The development of colorectal cancer is affected by many factors, especially the intestinal microbiota. However, precise knowledge of bacterial communities associated with the mucosa in various parts of the colon is limited. Herein, we applied the gentamicin protection assay and detected the presence of intracellular bacteria in colorectal biopsies from Slovak patients with colorectal adenoma and carcinoma, and we compared this with healthy controls. The ENTEROtest 24 and MALDI-TOF mass

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... etry identified the cultivated bacteria and results revealed the presence of intracellularly localized Escherichia coli, Proteus mirabilis and Proteus vulgaris in patients with colorectal adenomas and carcinomas. In addition to these species, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterococcus faecalis and Bacillus cereus were identified in colorectal biopsies, but these were extracellular. The marked increase in relative abundance of intracellular E. coli in patients with colorectal adenomas and carcinomas was statistically significant compared to controls, and our preliminary data supports E. coli's role as a pro-oncogenic pathogen.