Momose Yoshika, Hirayama Kazuhiro, Itoh Kikuji
Laboratory of Veterinary Public Health, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
Antonie Van Leeuwenhoek. 2008 Aug;94(2):165-71. doi: 10.1007/s10482-008-9222-6. Epub 2008 Feb 5.
Previously, we produced two groups of gnotobiotic mice, GB-3 and GB-4, which showed different responses to Escherichia coli O157:H7 challenge. E. coli O157:H7 was eliminated from GB-3, whereas GB-4 mice became carriers. It has been reported that the lag time of E. coli O157:H7 growth in 50% GB-3 caecal suspension was extended when compared to GB-4 caecal suspension. In this study, competition for nutrients between intestinal microbiota of GB-3 and GB-4 mice and E. coli O157:H7 was examined. Amino acid concentrations in the caecal contents of GB-3 and GB-4 differed, especially the concentration of proline. The supplementation of proline into GB-3 caecal suspension decreased the lag time of E. coli O157:H7 growth in vitro. When E. coli O157:H7 was cultured with each of the strains used to produce GB-3 mice in vitro, 2 strains of E. coli (proline consumers) out of 5 enterobacteriaceae strains strongly suppressed E. coli O157:H7 growth and the suppression was attenuated by the addition of proline into the medium. These results indicate that competition for proline with indigenous E. coli affected the growth of E. coli O157:H7 in vivo and may contribute to E. coli O157:H7 elimination from the intestine.
此前，我们培育了两组无菌小鼠，GB - 3和GB - 4，它们对大肠杆菌O157:H7攻击表现出不同的反应。GB - 3小鼠体内的大肠杆菌O157:H7被清除，而GB - 4小鼠则成为携带者。据报道，与GB - 4盲肠悬液相比，大肠杆菌O157:H7在50% GB - 3盲肠悬液中的生长延迟时间延长。在本研究中，检测了GB - 3和GB - 4小鼠肠道微生物群与大肠杆菌O157:H7之间对营养物质的竞争。GB - 3和GB - 4盲肠内容物中的氨基酸浓度不同，尤其是脯氨酸的浓度。向GB - 3盲肠悬液中补充脯氨酸可缩短大肠杆菌O157:H7在体外的生长延迟时间。当大肠杆菌O157:H7与用于培育GB - 3小鼠的每种菌株在体外共同培养时，5株肠杆菌科菌株中的2株大肠杆菌（脯氨酸消耗菌）强烈抑制大肠杆菌O157:H7的生长，并且通过向培养基中添加脯氨酸可减弱这种抑制作用。这些结果表明，与本土大肠杆菌对脯氨酸的竞争影响了大肠杆菌O157:H7在体内的生长，并且可能有助于从肠道中清除大肠杆菌O157:H7。
