In Vitro Modulatory Effect of Stimulant Beverages on the Growth Kinetics of Intestinal Bacteria Associated with Colorectal Cancer.

Colorectal cancer is increasingly linked to diet-induced gut microbiota modulations, whereas the role of oncogenic bacteria is discussed. This study investigated the in vitro growth-modulatory effects of hot-water extracts of six stimulant beverages, namely Aspalathus linearis (rooibos), Coffea arabica, Coffea canephora (coffee), Camellia sinensis var. assamica, C. sinensis var. sinensis (tea) and Ilex paraguariensis (yerba mate) against six colorectal cancer-associated bacteria. Although no minimum inhibitory concentration (MIC) was detected (MIC > 512 µg/mL), growth kinetics analysis revealed modulations in the case of several strains. At the concentration 512 µg/mL, C. sinensis var. assamica and I. paraguariensis modulated the growth (41-56%) and prolonged the lag phase (61-128 min) of Clostridium septicum. The same concentration of both extracts modulated Fusobacterium necrophorum (26-27%), whereas I. paraguariensis extended the lag phase by 72 and 21 min in the cases of Peptostreptococcus anaerobius and Escherichia coli, respectively. Both C. sinensis varieties also reduced the growth of Streptococcus bovis (49-60%), while some treatments stimulated the growth of E. coli. These findings demonstrate in vitro growth modulation of selected colorectal cancer-associated bacteria, especially C. sinensis and I. paraguariensis, and warrant validation using multiple strains, independently replicated assays, chemically characterized extracts, and more physiologically relevant microbial models.