Rojas Tomás, Vásquez Ysvette, Reyes Doris, Martínez Carlos, Medina Luís
Unidad de Microbiología Ambiental, Departamento de Microbiología, Facultad de Ciencias de la Salud, Universidad de Carabobo, Venezuela.
Arch Latinoam Nutr. 2006 Sep;56(3):257-64.
The utility of immunomagnetic separation (IMS) for the recovery of Escherichia coli O157:H7 in milk creams was evaluated. The efficiency of different pre-enrichments broths previous to ISM was determined and different agars were analyzed (differential and/or selective) for plating of the inmunobeads. Portions of 25 g from milk creams were inoculated with pathogen low levels (50, 10 and 1 cell/g) and then, were enriched in buffered peptone water with vancomycin (BPW-V), buffered peptone water with vancomycin and cefixime (BPW-VC) and triptone soya broth with vancomycin, cefixime and tellurite (TSB-VCT) being incubated 35 degrees C/18 hours. Then, IMS was applied and immunobeads were plated onto sorbitol MacConkey agar (SMA), sorbitol MacConkey agar with cefixime and tellurite (SMA-CT) and chromogenic agar with tellurite and cefixime (CRGA-TC). It was observed significant differences (p < 0.05) in the recovery percentages according to the pre-enrichment broth used, being obtained the biggest recovery rates with the use of TSB-VCT for the three inocula levels. The recovery rates did not vary significantly (p < 0.05) among the utilized agars, while the number of inoculated cells impacts the recovery percentages, being bigger as it increases the inocula. In conclusion, IMS is a sensitive method for the recovery of Escherichia coli O157:H7 in milk creams, recommending for isolation of this pathogen, the enrichment in TSB-VCT, application of IMS, and plating of immunobeads onto nonselective agar (SMA) and selective agar (SMA-TC or CRGA-TC).
评估了免疫磁珠分离（IMS）法用于从乳膏中回收大肠杆菌O157:H7的效用。确定了在免疫磁珠分离之前不同预增菌肉汤的效率，并分析了用于免疫磁珠平板培养的不同琼脂（鉴别性和/或选择性）。取25 g乳膏部分接种低水平病原体（50、10和1个细胞/g），然后在含万古霉素的缓冲蛋白胨水（BPW-V）、含万古霉素和头孢克肟的缓冲蛋白胨水（BPW-VC）以及含万古霉素、头孢克肟和亚碲酸盐的胰蛋白胨大豆肉汤（TSB-VCT）中增菌，在35℃下培养18小时。然后应用IMS法，并将免疫磁珠接种到山梨醇麦康凯琼脂（SMA）、含头孢克肟和亚碲酸盐的山梨醇麦康凯琼脂（SMA-CT）以及含亚碲酸盐和头孢克肟的显色琼脂（CRGA-TC）上。根据所用的预增菌肉汤，观察到回收率存在显著差异（p<0.05），对于三种接种水平，使用TSB-VCT时获得的回收率最高。在所使用的琼脂之间，回收率没有显著差异（p<0.05），而接种细胞数会影响回收率，随着接种量增加回收率也会更高。总之，IMS是一种用于从乳膏中回收大肠杆菌O157:H7的灵敏方法，推荐用于分离该病原体的方法为：在TSB-VCT中增菌、应用IMS法以及将免疫磁珠接种到非选择性琼脂（SMA）和选择性琼脂（SMA-TC或CRGA-TC）上。
