Bacterial and Parasitic Pathogens as Risk Factors for Cancers in the Gastrointestinal Tract: A Review of Current Epidemiological Knowledge

Abstract

The oncogenic potential of viral infections is well established and documented for many years already. However, the contribution of (commensal) bacteria and parasites to the development and progression of cancers has only recently gained momentum, resulting in a rapid growth of publications on the topic. Indeed, various bacteria and parasites have been suggested to play a role in the development of gastrointestinal cancer in particular. Therefore, an overview of the current epidemiological knowledge on the association between infections with bacteria and parasites and cancers of the gastrointestinal tract is needed. In this review, we summarized the methodological characteristics and main results of epidemiological studies investigating the association of 10 different bacteria (Bacteroides fragilis, Campylobacter spp., Clostridium spp., Enterococcus faecalis, Escherichia coli, Fusobacterium nucleatum, Porphyromonas gingivalis, non-typhoidal Salmonella, Salmonella Typhi, and Streptococcus spp.) and three parasites (Cryptosporidium spp., Schistosoma spp., and Strongyloides stercoralis) with gastrointestinal cancer. While the large body of studies based on microbiome sequencing provides valuable insights into the relative abundance of different bacterial taxa in cancer patients as compared to individuals with pre-malignant conditions or healthy controls, more research is needed to fulfill Koch’s postulates, possibly making use of follow-up data, to assess the complex role of bacterial and parasitic infections in cancer epidemiology. Studies incorporating follow-up time between detection of the bacterium or parasite and cancer diagnosis remain valuable as these allow for estimation of cause-effect relationships.

The Role of Microbiome in Brain Development and Neurodegenerative Diseases

“…Vitamins, such as vitamin B9, thiamine, vitamin B2, niacin, vitamin K, vitamin B1, riboflavin, etc., are produced by bacteria, such as Bifidobacterium bifidum , Bacillus Subtilis , Escherichia coli , Bacteroidetes, and are involved in immunological function, cellular metabolism, cell proliferation and offer vitamin sources for hosts. Polyphenols produced by Clostridium , E. coli , Salmonella , and Bacteroides function as antioxidants, and reduce the risk of colon cancer and inflammation [ 38 , 46 , 47 ].…”

Bile-volatile organic compounds in the diagnostics of pancreatic cancer and biliary obstruction: A prospective proof-of-concept study

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Spotlights on helminth pathogens’ innovative pathways of tumorigenesis

“…Subsequently these data suggested that, S. stercoralis, is a cofactor for the growth of HTLV-1-induced lymphocytic carcinoma [94] . The link between S. stercoralis and HTLV-1 was supported by data showing that the prevalence of S. stercoralis above two-folds, increased in HTLV-1 patients as compared to HTLV-1 free individuals [95] . Moreover, infection with S. stercoralis can last a lifetime, and patients may be prone to chronic inflammation of the bowel and colon.…”