Iranian HIV/AIDS patients with oropharyngeal candidiasis: identification, prevalence and antifungal susceptibility of Candida species.

Oropharyngeal candidiasis is the commonest mucocutaneous infection in HIV-positive individuals. Herein, samples were taken from oral cavities of 150 HIV-infected patients and cultured on Sabouraud-dextrose agar; 89 (59·3%) of 150 patients had positive culture for Candida and presented clinical sign of classical oral candidiasis. Totally, 102 morphologically distinct colonies were isolated from Candida positive cultures and subsequently identified by polymerase chain reaction and sequencing assay, presenting the following frequency: 54 C. albicans (52·9%), 16 C. dubliniensis (15·7%), 12 C. tropicalis (11·8%), 9 C. glabrata (8·8%), 7 C. kefyr (6·9%) and 4 C. africana (3·9%). Additionally, multiple Candida species were co-isolated from 13·5% (12/89) patients. Regarding the antifungal susceptibility test, which was performed by CLSI protocol (M27-A3/M27-S3), all Candida isolates were susceptible to amphotericin B and caspofungin, while some of them were resistant to fluconazole (17·6%; 16 C. albicans, 1 C. dubliniensis and 1 C. glabrata), itraconazole (16·7%; 15 C. albicans, 1 C. dubliniensis and 1 C. tropicalis) and voriconazole (5·9%; 5 C. albicans and 1 C. tropicalis). Collectively, our findings reinforce the urgent necessity to find new therapeutic agents to treat oral candidiasis in HIV-positive patients, especially due to the high incidence of azole-resistant Candida strains and the increased frequency of non-C. albicans species. SIGNIFICANCE AND IMPACT OF THE STUDY: The Candida species recovered from oral cavity of 150 Iranian HIV/AIDS patients and their antifungal susceptibility profiles were reported. Candida albicans was the commonest Candida species, followed by C. dubliniensis, C. tropicalis, C. glabrata, C. kefyr and C. africana. All Candida isolates were susceptible to amphotericin B and caspofungin, while resistance to azoles was detected. The growing drug-resistance profile reported in clinical isolates of C. albicans and non-C. albicans strains is a serious problem in hospitals worldwide. Consequently, the suitable antifungal choice to treat the HIV/AIDS population with oral candidiasis needs to be rethought and new therapeutic options must urgently arise.

Modeling T(1) and T(2) relaxation in bovine white matter.

The fundamental basis of T1 and T2 contrast in brain MRI is not well understood; recent literature contains conflicting views on the nature of relaxation in white matter (WM). We investigated the effects of inversion pulse bandwidth on measurements of T1 and T2 in WM. Hybrid inversion-recovery/Carr-Purcell-Meiboom-Gill experiments with broad or narrow bandwidth inversion pulses were applied to bovine WM in vitro. Data were analysed with the commonly used 1D-non-negative least squares (NNLS) algorithm, a 2D-NNLS algorithm, and a four-pool model which was based upon microscopically distinguishable WM compartments (myelin non-aqueous protons, myelin water, non-myelin non-aqueous protons and intra/extracellular water) and incorporated magnetization exchange between adjacent compartments. 1D-NNLS showed that different T2 components had different T1 behaviours and yielded dissimilar results for the two inversion conditions. 2D-NNLS revealed significantly more complicated T1/T2 distributions for narrow bandwidth than for broad bandwidth inversion pulses. The four-pool model fits allow physical interpretation of the parameters, fit better than the NNLS techniques, and fits results from both inversion conditions using the same parameters. The results demonstrate that exchange cannot be neglected when analysing experimental inversion recovery data from WM, in part because it can introduce exponential components having negative amplitude coefficients that cannot be correctly modeled with nonnegative fitting techniques. While assignment of an individual T1 to one particular pool is not possible, the results suggest that under carefully controlled experimental conditions the amplitude of an apparent short T1 component might be used to quantify myelin water.

Molecular identification of antagonistic bacteria from Tehran soils and evaluation of their inhibitory activities toward pathogenic fungi.

BACKGROUND AND OBJECTIVES: To find antagonistic bacteria with potential antifungal activity against some pathogenic fungi, including Aspergillus niger, A. flavus, Fusarium moniliforme and Penicillium marneffei, a total of 148 agricultural soil samples from different sites of Tehran were examined. MATERIALS AND METHODS: Antagonistic soils were selected by screening against A. niger on glucose-yeast extract (GY) agar using a visual agar plate assay method. All growing bacteria were examined for antifungal activity, and antagonistic bacteria identified based on 16S rRNA sequence analysis. Among a total number of 97 bacteria isolated form inhibitory soils (36 samples), 16 bacteria were reported as strong growth inhibitors in co-cultures on GY agar with all tested fungi at variable degrees. Fungal growth inhibitory bacteria were cultured against all fungi and growth inhibition was measured and analyzed between test and control groups by statistical analysis (ANOVA). RESULTS: Molecular identification of antagonistic bacteria indicated that most bacterial isolates belonged to the genus Bacillus (81.25%), including B. subtilis (5 isolates), B. amyloliquefaciens (6 isolates) and B. valismortis (2 isolates), followed by one isolate (6.25%) from each Streptomyces sp., Pseudomonas chlororaphis and Acinetobacter baumannii. Based on the visual plate assay results, total fungal growth inhibition of all bacteria was reported in the range of 13.2 to 68.3%. P. chlororaphis S105 was reported as the most potent antagonistic bacterium which inhibited the growth of A. niger by 68.3%, followed by F. moniliforme (66.4%), A. flavus (64.7%) and P. marneffei (57.1%). CONCLUSION: P. chlororaphis and some other inhibitory bacteria reported in the present study, they may be considered not only as a rich source of useful metabolites with potential application in antifungal drug discovery, but also as potential candidates for biological control programs.

Electron transfer reaction mechanism of cisplatin with DNA at the molecular level.

The cytotoxicity of cisplatin as a very effective chemotherapeutic anticancer drug is known to arise from its capacity to damage DNA. However, the mechanism of action of cisplatin at the molecular level, in particular, the reaction dynamics of cisplatin with DNA, remains elusive, and the reason why cisplatin binds to the guanine bases rather than to S-donor ligands available in cells remains a mystery. Using time-resolved femtosecond laser spectroscopy, for the first time, we reveal the high reactivity of cisplatin with electrons and its preferential electron-transfer reaction with the DNA guanine base. The results not only provide a molecular mechanistic understanding of cisplatin in cancer therapy but may have far-reaching significance for understanding the role of polar molecules such as NH3 and NH2 in biological reactions.

Impact of UV-C irradiation on the cell wall-degrading enzymes during ripening of tomato (Lycopersicon esculentum L.) fruit.

The effect of a hormic dose of UV-C (254 nm) on changes in fruit firmness and cell wall-degrading enzyme (CWDE) activity was determined using tomato fruit. Throughout the storage period, a decrease in firmness was jointly observed with an increase of the CWDE (polygalacturonase, pectin methyl esterase, cellulase, xylanase, beta-D-galactosidase, and protease) activity for all treatments, suggesting the involvement of these enzymes in the ripening process. However, the enhancement in the activity of the CWDE was significantly less in fruit subjected to the hormic dose of UV-C. This reduction may explain why irradiated fruit were firmer than control and consequently may explain how UV-C could delay the ripening and senescence process. We suggest that the CWDE are one of the targets of the UV-C, and by this action, irradiation contributed to a delay of the cell wall degradation and consequently retarded softening of the tomato fruit tissues.

Impairment of neuromotor and cognitive development in iodine-deficient schoolchildren with normal physical growth.

In order to detect somatic and psychomotor disturbances in children and adolescents residing in areas of iodine deficiency, schoolchildren from three areas with different degrees of iodine deficiency were studied. In Randan, the prevalence of severe endemic goiter was accompanied by alteration in thyroid function, increased thyrotropin levels and retardation of both bone and psychomotor age and decreased intellectual quotient. In Tehran, where iodine deficiency is mild, visible goiter was present in 15% of schoolchildren but no alterations in thyroid function, serum thyrotropin, somatic or psychomotor development could be detected. In Zagoon, where the prevalence and severity of goiter was less than Randan but more than Tehran, thyroid function was normal but slightly decreased as compared to Tehran; somatic development was unaltered, but retardation in psychomotor development was evident and the mean intellectual quotient was less than that of Tehranian schoolchildren. These findings indicate the occurrence of physical and psychomotor disturbances in apparently normal schoolchildren from areas of iodine deficiency. Alteration in psychomotor development may occur in children with normal physical growth, due to iodine deficiency.