Mucosa-Associated Escherichia coli in Colorectal Cancer Patients and Control Subjects: Variations in the Prevalence and Attributing Features

Abstract

Accumulating evidence indicates that specific strains of mucosa-associated <i>Escherichia coli</i> (<i>E. coli</i>) can influence the development of colorectal carcinoma. This study aimed to investigate the prevalence and characterization of mucosa-associated <i>E. coli</i> obtained from the colorectal cancer (CRC) patients and control group. At two referral university-affiliated hospitals in northwest Iran, 100 patients, 50 with CRC and 50 without, were studied over the course of a year. Fresh biopsy specimens were used to identify mucosa-associated <i>E. coli</i> isolates after dithiothreitol mucolysis. To classify the <i>E. coli</i> strains, ten colonies per sample were typed using enterobacterial repetitive intergenic consensus-based PCR (ERIC-PCR). The strains were classified into phylogroups using the quadruplex PCR method. The PCR method was used to examine for the presence of cyclomodulin, <i>bfp</i>, <i>stx</i>1, <i>stx</i>2, and <i>eae</i>-encoding genes. The strains were tested for biofilm formation using the microtiter plate assay. CRC patients had more mucosa-associated <i>E. coli</i> than the control group (<i>p</i> < 0.05). Enteropathogenic <i>Escherichia coli</i> (EPEC) was also found in 23% of CRC strains and 7.1% of control strains (<i>p</i> < 0.05). Phylogroup A was predominant in control group specimens, while <i>E. coli</i> isolates from CRC patients belonged most frequently to phylogroups D and B2. Furthermore, the frequency of cyclomodulin-encoding genes in the CRC patients was significantly higher than the control group. Around 36.9% of <i>E. coli</i> strains from CRC samples were able to form biofilms, compared to 16.6% <i>E. coli</i> strains from the control group (<i>p</i> < 0.05). Noticeably, cyclomodulin-positive strains were more likely to form biofilm in comparison to cyclomodulin-negative strains (<i>p</i> < 0.05). In conclusion, mucosa-associated <i>E. coli</i> especially cyclomodulin-positive isolates from B2 and D phylogroups possessing biofilm-producing capacity colonize the gut mucosa of CRC patients.