Our aim was to examine the humoral immune response against Streptococcus gallolyticus subspecies gallolyticus antigens in individuals subjected to a routine colonoscopy in which colon adenomatous polyps were present or not. Serum samples from 133 individuals with adenomatous polyps and serum samples from 53 individuals with a normal colonoscopy were included. Western blot was performed in all subjects using a whole cell antigen from S. gallolyticus ATCC 9809, and rabbit antisera against the whole cell bacteria was prepared as a control. By analyzing the immune profile of the rabbit-immunized sera by Western-blot, at least 22 proteins were identified as immunogenic in S. gallolyticus. When we evaluated sera from human subjects, two proteins of approximately 30 and 22 kDa were most prominent. Based on this 2-protein band pattern, Western-blot profiles from human subjects were compared. The detection of a protein band of 22 kDa was associated with the presence of adenomatous polyps in colon [odds ratios (OR) 7.98, 95% confidence intervals (CI): 3.54-17.93], p < 0.001. When the presence of the 30 kDa protein alone or both the 22 and 30 kDa proteins were analyzed, the OR increased to 22.37 (95% CI: 3.77-131.64), p < 0.001. The specificity was 84.9 for the presence of the 22 kDa protein, and 98.1 for the presence of the 30 kDa protein alone or both 22 and 30 kDa bands. Serum from individuals with adenomatous polyps recognized two proteins from S. gallolyticus. This result confirmed the possible association of S. gallolyticus with adenomatous polyps in the colon.
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