Demonstration of transient bacterobilia by foreign body implantation in feline biliary tract

The role of bacteria in gallstone formation

Gallstones are a prevalent biliary system disorder that is particularly common in women. They can lead to various complications, such as biliary colic, infection, cholecystitis, and even gallbladder cancer. However, the etiology of gallstones remains incompletely understood. The significant role of bacteria in gallstone formation has been demonstrated in recent studies. Certain bacteria not only influence bile composition and the gallbladder environment but also actively participate in stone formation by producing enzymes such as β-glucuronidase and mucus. Therefore, this review aimed to analyze the mechanisms involving the types and quantities of bacteria involved in gallstone formation, providing valuable references for understanding the etiology and clinical treatment of gallstones.

Insight into the mechanism of gallstone disease by proteomic and metaproteomic characterization of human bile

Introduction

Cholesterol gallstone disease is a prevalent condition that has a significant economic impact. However, the role of the bile microbiome in its development and the host's responses to it remain poorly understood.

Methods

In this study, we conducted a comprehensive analysis of microbial and human bile proteins in 40 individuals with either gallstone disease or gallbladder polyps. We employed a combined proteomic and metaproteomic approach, as well as meta-taxonomic analysis, functional pathway enrichment, and Western blot analyses.

Results

Our metaproteomic analysis, utilizing the lowest common ancestor algorithm, identified 158 microbial taxa in the bile samples. We discovered microbial taxa that may contribute to gallstone formation, including β-glucuronidase-producing bacteria such as Streptococcus, Staphylococcus, and Clostridium, as well as those involved in biofilm formation like Helicobacter, Cyanobacteria, Pseudomonas, Escherichia coli, and Clostridium. Furthermore, we identified 2,749 human proteins and 87 microbial proteins with a protein false discovery rate (FDR) of 1% and at least 2 distinct peptides. Among these proteins, we found microbial proteins crucial to biofilm formation, such as QDR3, ompA, ndk, pstS, nanA, pfIB, and dnaK. Notably, QDR3 showed a gradual upregulation from chronic to acute cholesterol gallstone disease when compared to polyp samples. Additionally, we discovered other microbial proteins that enhance bacterial virulence and gallstone formation by counteracting host oxidative stress, including sodB, katG, rbr, htrA, and ahpC. We also identified microbial proteins like lepA, rtxA, pckA, tuf, and tpiA that are linked to bacterial virulence and potential gallstone formation, with lepA being upregulated in gallstone bile compared to polyp bile. Furthermore, our analysis of the host proteome in gallstone bile revealed enhanced inflammatory molecular profiles, including innate immune molecules against microbial infections. Gallstone bile exhibited overrepresented pathways related to blood coagulation, folate metabolism, and the IL-17 pathway. However, we observed suppressed metabolic activities, particularly catabolic metabolism and transport activities, in gallstone bile compared to polyp bile. Notably, acute cholelithiasis bile demonstrated significantly impaired metabolic activities compared to chronic cholelithiasis bile.

Conclusion

Our study provides a comprehensive metaproteomic analysis of bile samples related to gallstone disease, offering new insights into the microbiome-host interaction and gallstone formation mechanism.

Feline cholangitis/cholangiohepatitis complex - what have we learned?

Cholangitis/cholangiohepatitis complex in cats is commonly encountered in clinical practice worldwide. Diagnosis and management of cats with this complex is difficult because of the ambiguity of clinical signs, diagnostic test results and commonality of comorbid disorders. These impediments can delay disease identification and treatment, which can increase morbidity and mortality. ​In this narrative review, we aimed to provide a thorough review of the unique physioanatomic features of the biliary system as well as clinically relevant updates on cholangitis/cholangiohepatitis complex in cats.

Bacterial culture and immunohistochemical detection of bacteria and endotoxin in cats with suppurative cholangitis-cholangiohepatitis syndrome

OBJECTIVE

To characterize the frequency and type of bacterial infection by culture- and immunohistochemical (IHC)-based methods and determine the impact of infection on clinical features and survival time in cats with suppurative cholangitis-cholangiohepatitis syndrome (S-CCHS).

ANIMALS

168 client-owned cats with S-CCHS (cases).

PROCEDURES

Clinical features, bacterial culture results, culture-inoculate sources, and survival details were recorded. Cases were subcategorized by comorbidity (extrahepatic bile duct obstruction, cholelithiasis, cholecystitis, ductal plate malformation, biopsy-confirmed inflammatory bowel disease, and biopsy-confirmed pancreatitis) or treatment by cholecystectomy or cholecystoenterostomy. Culture results, bacterial isolates, Gram-stain characteristics, and IHC staining were compared among comorbidities. Lipoteichoic acid IHC staining detected gram-positive bacterial cell wall components, and toll-like receptor expression IHC reflected pathologic endotoxin (gram-negative bacteria) exposure.

RESULTS

Clinical features were similar among cases except for more frequent abdominal pain and lethargy in cats with positive culture results and pyrexia, abdominal pain, and hepatomegaly for cats with polymicrobial infections. Bacteria were cultured in 93 of 135 (69%) cats, with common isolates including Enterococcus spp and Escherichia coli. IHC staining was positive in 142 of 151 (94%) cats (lipoteichoic acid, 107/142 [75%]; toll-like receptor 4, 99/142 [70%]). With in-parallel interpretation of culture and IHC-based bacterial detection, 154 of 166 (93%) cats had bacterial infections (gram-positive, 118/154 [77%]; gram-negative, 111/154 [72%]; polymicrobial, 79/154 [51%]). Greater frequency of bacterial isolation occurred with combined tissue, bile, and crushed cholelith inoculates. Infection and gram-positive bacterial isolates were associated with significantly shorter long-term survival times.

CLINICAL RELEVANCE

S-CCHS was associated with bacterial infection, pathologic endotoxin exposure, and frequent polymicrobial infection in cats. Combined tissue inoculates improved culture detection of associated bacteria.

Clinical features, concurrent disorders, and survival time in cats with suppurative cholangitis-cholangiohepatitis syndrome

OBJECTIVE

To characterize clinical features, comorbidities, frequency of bacterial isolation, and survival time in cats with suppurative cholangitis-cholangiohepatitis syndrome (S-CCHS).

ANIMALS

168 client-owned cats with S-CCHS.

PROCEDURES

Data were prospectively (1980 to 2019) collected regarding clinical features, comorbidities, bacterial infection, illness duration, and treatments. Variables were evaluated for associations with survival time.

RESULTS

Median age of cats was 10.0 years, with no breed or sex predilection observed. Common clinical features included hyporexia (82%), hyperbilirubinemia (80%), lethargy (80%), vomiting (80%), jaundice (67%), weight loss (54%), and hypoalbuminemia (50%). Comorbidities included extrahepatic bile duct obstruction (53%), cholelithiasis (42%), cholecystitis (40%), and ductal plate malformation (44%) as well as biopsy-confirmed inflammatory bowel disease (60/68 [88%]) and pancreatitis (41/44 [93%]). Bacterial cultures were commonly positive (69%) despite prebiopsy antimicrobial administration in most cats. Of surgically confirmed choleliths, diagnostic imaging identified only 58%. Among 55 cats with "idiopathic pancreatitis," 28 (51%) were documented to have transiting choleliths, and 20 had pancreatic biopsies confirming pancreatitis. Cholelithiasis (with or without bile duct obstruction) and cholecystectomy were associated with survival advantages. Survival disadvantages were found for leukocytosis, ≥ 2-fold increased alkaline phosphatase, and hyperbilirubinemia. Cholecystoenterostomy had no survival impact. Cats with ductal plate malformations were significantly younger at diagnosis and death than other cats. Chronic treatments with antimicrobials, S-adenosylmethionine, and ursodeoxycholic acid were common postbiopsy.

CLINICAL RELEVANCE

S-CCHS in cats was associated with bacterial infection and various comorbidities and may be confused with pancreatitis. Surgically correctable morbidities (ie, cholecystitis, cholecystocholelithiasis) and cholecystectomy provided a significant survival advantage.

Management of Patients With Acute Cholecystitis After Percutaneous Cholecystostomy: From the Acute Stage to Definitive Surgical Treatment

Percutaneous cholecystostomy (PC) has become an important procedure for the treatment of acute cholecystitis (AC). PC is currently applied for patients who cannot undergo immediate laparoscopic cholecystectomy. However, the management following PC has not been well-reviewed. The efficacy of PC tubes has already been indicated, and compared to complications of other invasive biliary procedures, complications related to PC are rare. Following the resolution of AC, patients who can tolerate anesthesia and the surgical risk should undergo interval cholecystectomy to reduce the recurrence of biliary events. For patients unfit for surgery, whether owing to comorbidities, anesthesia risks, or surgical risks, expectant management may be applied; however, a high incidence of recurrence has been noted. In addition, several interesting issues, such as the indications for cholangiography via the PC tube, removal or maintenance of the PC catheter before definitive treatment, and timing of elective surgery, are all discussed in this review, and a relevant decision-making flowchart is proposed. PC is an effective and safe intervention, whether as expectant treatment or bridge therapy to definitive surgery. High-level evidence of post-PC care is still necessary to modify current practices.

No evidence of improved efficacy of covered stents over uncovered stents in percutaneous palliation of malignant hilar biliary obstruction: results of a prospective randomized trial

OBJECTIVE

To investigate whether covered stents show a higher efficacy than uncovered stents in percutaneous treatment of malignant hilar biliary obstruction.

METHODS

Patients with obstructive jaundice caused by an unresectable hilar malignancy were included after failed endoscopic intervention in a prospective randomized trial comparing expanded polytetrafluoroethylene and fluorinated ethylene propylene (ePTFE-FEP)-covered nitinol stents with uncovered nitinol stents. Exclusion criteria were as follows: primary tumors existing more than 3 months, a biliodigestive anastomosis, previous stenting, and a Karnofsky score of less than 50. Safety, clinical success, and adjuvant chemotherapy were compared as well as occlusion rate, patency, and survival.

RESULTS

A total of 120 patients were included. One patient was post hoc excluded. Fourteen patients who died within 7 days and one patient without patency data were excluded from patency analysis. Serious adverse events (p = 0.4), 30-day mortality (p = 0.5), and clinical success (p = 0.8) were equivalent for both stent groups. Twenty-one out of 61 (34%) patients in the covered and 24/58 (41%) in the uncovered stent groups received adjuvant chemotherapy (p = 0.5). Occlusion rate was 54% (27/50) in the covered stent group and 57% (31/54) in the uncovered stent group (p = 0.8). Median patency was 229 days (95% CI 113-345) for covered stents and 130 days (95% CI 75-185) for uncovered stents (p = 0.1). Median survival in patients with covered stents was 79 days (95% CI 52-106) and with uncovered stents 92 days (95% CI 60-124) (p = 0.3).

CONCLUSION

In malignant hilar biliary obstruction, there is no evidence that ePTFE-FEP-covered stents are superior to uncovered stents in terms of safety, clinical success, adjuvant chemotherapy, patency, or survival.

KEY POINTS

• Percutaneous palliation of hilar biliary obstruction is feasible with both uncovered and covered stents. • Clinical success in terms of bilirubin decrease and adjuvant chemotherapy is achievable with both stents. • Thirty-day mortality is considerable when stenting is also offered to patients with a low performance status.

Feline biliary tree and gallbladder disease: Aetiology, diagnosis and treatment

Practical relevance Diseases of the biliary tree and gallbladder are more common in cats than diseases of the liver parenchyma. The parenchyma is usually affected secondarily to systemic illnesses, while the biliary system is the prime target for infectious agents (eg, bacteria and flukes) and non-infectious conditions (eg, neoplasia and cysts). Clinical approaches Cats with biliary disease are evaluated because of common feline clinical signs such as anorexia, nausea, vomiting and lethargy. Icterus may or may not be obvious. Biopsies for histological evaluation, and bile aspirates for culture and cytological evaluation are helpful diagnostically. Antibiotics and immunosuppressive drugs have been used successfully. Hepatosupportive drugs may help in liquefying thick bile and protecting hepatic tissue from damage. Ultrasound is a noninvasive diagnostic tool that may help in identifying dilated bile ducts, liver cysts and choleliths. It is also used to guide percutaneous bile aspiration. Audience This review, written for all veterinarians who treat cats, describes the various conditions that can affect the feline biliary tree and gallbladder. Treatment options are discussed, and brief summaries provided of surgical techniques and diagnostic approaches. Evidence base The veterinary literature pertaining to feline biliary disease is comprehensively reviewed. When appropriate, data on dogs and humans has been included to provide background information. Based on the available literature, more research into feline biliary diseases is needed.

The distributed genome hypothesis as a rubric for understanding evolution in situ during chronic bacterial biofilm infectious processes

Most chronic infectious disease processes associated with bacteria are characterized by the formation of a biofilm that provides for bacterial attachment to the host tissue or the implanted medical device. The biofilm protects the bacteria from the host's adaptive immune response as well as predation by phagocytic cells. However, the most insidious aspect of biofilm biology from the host's point of view is that the biofilm provides an ideal setting for bacterial horizontal gene transfer (HGT). HGT provides for large-scale genome content changes in situ during the chronic infectious process. Obviously, for HGT processes to result in the reassortment of alleles and genes among bacterial strains, the infection must be polyclonal (polymicrobial) in nature. In this review, we marshal the evidence that all of the factors are present in biofilm infections to support HGT that results in the ongoing production of novel strains with unique combinations of genic characteristics and that the continual production of large numbers of novel, but related bacterial strains leads to persistence. This concept of an infecting population of bacteria undergoing mutagenesis to produce a 'cloud' of similar strains to confuse and overwhelm the host's immune system parallels genetic diversity strategies used by viral and parasitic pathogens.

Population-level virulence factors amongst pathogenic bacteria: relation to infection outcome

The study of population-level virulence traits among communal bacteria represents an emerging discipline in the field of bacterial pathogenesis. It has become clear over the past decade-and-a-half that bacteria exhibit many of the hallmarks of multicellular organisms when they are growing as biofilms and communicating among each other using quorum- sensing systems. Each of these population-level behaviors provides for multiple expressions of virulence that individual free-swimming bacteria do not possess. Population-level virulence traits are largely associated with chronic or persistent infections, whereas individual bacterial virulence traits are associated with acute infections. Thus, there is a natural dichotomy between acute and chronic infectious processes, which helps to explain the medical community's success in combating the former, but its utter failure in dealing with the latter. The recent recognition of multicellularity among chronic bacterial pathogens will lead the way towards new multimodality therapies.

Gallstones containing bacteria are biofilms: bacterial slime production and ability to form pigment solids determines infection severity and bacteremia

OBJECTIVE

Gallstone bacteria provide a reservoir for biliary infections. Slime production facilitates adherence, whereas beta-glucuronidase and phospholipase generate colonization surface. These factors facilitate gallstone formation, but their influence on infection severity is unknown.

METHODS

Two hundred ninety-two patients were studied. Gallstones, bile, and blood (as applicable) were cultured. Bacteria were tested for beta-glucuronidase/phospholipase production and quantitative slime production. Infection severity was correlated with bacterial factors.

RESULTS

Bacteria were present in 43% of cases, 13% with bacteremia. Severe infections correlated directly with beta-glucuronidase/phospholipase (55% with vs 13% without, P < 0.0001), but inversely with slime production (55 vs 8%, slime <75 or >75, P = 0.008). Low slime production and beta-glucuronidase/phospholipase production were additive: Severe infections were present in 76% with both, but 10% with either or none (P < 0.0001). beta-Glucuronidase/phospholipase production facilitated bactibilia (86% with vs 62% without, P = 0.03). Slime production was 19 (+/-8) vs 50 (+/-10) for bacteria that did or did not cause bacteremia (P = 0.004). No bacteria with slime >75 demonstrated bacteremia.

CONCLUSIONS

Bacteria-laden gallstones are biofilms whose characteristics influence illness severity. Factors creating colonization surface (beta-glucuronidase/phospholipase) facilitated bacteremia and severe infections; but abundant slime production, while facilitating colonization, inhibited detachment and cholangiovenous reflux. This shows how properties of the gallstone biofilm determine the severity of the associated illness.

Biliary bacterial factors determine the path of gallstone formation

BACKGROUND

Bacteria cause pigment gallstones and can act as a nidus for cholesterol gallstone formation. Bacterial factors that facilitate gallstone formation include beta-glucuronidase (bG), phospholipase (PhL), and slime. The current study sought to determine whether bacterial factors influence the path of gallstone formation.

METHODS

A total of 382 gallstones were cultured and/or examined using scanning electron microscopy (SEM). Bacteria were tested for bG and slime production. Gallstone composition was determined using infrared spectrography. Ca-palmitate presence documented bacterial PhL production. Groups were identified based upon bacterial factors present: slime and bGPhL (slime/bGPhL), bGPhL only, and slime only. Influence of bacterial stone-forming factors on gallstone composition and morphology was analyzed.

RESULTS

Bacteria were present in 75% of pigment, 76% of mixed, and 20% of cholesterol stones. Gallstones with bGPhL producing bacteria contained more pigment (71% vs. 26%, P < .0001). The slime/bGPhL group was associated (79%) with pigment stones, bGPhL was associated (56%) with mixed stones, while slime (or none) only was associated (67%) with cholesterol stones (P < .031, all comparisons).

CONCLUSIONS

Bacterial properties determined the path of gallstone formation. Bacteria that produced all stone-forming factors promoted pigment stone formation, while those that produced only bGPhL promoted mixed stone formation. Bacteria that only produced slime lacked the ability to generate pigment solids, and consequently were more common in the centers of cholesterol stones. This shows how bacterial characteristics may govern the process of gallstone formation.

Bactobilia after liver transplantation: frequency and antibiotic susceptibility

After liver transplantation (LT), bactobilia occurs frequently in patients, leading in some cases to cholangitis and biliary sepsis. The present study is the first to investigate bactobilia after LT, and it gives an overview of predisposing factors for bactobilia, the microbial spectrum in the bile of LT patients, and the antibiotic susceptibility. A total of 172 endoscopic retrograde cholangiography (ERC) procedures were performed in 66 LT patients between 1 month and 5.8 years after LT. Bile samples were examined microbiologically. Sixty-eight nontransplanted patients without cholestasis, but requiring ERC for other reasons served as a control group. Of 172 samples obtained from LT patients, 126 (73.3%) were positive for microbes. A total of 236 organisms were isolated: 114 (48.3%) gram-positive bacteria, 92 (39.0%) aerobic gram-negative, 8 (3.4%) anaerobes, and 22 (9.3%) fungi. Ciprofloxacin and amoxycillin/clavulanic acid showed the best susceptibility results among oral antibiotics and piperacillin/tazobactam and imipenem/cilastatin among intravenous preparations. In contrast, only 15.7% of non-LT patients showed bactobilia. In conclusion, our study shows that bactobilia is a problem in patients after LT and that it is not only a contamination from endoscopic intervention. Mechanical obstruction, plastic stents, gallstones, and papillotomy increase the risk of bactobilia significantly. In our cohort we had the best antibiotic susceptibility results for positive cultures in LT patients with piperacillin/tazobactam, ciprofloxacin, or amoxycillin/clavulanic acid.

Bacterial adherence and biofilm formation on latex and silicone T-tubes in relation to bacterial contamination of bile

BACKGROUND

T-tube-related bacteriobilia causes infectious complications and obstruction. To prevent these, the choice of T-tube material may be of importance.

METHODS

Transected common bile ducts (CBDs) of 17 piglets were sutured over latex or silicone T-tubes, or without a T-tube.

RESULTS

After 6 weeks bacteriobilia was found in all of 12 CBDs with and in 1 of 5 CBDs without a T-tube (p < 0.05). By scanning electron microscopy (SEM) four of five latex and none of five silicone T-tubes had bacterial biofilms (p < 0.05). All tubes remained patent. Segments of T-tubes were incubated with five different bacterial strains. Sonication and SEM showed that 0.1-1.1% of 10(7) colony-forming units of inoculum adhered to T-tubes. Two to six times more bacteria adhered to latex than to silicone (p < 0.05).

CONCLUSIONS

Silicone offers better long-term patency than latex. Less infectious complications occur if T-tubes are omitted.

A bacteriologic and scanning electron microscope study after implantation of foreign bodies in the biliary tract in rats

BACKGROUND

Bacterial adherence to the stent surfaces, concomitant colonization, and possible stent blockage are the main complications after the use of biliary stents. The present study was assigned to investigate bacteriologic and morphologic changes in the biliary tract after the implantation of biliary drain materials.

METHODS

Rubber and silicone pieces with a surface area of 1 cm2 were implanted into the biliary tract in rats after temporary obstruction of the common bile duct by the use of a mini-occluder. The animals were killed at 4, 8 and 14 weeks, respectively, after implantation, and the implants were retrieved, cultured, and examined by scanning electron microscopy (SEM). Bacterial culture and SEM were also performed on tissue samples obtained from the mucosal surface of the biliary tract.

RESULTS

Bacterial colonization and biofilm formation were found on the surfaces of the implanted materials and on the mucosal surface of the biliary tract in animals with implants but not on the biliary tract mucosa in rats without implants.

CONCLUSION

Foreign bodies implanted in the biliary tract facilitate bacterial adherence not only to the surface of the implants but also to the mucosal surface in the biliary tract.

Bacterial biofilm and clogging of biliary stents

Endoscopic biliary stenting has become a standard palliative treatment for obstructive jaundice due to malignancies of the pancreas and the hepatobiliary system. Despite the high initial success rate in achieving biliary drainage, durable endoscopic stenting has been limited by the clogging of biliary stents, usually after 4-5 months, due to formation of an adherent bacterial biofilm. Various methods have been investigated for the prevention of bacterial adhesion and prolongation of stent patency. These include: 1) prophylactic use of antimicrobial agents and bile salts; 2) testing of new stent material and new designs for these biliary stents; and 3) the recent introduction of self-expandable metal stents. Each method has its own merits as well as specific problems. This article reviews the pathogenesis of biofilm formation on the biliary stents and the latest status of research in avoiding the problem of stent occlusion.

Endoscopic stenting for palliation of malignant biliary obstruction. A review of progress in the last 15 years

Since the late 1970s, endoscopic biliary stenting has become a standard palliative treatment for obstructive jaundice due to malignancies of the pancreas and the hepatobiliary system. Despite the high initial success rate in achieving biliary drainage, endoscopic stenting therapy has been limited by the clogging of biliary stents, usually after four to five months, due to formation of adherent bacterial biofilm and accumulation of biliary sludge. Various methods for the prevention of bacterial adhesion and prolongation of stent patency have been investigated, including prophylactic antimicrobial agents and bile salts, new stent materials, and new stent designs. Recently, the introduction of self-expandable metal stents has significantly improved the duration of stent patency but the cost is considerably higher. Each method has its own merits as well as specific problems. This article reviews the pathogenesis of biofilm formation on the biliary stents and the latest status of research in avoiding stent occlusion.

Bacterial biofilm, brown pigment stone and blockage of biliary stents

Bacterial pathogens gain access into the biliary system by descending via the portal venous circulation or ascending through the sphincter of Oddi in duodenal-biliary reflux. Bacteria thrive as glycocalyx-enclosed microcolonies, coalescing to form an adherent biofilm. The establishment of biofilm is a key event in the formation of biliary sludge and pigment gallstones, and the blockage of biliary stents. The biofilm mode of growth is very effective because it provides bacteria with a measure of protection from antibacterial agents and phagocytic leucocytes. Calcification of the matrix confers further protection for the micro-organisms living inside the biofilm. To date, attempts to prevent blockage of biliary stent have employed physical methods by using large self-expandable stents and stents without side hole. Incorporation of antibiotics within stents has not been successful presumably because bacteria once living in their biofilm are quite resistant to antimicrobial agents. Even the most toxic bile salts have no effect on the biofilm bacteria. Yet, hydrophobic bile salts reduce bacterial adhesion on biomaterial, suggesting that incorporation of such bile salts might prevent the formation of bacterial biofilm.

Temporary bile diversion in cats with experimental extrahepatic bile duct obstruction

The use of a cholecystostomy catheter for temporary bile diversion was investigated in four cats with experimentally induced extrahepatic bile duct obstruction. Eighteen days after ligation of the common bile duct, a 6.5 F accordion catheter was placed in the gallbladder with a 22 g Hawkins needle-guide system through a paracostal incision. Biochemical parameters and fasting serum bile acids were monitored for 16 days. There were significant decreases in mean total bilirubin, aspartate aminotransferase, and fasting serum bile acids within 72 hours of bile diversion, and in mean alanine aminotransferase within 96 hours. Attitude and appetite improved, and the catheter was tolerated well. Positive bile cultures developed in three cats. Histologic changes in the gallbladder included mucosal ulcerations, a mixed inflammatory cellular infiltration, and fibrosis of the submucosa.

Defense system in the biliary tract against bacterial infection

Bacteria can invade the biliary tract by ascending from the duodenum and via the hematogenous route from the hepatic portal venous blood. The sphincter of Oddi, situated at the junction of the biliary tract and the upper gastrointestinal tract, forms an effective mechanical barrier to duodenal reflex and ascending bacterial infection. Conversely, Kupffer cells and the tight junctions between hepatocytes help prevent bacteria and toxic metabolites from entering the hepatobiliary system from the portal circulation. The continuous flushing action of bile and the bacteriostatic effects of bile salts keeps the biliary tract sterile under normal conditions. Secretory immunoglobulin A (sIgA), the predominant immunoglobulin in the bile, and mucus excreted by the biliary epithelium probably function as antiadherence factors, preventing microbial colonization. When barrier mechanisms break down, as in surgical or endoscopic sphincterotomy and with insertion of biliary stents, pathogenic bacteria enter the biliary system at high concentrations and take up residence on any foreign bodies. Intrabiliary pressure is a key factor in the development of cholangitis. Chronic biliary obstruction raises the intrabiliary pressure. This adversely influences the defensive mechanisms such as the tight junctions, Kupffer cell functions, bile flow, and sIgA production in the system, resulting in a higher incidence of septicemia and endotoxemia in these patients. Knowledge of biliary defense against infection is still quite primitive. Unclear are the roles of sIgA in the bile, mechanism of bacterial adhesion to the biliary epithelium, Kupffer cell function in biliary obstruction, and the antimicrobial activity of bile salts.

Ascending infection of the biliary tract after surgical sphincterotomy and biliary stenting

It has been widely accepted that there is an ascending route of bacterial infection of the biliary tract but there is a lack of direct evidence. This hypothesis was tested in an animal experiment using the cat as an animal model. The implantation of biliary stents and surgical sphincterotomy were performed in these animals, with sham controls. Stents bypassing the sphincter of Oddi with the tip in the duodenal micro-organisms and the biliary tract was heavily contaminated. Blockage of these stents resulted in biliary obstruction. Stents implanted within the common bile duct, proximal to the sphincter were largely unaffected by biofilm formation. After surgical sphincterotomy the biliary tract was also contaminated but, in the absence of obstruction, the animals did not develop any symptoms. It was concluded that ascending infection by duodenal biliary reflux, via the sphincter of Oddi, is an important route of infection in the biliary system.