The effect of antimicrobial photodynamic therapy (aPDT) on Gram-positive bacterium Staphylocccus aureus was studied. Methylene blue (MB) at non-toxic concentration of 31.25µg/ml was used as a photosensitizer. LEDs diodes were used as a light source to study the effect of methylene blue alone and the MB-gold nanoparticle mixture on the viability of S. aureus cells. Biogenic gold nanoparticles (biolAuNPs, 10ppm) and chemically synthesized gold nanoparticles (chemAuNPs, 3ppm) were tested as enhancement agents. In the presence of MB alone as a photosensitizer, the killing effect was about 92% after 30min of irradiation. The aPDT therapy was enhanced by addition of biolAuNPs and chemAuNPs and killing rate of S. aureus was 95-96% after 30min of irradiation. The probable mechanism of enhancement of MB-mediated photodynamic bactericidal efficacy against S. aureus in the presence of gold nanoparticles is discussed leading to the conclusion that colloidal gold increases the accumulation of MB in bacterial cells.
Określono jakość mikrobiologiczną 23 rodzajów wyrobów wegetariańskich po wyprodukowaniu oraz po zadeklarowanych przez producentów okresach przydatności do spożycia. W produktach określano [w 1 g]: ogólną liczbę drobnoustrojów tlenowych mezofilnych, liczbę .Staphylococcus aureus, pleśni i drożdży oraz obecność bakterii z grupy coli w 0,001 g, laseczek beztlenowych przetrwalnikujących w 0,01 g i pałeczek Salmonella w 25 g. Zanieczyszczenie mikrobiologiczne wyrobów wegetariańskich bezpośrednio po wyprodukowaniu stanowiły głównie bakterie tlenowe mezofilne w liczbie 102-103 jtk/g. W badanych produktach nie wykryto obecności bakterii chorobotwórczych oraz drożdży. Po przechowywaniu w warunkach chłodniczych w większości wyrobów znacznie wzrastała liczba bakterii tlenowych mezofilnych, nawet powyżej 107 jtk/g oraz pleśni, drożdży i bakterii z grupy coli. Zastosowanie odpowiednich procesów technologicznych oraz przestrzeganie zasad Dobrej Praktyki Higienicznej w przetwórni znacznie poprawiło jakość mikrobiologiczną przechowywanych produktów.
EN
There was determined the microbiological quality of 23 vegetarian products immediately after the production process, and after the products have been stored for periods equalling their shelf-life as declared by the manufacturers. The following parameters of the products investigated were determined [in 1 g of each product]: total count of aerobic mesophilic micro-organisms; counts of Staphylococcus aureus, moulds, and yeasts; the occurrence of coliform bacteria and spore-forming bacilli anaerobes in 0.001 g of the product, and of Salmonella bacilli in 25 g of the product. In the vegetarian food products, investigated immediately upon their manufacturing, the bacterial contamination was caused mainly by aerobic mesophillic bacteria, and their counts amounted to 102-103 [cfu/g]. In all the products investigated, no pathogenic bacteria were found, as were no yeasts. After the cold storing of the vegetarian products, in the majority of the products, the total counts of aerobic micro-organisms essentially increased, and their levels exceeded 107 [cfu/g], as did the content levels of yeasts, and coliform bacteria. The indispensable improvement in the microbiological quality of products stored was obtained as soon as the adequate technological processes were applied and the rules of good hygienic practices (GHP) were obeyed in the entire food-processing plant.
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