Earnshaw A M, Lawrence L M
Department of Food Science, Queen's University of Belfast, UK.
J Appl Microbiol. 1998 Apr;84(4):642-8. doi: 10.1046/j.1365-2672.1998.00395.x.
The European Suspension Test was used to assess the relative resistance of 19 individual Listeria monocytogenes genotypes, isolated from the poultry processing environment, to three commercially used disinfectants employed in the plant at the time of their isolation. To establish the relative resistance between the strains, the concentration of each disinfectant was reduced until inter-strain variation became apparent. For Darasan 214 and 7058, variation was detected at 0.1% and 0.5% v/v, respectively, while Daraclean 7361 had to be reduced to only 2.5% v/v. At these concentrations, the mean microbiocidal effect (ME) of each disinfectant ranged between 4.3 and 3.1 log10 reduction in cfu ml-1. Significant differences between the strains were obtained with respect to their resistance to the disinfectants employed (P < 0.01), but the overall log10 reduction for genotypes 'A1' and 'A2', which were found to persist in the poultry processing environment, were not found to be significantly different from the genotypes which had been isolated on a more sporadic basis (P > 0.05). The L. monocytogenes strains fell into four groups with respect to incidence and size of plasmids isolated. The first group contained strains which carried two plasmids (5 and 40 MDa) and the other three (groups 2, 3 and 4) comprised strains which carried a single plasmid (14, 47 and 52 MDa, respectively). There was no correlation between persistent and sporadic strains with respect to incidence and size of plasmids isolated. Moreover, the strains which carried no plasmids were found to be as resistant to the disinfectants as those which did carry plasmids, suggesting that the plasmids isolated did not confer resistance of L. monocytogenes planktonic cells to the disinfectants tested. Therefore, it is unlikely that the strains which had been found to persist in the poultry processing environment did so by means of plasmid-mediated resistance to the commercial disinfectants used.
欧洲悬液试验用于评估从家禽加工环境中分离出的19种单核细胞增生李斯特菌基因型对分离时工厂使用的三种商用消毒剂的相对抗性。为确定菌株之间的相对抗性，降低每种消毒剂的浓度，直至菌株间差异明显。对于达拉散214和7058，分别在0.1%和0.5%（v/v）时检测到差异，而达拉净7361只需降至2.5%（v/v）。在这些浓度下，每种消毒剂的平均杀菌效果（ME）在cfu ml-1降低4.3至3.1 log10之间。就所使用的消毒剂抗性而言，菌株间存在显著差异（P < 0.01），但在家禽加工环境中持续存在的“A1”和“A2”基因型的总体log10降低与偶尔分离出的基因型相比，未发现显著差异（P > 0.05）。单核细胞增生李斯特菌菌株根据分离出的质粒的发生率和大小分为四组。第一组包含携带两个质粒（5和40 MDa）的菌株，其他三组（第2、3和4组）包含携带单个质粒（分别为14、47和52 MDa）的菌株。在分离出的质粒的发生率和大小方面，持续存在的菌株和偶尔出现的菌株之间没有相关性。此外，未携带质粒的菌株对消毒剂的抗性与携带质粒的菌株相同，这表明分离出的质粒并未赋予单核细胞增生李斯特菌浮游细胞对测试消毒剂的抗性。因此，在家禽加工环境中发现持续存在的菌株不太可能是通过对所用商用消毒剂的质粒介导抗性而如此。
