A method for evaluating the antibacterial ability of bile salt and sodium deoxycholate

Abstract

The invention discloses a method for evaluating bactericidal capacity of bile salts and sodium deoxycholate. Micrococcus luteus and staphylococcus epidermidis are used as sensibility testing strains, and bile salts No. 3 of Oxoid are used as a reference substance. By comparing growth state of the testing strains, bactericidal capacity of bile salts and sodium deoxycholate with different batches and different sources is evaluated. Therefore, accurate use amount of bile salts and sodium deoxycholate in a culture medium is guided, and performance stability of a culture medium in which bile salts or sodium deoxycholate needs to be added is guaranteed.

Description

Technical field [0001] The invention relates to a method for determining the bacteriostatic effect of a natural bacteriostatic agent in a bacterial culture medium, in particular to a method for determining the bacteriostatic effect of bile salt and sodium deoxycholate. Background technique [0002] The culture medium is the basic reagent for studying the physiological characteristics of bacteria, isolating and identifying the target bacteria. In addition to containing nutrients such as peptone, yeast powder, meat extract powder, carbohydrates and carriers (referring to solid medium), the culture medium also contains It is often necessary to add inhibitors such as antibiotics, inorganic salts, and bile salts to improve the separation efficiency of target bacteria by inhibiting miscellaneous bacteria. [0003] Among these bacteriostatic agents, there is a natural bacteriostatic agent--bile salt that is more special. It can not only inhibit gram-positive bacteria, but also show differ...

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Problems solved by technology

[0003] Among these antibacterial agents, there is a special natural antibacterial agent - bile salt, which not only inhibits Gram-positive bacteria, but also shows different antibacterial effects on different Gram-negative bacteria. The irreplaceable advantage of single-component chemical substances, therefore, has been used until now. At present, more than 50 kinds of conventional culture media use bile salts, such as crystal violet neutral red bile salt agar (VRBA) for isolating Enterobacteriaceae bacteria, and Bile salt agar for isolating Vibrio. Thiosulfate citrate bile salts sucrose agar (TCBS). Secondly, bile salts are different from antibiotics and chemical inhibitors in terms of composition. Bile salts are extracted from animal bile and contain bile acids, combined bile acids and bile Alcohols are multi-component substances. The content of various components not only varies with the species of animals, but also the difference in manufacturing process also leads to a large difference in antibacterial effect. In addition, in order to enhance the antibacterial effect, sometimes the Several bile salts are mixed, such as No. 3 bile salt, which makes its composition more complicated

However, the amount of bile salts usually given in existing formulas including standard methods is a fixed amount (eg: GB4789.4-2010 National Food Safety Standard Food Microbiological Examination Salmonella Examination Appendix A.5, A.6) , which leads to deviations in the performance of the prepared medium, although there are also quality control methods for the performance of the medium (such as: GB4789.28-2010 National Food Safety Standard Food Microbiology Inspection Medium and Reagent Quality Requirements), that is, through Observing the growth of the quality control strains on the culture medium and the inhibition received, but there are obvious problems. Because the culture medium is not only an inhibitory component of bile salts, the observed antibacterial effect cannot accurately reflect the inhibition of bile salts. Antibacterial ability, such as SS agar

There is also a method to evaluate the antibacterial ability of bile salts by measuring the content of cholic acid, but the total cholic acid is composed of several different types of cholic acid, and the ratio of the composition is different. And the determination method is loaded down with trivial details time-consuming and laborious, therefore, existing method all can't accurately evaluate the bacteriostasis ability of bile salt, sodium deoxycholate, just can't correctly guide different kinds, different batches of bile salt, sodium deoxycholate product in The most suitable amount in the culture medium

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