科研之友
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摘要
A novel procedure on vancomycin, -glucosidase activity, cephalothin and sucrose for isolation of Cronobacter spp. from powdered infant formula (PIF) was developed. Meanwhile, a comparison between the new procedure, Druggan-Forsythe-Iversen (DFI) and modified lauryl sulfate tryptose (mLST) procedure was also carried out. The recovery rate is higher by the new procedure than those by DFI and mLST procedures. In combination with API-20e test, 9, 9 and 8 PIF samples were found to be contaminated by Cronobacter spp. by the new procedure, DFI and mLST procedure, respectively. The sensitivity of 100, 87.5 and 87.5% and the specificity of 88.8, 77.7 and 87.5% were observed by the new procedure, DFI and mLST method, respectively. The new procedure, DFI and mLST procedure also gave the false-positive/false-negative rates of 11.1/0.0, 22.2/12.5 and 12.5/12.5%. The data presented here indicated that the new protocol could be widely used for monitoring Cronobacter in PIF and a combination of traditional methods and molecular assays is strongly recommended. Practical ApplicationsThe current culture-based procedures for isolation of Cronobacter should be improved for assuring microbial safety of PIF. In this study, a selective and efficient procedure for isolation of Cronobacter was developed. The recovery rate was higher from artificially contaminated PIF by the new procedure than those by DFI and mLST procedures. In addition, the new procedure was found to be sensitive and specific for isolation of Cronobacter from commercial PIF.
