Impact of the Microbiota on Bacterial Infections during Cancer Treatment

Patients being treated for cancer are at high risk for infectious complications, generally due to colonizing organisms that gain access to sterile sites via disrupted epithelial barriers. There is an emerging understanding that the ability of bacterial pathogens, including multidrug-resistant organisms, to colonize and subsequently infect humans is largely dependent on protective bacterial species present in the microbiome. Thus, herein we review recent studies demonstrating strong correlations between the microbiome of the oncology patient and infections occurring during chemotherapy. An increased knowledge of the interplay between potential pathogens, protective commensals, and the host immune system may facilitate the development of novel biomarkers or therapeutics that could help ameliorate the toll that infections take during the treatment of cancer. Bacterial infections occur frequently in the oncologic setting, and antibiotic treatment is increasingly problematic. Therefore, alternative prognostic and treatment strategies for infection are necessary. Recent characterization of the microorganisms (bacteria, fungi, and viruses) inhabiting the human body has revealed the microbiome as an important contributor to host physiology and pathology. The importance of host immune system–microbiota interface has been highlighted by studies demonstrating that microbiota dysbiosis is associated with immune dysfunction, mucosal barrier disruption, and impaired colonization resistance against translocating microbes. Novel microbiome-based therapeutic strategies, using fecal microbiome transplant, probiotics, or prebiotics, are being studied in order to mitigate infections as well as improve cancer outcomes through immunomodulation.