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目的比较两种沙门菌选择性培养基HE和CAS在食物样本检测中的敏感性、准确性和时效性。方法观察典型沙门菌和非沙门菌在两种选择培养基上的生长状况和菌落形态。通过人工染菌实验,比较两种选择性培养基分离沙门菌的检测效果。采集16份市售整鸡样本,进一步比较两种培养基沙门菌的阳性检出率。结果沙门菌在HE平板上为绿色菌落,大多有黑心;在CAS平板上为紫色菌落。含菌量为10 CFU/25 g鸡肉样本,经SC增菌液增菌培养8 h,可用CAS检出沙门菌;而采用HE则需增菌18 h才可检出。16份整鸡样本,增菌8、12和18 h,采用CAS的阳性检出率分别为43.75%、31.25%和37.5%,相应时间下采用HE的阳性检出率分别为18.75%、25%和18.75%。8份新鲜整鸡样本,检出4份阳性;8份冷冻整鸡样本,检出3份阳性。结论 CAS选择性平板可抑制大多杂菌生长,沙门菌在其上菌落形态较易鉴别。CAS分离沙门菌的检出时限和检测灵敏度都明显优于HE,建议在食物样本检测沙门菌时应首选CAS。
Objective To compare the sensitivity, accuracy and timeliness of two Salmonella selective medium HE and CAS in the detection of food samples. Methods The growth and colony morphology of typical Salmonella and non-Salmonella on two selective media were observed. Artificial dye-in-place experiments were performed to compare the detection results of Salmonella isolated from two selective media. Sixteen commercial whole chicken samples were collected to further compare the positive detection rates of Salmonella in both culture media. Results Salmonella were green colonies on HE plates, mostly with black heart; purple colonies on CAS plates. Salmonella could be detected by CAS when the amount of bacteria in 10 CFU / 25 g chicken samples was increased by SC enrichment broth for 8 h. However, the detection of Salmonella by HE was required for 18 h. The positive detection rates of CAS were 43.75%, 31.25% and 37.5% in 16 whole chicken samples at 8, 12 and 18 h respectively. The positive detection rates of HE with the corresponding time were 18.75%, 25% And 18.75%. 8 fresh whole chicken samples, 4 were positive; 8 frozen whole chicken samples, 3 were positive. Conclusion CAS selective plate can inhibit the growth of most bacteria, Salmonella in its colony morphology easier to identify. The detection limit and detection sensitivity of Salmonella isolates from CAS were significantly better than that of HE, suggesting that CAS should be the first choice when detecting salmonella in food samples.