bovis bacteremia have colorectal tumors and the incidence of association of colonic neoplasia with S. CB-839 price bovis endocarditis has been shown to be 18 to 62% [1–7]. It was shown that 94% of S. bovis bacteremia associated with colorectal cancer was in fact S. bovis biotype I while only 18% was associated with biotype II [8]. Later, a new species resembling S. bovis was detected which was named S. gallolyticus [9]. Interestingly, S. bovis biotype I and II/2 isolates were then found to be S. gallolyticus [10]. Accordingly, S. bovis biotype I was renamed as S. gallolyticus subspecies

gallolyticus and biotype II/2 was renamed as S. gallolyticus subspecies pasterianus and S. gallolyticus subspecies macedonicus [11] (Table 1). S. gallolyticus subspecies gallolyticus bacteria, more than other related taxa, have been found to be constantly associated with underlying colorectal cancer [10]. Therefore, the term S. bovis/gallolyticus is used in the current

review. Table 1 The milestone of the taxonomy of S. bovis/gallolyticus and the closely related members of group D streptococci [11, 127]. Old nomenclature Later nomenclature Recent nomenclature GDC-0973 mouse S. bovis biotype I S. gallolyticus S. gallolyticus subsp. gallolyticus S. bovis biotype II/1 S. infantarius S. infantarius subsp. infantarius   S. infantarius subsp. Coli S. lutetiensis S. bovis biotype II/2 S. pasteurianus S. macedonicus S. gallolyticus subsp. Pasteurianus S. gallolyticus subsp. very macedonicus Unfortunately, the nature of the association between S. bovis/gallolyticus and colorectal cancer has long been underestimated. It has been controversial whether the association of S. bovis/gallolyticus bacteremia or endocarditis with colorectal tumors is merely a consequence of the gastrointestinal lesion or it could be of etiological nature. Furthermore, there is a growing need to highlight the possible mechanisms that S. bovis/gallolyticus might play in triggering or promoting

colorectal cancer, if any. Moreover, the relationship of this bacterium with oncogenic factors, cell growth factors, and pro-inflammatory cytokines has not yet been clarified well. Therefore, the current review was done to scrutinize the nature and the underlying mechanisms of the association of S. bovis/gallolyticus with colorectal cancer. Bacterial pathogens and cancer Traditionally, bacterial infections have not been considered a major cause of cancer. However, bacteria have been linked to cancer by two mechanisms: chronic inflammation and production of carcinogenic metabolites [12]. It was stated that bacteria in general are thought to contribute to carcinogenesis by the formation of potentially toxic by-products of carbohydrates or bile acid metabolism, as well as hydrolysis of other mutagenic precursors [12]. The association of Helicobacter pylori (H. pylori) with gastric cancer is the best studied relationship between a bacterial infection and cancer [13]. H.