**6. Concept of infection in anastomosis site promote anastomotic leak**

According to John C. Alverdy (from Chicago American College of Surgeons, San Francisco, 2019), there is uncontestable and unambiguous evidence that bacteria at the site of anastomosis promote anastomotic leak, and surgeons should consider anastomosis as a wound and therefore put one focus on wound healing. This concept that the bacteria at the site of anastomosis play a causative role in anastomotic leak infection is a seductive hypothesis [22]. It can change CAL prevention and management paradigm.

We cannot forget that many factors can be present and act in microbiota patient with colorectal pathology with the collapse of the core microbiome: radiation, NSAIDS, cancer, tissue trauma, opioids, ischemia, blood loss, obesity, and smoking. It can lead to a predominance of collagenolytic microbe (*P. aeruginosa*, *Enterococcus faecalis*). These bacteria have in vivo virulence activation, adherence to tissues, immune escape, and cleavage of gelatinase B (MMP-9). This sequence promotes amplification of tissue inflammation and may lead to a clinical manifestation of a leak. Intestinal tissues induce a single nucleotide polymorphism (SNP) mutation in *Pseudomonas aeruginosa*. That enhances its virulence with a possible role in the anastomotic leak. About this issue, a study was realized in 2021 in rats where Olivas demonstrated a direct relation between leak anastomosis probability plus irradiation plus *P. aeruginosa* presence [23]. Furthermore, the phenotypic change from P1 to P2 at anastomosis is associated with increased collagenase activity, high swarming motility, and destructive phenotype [23].

On the other hand, *E. faecalis* can promote virulent activation of human plasminogen [24]. It happens because collagenase-producing bacteria, particularly *E. faecalis*, promotes anastomotic leak by degrading healing anastomotic tissue [25]. Furthermore, *Clostridium difficile* infection can also increase anastomotic leak after colectomy [26].

Based on the premises previously mentioned, it makes sense that an anastomotic leak should be thought of and treated as an infected wound.

### *Colorectal Anastomosis: The Critical Aspect of Any Colorectal Surgery DOI: http://dx.doi.org/10.5772/intechopen.107952*

In intestinal surgery, the sutures approximate tissue until the collagen is laid down. It requires meticulous attention to detail: minimize tissue trauma, ensure good blood supply, avoid tension, and beware of local sepsis.

At this point, beware of local sepsis; we must be concerned about changes in the local environment that results in a significant alteration in anastomotic tissue-associated microbiota. There are no modifiable factors such as inflammation surrounding anastomotic tissue due to infection, radiation, ischemia, or the presence of cytokines pro-inflammatory. Nevertheless, modifiable factors such as the colorectal bacterial community are present in the intestinal lumen. This presence can have either detrimental or beneficial effects depending on how the bacterial community composition is affected [27]. For that reason, a lot has been discussed about the benefits of bowel preparation before colorectal surgery with oral antibiotics and mechanical preparation. In addition, it seems appealing to implement pre-habilitation nutrition weeks before surgery to modify the patient's intestinal microbiota quality [28]. Moreover, in an unfavorable environment, the utilization of tranexamic acid can also inhibit the virulent activation of human plasminogen by *E. faecalis* [29].
