Pentamidine Is Active In Vitro againstFusariumSpecies

Abstract

Fusariosis is an emerging opportunistic mycosis against which currently used antifungals have limited activity. Here, we investigated the in vitro activities of pentamidine (PNT) against 10 clinical isolates of Fusarium species (five Fusarium solani isolates and five non-F. solani isolates) by using the National Committee for Clinical Laboratory Standards microdilution method in three different media (RPMI, RPMI-2, and a yeast nitrogen base medium), disk diffusion testing, and viability dye staining. PNT had significant activities against all 10 Fusarium isolates. Non-F. solani isolates were more susceptible than F. solani isolates (P < 0.05). Additionally, PNT was fungicidal against all non-F. solani isolates, whereas it had fungistatic effects against four of the five F. solani isolates. PNT also exhibited greater activity against conidial than against hyphal development of the fungus. This fungicidal activity against non-F. solani Fusarium isolates was confirmed microscopically after staining of PNT-treated Fusarium oxysporum hyphae with the fluorescent viability dyes 5,(6)-carboxyfluorescein diacetate (CFDA) and bis-(1,3-dibutylbarbituric acid) trimethine oxonol (DiBAC). The MICs at which 50% of the isolates were inhibited (2 g/ml for non-F. solani isolates and 4 g/ml for F. solani isolates) and the minimum fungicidal concentration at which 50% of the isolates were killed (8 g/ml for non-F. solani isolates) were much lower than the PNT tissue concentrations previously reported in humans using conventional daily intravenous PNT dosing. Finally, PNT was more active against Fusarium isolates in a hypoxic environment of in vitro growth (P < 0.05). This finding may be clinically significant, because Fusarium, an angiotropic mold, causes tissue infarcts with resultant low tissue perfusion. Our findings suggest that PNT may have a role in the management of Fusarium infections. Future in vivo studies are needed to verify these in vitro findings.

Lovastatin Has Significant Activity against Zygomycetes and Interacts Synergistically with Voriconazole

“…Of note, there was a trend toward lower LOV MICs and EC 50 s in YNB media. Our group and others have postulated that because enriched YNB medium facilitates fungal growth compared with RPMI and RPMI-2, it might result in increased metabolic activity of fungal cells and better drug penetration into the intracellular sites of drug action (20,24).…”

“…In different experiments, we infected Toll-deficient flies (Tl flies) (2-to 4-day-old female flies, 30 per experimental group) with two representative Zygomycetes isolates (M. circinelloides 424760 and R. oryzae 557969). We injected the thoraxes of Tl flies with a thin sterile needle that had been dipped into a concentrated solution (10 8 conidia/ml) of each Zygomycetes isolate, as described previously (17,20). After injection, we housed the flies at 29°C and transferred them to fresh vials every 2 days.…”

“…LOV protection was assessed daily until day 6 after infection. For the combination drug experiments, vials containing VRC alone (1 mg/ml), LOV alone (10 mg/ml), or VRC plus LOV (1 and 10 mg/ml, respectively) were prepared as described previously (20). Each experiment was performed at least in triplicate on different days.…”

“…We performed disk diffusion susceptibility testing on RPMI agar plates previously prepared by using standardized methods (20). Two hundred microliters of a standardized suspension of conidia (10 6 conidia/ ml) of each Zygomycetes isolate was plated.…”

Pentamidine Is Active in a Neutropenic Murine Model of Acute Invasive Pulmonary Fusariosis

“…Fusarium conidia versus hyphae in vitro (10). This relative resistance of hyphae versus conidia to antifungals (i.e., AMB, azoles) has been shown in several filamentous fungi (i.e., Aspergillus, Cladosporium, Paecilomyces, Scopulariopsis, Cladophialophora species) (4, 7).…”