Normal viral and bacterial flora of the human small and large intestine

Research progress regarding the effect and mechanism of dietary phenolic acids for improving nonalcoholic fatty liver disease via gut microbiota

Phenolic acids (PAs), a class of small bioactive molecules widely distributed in food and mainly found as secondary plant metabolites, present significant advantages such as antioxidant activity and other health benefits. The global epidemic of nonalcoholic fatty liver disease (NAFLD) is becoming a serious public health problem. Existing studies showed that gut microbiota (GM) dysbiosis is highly associated with the occurrence and development of NAFLD. In recent years, progress has been made in the study of the relationship among PA compounds, GM, and NAFLD. PAs can regulate the composition and functions of the GM to promote human health, while GM can increase the dietary sources of PAs and improve its bioavailability. This paper discussed PAs, GM, and their interrelationship while introducing several representative dietary PA sources and examining the absorption and metabolism of PAs mediated by GM. It also summarizes the effect and mechanisms of PAs in improving and regulating NAFLD via GM and their metabolites. This helps to better evaluate the potential preventive effect of PAs on NAFLD via the regulation of GM and expands the utilization of PAs and PA-rich food resources.

Current Sampling Methods for Gut Microbiota: A Call for More Precise Devices

The development of next-generation sequencing technology has enabled researchers to explore and understand the gut microbiome from a broader and deeper perspective. However, the results of different studies on gut microbiota are highly variable even in the same disease, which makes it difficult to guide clinical diagnosis and treatment. The ideal sampling method should be non-invasive, involve little cross-contamination or bowel preparation, and collect gut microbiota at different sites. Currently, sequencing technologies are usually based on samples collected from feces, mucosal biopsy, intestinal fluid, etc. However, different parts of the gastrointestinal tract possess various physiological characteristics that are essential for particular species of living microbiota. Moreover, current sampling methods are somewhat defective. For example, fecal samples are just a proxy for intestinal microbiota, while biopsies are invasive for patients and not suitable for healthy controls. In this review, we summarize the current sampling methods and their advantages and shortcomings. New sampling technologies, such as the Brisbane Aseptic Biopsy Device and the intelligent capsule, are also mentioned to inspire the development of future precise description methods of the gut microbiome.

Colonization factors of enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) is a major cause of life-threatening diarrheal disease around the world. The major aspects of ETEC virulence are colonization of the small intestine and the secretion of enterotoxins which elicit diarrhea. Intestinal colonization is mediated, in part, by adhesins displayed on the bacterial cell surface. As colonization of the intestine is the critical first step in the establishment of an infection, it represents a potential point of intervention for the prevention of infections. Therefore, colonization factors (CFs) have been important subjects of research in the field of ETEC virulence. Research in this field has revealed that ETEC possesses a large array of serologically distinct CFs that differ in composition, structure, and function. Most ETEC CFs are pili (fimbriae) or related fibrous structures, while other adhesins are simple outer membrane proteins lacking any macromolecular structure. This chapter reviews the genetics, structure, function, and regulation of ETEC CFs and how such studies have contributed to our understanding of ETEC virulence and opened up potential opportunities for the development of preventive and therapeutic interventions.

Infections of the biliary tract

Infection of the biliary tract, or cholangitis, is a potentially life-threatening condition. Bile duct stones are the most common cause of biliary obstruction predisposing to cholangitis. The key components in the pathogenesis of cholangitis are biliary obstruction and biliary infection. Several underlying mechanisms of bactibilia have been proposed. Characteristic clinical features of cholangitis include abdominal pain, fever, and jaundice. A combination of clinical features with laboratory tests and imaging studies are frequently used to diagnose cholangitis. Endoscopic retrograde cholangiopancreatography is the best diagnostic test. Less invasive imaging tests may be performed initially in clinically stable patients with uncertain diagnoses.

A novel sampling method for the investigation of gut microbiota

AIM: In order to characterize the qualitative and quantitative microorganisms in different sites of the lower digestive tract (LDT) in healthy volunteers, a specific technique was developed for collecting mucous of the distal ileum, colon and rectum.

METHODS: A polyethylene tube was designed to go through the colonoscope channel with a No. 8 French tube. In order to avoid internal contamination, the distal extremity was protected with a membrane of microfilm after being sterilized in ethilene oxid. To facilitate the aspiration of a precise volume, its interior was coated with silicone. One hundred microlliter (0.1 mL) sample of mucous was collected and transferred into an Eppenddorff tube containing nine hundred microlliter (0.9 mL) of VMGA-3 (viable medium of Goteborg). This procedure was repeated at each site of the LDT with a new sterilized catheter.

RESULTS: All sites revealed the “non pathogenic” anaerobic bacteria Veillonella sp (average 10⁵ colony forming units/mL-CFU/mL), allowing to conclude an environment of low oxidation-reduction potential (redox) in the LDT. It was also characterized the presence of Klebisiella sp with significant statistical predominance (SSP) in the ileum. Enterobacter sp was found with SSP in the sigmoid colon, Bacteroides sp non-pigmented (npg) and E.coli with SSP in the sigmoid colon and rectum, Enterococcus sp and Lactobacillus sp with SSP in the rectum, all in a mean concentration of 10⁵ CFU/mL.

CONCLUSION: This procedure is feasible and efficient and can point out a similar distribution of the aerobic and anaerobic bacteria with the presence of biological markers of normal microbiota in the LDT.

Meta-analysis: randomized controlled trials of clindamycin/aminoglycoside vs. beta-lactam monotherapy for the treatment of intra-abdominal infections

AIM

To compare the effectiveness and safety of clindamycin/aminoglycoside with broad-spectrum beta-lactam monotherapy in patients with intra-abdominal infections by performing a meta-analysis of randomized controlled trials (RCTs).

METHODS

The relevant 28 RCTS were retrieved from PubMed searches and reviewed by two reviewers independently.

RESULTS

beta-lactam monotherapy was more effective regarding cure of the infection than clindamycin/aminoglycoside (3177 clinically evaluable patients, fixed effects model, OR = 0.67, 95% CI: 0.55-0.81). The same result was found in several subset analyses. There was no difference in all-cause mortality and attributable-to-infection mortality [2382 intention-to-treat (ITT) patients, fixed effects model, OR = 1.25, 95% CI: 0.74-2.11 and 1976 ITT patients, OR = 1.19, 95% CI: 0.59-2.41, respectively]. There was no difference regarding overall adverse events and ototoxicity (1460 ITT patients, OR = 1.05, 95% CI: 0.80-1.37, and 1404 ITT patients, OR = 3.22, 95% CI: 0.72-14.45, respectively). However, treatment with clindamycin/aminoglycoside was more likely to be associated with nephrotoxicity compared to beta-lactam (3065 ITT patients, OR = 3.7, 95% CI: 2.09-6.57). Clindamycin/aminoglycoside was less likely to be associated with antibiotic-associated diarrhoea compared to beta-lactam (3050 ITT patients, OR = 0.68, 95% CI: 0.46-1.00).

CONCLUSION

The results of our meta-analysis suggest that beta-lactams are more effective in the treatment of intra-abdominal infections compared with clindamycin/aminoglycoside.

Digestive tract microbiota in healthy volunteers

PURPOSE

The aim of this study was to standardize the methods of sample collection of mucus from the digestive tract and to determine the microbiota in healthy volunteers from Brazil, collecting samples from the mouth, esophagus, stomach, duodenum, jejunum, ileum, colon, and rectum.

METHODS

Microbiota of selected healthy volunteers from the oral cavity (n=10), the esophagus (n=10), the upper digestive tract (n=20), and the lower digestive tract (n=24) were evaluated through distinct collection methods. Collection methods took into account the different sites, using basic scraping and swabbing techniques, stimulated saliva from the oral cavity, irrigation-aspiration with sterile catheters especially designed for the esophagus, a probe especially designed for upper digestive tract, and a special catheter for the lower digestive tract.

RESULTS

(i) Mixed microbiota were identified in the oral cavity, predominantly Gram-positive aerobic and anaerobic cocci; (ii) transitional flora mainly in the esophagus; (iii) Veillonella sp, Lactobacillus sp, and Clostridium sp in the stomach and duodenum; (iv) in the jejunum and upper ileum, we observed Bacteroides sp, Proteus sp, and Staphylococcus sp, in addition to Veillonella sp; (v) in the colon, the presence of "nonpathogenic" anaerobic bacteria Veillonella sp (average 10(5) UFC) indicates the existence of a low oxidation-reduction potential environment, which suggests the possibility of adoption of these bacteria as biological markers of total digestive tract health.

CONCLUSIONS

The collection methods were efficient in obtaining adequate samples from each segment of the total digestive tract to reveal the normal microbiota. These procedures are safe and easily reproducible for microbiological studies.

Bacterial translocation of enteric organisms in patients with cirrhosis

BACKGROUND/AIMS

The aim of the study was to investigate the prevalence and associated risk factors for bacterial translocation in patients with cirrhosis, a mechanism involved in the pathogenesis of bacterial infections in experimental cirrhosis.

METHODS

Mesenteric lymph nodes were obtained for microbiological culture from 101 patients with cirrhosis and from 35 non-cirrhotic patients.

RESULTS

Enteric organisms were grown from mesenteric lymph nodes in 8.6% of non-cirrhotic patients. In the 79 cirrhotic patients without selective intestinal decontamination, the prevalence of bacterial translocation significantly increased according to the Child-Pugh classification: 3.4% in Child A, 8.1% in Child B and 30.8% in Child C patients (chi2 = 6.106, P < 0.05). However, translocation by Enterobacteriaceae, the organisms commonly responsible for spontaneous bacteremia and peritonitis in cirrhosis, was only observed in 25% of the cases. The prevalence of bacterial translocation in the 22 cirrhotic patients undergoing selective intestinal decontamination, all Child-Pugh class B and C, was 4.5%. The Child-Pugh score was the only independent predictive factor for bacterial translocation (odds ratio 2.22, P = 0.02).

CONCLUSIONS

Translocation of enteric organisms to mesenteric lymph nodes is increased in patients with advanced cirrhosis and is reduced to the level found in non-cirrhotic patients by selective intestinal decontamination.

Malabsorption secondary to Meckel's diverticulum

This case report of a patient with a large Meckel's diverticulum with associated stagnation and bacterial proliferation demonstrates the resultant metabolic and nutritional alterations that have classically been described with the blind loop syndrome. A lesion as large as the one presented herein has rarely been reported with iron, vitamin B12, and folic acid deficiency anemias secondary to the contaminated small bowel (ileum) syndrome. A discussion of the pathophysiology, diagnosis, and treatment of this disorder and the multiple disease entities incorporated in the contaminated small bowel syndrome are included.

Bile bacteria in patients with benign bile duct stricture

In a prospective study of 73 patients undergoing hepatodochojejunostomy for benign bile duct stricture who were covered by antibacterial prophylaxis with gentamicin and cephalolothin, bacteria were cultured from bile sampled at operation in 80 per cent of cases. Aerobic organisms were found in 50 cases (82 per cent) and anaerobic organisms in 11 cases (18 per cent). Seventy-three per cent of the patients with postoperative septic complications had bile cultures positive for anaerobes at operation, and the same organisms were cultured from pus. All patients with anaerobes in the bile at some time in the perioperative period developed postoperative sepsis. Antibacterial prophylaxis with gentamicin and cephalothin, together with specific therapy with drugs effective against anaerobes when indicated, are recommended in the management of these cases.

Assessment of the 14C-glycocholic acid breath test

The 1-((14)C)-glycine-glycocholic-acid breath test has been performed on 104 subjects and a normal range established. Abnormal results due to bacterial deconjugation of bile salts were found not only in patients with the "contaminated bowel" syndrome and in those with ileal resection but also in a third group, patients with cholangitis. Abnormal results were also found in patients with gastrocolic fistula and staphylococcal enterocolitis, while mildly abnormal results were also found in some patients with liver disease.