Letter: investigating the intestinal mucosa-associated microbiota - relevance and potential pitfalls

Mucosa-associated cultivable aerobic gut bacterial microbiota among colorectal cancer patients attending at the referral hospitals of Amhara Regional State, Ethiopia

Background

Colorectal cancer (CRC) is one of the top ten causes of cancer deaths in the world. Despite an increased prevalence of colorectal cancer has been documented from developing countries, there is no any report regarding gut microbiota among colorectal cancer patients in Ethiopia. Therefore, the current study evaluated cultivable aerobic gut bacterial distributions among malignant and its adjacent normal biopsies of CRC patients.

Methods

CRC patients who were under colorectal cancer resection surgery during April 2017 to February 2018 at Felege Hiwot Referral and University of Gondar Teaching Hospitals enrolled in the study. Biopsy specimens were taken from malignant and its adjacent normal-appearing tissues. Bacterial cultivation, quantification and characterization of saline washed biopsies were performed under aerobic and candle jar conditions. Differences in bacterial microbiota compositions between malignant and normal tissue biopsies were evaluated and analyzed using Microsoft excel 2010 and GraphPad Prism5 statistical software.

Results

Fifteen CRC patients were participated with a mean age of 53.8 ± 10.8 years old and majorities (73.3 %) of patients were in between the age groups of 40 and 60 years old. The mean ± SD bacterial microbiota of malignant biopsies (3.2 × 10⁵ ± 1.6 × 10⁵ CFU/ml) was significantly fewer than that of adjacent normal tissue biopsies (4.0 × 10⁵ ± 2.2 × 10⁵ CFU/ml). This dysbacteriosis is positively correlated with the occurrence of CRC (p = 0.019). Proteobacteria (55.6 %), Firmicutes (33.3 %) and Fusobacteria (11.1 %) were the most frequently isolated phyla from non-malignant biopsies while only Proteobacteria (58.8 %) and Firmicutes (41.2 %) were from malignant ones. Family level differences were observed among phyla (Firmicutes and Proteobacteria) isolated from the study participants. For instance, the relative abundance of family Bacillaceae from malignant (26 %) was lower than the normal biopsies (39 %). On other hand, family Enterobacteriaceae was twice more abundant in malignant tissues (45 %) than in its matched normal tissues (23 %). Furthermore, the family Enterococcaceae (14 %) of phylum Firmicutes was solely isolated from malignant tissue biopsies.

Conclusions

The overall microbial composition of normal and malignant tissues was considerably different among the study participants. Further culture independent analysis of mucosal microbiota will provide detail pictures of microbial composition differences and pathogenesis of CRC in Ethiopian settings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13099-021-00415-7.