جستجوی مقالات مرتبط با کلیدواژه "minimum inhibitory concentration" در نشریات گروه "شیلات"

Probiotics are non-pathogenic microorganisms that have beneficial effects on living organisms. Also, zinc as a micronutrient has useful properties and is essential for the body of living organisms. Probiotics and zinc can have a positive role in the health of living organisms with their synergistic effects. Small amounts of micronutrients are needed for the growth and development of living organisms, but large amounts of them can be toxic. Micronutrients are found in nature in two forms, inorganic and organic, which the organic form is less toxic. Bacteria and fungi are among the microorganisms that can convert minerals into organic forms and reduce their toxicity. Therefore, in this study, two probiotics, Lactobacillus acidophilus and Candida utilis, were selected and their ability to absorb and accumulate mineral zinc as well as the growth rate of the microorganisms were investigated. For this purpose, 9 different concentrations of zinc sulfate including 0.05, 0.2, 15, 10, 5, 25, 50, 75, and 100 mmol/l were used. Based on the results, the growth inhibition of L. acidophilus and C. utilis probiotics was obtained at 100 and above 50 mmol/L, respectively. The highest and lowest amounts of zinc absorption in L. acidophilus were 2364 and 498.8 ppm, respectively, and in C. utilis were 41830 and 13174 ppm, respectively. Based on the findings of the present study, it can be concluded that each of these two probiotics has specific capacities in zinc absorption and tolerance based on their cellular structure. The reason for that can be in the mechanism and mode of action and intracellular mechanisms and bacteria have a lower absorption rate than yeast due to the presence of a cell wall. Therefore, the selected bacteria and yeast can absorb zinc and they have various applications in the food and drug industry as a zinc-enriched probiotics.

The present study aimed to isolate the steroids and fatty acids from the liver of the Persian Gulf spot tail shark Carcharhinus sorrah and to assess their antifungal activity. Extraction was done by methanol 70% and then, the lipids were separated through column chromatography with silica gel. Identification of the extracted lipids was done by thin layer chromatography and gas chromatography coupled with mass spectrometry. Then, antifungal activity of the steroids was investigated through determining the minimum inhibition concentration and minimum fungicidal concentration by tubular dilution method against Aspergillus fumigatus and Candida albicans. Identification of the extracted compounds by GC-MS confirmed the presence of these steroids in the shark liver. The identified steroids included compounds of Y-Sitosterol, Desmosterol and Squalene, which showed different results regarding the growth inhibition and fungicidal effects against the microorganisms at different experimental doses. Desmosterol and Squalene at minimum concentration induced the highest inhibitory effect on the fungus but Y-Sitosterol induced the highest inhibitory effect on the yeast. Squalene showed fungicidal effect only on the fungus and totally, A. fumigatus was more sensitive to the antimicrobial activity of the liver compounds than C.  albicans. In conclusion, promising results were found regarding the antimicrobial activity of the lipid compounds derived from Persian Gulf shark liver, revealing the importance of more comprehensive investigations of these natural compounds for the synthesis of biomedicines from the marine organisms.

Microbial infections outbreak in aquatics are important challenges, and farmers have major difficulties dealing with microbes especially regarding their antibiotic resistance. The purpose of this study was comparative evaluating of antimicrobial activity of silver nanoparticles (Ag NPs) against one gram-positive bacteria (Bacillus spp) and a gram-negative (Vibrio harveyi). In this experimental study, the antibacterial effects of Ag NPs was determined by agar well diffusion method through the measurement of the inhibitory zone diameter and micro-broth dilution for determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). According to the results of well diffusion test in agar, the maximum diameter of inhibition zone (44.6 ± 0.15 mm) was related to Bacillus spp. MIC of Ag NPs against Bacillus spp and Vibrio harveyi  were 1.95 and 3.91 mg/ml respectively and MBC was recorded 3.91 mg/ml for both bacteria. Also the kinetic study confirmed the results, So that growth of Bacillus spp 5 hours and V. harveyi 6 hours after exposure to silver nanoparticles was stopped.This study showed that colloidal Ag NPs have higher bactericidal effects on gram-positive bacteria compared with gram-negative bacteria and of course can be a candidate for the elimination of both gram negative and gram positive bacteria, especially in control of infective aquatic microorganisms.

Using natural extracts, as a source of anti-microbial, to improve the quality of fish is increasing. In this study, the ethanolic extract of orange (Citrus sinensis L.) was used due to having this property. Agar dilution method was employed in order to determine the minimum inhibitory concentration (MIC) of the ethanolic extract of orange peel on Pseudomonas aeruginosa, E. coli and Aeromonas hydrophila bacteria. The fish fillets were treated with aqueous solution of orange peel extract (5, 6 and 7% w/w) and dipped in distilled water for 30 minutes. These samples were analyzed during storage (0, 5, 10 and 15 days) for the total viable count (TVC), psychrotrophic count, coliform count. The MIC of the ethanolic extract of orange peel on the bacteria was 5%. The results of the microbial analysis indicated that the orange peel extracts reduced the growth of the bacterial counts in contrast control sample (p<0.01). The ethanol extract of orange peel as a natural preservative could increase shelf life during refrigerated storage because of having antimicrobial properties.