• Korean Journal of Environmental Agriculture
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• v.28 no.1
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• pp.75-81
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• 2009

This study was carried out to assess the antilisterial potential of ethyl acetate (EtOAc) extract of a marine isolate of Aspergillus sp. The in vitro antilisterial efficacy of ethyl acetate extract was examined using disc diffusion, minimum inhibitory concentration (MIC) determination, cell viable count and scanning electron microscopic (SEM) methods against the employed strains of Listeria monocytogenus. The ethyl acetate extract ($300{\mu}g\;disc^{-1}$) exhibited a promising antilisterial effect as diameters of inhibition zones against L. monocytogenes ATCC 19111, 19116, 19118, 19166 and 15313, which were found in the range of 11-17 mm along with their MIC values ranging from 125 to $1000{\mu}g\;ml^{-1}$ respectively. Also the EtOAc extract had strong detrimental effect on the viable count of the tested L. monocytogens ATCC 19166. Furthermore, scanning electron microscopic (SEM) study demonstrated potential detrimental effect of ethyl acetate extract on the morphology of L. monocytogenes ATCC 19116 at the used MIC concentration. These findings strongly support the role of ethyl acetate extract of a marine isolate of Aspergillus sp. as an antiliterial potential.

• Journal of Microbiology and Biotechnology
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• v.26 no.6
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• pp.1026-1034
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• 2016

In the current study, a total of 135 enterococci strains from different sources were screened for the presence of the enterocin-encoding genes entA, entP, entB, entL50A, and entL50B. The enterocin genes were present at different frequencies, with entA occurring the most frequently, followed by entP and entB; entL50A and L50B were not detected. The occurrence of single enterocin genes was higher than the occurrence of multiple enterocin gene combinations. The 80 isolates that harbor at least one enterocin-encoding gene (denoted "Gene⁺ strains") were screened for antimicrobial activity. A total of 82.5% of the Gene⁺ strains inhibited at least one of the indicator strains, and the isolates harboring multiple enterocin-encoding genes inhibited a larger number of indicator strains than isolates harboring a single gene. The indicator strains that exhibited growth inhibition included Listeria innocua strain CLIP 12612 (ATCC BAA-680), Listeria monocytogenes strain CDC 4555, Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 25923, S. aureus ATCC 29213, S. aureus ATCC 6538, Salmonella enteritidis ATCC 13076, Salmonella typhimurium strain UK-1 (ATCC 68169), and Escherichia coli BAC 49LT ETEC. Inhibition due to either bacteriophage lysis or cytolysin activity was excluded. The growth inhibition of antilisterial Gene⁺ strains was further tested under different culture conditions. Among the culture media formulations, the MRS agar medium supplemented with 2% (w/v) yeast extract was the best solidified medium for enterocin production. Our findings extend the current knowledge of enterocin-producing enterococci, which may have potential applications as biopreservatives in the food industry due to their capability of controlling food spoilage pathogens.