Little progress has been made in decreasing the incidence rate of salmonellosis in the US over the past decade. Mitigating the contribution of contaminated raw meat to the salmonellosis incidence rate requires rapid methods for quantifying Salmonella, so that highly contaminated products can be removed before entering the food chain. Here we evaluated the use of Time-to-Positivity (TTP) as a rapid, semi-quantitative approach for estimating Salmonella contamination levels in ground beef. Growth rates of 14 Salmonella strains (inoculated at log 1 to −2 CFU/g) were characterized in lean ground beef mTSB enrichments and time-to-detection was determined using culture and molecular detection methods. Enrichments were sampled at five timepoints and results were used to construct a prediction model of estimated contamination level by TTP (superscript indicates time in hours) defined as TTP⁴: $\ge$5 CFU/g; TTP⁶: $\le$5, $\ge$1 CFU/g; TTP⁸: $\le$1, $\ge$0.01 CFU/g; with samples negative at 8 h estimated $\le$0.01 CFU/g. Model performance measures showed high sensitivity (100%) and specificity (83% and 93% for two detection methods) for samples with a TTP⁴, with false negative rates of 0%.

在过去的十年中，在降低沙门氏菌病的发病率方面进展甚微。减轻受污染的生肉对沙门氏菌病发病率的影响，需要快速定量沙门氏菌的方法，以便可以在进入食物链之前去除高污染的产品。在这里，我们评估了正定时间（TTP）作为一种快速，半定量方法来估算碎牛肉中沙门氏菌污染水平的方法。14沙门氏菌的增长率在瘦肉牛mTSB富集中鉴定了菌株（以log 1到-2 CFU / g接种），并使用培养和分子检测方法确定了检测时间。在五个时间点对富集进行采样，结果用于构建通过TTP定义为TTP ⁴的估计污染水平的预测模型（上标表示以小时为单位的时间）：$\ge$5 CFU /克；TTP ⁶：$\le$5 $\ge$1 CFU /克；TTP ⁸：$\le$1， $\ge$0.01 CFU /克；估计8 h样品阴性$\le$0.01 CFU /克。模型性能指标显示，对于TTP ⁴样品，假阴性率为0％，显示出高灵敏度（100％）和特异性（两种检测方法分别为83％和93％）。