Teramura H, Sota K, Iwasaki M, Ogihara H
Yokohama Research Center, JNC Corporation, Yokohama, Japan.
Department of Food Bioscience and Biotechnology, College of Bioresource Science, Nihon University, Fujisawa, Japan.
Lett Appl Microbiol. 2017 Jul;65(1):57-65. doi: 10.1111/lam.12744. Epub 2017 May 30.
Sanita-kun™ CC (coliform count) and EC (Escherichia coli/coliform count), sheet quantitative culture systems which can avoid chromogenic interference by lactase in food, were evaluated in comparison with conventional methods for these bacteria. Based on the results of inclusivity and exclusivity studies using 77 micro-organisms, sensitivity and specificity of both Sanita-kun™ met the criteria for ISO 16140. Both media were compared with deoxycholate agar, violet red bile agar, Merck Chromocult™ coliform agar (CCA), 3M Petrifilm™ CC and EC (PEC) and 3-tube MPN, as reference methods, in 100 naturally contaminated food samples. The correlation coefficients of both Sanita-kun™ for coliform detection were more than 0·95 for all comparisons. For E. coli detection, Sanita-kun™ EC was compared with CCA, PEC and MPN in 100 artificially contaminated food samples. The correlation coefficients for E. coli detection of Sanita-kun™ EC were more than 0·95 for all comparisons. There were no significant differences in all comparisons when conducting a one-way analysis of variance (anova). Both Sanita-kun™ significantly inhibited colour interference by lactase when inhibition of enzymatic staining was assessed using 40 natural cheese samples spiked with coliform. Our results demonstrated Sanita-kun™ CC and EC are suitable alternatives for the enumeration of coliforms and E. coli/coliforms, respectively, in a variety of foods, and specifically in fermented foods.
Current chromogenic media for coliforms and Escherichia coli/coliforms have enzymatic coloration due to breaking down of chromogenic substrates by food lactase. The novel sheet culture media which have film layer to avoid coloration by food lactase have been developed for enumeration of coliforms and E. coli/coliforms respectively. In this study, we demonstrated these media had comparable performance with reference methods and less interference by food lactase. These media have a possibility not only to be useful alternatives but also to contribute for accurate enumeration of these bacteria in a variety of foods, and specifically in fermented foods.
对Sanita-kun™ CC（大肠菌群计数）和EC（大肠杆菌/大肠菌群计数）这两种可避免食品中乳糖酶产生显色干扰的片状定量培养系统，与检测这些细菌的传统方法进行了比较评估。基于使用77种微生物进行的包容性和排他性研究结果，Sanita-kun™这两种产品的灵敏度和特异性均符合ISO 16140标准。在100份天然污染食品样本中，将这两种培养基与脱氧胆酸盐琼脂、紫红胆盐琼脂、默克Chromocult™大肠菌群琼脂（CCA）、3M Petrifilm™ CC和EC（PEC）以及3管MPN作为参考方法进行了比较。在所有比较中，Sanita-kun™两种产品检测大肠菌群的相关系数均大于0.95。对于大肠杆菌检测，在100份人工污染食品样本中，将Sanita-kun™ EC与CCA、PEC和MPN进行了比较。在所有比较中，Sanita-kun™ EC检测大肠杆菌的相关系数均大于0.95。进行单因素方差分析（anova）时，所有比较均无显著差异。当使用40份添加了大肠菌群的天然奶酪样本评估酶促染色抑制情况时，Sanita-kun™两种产品均显著抑制了乳糖酶的颜色干扰。我们的结果表明，Sanita-kun™ CC和EC分别是在各种食品，特别是发酵食品中计数大肠菌群和大肠杆菌/大肠菌群的合适替代方法。
当前用于大肠菌群和大肠杆菌/大肠菌群的显色培养基由于食品乳糖酶分解显色底物而产生酶促显色。已开发出具有薄膜层以避免食品乳糖酶显色的新型片状培养基，分别用于计数大肠菌群和大肠杆菌/大肠菌群。在本研究中，我们证明这些培养基与参考方法具有可比的性能，且受食品乳糖酶的干扰较小。这些培养基不仅有可能成为有用的替代方法，而且有助于在各种食品，特别是发酵食品中准确计数这些细菌。
