Ahmed A. Ismaiel

Efficacy of aqueous garlic extract on growth, aflatoxin B1 production, and Cyto-morphological aberrations of Aspergillus flavus, causing human ophthalmic infection: topical treatment of A. flavus keratitis

By using agar well diffusion assay, antifungal activity of aqueous extract prepared from Egyptian garlic (Allium sativum L.) was evaluated in vitro against two strains of Aspergillus flavus (OC1 and OC10) causing human ocular infection. The recorded minimum inhibitory concentration (MIC) for growth inhibition of both strains was 3.60 mg/ml. Aqueous garlic extract (AGE) was used in successive in vivo tests as an attempt to cure rabbits fungal keratitis caused by A. flavus OC1. Findings showed that diluted preparation of AGE was effective topical antifungal agent and succeeded to cure severe A. flavus keratitis in a time course less than 10 days without any observable side effects. Microscopic examination showed that AGE induced deleterious cyto-morphological aberrations inA. flavus target cells. AGE applied to Czapeks broth via contact method was more effective on growth, spores and aflatoxin B1 production than AGE applied to the same broth at the same concentration via fumigation method.

Incidence of Listeria in Egyptian meat and dairy samples

A total of 180 food samples including meat (raw lean beef, frozen lean beef, and frozen chicken) and dairy products (raw milk, Zabady and Kareesh cheese) were analysed for Listeria. Isolates were differentiated using morphological, cultural, and biochemical tests and an API-Listeria kit. Zabady cheese was completely free of Listeria. The highest incidence rate (13.33%) was in frozen lean beef. Raw lean beef and milk products showed an incidence rate of 6.67%. The lowest incidence rate (3.33%) was in Kareesh cheese and frozen chicken meat samples. L. monocytogenes showed the lowest incidence rate (0.55%), isolated from one frozen lean beef sample. L. ivanovii and L. grayi showed the highest incidence rate (2.22%), isolated from 4 samples. L. innocua and L. seeligeri were positive in 3 samples (1.67%), and L. welshimeri in 2 samples (1.11%). L. monocytogenes and L. ivanovii were positive for virulence factors (hemolytic properties, and extracellular enzyme activities).

Some optimal culture conditions for production of cyclosporin a by Fusarium roseum

A suitable chemically defined culture medium was selected and some optimal conditions for the production of the highly immunosuppressive compound, cyclosporin A (Cyc A) are reported. Medium of the following composition was favorable for the production of Cyc A by Fusarium roseum: glucose, 30; NaNO3, 2; KH2PO4, 1; MgSO4.7H2O, 0.5 and KCL, 0.5 (g/l). Maximum productivity of Cyc A was achieved at pH 6.0 when 50 ml of the fermentation medium/250 ml flask, inoculated with five fungal agar discs (6 mm, diameter) of 7-days old F. roseum culture after incubation at 30 oC at 120 rpm for 7 days.

Detoxification of Patulin by Kombucha tea culture

Kombucha is a refreshing beverage, obtained by fermenting sugared tea with a symbiotic culture of acetic acid bacteria and yeast, consumed for its positive effects on human health. In this study, the potential of kombucha supernatant for reduction of patulin (PAT) of three toxigenic fungal strains (Penicillium expansum LC015096, Talaromyces purpureogenus LC015095, and Acremonium implicatum LC015097) in liquid medium and apple fruit was investigated. In liquid medium, kombucha up to 10% (v/v) significantly inhibited PAT production of P. expansum by 77.2% and that of T. purpureogenus and A. implicatum by 100%. In apple fruit, inhibition percent of PAT accumulation by the respective fungal strains was 49.8%, 100%, and 53%. In aqueous solution, kombucha cells showed a relative greater PAT uptake capacity than Sacchromyces cerevisiae. The maximum PAT uptake (64.67% and 60.69%) by viable and heat-treated kombucha cells was achieved at pH 3.0 throughout 48 h incubation, respectively.

Effect of Patulin from Penicillium vulpinum on the Activity of Glutathione-S-Transferase and Selected Antioxidative Enzymes in Maize

The mycotoxin patulin (PAT) was purified from Penicillium vulpinum CM1 culture that has been isolated from a soil cultivated with maize. The effect of PAT and of a fungal culture filtrate on the activities of glutathione-S-transferase (GST) and some antioxidant enzymes viz. ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR) was investigated in roots and shoots of 8-day-old maize seedlings. PAT and culture filtrate caused significant reduction effects in a dose-related manner on the total GST activity. Upon application of the high PAT concentration (25 μg·mL−1) and of the concentrated fungal filtrate (100%, v/v), the reduction in GST activity of roots was 73.8–76.0% and of shoots was 60–61.7%. Conversely, significant increases in the activities of antioxidant enzymes were induced. Application of 25 μg·PAT·mL−1 increased APX, GR, DHAR, and MDHAR activity of root by 2.40-, 2.00-, 1.24-, and 2.16-fold, respectively. In shoots, the enzymatic activity was increased by 1.57-, 1.45-, 1.45-, and 1.61-fold, respectively. Similar induction values of the enzymatic activity were obtained upon application of the concentrated fungal filtrate. This is the first report describing the response of GST and antioxidant enzyme activities of plant cells to PAT toxicity.

Antimicrobial properties of 6-pentyl-α-pyrone produced by endophytic strains of Trichoderma koningii and its effect on aflatoxin B1 production

Abstract A total of 60 endophytic fungal strains were isolated and screened for their producing-ability of 6-pentyl-α-pyrone (6PP), which has a coconut-like aroma. Of these isolated strains, four strains of Trichoderma koningii Oudemans were positive for 6PP production. Agar well diffusion assay was employed to test the antimicrobial activity of 6PP against 22 microbial strains. Although 6PP showed no antibacterial activity against several bacterial strains, it interestingly exhibited positive inhibitory activity against Staphylococcus aureus recording a minimal inhibitory concentration (MIC) of 100 µg/mL. The 6PP displayed a good antifungal activity against all filamentous fungi tested with MICs ranged from 80 to 90 µg.mL. To demonstrate its mode of antimicrobial activity, Staphylococcus aureus, Aspergillus flavus, Penicillium expansum and Fusarium acuminatum were treated with 6PP at sub-MICs and examined by scanning and transmission electron microscopy. Several morphological alterations were caused by 6PP, such as induction of a bleb-like structure on the outer surface of the treated bacteria and surface depression with loosing hyphal linearity of the treated fungi. Additionally, several extensive cellular damages were also observed in microbial cells and the most frequent alteration noticed was the detachment of plasma membrane from cell wall. The inhibitory activity of 6PP was further demonstrated on aflatoxin B1 (AFB1) production by several strains of Aspergillus flavus and Aspergillus parasiticus grown in liquid medium and results showed that 6PP had a good efficacy in suppression of AFB1 by 34.28–54.63%. These findings hold a promise to control pathogenic organisms and their toxicity using a lactone metabolite.

Antimicrobial and morphogenic effects of emodin produced by A spergillus awamori WAIR120

Abstract The antimicrobial activity of anthraquinone emodin isolated from Aspergillus awamori WAIR120 (LC032125) culture was investigated against some clinical, phytopathogenic and foodborne pathogenic microorganisms using an agar diffusion method. Among bacterial and fungal strains tested, the highest activity was obtained against Enterococcus faecalis AHR7 as well as Aspergillus niger OC20 with minimal inhibitory emodin concentration of 125 and 85 μg/mL, respectively. Emodin was found to induce morphogenic effects including swelling and elongation of bacterial cell and conidiation decrease, pigmentation loss, and cytoplasmic retraction of fungal cell, as was shown by light microscopy. Additionally, cellular effects were also resulted, in which emodin caused considerable changes in the nature of cell membrane and submicroscopic structure of bacterial and fungal cell, as was shown by transmission electron microscopy. Furthermore, there was an evidence of a disruption of lipid metabolism of fungal cell. These findings thus indicate the future possibility of exploiting emodin as an effective inhibitor of clinical, phytopathogenic and foodborne pathogenic microorganisms.

Immobilization technique for enhanced production of the immunosuppressant mycophenolic acid by ultraviolet and gamma-irradiated Penicillium roqueforti.

Different entrapment matrices were screened to immobilize two strains of Penicillium roqueforti (AG101 and LG109) for more effective production of mycophenolic acid (MPA). Further improvement in the MPA productivity from immobilization of spores and mycelia was adopted by UV and gamma irradiation.