Medical mycology

Posaconazole inhibits dengue virus replication by targeting oxysterol-binding protein

Dengue virus (DENV) is associated with an estimated 390 million infections per year, occurring across approximately 100 countries in tropical and sub-tropical regions. To date, there are no antiviral drugs or specific therapies to treat DENV infection. Posaconazole and itraconazole are potent antifungal drugs that inhibit ergosterol biosynthesis in fungal cells, but also target a number of human proteins. Here, we show that itraconazole and posaconazole have antiviral activity against DENV. Posaconazole inhibited replication of multiple serotypes of DENV and the related flavivirus Zika virus, and reduced viral RNA replication, but not translation of the viral genome. We used a combination of knockdown and drug sensitization assays to define the molecular target of posaconazole that mediates its antiviral activity. We found that knockdown of oxysterol-binding protein (OSBP) inhibited DENV replication. Moreover, knockdown of OSBP, but not other known targets of posaconazole, enhanced the inhibitory effect of posaconazole. Our findings imply OSBP as a potential target for the development of antiviral compounds against DENV.

Prevalence of tinea capitis in southern Kuwait

Tinea capitis of the scalp, an infection caused by dermatophytes, produces a significant health problem especially among school children. The object of this study was to highlight the prevalence of tinea capitis in southern Kuwait. During this retrospective study from 1998 to 2003, 1737 suspected cases were examined, 986 (58.6%) were men and 751 (43.2%) were women of which 371 cases were diagnosed as tinea capitis. Of 371 cases of tinea capitis, males comprised 54.2% and females 45.8%. Young children (up to age five) were more frequently infected than other age groups, grey type lesions were more common than other types. Microsporum canis was the most common organism noticed with 62.5% followed by Trichophyton violaceum with 19.3%, Trichophyton tonsurans with 13.1%, while Trichophyton rubrum was the least common. Tinea capitis of scalp is a significant health problem in southern Kuwait especially among young children of school age. The spread of infection can be prevented by health education, proper diagnosis and treatment.

Aetiological agents of tinea capitis in Tehran (Iran)

A total of 1568 patients with suspected tinea capitis were examined for causative fungal agents between 1994 and 2001. Laboratory examination confirmed tinea capitis in 209 patients. Males were affected more frequently (67.5%) than females (32.5%) and in both sexes, those who were 3-11 years old, were more infected. Trichophyton violaceum was the most common aetiological agent (37.3%) followed by Trichophyton schoenleinii (21.5%), Microsporum canis (18.6%), Trichophyton verrocosum (14.8%), Trichophyton tonsurans (5.3%), Trichophyton rubrum (1%), Microsporum gypseum (1%) and Trichophyton mentagrophytes (0.5%). A higher incidence of the disease was found to be correlated with larger family and class size. The findings are discussed in relation to different socioeconomic and hygienic backgrounds of the children.

Prediction of toxigenic fungal growth in buildings by using a novel modelling system

There is growing concern about the adverse effects of fungal bioaerosols on the occupants of damp dwellings. Based on an extensive analysis of previously published data and on experiments carried out within this study, critical limits for the growth of the indoor fungi Eurotium herbariorum, Aspergillus versicolor, and Stachybotrys chartarum were mathematically described in terms of growth limit curves (isopleths) which define the minimum combination of temperature (T) and relative humidity (RH) at which growth will occur. Each growth limit curve was generated from a series of data points on a T-RH plot and mathematically fitted by using a third-order polynomial equation of the form RH = a(3)T(3) + a(2)T(2) + a(1)T + a(0). This fungal growth prediction model was incorporated within the ESP-r (Environmental Systems Performance [r stands for "research"]) computer-based program for transient simulation of the energy and environmental performance of buildings. For any specified location, the ESP-r system is able to predict the time series evolution of local surface temperature and relative humidity, taking explicit account of constructional moisture flow, moisture generation sources, and air movement. This allows the predicted local conditions to be superimposed directly onto fungal growth curves. The concentration of plotted points relative to the curves allows an assessment of the risk of fungal growth. The system's predictive capability was tested via laboratory experiments and by comparison with monitored data from a fungus-contaminated house.

Characteristics of the heterologously expressed human lanosterol 14alpha-demethylase (other names: P45014DM, CYP51, P45051) and inhibition of the purified human and Candida albicans CYP51 with azole antifungal agents

Human and Candida albicans CYP51 were purified to homogeneity after GAL10-based heterologous expression in yeast in order to resolve the basis for the selective inhibition of the fungal enzyme over the human orthologue by the azole drugs ketoconazole and itraconazole, used in the treatment of systemic fungal infection. The purified proteins have similar spectral characteristics, both giving a maximum at 448 nm in reduced carbon monoxide difference spectra. Substrate affinity constants of 20.8 and 29.4 microM and Vmax of 0. 15 and 0.47 nmol/min/nmol were observed for C. albicans and human enzymes, respectively, in reconstituted enzymatic assays, using an intermediate of the demethylation reaction [32-3H]-3beta-hydroxylanost-7-en-32-ol as the substrate. Both enzymes gave similar type II spectra on titration with drugs, but a reduced affinity was observed for human CYP51 using the ability of carbon monoxide to displace the drug as a ligand and by calculation of IC50. However, although the results indicate higher affinity of the drugs for their target CYP51 in the major fungal pathogen C. albicans, when compared directly to CYP51 from humans, the difference was less than 10-fold. This difference is an order of magnitude lower than previously reported data based on measurements using unpurified human CYP51 enzyme preparations. Consequently, increased azole doses to combat resistant candidaemia may well inhibit endogenous human CYP51 and the potential consequences are discussed.

Epidemiological study of tinea capitis in schoolchildren in the Nablus area (West Bank)

A study of tinea capitis was carried out during the period January-June 1996 in 7525 primary schoolchildren aged 6-14 years comprising 4050 boys and 3475 girls in the Nablus district in the Palestinian area. Fourteen primary schools located in rural, urban and refugee camp areas were surveyed in this study. Seventy-five (1.0%) mycologically proven cases of tinea capitis were detected. The incidence was higher in schools in rural areas (1.9%) than in refugee camps (1.1%) or urban areas (0.4%). Also, the incidence was higher in young children (1.4%) aged 6-10 years than in older children (0.5%) aged 10-14 years. Boys 52 (1.3%) were more commonly affected than girls 23 (0.7%). Higher disease incidence was found to be correlated with larger family and class sizes. Trichophyton violaceum was the most common aetiological agent (82.7%) followed by Microsporum canis (16%) and Trichophyton schoenleinii (1.3%). The findings are discussed in relation to the children's different socioeconomic and hygienic backgrounds. A mycological investigation carried out on 117 tinea capitis cases at a clinic in the area under study showed similar results to those of the school survey.