Nowrouzian Forough L, Friman Vanda, Adlerberth Ingegerd, Wold Agnes E
Department of Clinical Bacteriology, Guldhedsgatan 10, S-413 46 Göteborg, Sweden.
Infect Immun. 2007 Feb;75(2):932-40. doi: 10.1128/IAI.00736-06. Epub 2006 Nov 13.
The mannose-specific adhesin of type 1 fimbriae is the most common adhesin in Escherichia coli. One receptor for this adhesin is the carbohydrate chains of secretory immunoglobulin A (S-IgA), and intestinal E. coli from IgA-deficient individuals has a reduced capacity to adhere to mannose-containing receptors. Here, we investigated the expression of the mannose-specific adhesin and its capacity to switch to the fimbriated phenotype in colonic resident and transient E. coli strains isolated from control (n = 16) and IgA-deficient (n = 17) persons. Resident E. coli strains from IgA-deficient individuals displayed weaker mannose-specific adherence to colonic cells than resident strains from control individuals (21 versus 44 bacteria/cell, P = 0.0009) due to three mechanisms: a lower carriage rate of the fimH gene (90% versus 97%, not significant), more frequent failure to switch on the fim genes (30% versus 6%, P = 0.02), and the reduced adhesive potential of fimH(+) isolates capable of phase switch (26 versus 46 bacteria/cell, P = 0.02). On the other hand, resident strains from IgA-deficient individuals displayed stronger mannose-resistant adherence than resident strains from control individuals (P = 0.04) and transient strains from IgA-deficient individuals (P = 0.01). The presence of S-IgA appears to favor the establishment of E. coli clones which readily express mannose-specific adhesins in the bowel microbiota.
1型菌毛的甘露糖特异性黏附素是大肠杆菌中最常见的黏附素。这种黏附素的一种受体是分泌型免疫球蛋白A（S-IgA）的碳水化合物链，来自IgA缺乏个体的肠道大肠杆菌对含甘露糖受体的黏附能力降低。在此，我们研究了从对照者（n = 16）和IgA缺乏者（n = 17）分离出的结肠常驻和短暂性大肠杆菌菌株中甘露糖特异性黏附素的表达及其转换为菌毛表型的能力。来自IgA缺乏个体的常驻大肠杆菌菌株对结肠细胞的甘露糖特异性黏附比来自对照个体的常驻菌株弱（分别为21个细菌/细胞和44个细菌/细胞，P = 0.0009），原因有三种：fimH基因的携带率较低（90%对97%，无显著性差异），fim基因开启失败更频繁（30%对6%，P = 0.02），以及能够进行相转换的fimH(+)分离株的黏附潜力降低（26个细菌/细胞对46个细菌/细胞，P = 0.02）。另一方面，来自IgA缺乏个体的常驻菌株比来自对照个体的常驻菌株（P = 0.04）和来自IgA缺乏个体的短暂性菌株（P = 0.01）表现出更强的甘露糖抗性黏附。S-IgA的存在似乎有利于在肠道微生物群中建立易于表达甘露糖特异性黏附素的大肠杆菌克隆。
