Van Langendonck N, Bottreau E, Bailly S, Tabouret M, Marly J, Pardon P, Velge P
Institut National de la Recherche Agronomique de tours, Laboratoire de Pathologie Infectieuse et Immunologie, Nouzilly, France.
J Appl Microbiol. 1998 Aug;85(2):337-46. doi: 10.1046/j.1365-2672.1998.00515.x.
Within the group of Listeria sp., only L. monocytogenes is pathogenic for humans and numerous studies of L. monocytogenes strains have described non-virulent isolates. In this study, the potential value of two tissue culture assays (TCA) was analysed to ascertain the virulence properties of L. monocytogenes strains, initially typed for virulence using the immunocompromised mouse model (ICMM). The first assay assessed both the penetration into, and multiplication within, Caco-2 cells (PM assay): the second was a plaque-forming assay (PF assay). All the clinical isolates (nine strains) were virulent in both TCA. Conversely, all the non-pathogenic species (seven strains) were non-virulent in PM and PF assays. Compared with the virulence obtained in the ICMM with 29 Listeria strains, including 12 non-virulent L. monocytogenes strains, the sensitivity of both TCA was equal to1. Specificity was 0.89 and 0.84 for the PF and PM assays, respectively. However, a study of strains exhibiting virulence differences in three other in vivo virulence models showed that ICMM only detected highly virulent strains. The specificity of the PF test could, therefore, be higher, and close to that obtained by the enumeration of viable bacteria in the spleen of mice infected by subcutaneous injection in the footpad and by intravenous injection. Taken together, this study confirms the existence of low-virulence L. monocytogenes strains and shows that the virulence status of some non-clinical L. monocytogenes isolates depends on the virulence models used. The data suggest that the PF assay could be used as a primary test to evaluate the virulence of Listeria strains in order to reduce the cost of testing all strains in vivo.
在李斯特菌属中，只有单核细胞增生李斯特菌对人类具有致病性，并且对单核细胞增生李斯特菌菌株的大量研究已经描述了无毒力的分离株。在本研究中，分析了两种组织培养试验（TCA）的潜在价值，以确定单核细胞增生李斯特菌菌株的毒力特性，这些菌株最初使用免疫受损小鼠模型（ICMM）进行毒力分型。第一种试验评估了在Caco-2细胞中的侵入和增殖情况（PM试验）；第二种是噬斑形成试验（PF试验）。所有临床分离株（9株）在两种TCA中均具有毒力。相反，所有非致病菌种（7株）在PM和PF试验中均无毒力。与用29株李斯特菌（包括12株无毒力的单核细胞增生李斯特菌菌株）在ICMM中获得的毒力相比，两种TCA的敏感性均为1。PF试验和PM试验的特异性分别为0.89和0.84。然而，一项对在其他三种体内毒力模型中表现出毒力差异的菌株的研究表明，ICMM只能检测到高毒力菌株。因此，PF试验的特异性可能更高，接近通过在脚垫皮下注射和静脉注射感染的小鼠脾脏中活菌计数获得的特异性。综上所述，本研究证实了低毒力单核细胞增生李斯特菌菌株的存在，并表明一些非临床单核细胞增生李斯特菌分离株的毒力状态取决于所使用的毒力模型。数据表明，PF试验可作为评估李斯特菌菌株毒力的初步试验，以降低在体内检测所有菌株的成本。
