ABSTRACT
BACKGROUND AND PURPOSE: Aspergillus fumigatus is one of the most common opportunistic fungus, which causes infection in immunocompromised and neutropenic patients. The current guidelines recommend voriconazole as the initial therapeutic and prophylactic agent for almost all cases, especially in patients with organ transplants, which leads to increased medication resistance in A. fumigatus. The aim of the present study was to evaluate the antifungal activity and effect of kombucha as a natural compound on A. fumigatus growth, as well as on the expression of cgrA and cyp51A genes. MATERIALS AND METHODS: A panel of 15 A. fumigatus strains with two quality controls of CM237 and CM2627 as susceptible and resistant strains were obtained from Tehran Medical Mycology Laboratory, Tehran,Iran(TMML).Antifungal susceptibility testing assay was performed according to the Clinical and Laboratory Standards Institute (CLSI) M38-A2 document. Moreover, the mycelial dry weight of the fungus was calculated before and after being treated with kombucha. In addition, the quantitative changes in the expression of cgrA and cyp51A genes were analyzed by real-time polymerase chain reaction (real-time PCR) technique. RESULTS: In the present study, the minimum inhibitory concentration ranges of kombucha were measured at 6,170 and 12,300 µg/mL for ten A. fumigatus azole-susceptible strains and 24,700 µg/mL for five A. fumigatus resistant strains. Moreover, changes in mycelial dry weight under kombucha treatment conditions underwent a significant reduction (P≤0.05). A coordinate down-regulation of expression in cgrA and cyp51A genes was observed in all azole-susceptible and -resistant A. fumigatus strains, after treating the fungus with different concentrations of kombucha (P≤0.05). CONCLUSION: According to the obtained results, kombucha as a natural antioxidant , can exert inhibitory effects against the growth and expression of some genes in A. fumigatusstrains.
ABSTRACT
BACKGROUND AND PURPOSE: Aspergillus flavus is an important pathogen in immunodeficient patients. Due to the abundance of this fungus in nature, fungicides are commonly used to preserve and maintain agricultural products. Long-term exposure to these pesticides can lead to the induction of drug resistance in this fungus. MATERIALS AND METHODS: For the purpose of the study, 10 strains of A. flavus ATCC 204304 were cultured in benomyl and diazinon pesticides at the concentrations of 62.5, 125, 250.500, 750, 1000, 1500, 2000, and 2500 mg/L in nine steps. Morphological changes and resistance to voriconazole, itraconazole, and amphotericin B were evaluated at the end of each step. Subsequently, changes in the expression of mdr1 and cyp51C genes were studied in the strains showing drug resistance. RESULTS: The results showed that during the nine stages of the adjacency of strains with benomyl and diazinon at different concentrations, resistance to voriconazole, itraconazole, and amphotericin B in these toxins increased by 30% and 10%, respectively. In addition, the microscopic examination of resistant strains revealed the absence of sporulation, and only mycelium was found. Macroscopically, the color of the colonies changed from green to white. Furthermore, the investigation of the expression of mdr1 and cyp51c genes in these strains showed a decrease and increase in adjacency with diazinon and benomyl, respectively. CONCLUSION: As the findings indicated, exposure to agricultural pesticides can lead to the incidence of morphological changes and resistance to amphotericin B, itraconazole, and voriconazole in the sensitive species of A. flavus by altering the expression of genes involved in drug resistance.
ABSTRACT
BACKGROUND AND PURPOSE: Aflatoxin is known as one of the most important mycotoxins threatening human life. This toxin is produced by Aspergillus species, which is the common cause of agricultural product contamination. The use of organic compounds has been always considered for the inhibition of fungal growth and toxin production. Regarding this, the aim of the present study was to investigate the effect of vitamin C on the rate of fungal growth, aflR gene expression, and toxin production. MATERIALS AND METHODS: For the purpose of the study, first, Aspergillus parasiticus ATCC15517 was cultured in Sabouraud dextrose agar medium containing vitamin C at concentrations of 200, 100, 50, 25, 12.5, 6.25, and 3.1 mg/ml and temperature of 28°C for 72 h. Then, the amount of aflatoxin produced in the presence of vitamin C was measured through high performance liquid chromatography. Finally, by extracting the DNA of the cultured samples, the aflR gene expression level was evaluated by means of real-time polymerase chain reaction at different concentrations of vitamin C. RESULTS: The results showed that mycelium deformation was started at the vitamin C concentration of 50 mg/ml, and that only fungal spores were observed at higher concentrations. The levels of total aflatoxin and its subsets, namely B1, B2, G1, and G2, in the presence of vitamin C were estimated as 5.9, 1.9, 0.2, 3.5, and 0.3 ppm, respectively. On the other hand, these values were respectively obtained as 207.5, 73.6, 4.5, 123.4, and 6 ppm in the absence of vitamin C. Measurement of the expression level of aflR genes showed that the level of gene expression decreased to 68% and up to 81% at the vitamin C concentrations of 25 and 50 mg/ml, respectively. CONCLUSION: This study showed that vitamin C, as a human-compatible compound, could be considered a good agent to protect agricultural products against fungal aflatoxin.
ABSTRACT
BACKGROUND AND PURPOSE: Aspergillosis is one of the most common opportunistic fungal infections in immunocompromised and neutropenic patients. Aspergillus fumigatus (A. fumigatus) is the most common causative agent of this infection. Due to variable CO2 concentrations that pathogens are exposed to during the infection process and to understand the role of CO2, we examined the effects of various CO2 concentrations as one of the environmental factors on morphological changes and induction of antifungal resistance in A. fumigatus. MATERIALS AND METHODS: A. fumigatus strains were cultured and incubated under 1%, 3%, 5%, and 12% CO2 atmospheres, each time for one, two, and four weeks. The control culture was maintained for one week without CO2 atmosphere. Morphological changes were investigated and antifungal susceptibility test was performed according to the recommendations of the Clinical and Laboratory Standards Institute (CLSI) M38-A2 document. The results of different CO2 atmospheres were compared with that of the control sample. RESULTS: We found that 1%, 3%, 5%, and 12% CO2 atmospheres were associated with morphological colony changes. Macroscopically, the colonies were shallow dark green, smooth, crisp to powdery with reduced growth; microscopic examination revealed the absence of conidiation. The induction of antifungal resistance in the susceptible strains to itraconazole, voriconazole, and amphotericin B increased after exposure to 12% CO2 atmosphere and four weeks of incubation. The MIC values for itraconazole, voriconazole, and amphotericin B were 16 g/ml, 1 g/ml, and 16 g/ml, respectively. These values for the control group were 0.125 g/ml, 0.125 g/ml, and 2 g/ml, respectively. CONCLUSION: Exposure to different CO2 atmospheres induced morphological changes in A. fumigatus, it seems to increase the MIC values, as well. In parallel, resistance to both itraconazole and voriconazole was also observed.
