandidal antibody to the surfaces of liposomes encapsulating amphotericin B in the treatment of murine candidiasis.

The effect produced by antibody specific to Candida albicans when attached to liposomes containing amphotericin B was studied in vivo. Liposomal amphotericin B bearing specific immunoglobulin (LAMB-Ab) was compared with the unencapsulated drug (fAMB) and other liposomal amphotericin B formulations in the short-term survival (21 days) of mice with disseminated candidiasis. Both the treatment and prophylaxis of the murine model of candidiasis were explored in these trials. LAMB-Ab increased survival rates in the model more than other liposomal preparations containing amphotericin B. Liposomal amphotericin B compounds as a group prolonged survival over fAMB. Liposomal preparations used for comparison included liposomes with attached nonspecific antibody (LAMB-Ab-), liposomes without antibody (LAMB), and liposomes with unattached specific antibody (LAMB+).