Pietzsch O, Kretschmer F J, Bulling E
Zentralbl Bakteriol Orig A. 1975 Jul;232(2-3):232-46.
Eight different methods of salmonella enrichment were compared in two series of experiments involving 100 samples of whole-egg powder and 80 samples of frozen whole liquid egg, respectively. 66 out of a total of 100 samples of whole-egg powder had been artificially infected with varying numbers of S. typhi-murium; 60 out of 80 samples of frozen whole liquid egg were found to be naturally infected with various salmonella species. 3 of the 8 methods (Table 1) were compared within an international collaborative study with 14 laboratories in 11 countries participating. A reduction of the pre-enrichment period from 18 to 6 hours and of volumes used in pre-enrichment and selective enrichment from 10 and 100 ml, respectively to 1 and 10 ml, respectively were found to have adverse influence upon the result of isolations, in particular in the case of weakly infected samples. In contrast, extended incubation over 48 hours as well as preparation of two sub-cultures on solid selective media following incubation of enrichment cultures over 18-24 hours and 42-48 hours, respectively always resulted in a certain increase of salmonella yield which, however, exhibited gradual differences for the individual methods examined. Preparation of a 2nd sub-culture meant, in particular, a decisive improvement of the result of isolations from artificially infected samples if selenite-cystine enrichment volumes were 10 and 100 ml, respectively. The best results could be obtained by means of the following methods of enrichment: Pre-enrichment of material in buffered peptone water at 37 degrees C over 18 hours; pipetting of 10 ml inoculated and incubated pre-enriched material into 100 ml selenite-cystine or tetrathionate enrichment medium according to MULLER-KAUFFMANN; onward incubation of the enrichment culture at 43 degrees C over 48 hours; and preparation of sub-cultures on solid selective media after 24 and 48 hours. The method using tetrathionate enrichment medium was found to be most expensive, results, however, were the most consistent ones.
在两个系列的实验中，分别对100份全蛋粉样品和80份冷冻全蛋液样品，比较了八种不同的沙门氏菌增菌方法。在总共100份全蛋粉样品中，有66份被人工接种了不同数量的鼠伤寒沙门氏菌；在80份冷冻全蛋液样品中，有60份被发现自然感染了各种沙门氏菌。在一项国际合作研究中，对8种方法中的3种（表1）进行了比较，有11个国家的14个实验室参与。结果发现，将预增菌时间从18小时缩短至6小时，以及将预增菌和选择性增菌所用的体积分别从10毫升和100毫升分别减少至1毫升和10毫升，会对分离结果产生不利影响，特别是对于感染程度较弱的样品。相比之下，延长培养48小时，以及在富集培养物分别培养18 - 24小时和42 - 48小时后，在固体选择性培养基上制备两代继代培养物，总是会使沙门氏菌的回收率有一定提高，不过，对于所检测的各个方法，提高的幅度存在逐渐的差异。制备第二代继代培养物尤其意味着，如果亚硒酸盐 - 胱氨酸增菌体积分别为10毫升和100毫升，那么从人工感染样品中分离的结果会有决定性的改善。通过以下增菌方法可获得最佳结果：将材料在37℃的缓冲蛋白胨水中预增菌18小时；将10毫升接种并培养后的预增菌材料移液至100毫升根据MULLER - KAUFFMANN方法配制的亚硒酸盐 - 胱氨酸或四硫磺酸盐增菌培养基中；将富集培养物在43℃下继续培养48小时；并在24小时和48小时后在固体选择性培养基上制备继代培养物。发现使用四硫磺酸盐增菌培养基的方法成本最高，不过结果最为稳定。
