Colorectal cancer (CRC), which develops from the gradual evolution of tubular adenomas and serrated polyps in the colon and rectum, has a poor prognosis and a high mortality rate. In addition to genetics, lifestyle, and chronic diseases, intestinal integrity and microbiota (which facilitate digestion, metabolism, and immune regulation) could promote CRC development. For example, enterotoxigenic Bacteroides fragilis, genotoxic Escherichia coli (pks+ E. coli), and Fusobacterium nucleatum, members of the intestinal microbiota, are highly correlated in CRC. This review describes the roles and mechanisms of these three bacteria in CRC development. Their interaction during CRC initiation and progression has also been proposed. Our view is that in the precancerous stage of colorectal cancer, ETBF causes inflammation, leading to potential changes in intestinal ecology that may provide the basic conditions for pks+ E. coli colonization and induction of oncogenic mutations, when cancerous intestinal epithelial cells can further recruit F. nucleatum to colonise the lesion site and F. nucleatum may contribute to CRC advancement by primarily the development of cancer cells, stemization, and proliferation, which could create new and tailored preventive, screening and therapeutic interventions. However, there is the most dominant microbiota in each stage of CRC development, not neglecting the possibility that two or even all three bacteria could be engaged at any stage of the disease. The relationship between the associated gut microbiota and CRC development may provide important information for therapeutic strategies to assess the potential use of the associated gut microbiota in CRC studies, antibiotic therapy, and prevention strategies.

The occurrence and development of colorectal cancer (CRC) is an incredibly long process that involves continuous changes in the tumor microenvironment. These constant changes may ultimately result in genetic alterations and changes in the metabolic processes of some symbiotic bacteria as a way to adapt to the changing environment. Patients with CRC exhibit an altered abundance of Bacteroides fragilis (B. fragilis) as indicated by several studies. To better understand the genomic characteristics and virulence spectrum of B. fragilis strains in tumor tissues, B. fragilis strains were isolated from tumor and paracancerous tissues of CRC patients. The isolates were identified using 16 S rRNA sequencing, morphological analysis, physiological and biochemical characterization and PCR, and they were then subjected to whole genome sequencing (WGS) analysis. A strain of B. fragilis enterotoxin (BFT) bft1-producing ZY0302 and a non-enterotoxin-producing B. fragilis ZY0804 were isolated from cancerous and paraneoplastic tissues, respectively. Analysis based on the core and nonessential genes showed that the genomic profiles of the isolates, ZY0302 and ZY0804, differed from those of B. fragilis from other tissue sources. This core and the co-evolution of non-essential genes may be the result of their adaptation to fluctuations in the tumor microenvironment and enhancing their survival. In addition, the ZY0302 and ZY0804 genomes underwent extensive horizontal gene transfer and varying degrees of genomic rearrangements, inversions, insertions, and deletion events, which may favor the enhancement of bacteria’s ability to adapt to environmental changes. For instance, the virulence factors, such as the capsular biosynthesis gene clusters and components of the type IV secretion system, acquired through horizontal gene transfer, may facilitated B. fragilis in evading immune responses and managing oxidative stress. Moreover, our analysis revealed that multiple virulence factors identified in the isolates were mainly involved in bacterial adhesion and colonization, oxidative stress, iron acquisition, and immune evasion. This observation is worth noting given that enzymes such as neuraminidase, lipase, hemolysin, protease, and phosphatase, along with genes responsible for LPS biosynthesis, which are recognized for their association with the virulence of B. fragilis, were prevalent among the isolates. In summary, it is our assertion that the alterations observed in both core and nonessential genes of B. fragilis, which have been isolated from tissues of colorectal cancer patients, along with significant instances of horizontal gene transfer to the genome, are likely intended to enhance adaptation to the evolving conditions of the tumor microenvironment. This study may provide new insights into the interaction between B. fragilis and the CRC microenvironment.

Phlegmonous gastritis is a rare bacterial infection of the gastric wall, characterised by purulent inflammation of the gastric mucosa, submucosa and muscularis layers. Phlegmonous gastritis has a high mortality rate, even with correct diagnosis and antimicrobial therapy. A 22-year-old man presented for acute epigastric pain associated with aqueous diarrhoea, vomiting and sustained fever. Abdominal computed tomography showed diffuse oedema and thickened gastric wall, increased number and size of abdominal lymph nodes and the absence of pneumoperitoneum. Fibregastroscopy revealed oedematous, ridged and thickened gastric mucosa with abundant purulent secretion, especially in the antrum, consistent with phlegmonous gastritis, which was confirmed by histological evaluation of gastric biopsies. Cultures of the tissue biopsies and purulent secretion were positive for Enterococcus cecorum. He was treated with sensitive antibiotics according to the antibiogram, and importantly, with continuous gastric lavage and individualised nutritional support therapy. He eventually recovered well and was discharged with no abdominal symptoms. Our case indicates that early diagnosis and immediate treatment are crucial to achieve positive outcomes. The combination of sensitive antibiotics, gastric lavage and early enteral nutrition via nasojejunal feeding might be an effective alternative for the comprehensive treatment of acute phlegmonous gastritis.

Letter to the Editor Impact of perioperative blood transfusion on elderly gastric cancer patients Mingyu Zhang, Qingbo Feng, Maijian Wang

The efficacy and safety of endoscopic mucosal dissection for early gastrointestinal cancer and precancerous lesions