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KMID : 1011620180340040434
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Korean Journal of Food and Cookey Science
2018 Volume.34 No. 4 p.434 ~ p.439
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Comparative Growth of Listeria monocytogenes in Commercially Available Tryptic Soy Broth
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Chung Yoon-Kyung
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Abstract
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Purpose: The culture medium must provide the essential growth requirements for bacterial growth to occur. The manufacturing processes and preparation methods of the culture media can affect the culture medium composition and final growth of microorganisms. This study compared the growth of Listeria monocytogenes in two different brands of tryptic soy broth (TSB) and investigated which factors are responsible for the different growth response of this organism.
Methods: Two commercially available TSB products, i.e., BBL and Difco, were compared for their ability to support the growth of L. monocytogenes. Commercial TSB and lab-formulated TSB, which was made from individual components, were also compared. Yeast extract (YE), casamino acid, ferric citrate, biotin, choline, folic acid, niacin, pantothenic acid, pyridoxine, riboflavin, thiamine, and paraaminobenzoic acid were added individually as growth supplements. The optical density was measured using a spectrophotometer at 600 nm.
Results: The Difco TSB supported better growth than BBL TSB in all strains of L. monocytogenes tested. The addition of YE (0.3% or 0.6%) improved the growth in BBL TSB markedly. The difference in growth responses between BBL and Difco TSB was neutralized by YE supplementation. The Lab-formulated Difco TSB gave a lower growth response than commercial Difco TSB. The Lab-formulated BBL TSB also failed to support the growth of L. monocytogenes and gave a similar growth response to commercial BBL TSB. None of the growth supplements, except for riboflavin, improved growth in BBL TSB.
Conclusion: These results suggest that Difco TSB may contain the essential components in YE or YE itself.
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KEYWORD
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Listeria monocytogenes, growth medium, nutrient requirement
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