Thirty six clinical isolates of Cryptococcus neoformans were tested for their susceptibility to 5-fluorocytosine and amphotericin B by the determination of minimum inhibitory concentrations and minimum fungicidal concentrations. 22.2% of the isolates were resistant to 5-fluorocytosine and 36.1% indicated 5-fluorocytosine tolerance. All strains were sensitive to amphotericin B.
The in vitro susceptibilities of Malaysian clinical isolates of Cryptococcus neoformans var. grubii and C . gattii to five antifungal drugs (amphotericin B, flucytosine, fluconazole, itraconazole and ketoconazole) were determined using the Etest method. None of the Malaysian isolates was resistant to amphotericin B and ketoconazole. Isolates resistant to flucytosine, fluconazole and itraconazole were observed in this study. Minimum inhibition concentrations (MICs) of > or = 32 microg ml(-1) against flucytosine, > or = 64 microg ml(-1) against fluconazole and > or = 1 microg ml(-1) against itraconazole were noted in four (8.3%), two (4.2%) and one (2.1%) isolates respectively. There was no significant difference in the MICs for both Cryptococcus species (P > 0.05), indicating that C. gattii was as susceptible as var. grubii to all the antifungal drugs tested. No significant difference in the MICs for both Cryptococcus species collected from 1980 to 1990 and 2002 to 2004 were observed (P > 0.05).
In vitro sensitivity of Acanthamoeba castellani was tested to three drugs: Chloroquine, ivermectin and fungizone (amphotericin B). Sensitivity was demonstrated to the latter two compounds but not to chloroquine. Thus ivermectin and amphotericin B show promise as therapeutic agents against this parasite.
Glucose is an important fuel source to support many living organisms. Its importance in the physiological fitness and pathogenicity of Candida glabrata, an emerging human fungal pathogen has not been extensively studied. The present study aimed to investigate the effects of glucose on the growth, biofilm formation, antifungal susceptibility and oxidative stress resistance of C. glabrata. In addition, its effect on the expression of a putative high affinity glucose sensor gene, SNF3 was also investigated. Glucose concentrations were found to exert effects on the physiological responses of C. glabrata. The growth rate of the species correlated positively to the amount of glucose. In addition, low glucose environments were found to induce C. glabrata to form biofilm and resist amphotericin B. Conversely, high glucose environments promoted oxidative stress resistance of C. glabrata. The expression of CgSNF3 was found to be significantly up-regulated in low glucose environments. The expression of SNF3 gene in clinical isolates was found to be higher compared to ATCC laboratory strains in low glucose concentrations, which may explain the better survivability of clinical isolates in the low glucose environment. These observations demonstrated the impact of glucose in directing the physiology and virulence fitness of C. glabrata through the possible modulation by SNF3 as a glucose sensor, which in turn aids the species to adapt, survive and thrive in hostile host environment.
Trichosporon asahii is a yeast-like fungus that is emerging as an important cause of invasive infections in tertiary medical centres. A 58-year-old Chinese man with no known medical illnesses presented with liver lacerations and multiple fractures following an alleged 12-foot fall at a construction site. The gravity of his injuries and poor haemodynamic status necessitated an intensive care unit (ICU) admission, during which several febrile episodes were detected and multiple antibiotics were administered. After being in the ICU for at least two weeks, a urease-positive yeast was isolated from the patient's blood. The yeast formed dry, fuzzy and wrinkled white colonies on Sabouraud dextrose agar following prolonged incubation, and produced blastoconidia, true hyphae, pseudohyphae and arthroconidia on slide culture. It was identified biochemically by the ID 32 C kit as T. asahii. The yeast had elevated minimal inhibitory concentration (MIC) values to fluconazole, amphotericin B, flucytosine and all echinocandins tested. In view of this, the patient was treated with voriconazole and was successfully transferred to the general medical ward.
Oral delivery of pharmaceuticals requires that they retain their physical and chemical attributes during transit within the gastrointestinal (GI) tract, for the manifestation of desired therapeutic profiles. Solid lipid nanoparticles (SLNs) are used as carriers to improve the absorption of hydrophobic drugs. In this study, we examine the stability of amphotericin B (AmB) and paracetamol (PAR) SLNs in simulated GI fluids during gastric emptying. On contact with the simulated fluids, the particles increased in size due to ingress of the dissolution media into the particles. Simulated gastric emptying revealed that the formulations had mean sizes <350nm and neutral surface charges, both of which are optimal for intestinal absorption of SLNs. There was ingress of the fluids into the SLNs, followed by diffusion of the dissolved drug, whose rate depended on the solubility of the loaded-drug in the particular medium. Time-of-flight secondary ion mass spectrometry analyses indicated that drug loading followed the core-shell model and that the AmB SLNs have a more drug-enriched core than the PAR SLNs do. The AmB SLNs are therefore a very suitable carrier of AmB for oral delivery. The stability of the SLNs in the simulated GI media indicates their suitability for oral delivery.
Infectious diseases are the leading cause of morbidity and mortality, killing more than 15 million people worldwide. This is despite our advances in antimicrobial chemotherapy and supportive care. Nanoparticles offer a promising technology to enhance drug efficacy and formation of effective vehicles for drug delivery. Here, we conjugated amphotericin B, nystatin (macrocyclic polyenes), and fluconazole (azole) with silver nanoparticles. Silver-conjugated drugs were synthesized successfully and characterized by ultraviolet-visible spectrophotometry, Fourier transform infrared spectroscopy, and atomic force microscopy. Conjugated and unconjugated drugs were tested against Acanthamoeba castellanii belonging to the T4 genotype using amoebicidal assay and host cell cytotoxicity assay. Viability assays revealed that silver nanoparticles conjugated with amphotericin B (Amp-AgNPs) and nystatin (Nys-AgNPs) exhibited significant antiamoebic properties compared with drugs alone or AgNPs alone (P
For the past several decades, there has been little improvement in the morbidity and mortality associated with Acanthamoeba keratitis and Acanthamoeba encephalitis, respectively. The discovery of a plethora of antiacanthamoebic compounds has not yielded effective marketed chemotherapeutics. The rate of development of novel antiacanthamoebic chemotherapies of translational value and the lack of interest of the pharmaceutical industry in developing such chemotherapies have been disappointing. On the other hand, the market for contact lenses/contact lens disinfectants is a multi-billion-dollar industry and has been successful and profitable. A better understanding of drugs, their targets, and mechanisms of action will facilitate the development of more-effective chemotherapies. Here, we review the progress toward phenotypic drug discovery, emphasizing the shortcomings of useable therapies.
Surface-modified nanostructured lipid carriers (NLC) represent a promising mode of drug delivery used to enhance retention of drugs at absorption site. Formulated chitosan-coated amphotericin-B-loaded NLC (ChiAmp NLC) had a size of 394.4 ± 6.4 nm, encapsulation and loading efficiencies of 86.0 ± 3% and 11.0 ± 0.1% respectively. Amphotericin-B release from NLCs was biphasic with no changes in physical properties upon exposure to simulated gastrointestinal conditions. Antifungal properties of Amphotericin-B and ChiAmpB NLC were comparable but ChiAmpB NLC was twice less toxic to red blood cells and ten times safer on HT-29 cell lines. In vitro mucoadhesion data were observed ex vivo, where ChiAmpB NLC resulted in higher retention within the small intestine compared to the uncoated formulation. The data strongly offers the possibility of orally administering a non-toxic, yet effective Amphotericin-B nanoformulation for the treatment of systemic fungal infections.
Feline sporotrichosis has been reported in Malaysia since the 1990's. Since then, studies have revealed that clinical clade D, Sporothrix schenckii sensu stricto, of a single clonal strain is the most common cause of this disease in Malaysia. The prevalence of a single clonal strain from a clinical clade was never before reported in Asia in a specific geographical niche. This raises the possibility of a process of purifying selection and subsequent clonal proliferation. While agricultural practices may serve as the selective pressure, direct causality has yet to be established. Studies into the thermo-tolerability of the Malaysian clonal strain of S. schenckii sensu stricto revealed that a small minority of clinical isolates have the capacity to grow at 37℃, while the majority displayed low susceptibility to commonly used antifungals in clinical practice, such as itraconazole (ITZ) and terbinafine (TRB). Despite unestablished breakpoints, suspected resistance (MIC > 4 mg/mL) towards amphotericin B (AMB) and fluconazole (FLC) was recorded in the isolates. This explains the often lack of clinical response in feline patients treated with recommended doses of antifungals, including ITZ. Coupled with the potential zoonotic transmission to clients and veterinarians, protracted treatment period, and subsequent cost of treatment, prognosis of feline sporotrichosis is often regarded to be poor. The use of a higher dose of ITZ has been reported, and an adoption of this high-dose treatment regime is reported in this manuscript, with complete cure achieved in cases of recalcitrant and/or unresponsive feline sporotrichosis, which would otherwise be euthanized.