National Center for Food Safety and Technology, US Food and Drug Administration, 6502 S. Archer Road, Summit-Argo, IL 60501, USA.
Food Microbiol. 2010 Aug;27(5):613-7. doi: 10.1016/j.fm.2010.02.004. Epub 2010 Feb 19.
The effect of additives and post-treatment incubation conditions on the recovery of high pressure and heat-injured (i.e., processed at 620 MPa and 95 and 100 degrees C for 5 min) spores of Clostridium botulinum strains, 62-A (proteolytic type A) and 17-B (nonproteolytic type B) was studied. High pressure and heat-injured spores were inoculated into TPGY (Trypticase-Peptone-Glucose-Yeast extract) anaerobic broth media containing additives (lysozyme, L-alanine, L-aspartic acid, dipicolonic acid, sodium bicarbonate, and sodium lactate) at various concentrations (0-10 microg/ml) individually or in combination. The spore counts of high pressure and heat-injured 62-A and 17-B recovered from TPGY broth containing lysozyme (10 microg/ml) incubated for 4 months versus that recovered from peptone-yeast extract-glucose-starch (PYGS) plating agar containing lysozyme (10 microg/ml) incubated under anaerobic conditions for 5 days were also compared. None of the additives either individually or in combination in TPGY broth improved recovery of injured spore enumeration compared to processed controls without additives. Addition of lysozyme at concentrations of 5 and 10 microg/ml in TPGY broth improved initial recovery of injured spores of 17-B during the first 4 days of incubation but did not result in additional recovery at the end of the 4 month incubation compared to the processed control without lysozyme. Adding lysozyme at a concentration of 10 microg/ml to PYGS plating agar resulted in no effect on the recovery of high pressure and heat-injured 62-A and 17-B spores. The recovery counts of high pressure and heat-injured spores of 62-A and 17-B were lower (i.e., <1.0 log units) with PYGS plating agar compared to the MPN method using TPGY broth as the growth medium.
研究了添加剂和后处理孵育条件对高压热损伤（即在 620 MPa 和 95°C 和 100°C 下处理 5 分钟）的肉毒梭菌 62-A（蛋白水解型 A）和 17-B（非蛋白水解型 B）菌株孢子的回收效果。将高压热损伤孢子接种到 TPGY（胰蛋白酶-蛋白胨-葡萄糖-酵母提取物）厌氧肉汤培养基中，其中含有不同浓度（0-10μg/ml）的添加剂（溶菌酶、L-丙氨酸、L-天冬氨酸、二吡啶酸、碳酸氢钠和乳酸钠）单独或组合使用。将在含有 10μg/ml 溶菌酶的 TPGY 肉汤中孵育 4 个月的高压热损伤 62-A 和 17-B 孢子的计数与在含有 10μg/ml 溶菌酶的胰蛋白酶-酵母提取物-葡萄糖-淀粉（PYGS）平板琼脂中孵育 5 天的计数进行了比较。与不含添加剂的处理对照相比，在 TPGY 肉汤中添加任何一种添加剂或组合都不能提高损伤孢子计数的回收率。在 TPGY 肉汤中添加 5 和 10μg/ml 的溶菌酶可提高 17-B 损伤孢子的初始回收率，在孵育的前 4 天，但与不含溶菌酶的处理对照相比，在 4 个月的孵育结束时并没有额外的回收。在 PYGS 平板琼脂中添加 10μg/ml 的溶菌酶对高压热损伤的 62-A 和 17-B 孢子的回收没有影响。与使用 TPGY 肉汤作为生长培养基的 MPN 方法相比，PYGS 平板琼脂中高压热损伤的 62-A 和 17-B 孢子的回收计数较低（即，<1.0 个对数单位）。
