Licht T R, Krogfelt K A, Cohen P S, Poulsen L K, Urbance J, Molin S
Department of Gastrointestinal Infections, Statens Seruminstitut, Copenhagen S, Denmark.
Infect Immun. 1996 Sep;64(9):3811-7. doi: 10.1128/iai.64.9.3811-3817.1996.
An avirulent, streptomycin-resistant Salmonella typhimurium strain, SL5319, and its lipopolysaccharide (LPS)-deficient mutant strain, SL5325, differ in their ability to colonize the large intestines of streptomycin-treated mice. When fed to mice independently, the strains colonize equally well, but when fed together, the LPS-deficient mutant is outcompeted by the wild-type strain during establishment in the gut (J.J. Nevola, B.A.D. Stocker, D.C. Laux, and P.S. Cohen, Infect. Immun. 50:152-159, 1985). In the present study, the spatial distribution in the intestinal mucosal layer of the two strains was visualized by specific hybridization to bacterial rRNA in histological sections of mouse colon and cecum. The first day after infection, 9.8% of the smooth SL5319 cells observed in mucus were found to be associated with the mouse epithelial cells, but three days after infection, the corresponding fraction of adhering bacteria was reduced to 2.1%. The LPS-deficient S. typhimurium strain was confined to the part of the mucosal layer closest to the colonic lumen and was not observed to adhere to the epithelium either at day 1 or 3 after infection. Quantitative determinations of the distance from the S. typhimurium cells to the epithelial wall confirmed that the average distance for the rough S. typhimurium SL5325 was much larger than for its smooth counterpart, S. typhimurium SL5319. Quantification of the hybridization signal from bacteria isolated from the cecal mucus revealed that the two strains had the same ribosome concentration, indicating that they have the same potential for growth in the intestinal environment. On the basis of these observations, we suggest that the better colonization ability of the strain carrying wild-type LPS is due to the better abilities to penetrate the intestinal mucosal layer and to subsequently bind to the epithelial cells in vivo.
一种无毒的、对链霉素耐药的鼠伤寒沙门氏菌菌株SL5319及其脂多糖（LPS）缺陷型突变菌株SL5325，在定殖于经链霉素处理的小鼠大肠的能力方面存在差异。当单独给小鼠喂食时，这两种菌株的定殖情况相同，但当一起喂食时，在肠道定殖过程中，LPS缺陷型突变株会被野生型菌株淘汰（J.J. Nevola、B.A.D. Stocker、D.C. Laux和P.S. Cohen，《感染与免疫》50:152 - 159，1985年）。在本研究中，通过对小鼠结肠和盲肠组织切片中的细菌rRNA进行特异性杂交，观察了这两种菌株在肠黏膜层中的空间分布。感染后第一天，在黏液中观察到的光滑型SL5319细胞中有9.8%被发现与小鼠上皮细胞相关，但感染三天后，附着细菌的相应比例降至2.1%。LPS缺陷型鼠伤寒沙门氏菌菌株局限于最靠近结肠腔的黏膜层部分，在感染后第1天或第3天都未观察到其黏附于上皮细胞。对鼠伤寒沙门氏菌细胞到上皮壁距离的定量测定证实，粗糙型鼠伤寒沙门氏菌SL5325的平均距离远大于其光滑型对应菌株鼠伤寒沙门氏菌SL5319。对从盲肠黏液中分离出的细菌的杂交信号进行定量分析表明，这两种菌株的核糖体浓度相同，这表明它们在肠道环境中的生长潜力相同。基于这些观察结果，我们认为携带野生型LPS的菌株具有更好的定殖能力，是因为其在体内穿透肠黏膜层并随后与上皮细胞结合的能力更强。
