Streptococcus bovis/gallolyticus Induce the Development of Colorectal Cancer

The role, of microbial agents and the infection of the intestinal mucosa in the carcinogenesis, or the development of colorectal cancer (CRC) is one of the hot topics in the field of CRC where much research has been done. However, this topic has long been underestimated by most of the related books. This chapter is intended to cover the relationship of CRC development with bacteria implicated in the development of CRC such as S. bovis, S. gallolyticus, S. equines, S. infantarius, E .coli, C. difficile...etc. However, S. gallolyticus and S. bovis will be discussed thoroughly in this chapter as they are considered the prototype for intestinal microorganisms related to CRC and colorectal premalignant lesions. Studying CRC association with infection of intestinal mucosa is not complete without studying the underlying mechanisms. There is compelling evidence that CRC is largely affected by the status of intestinal bioflora. CRC has been found to be affected by certain microbial agents that have particular characteristics capable of inducing dysplastic changes in intestinal mucosa. However, the underlying mechanisms of the association of implicated infective agents with CRC development are yet not clear. In addition, the role of oncogenic factors, cell growth factors, and pro-inflammatory cytokines in the association of bacterial infection in intestinal mucosa with CRC has not yet been clarified well. Therefore, the current chapter attempts to scrutinize the nature and the underlying mechanisms of the association of infective agents represented by S. bovis/gallolyticus with CRC. Nevertheless, the association of S. bovis/gallolyticus with CRC is still under controversy regarding whether the bacterial infection of intestine, along with associated bacteremia/endocarditis, is a consequence or the etiological factor of CRC. Hence, this chapter also attempts to explore the facts available in the field to assess which scenario is more favorable for the association of S. bovis/gallolyticus with CRC namely, the consequence or the etiology scenario. One of the bacterial agents that have been most associated with cancer is Streptococcus bovis (S. bovis). S. bovis has been shown to be important in human health because 25 to 80% of patients with S. bovis bacteremia had also colorectal tumor, and the incidence of association of colonic neoplasia with S. bovis endocarditis was shown to be 18 to 62% (Gupta et al., 2009; Kok et al., 2007; Leport et al., 1987; Malkin et al., 2008; Reynolds et al., 1983; Wilson et al.,