Can Clostridium Difficile infection be prevented?

Paper for discussion: Fachi JL, Felipe JS, Pral LP, Silva BK, Correa RO, Cristiny M et al.Butyrate Protects Mice from Clostridium difficile-Induced Colitis through an HIF-1-Dependent Mechanism. Cell Rep. 2019 Apr 16; 27: 750-761.e7.

Although rare, Clostridium difficile-induced diarrhoea or colitis can complicate what otherwise appeared to be an uneventful elective operation. This rare, but potentially lethal complication results from multiple factors inherent to performing surgery, such as prolonged periods of starvation, antibiotic exposure, major physiological stress, and sleep deprivation¹. C. difficile spores can spread easily, can resist multiple methods of decontamination and can remain viable for long periods of time. In many cases, the bacteria can remain hidden within the host’s gut microbiome and transferred to the healthcare setting by the patient themselves, rather than vice versa.

While prevention is the best treatment, C. difficile infections (CDI) often prove resistant to antibiotics, and other modalities may be needed to restore homeostasis to the gut microbiome. Although faecal microbiota transplant has been proposed as a method for both prevention and treatment of CDI, even when severe colitis is present, many believe the most important action of the microbiome is to preserve its ability to produce key multifunctional metabolites ². For example, the ability of the microbiota to produce the short-chain fatty acids (SCFAs) acetate, propionate, and butyrate has been identified to be an important therapeutic aspect in the prevention and treatment of CDI. SCFAs are absorbed by host intestinal epithelial cells (IECs) and participate in several immunoregulatory roles that influence the host response to inflammation and infection. Past studies have detected reduced SCFA concentrations, particularly butyrate, in patients with CDI³. Elevation of butyrate via dietary modulation or provision of SCFA-producing bacteria has been shown to attenuate CDI severity in animal studies^4,5.

In this study, Fachi et al. investigate how butyrate potentially alters the course of CDI in mice⁶. Oral administration of butyrate protects against CDI, improving both clinical symptoms and colonic histological score, with evidence of reduced ulceration and leukocyte infiltration within two days of the onset of infection. Similar effects were observed both with addition of tributyrin, a pro-drug of butyrate, as well as with inulin, a fibrous substrate for SCFA production, which both increased colonic butyrate levels. Once confirming butyrate’s protective effects against CDI, the investigators examined butyrate’s effect on four key parameters of CDI: the growth of C. difficile itself and the viability of the surrounding gut microbiota, IECs, and various other immune cells adjacent to the intestinal track. Although, butyrate was demonstrated to interfere with C. difficile growth and toxin production in vitro, these findings were not observed in vivo, suggesting that butyrate’s protective effects against CDI may not be a function of its direct action on C. difficile colonization or virulence. Furthermore, while butyrate affected overall gut microbiota community structure, it also maintained its protective effects in germ-free mice, indicating some of its protective effects extended beyond its influence on the gut microbiota. In turn, Fachi et al. then examined the effect of butyrate on immune cells, where they observed that butyrate administration reduced colonic pro-inflammatory cytokines IL-6, IL-1b, and Cxcl-1, as well as increased colonic anti-inflammatory cytokines such as IL-10. Also observed were elevated regulatory T cells, Foxp-3, and IL-10 in the mesenteric lymph nodes, supporting an overall anti-inflammatory influence. Even in Rag1- or IL-10-deficient knockout (KO) mice, butyrate still maintained its protective effect, suggesting that pathways independent of regulatory T cell or IL-10 signaling are involved.

Finally, when examining the interaction of C. difficile and butyrate on IECs in this study, investigators observed that butyrate could attenuate the intestinal permeability defects induced by CDI using FITC-dextran as a permeability probe. C. difficile dissemination from the gut was also decreased, as judged by fewer C. difficile colony-forming units in the liver and spleen in butyrate-treated mice. Gene expression studies and immunostaining revealed that butyrate increased key paracellular junction proteins Claudin-1 and Occludin that maintain the gut barrier. To further understand how permeability might be altered by C. difficile and/or butyrate functionally, investigators measured transepithelial/transendothelial electrical resistance (TEER) across cells, which demonstrated that butyrate partially prevented the increased IEC permeability caused by exposure to C. difficile supernatant. Previous studies had shown butyrate could stabilize the transcription factor HIF-1α, which is involved in regulating IEC permeability. To confirm this, the group showed that oral butyrate increased colonic HIF-1α and downstream gene expression. Using a LysMCre mouse model that selectively knocked out HIF-1α expression in IECs, they showed that butyrate no longer prevented the intestinal permeability defect and also failed to attenuate C. difficile dissemination to the liver and spleen. Furthermore, in the HIF-1α IEC KO mice, butyrate no longer reduced CDI severity. In the aggregate, these studies indicate that the permeability defect induced by CDI requires participation by key regulatory elements in the host cellular response to this pathogen, which can be modulated by gut microbiota-derived metabolites such as butyrate.

Several conclusions can be made that may be relevant to the surgical patient. First, it may be important to know a patient’s colonic (faecal) butyrate level before surgery. This should not only be able to be easily measured as a point-of-care assay, but should also be easily modifiable via dietary prehabilitation. This may involve dietary consultation, attention to when antibiotics have been most recently prescribed, changes in life-style (smoking cessation, reducing alcohol consumption) and removal of unnecessary medication until which time it can be determined that a patient’s microbiome is “ready” for a major operative intervention⁷. Second, over the course of surgery when butyrate and other relevant ­microbiome metabolites may become deficient, it may be possible to develop a protocol of microbiome maintenance that involves orally administered butyrate with specific release patterns packaged in microparticles. Studies such as the one highlighted above demonstrate that defining microbiome “readiness” for surgery, identifying the metabolites that activate immune function, and validating their role in CDI and other infection-related complications after surgery is now within our reach.  This approach is not only exciting as a countermeasure to the fact that we are often operating on sicker, older patients with advanced disease, but also as a potential solution to many of the most dreaded infection-related complications that can occur when we perform what otherwise is expected to be an uneventful surgical procedure.