Nowrouzian Forough, Hesselmar Bill, Saalman Robert, Strannegard Inga-Lisa, Aberg Nils, Wold Agnes E, Adlerberth Ingegerd
Department of Clinical Bacteriology, Sahlgrenska University Hospital, Göteborg, Sweden.
Pediatr Res. 2003 Jul;54(1):8-14. doi: 10.1203/01.PDR.0000069843.20655.EE. Epub 2003 Apr 16.
Colonization by Escherichia. coli in infants might have decreased in the last decades, owing to changes in hospital routines and family lifestyle. In this study, the E. coli flora was characterized in 70 healthy Swedish infants followed for the first year of life. E. coli was isolated from rectal swabs obtained at 3 d of age and quantified in fecal samples collected at 1, 2, 4, and 8 wk of age and at 6 and 12 mo of age. Strains were typed using random amplified polymorphic DNA, and their virulence factor genes were identified by multiplex PCR. Colonization by E. coli occurred late; only 61% of the infants were positive by 2 mo of age. The turnover of individual strains in the microflora was slow (1.5 strains per infant during 6 mo, 2.1 during 1 y). Environmental factors, such as siblings, pets, or feeding mode, did not influence colonization kinetics or strain turnover rate. Genes encoding type 1 fimbriae, P fimbriae, and hemolysin were significantly more common in E. coli strains persisting for at least 3 wk in the microflora than in transient strains. The P-fimbrial class III adhesin gene was more common in E. coli from children who had a cat in their homes than in E. coli from children without pets (p = 0.01); this adhesin type is common in E. coli from cats. The late colonization and low E. coli strain turnover rate suggest limited exposure of Swedish infants to E. coli. Our results confirm that P fimbriae and other virulence factors facilitate persistence of E. coli in the human colonic microflora.
由于医院常规和家庭生活方式的改变，过去几十年里婴儿被大肠杆菌定植的情况可能有所减少。在本研究中，对70名瑞典健康婴儿在出生后第一年进行随访，对其大肠杆菌菌群进行了特征分析。在3日龄时采集直肠拭子分离大肠杆菌，并对1、2、4和8周龄以及6和12月龄时采集的粪便样本中的大肠杆菌进行定量。使用随机扩增多态性DNA对菌株进行分型，并通过多重PCR鉴定其毒力因子基因。大肠杆菌的定植发生较晚；到2月龄时，只有61%的婴儿呈阳性。微生物群落中单个菌株的更替缓慢（6个月内每个婴儿1.5个菌株，1年内2.1个菌株）。环境因素，如兄弟姐妹、宠物或喂养方式，不影响定植动力学或菌株更替率。在微生物群落中持续至少3周的大肠杆菌菌株中，编码1型菌毛、P菌毛和溶血素的基因明显比短暂菌株中更常见。在家中有猫的儿童的大肠杆菌中，P菌毛III类粘附素基因比没有宠物的儿童的大肠杆菌中更常见（p = 0.01）；这种粘附素类型在猫的大肠杆菌中很常见。定植较晚和大肠杆菌菌株更替率较低表明瑞典婴儿接触大肠杆菌的机会有限。我们的结果证实，P菌毛和其他毒力因子有助于大肠杆菌在人类结肠微生物群落中持续存在。
