Bonardi Silvia, Bolzoni Luca, Brindani Franco, Scaltriti Erika, Cavallini Pierugo, Giuseppe Carnovale, Pongolini Stefano
1 Department of Veterinary Science, Unit of Food Inspection, University of Parma , Parma, Italy .
2 Risk Analysis Unit, Sezione di Parma, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia-Romagna , Parma, Italy .
Foodborne Pathog Dis. 2018 Jun;15(6):339-345. doi: 10.1089/fpd.2017.2375. Epub 2018 May 3.
During 2014-2015, 300 pig carcasses before chilling and 85 food contact surfaces (FCSs) at cutting lines were tested for Salmonella in three slaughterhouses (namely A, B, and C) of northern Italy. In slaughterhouses A and B, four carcass sites of 100 cm each (from both the exterior and interior side) were swabbed with a single sponge. In abattoir C, four 100 cm sites of the exterior and the interior sides were swabbed with two independent sponges. The population average prevalence of Salmonella-positive carcasses (which takes into account the structure of the study design, with multiple samples collected in a single day) in slaughterhouses A and B was 12.3%, while in slaughterhouse C it was 11.2%. Presence of Salmonella on exterior and interior sides of carcasses showed a low level of concordance (only 3/12 of the contaminated carcasses were positive on both sides). No significant difference was found for FCSs contamination in the three slaughterhouses, with a population average prevalence of Salmonella-positive FCSs of 19.9%. In addition, we found that the clustering due to the day of sampling account for more than 36% and 60% of the overall prevalence variation on carcasses and FCSs, respectively. Eight serovars were identified, with Salmonella Derby as the most common type. The counting of Salmonella on carcasses showed large variability. It was low (<0.0075 most probable number [MPN]/cm) in 46.6% of the carcasses and as high as 2.7 MPN/cm in 4.7%. Specifically, we found that counts on carcasses fit with "heavy tailed" distributions (lognormal and Weibull with a small shape parameter), suggesting not negligible probability of episodes of high Salmonella contamination. The mean values of contamination obtained with the two distributions ranged from 0.235 to 0.435 MPN/cm.
2014年至2015年期间，在意大利北部的三家屠宰场（即A、B和C）对300头屠宰前的猪胴体以及切割线上的85个食品接触面（FCS）进行了沙门氏菌检测。在屠宰场A和B，用一块海绵对每个100厘米的四个胴体部位（从外侧和内侧）进行擦拭取样。在屠宰场C，用两块独立的海绵对外侧和内侧的四个100厘米部位进行擦拭取样。屠宰场A和B中沙门氏菌阳性胴体的总体平均患病率（考虑到研究设计结构，在同一天采集多个样本）为12.3%，而在屠宰场C中为11.2%。胴体外侧和内侧沙门氏菌的存在显示出较低的一致性水平（只有3/12受污染的胴体两侧均呈阳性）。三家屠宰场的食品接触面污染情况未发现显著差异，沙门氏菌阳性食品接触面的总体平均患病率为19.9%。此外，我们发现，由于采样日导致的聚集分别占胴体和食品接触面上总体患病率变化的36%以上和60%以上。鉴定出了8种血清型，其中德比沙门氏菌是最常见的类型。胴体上沙门氏菌的计数显示出很大的变异性。46.6%的胴体计数较低（<0.0075最可能数[MPN]/厘米），4.7%的胴体计数高达2.7 MPN/厘米。具体而言，我们发现胴体上的计数符合“重尾”分布（对数正态分布和形状参数较小的威布尔分布），这表明沙门氏菌高污染事件的概率不可忽略。两种分布获得的污染平均值范围为0.235至0.435 MPN/厘米。
