Liver abscess caused by Clostridium difficile

Tubo-ovarian abscess caused by Clostridioides difficile after eight months of surgery: Case report and review of extraintestinal abdominal abscess cases

We present a case of tubo-ovarian abscess (TOA) caused by Clostridioides difficile (CD) in a 43-year-old female. Despite lacking a history of sexually transmitted diseases, the patient had undergone paraovarian cystectomy nine months before admission. Transvaginal ultrasonography performed eight months post-surgery revealed left ovarian enlargement, accompanied by subsequent lower abdominal pain and fever exceeding 38 °C. As oral antibiotic treatment was ineffective, the patient was admitted to our hospital. Computed tomography upon admission revealed a massive TOA. Surgical drainage of the abscess was performed, and CD was identified in the culture from the pus. The TOA was treated with a three-month course of metronidazole and oral amoxicillin/clavulanic acid. While CD is commonly associated with colitis, extraintestinal manifestations are exceptionally rare. This case represents the inaugural report of TOA resulting from CD. A literature review on abdominal and pelvic CD abscesses found that patients undergoing surgical drainage had a favorable prognosis. Therefore, surgical intervention plays an important role in the management of CD abscesses.

Human C. difficile toxin-specific memory B cell repertoires encode poorly neutralizing antibodies

Clostridioides difficile is a leading cause of nosocomial infection responsible for significant morbidity and mortality with limited options for therapy. Secreted C. difficile toxin B (TcdB) is a major contributor to disease pathology, and select TcdB-specific Abs may protect against disease recurrence. However, the high frequency of recurrence suggests that the memory B cell response, essential for new Ab production following C. difficile reexposure, is insufficient. We therefore isolated TcdB-specific memory B cells from individuals with a history of C. difficile infection and performed single-cell deep sequencing of their Ab genes. Herein, we report that TcdB-specific memory B cell–encoded antibodies showed somatic hypermutation but displayed limited isotype class switch. Memory B cell–encoded mAb generated from the gene sequences revealed low to moderate affinity for TcdB and a limited ability to neutralize TcdB. These findings indicate that memory B cells are an important factor in C. difficile disease recurrence.

The C. difficile toxin-specific human memory B cell repertoire encodes low-affinity, non-neutralizing antibodies.

Extraintestinal Clostridioides difficile Infections: Epidemiology in a University Hospital in Hungary and Review of the Literature

Extraintestinal manifestations of Clostridioides difficile infections (CDIs) are very uncommon, and according to the literature, poor outcomes and a high mortality have been observed among affected individuals. The objective of this study was to investigate the incidence rate of extraintestinal infections caused by C. difficile (ECD) in a tertiary-care university hospital in Hungary. During a 10-year study period, the microbiology laboratory isolated 4129 individual strains of C. difficile; among these, the majority were either from diarrheal fecal samples or from colonic material and only n = 24 (0.58%) were from extraintestinal sources. The 24 extraintestinal C. difficile isolates were recovered from 22 patients (female-to-male ratio: 1, average age: 55.4 years). The isolates in n = 8 patients were obtained from abdominal infections, e.g., appendicitis, rectal abscess or Crohn’s disease. These extraintestinal cases occurred without concomitant diarrhea. In all, but two cases C. difficile was obtained as a part of a polymicrobial flora. Our isolates were frequently toxigenic and mostly belonged to PCR ribotype 027. Resistance to metronidazole, vancomycin, clindamycin and rifampin were 0%, 0%, 20.5% and 9.7%, respectively. The increasing amount of reports of C. difficile extraintestinal infections should be noted, as these infections are characterized by a poor outcome and high mortality rate.

Recurrent bacteremia and liver abscess caused by Clostridium difficile: A case report

RATIONALE

Clostridium difficile bacteremia (CDB) and liver abscess is a quite rare presentation of C. difficile infection.

PATIENTS CONCERNS

A 74-year-old male with primary biliary cirrhosis and hepatocellular carcinoma who underwent transarterial chemoembolization (TACE) developed a high fever on post-TACE day 14. Intravenous ceftriaxone and following meropenem were administered, however, his clinical response was poor. On post-TACE day 24, 2 sets of blood culture were taken due to elevation of C-reactive protein levels.

DIAGNOSIS

CDB, caused by bacterial translocation.

INTERVENTIONS

Intravenous vancomycin and oral metronidazole were administered for two weeks.

OUTCOMES

One month after recurrent CDB, the patient was re-admitted due to a liver abscess at the same site of TACE. C. difficile was isolated from the liver abscess and the patient received 6 weeks of oral metronidazole treatment. CDB and liver abscess have not recurred since completion of antibiotic treatment.

LESSONS

The spore-forming ability of C. difficile may contributed to the recurrent CDB episodes and liver abscess formation in necrotic liver tissue following TACE, and long-term metronidazole therapy was considered to be effective to C. difficile liver abscess.

Invading beyond bounds: extraintestinal Clostridium difficile infection leading to pancreatic and liver abscesses

Clostridium difficile has become a common healthcare-associated infection over the past few years and gained more attention. C. difficile was estimated to cause almost half a million infections in USA in 2011 and 29 000 died within 30 days of the initial diagnosis. Although colitis due to C. difficile is the most common presentation, there have been reported cases of extraintestinal infections. As per our review of literature, this is the third reported case of liver abscess due to the organism.

Clostridium difficile extraintestinal abscess: a rare complication

Extraintestinal Clostridium difficile is rare. A 74-year-old man with a history of ulcerative colitis presented after a fall. Trauma work-up showed liver cirrhosis. Two days later he developed abdominal pain, distension, diarrhoea and leucocytosis. Stool tested positive for C. difficile CT abdomen showed pancolitis with toxic megacolon. Total abdominal colectomy and ileostomy with a rectal stump was performed. He was discharged, but was readmitted with sepsis. CT abdomen showed a 10.4×7.2 cm fluid collection in the pelvis. C. difficile stool was negative. CT-guided abscess drainage grew C. difficile Barium enema was negative for communication from the rectal stump to the abscess. The patient was treated with metronidazole for 2 weeks. In summary, extraintestinal C. difficile can develop from recent antibiotics use, gastrointestinal surgery and microperforations from toxic megacolon. We recommend abscess drainage, concomitant treatment with metronidazole and or vancomycin, and reimaging of abscess location 2-4 weeks after cessation of antibiotics.

Vancomycin-Induced Elevation of Liver Enzyme Levels

Objective:

To report a case of oral vancomycin-induced elevation of liver enzyme levels.

Case Summary:

A 57-year-old man with multiple medical conditions requiring systemic antibiotic therapy developed numerous Clostridium difficile–associated enterocolitis episodes. The patient did not respond adequately to oral metronidazole, as evidenced by his continuing diarrhea. He was treated with oral vancomycin on 5 separate occasions (with doses from 125 to 500 mg/day), each of which resulted in significant elevations in alanine aminotransferase (to 371 U/L) and aspartate aminotransferase (to 203 U/L) levels. The elevations resolved on each occasion with discontinuation of vancomycin.

Discussion:

Vancomycin, a glycopeptide antibiotic, has primary activity against gram-positive bacteria. Oral vancomycin can be used for the treatment of C. difficile–associated enterocolitis in patients who fail to respond to or are intolerant to metronidazole therapy. Oral vancomycin has very poor bioavailability and, as of May 4, 2006, has not been associated with hepatic toxicity. Inflammatory bowel disease processes can result in increased absorption of oral vancomycin.

Conclusions:

This is the first reported case of oral vancomycin–induced elevation of hepatic enzyme levels. Use of the Naranjo probability scale indicated that this was a probable adverse drug-associated event.

Clostridium difficile: A rare cause of pyogenic liver abscess

Extra-intestinal infections due to Clostridium difficile have been reported rarely. Herein we report a case of pyogenic liver abscess from toxigenic C. difficile in an 80-year-old non-hospitalized woman with diabetes mellitus, cerebrovascular and cardiovascular diseases. The patient was admitted to the emergency department with fever and abdominal pain. There was no history of diarrhea or use of antibiotics. Laboratory parameters revealed signs of inflammation and elevated AST and ALT levels. Abdominal ultrasound and computer tomography showed multiple focal lesions in the bilateral liver lobes and hydropic gallbladder with stones. The patient underwent cholecystectomy and the liver abscesses were drained. Toxigenic C. difficile strains were isolated from the drained pus and also from the stool sample. According to repetitive-element PCR (rep-PCR) analyses both organisms were the same. The organisms were susceptible to antibiotics. Despite proper antibiotic therapy and surgical drainage, the patient succumbed to her illness.

Clostridium difficile Toxins A and B: Insights into Pathogenic Properties and Extraintestinal Effects

Clostridium difficile infection (CDI) has significant clinical impact especially on the elderly and/or immunocompromised patients. The pathogenicity of Clostridium difficile is mainly mediated by two exotoxins: toxin A (TcdA) and toxin B (TcdB). These toxins primarily disrupt the cytoskeletal structure and the tight junctions of target cells causing cell rounding and ultimately cell death. Detectable C. difficile toxemia is strongly associated with fulminant disease. However, besides the well-known intestinal damage, recent animal and in vitro studies have suggested a more far-reaching role for these toxins activity including cardiac, renal, and neurologic impairment. The creation of C. difficile strains with mutations in the genes encoding toxin A and B indicate that toxin B plays a major role in overall CDI pathogenesis. Novel insights, such as the role of a regulator protein (TcdE) on toxin production and binding interactions between albumin and C. difficile toxins, have recently been discovered and will be described. Our review focuses on the toxin-mediated pathogenic processes of CDI with an emphasis on recent studies.

Memory B Cells Encode Neutralizing Antibody Specific for Toxin B from the Clostridium difficile Strains VPI 10463 and NAP1/BI/027 but with Superior Neutralization of VPI 10463 Toxin B

Secreted toxin B (TcdB) substantially contributes to the pathology observed during Clostridium difficile infection. To be successfully incorporated into a vaccine, TcdB-based immunogens must stimulate the production of neutralizing antibody (Ab)-encoding memory B cells (Bmem cells). Despite numerous investigations, a clear analysis of Bmem cellular responses following vaccination against TcdB is lacking. B6 mice were therefore used to test the ability of a nontoxigenic C-terminal domain (CTD) fragment of TcdB to induce Bmem cells that encode TcdB-neutralizing antibody. CTD was produced from the historical VPI 10463 strain (CTD1) and from the hypervirulent strain NAP1/BI/027 (CTD2). It was then demonstrated that CTD1 induced strong recall IgG antibody titers, and this led to the development of functional Bmem cells that could be adoptively transferred to naive recipients. Bmem cell-driven neutralizing Ab responses conferred protection against lethal challenge with TcdB1. Further experiments revealed that an experimental adjuvant (Imject) and a clinical adjuvant (Alhydrogel) were compatible with Bmem cell induction. Reactivity of human Bmem cells to CTD1 was also evident in human peripheral blood mononuclear cells (PBMCs), suggesting that CTD1 could be a good vaccine immunogen. However, CTD2 induced strong Bmem cell-driven antibody titers, and the CTD2 antibody was neutralizing in vitro, but its protection against lethal challenge with TcdB2 was limited to delaying time to death. Therefore, CTD from different C. difficile strains may be a good immunogen for stimulating B cell memory that encodes in vitro neutralizing Ab but may be limited by variable protection against intoxication in vivo.

Clostridium difficile infection in patients with liver disease: a review

Over the past two decades, there has been a dramatic worldwide increase in both the incidence and severity of Clostridium difficile infection (CDI). Paralleling the increased incidence of CDI in the general population, there has been increased interest in CDI among patients with liver disease, particularly in those with liver cirrhosis and post liver transplantation. MEDLINE and several other electronic databases from January 1995 to December 2014 were searched in order to identify potentially relevant literature. Patients with cirrhosis and liver transplant recipients are at high risk for the development CDI because of antibiotics and proton pump inhibitors use, frequent and prolonged hospitalization, immunosuppressant therapy, and multiple comorbidities. Enzyme immunoassay to detect C. difficile toxins A and B in stool remains the most widely used test for CDI diagnosis, although, more recently, polymerase chain reaction (PCR)-based assays have become the preferred diagnostic test in many laboratories. Metronidazole and vancomycin, given orally, have proved to be effective in the treatment of CDI. Both cirrhotic patients and liver transplant recipients with CDI have longer length of hospital stay, increased mortality, and higher healthcare costs than those without CDI. A rapid diagnosis and adequate therapy of CDI are of paramount importance to improve liver disease patients' outcome. The aim of this review is to provide up-to-date information on the epidemiology, risk factors, pathogenesis, treatment, and outcomes in liver disease patients with CDI.

Identification of toxemia in patients with Clostridium difficile infection

Toxemia can develop in Clostridium difficile-infected animals, and correlates with severe and fulminant disease outcomes. Circumstantial evidence suggests that toxemia may occur in patients with C. difficile infection (CDI), but positive diagnosis is extremely rare. We analyzed the potential for C. difficile toxemia in patients, determined its characteristics, and assessed challenges. C. difficile toxins in serum from patients were tested using an ultrasensitive cell-based assay and further confirmed by Rac1 glucosylation assay. The factors that hinder a diagnosis of toxemia were assessed, including investigation of toxin stability, the level of toxins-specific neutralizing antibodies in sera and its effect on diagnosis limits. CDI patients develop detectable toxemia in some cases (2.3%). Toxins were relatively stable in stored sera. Neutralizing anti-toxin antibodies were present during infection and positively correlated with the diagnosis limits. Thus, the masking effect of toxin-specific neutralizing antibodies is the major obstacle in diagnosing C. difficile toxemia using cell-based bioassays.

Clostridium difficile infection: molecular pathogenesis and novel therapeutics

The Gram-positive anaerobic bacterium Clostridium difficile produces toxins A and B, which can cause a spectrum of diseases from pseudomembranous colitis to C. difficile-associated diarrhea. A limited number of C. difficile strains also produce a binary toxin that exhibits ADP ribosyltransferase activity. Here, the structure and the mechanism of action of these toxins as well as their role in disease are reviewed. Nosocomial C. difficile infection is often contracted in hospital when patients treated with antibiotics suffer a disturbance in normal gut microflora. C. difficile spores can persist on dry, inanimate surface for months. Metronidazole and oral vancomycin are clinically used for treatment of C. difficile infection but clinical failure and concern about promotion of resistance are motivating the search for novel non-antibiotic therapeutics. Methods for controlling both toxins and spores, replacing gut microflora by probiotics or fecal transplant, and killing bacteria in the anaerobic gut by photodynamic therapy are discussed.

An optimized, synthetic DNA vaccine encoding the toxin A and toxin B receptor binding domains of Clostridium difficile induces protective antibody responses in vivo

Clostridium difficile-associated disease (CDAD) constitutes a large majority of nosocomial diarrhea cases in industrialized nations and is mediated by the effects of two secreted toxins, toxin A (TcdA) and toxin B (TcdB). Patients who develop strong antitoxin antibody responses can clear C. difficile infection and remain disease free. Key toxin-neutralizing epitopes have been found within the carboxy-terminal receptor binding domains (RBDs) of TcdA and TcdB, which has generated interest in developing the RBD as a viable vaccine target. While numerous platforms have been studied, very little data describes the potential of DNA vaccination against CDAD. Therefore, we created highly optimized plasmids encoding the RBDs from TcdA and TcdB in which any putative N-linked glycosylation sites were altered. Mice and nonhuman primates were immunized intramuscularly, followed by in vivo electroporation, and in these animal models, vaccination induced significant levels of both anti-RBD antibodies (blood and stool) and RBD-specific antibody-secreting cells. Further characterization revealed that sera from immunized mice and nonhuman primates could detect RBD protein from transfected cells, as well as neutralize purified toxins in an in vitro cytotoxicity assay. Mice that were immunized with plasmids or given nonhuman-primate sera were protected from a lethal challenge with purified TcdA and/or TcdB. Moreover, immunized mice were significantly protected when challenged with C. difficile spores from homologous (VPI 10463) and heterologous, epidemic (UK1) strains. These data demonstrate the robust immunogenicity and efficacy of a TcdA/B RBD-based DNA vaccine in preclinical models of acute toxin-associated and intragastric, spore-induced colonic disease.

Liver abnormalities in bowel diseases

Liver abnormalities are often seen in bowel diseases. Whether these represent aspects of two separate diseases, or if one is causing the other, is not always easy to decide. Extraintestinal manifestations of inflammatory bowel disease (IBD) or coeliac disease are frequently observed. Of these extraintestinal manifestations, hepatic disorders are among the most common. Primary sclerosing cholangitis (PSC) and primary biliary cirrhosis are the most frequent hepatic disorders in IBD and coeliac disease, respectively. Genetic studies have lately elucidated the associations between IBD and PSC, but there is still a long way until we have complete understanding of the molecular aetiology and pathophysiology of these conditions. There is no curative treatment available for PSC, besides liver transplantation. Steatosis and cholelithiasis are also common in IBD, as are signs of hepatic injury due to IBD treatment. Less common liver abnormalities include liver abscesses, hepatic thromboembolic events, granulomatous liver disease and hepatic amyloidosis.

Clostridium difficile 027/BI/NAP1 encodes a hypertoxic and antigenically variable form of TcdB

The Clostridium difficile exotoxin, TcdB, which is a major virulence factor, varies between strains of this pathogen. Herein, we show that TcdB from the epidemic BI/NAP1/027 strain of C. difficile is more lethal, causes more extensive brain hemorrhage, and is antigenically variable from TcdB produced by previously studied strains of this pathogen (TcdB₀₀₃). In mouse intoxication assays, TcdB from a ribotype 027 strain (TcdB₀₂₇) was at least four fold more lethal than TcdB₀₀₃. TcdB₀₂₇ caused a previously undescribed brain hemorrhage in mice and this correlated with a heightened sensitivity of brain microvascular endothelial cells to the toxin. TcdB₀₀₃ and TcdB₀₂₇ also differed in their antigenic profiles and did not share cross-neutralizing epitopes in a major immunogenic region of the protein. Solid phase humoral mapping of epitopes in the carboxy-terminal domains (CTD) of TcdB₀₂₇ and TcdB₀₀₃ identified 11 reactive epitopes that varied between the two forms of TcdB, and 13 epitopes that were shared or overlapping. Despite the epitope differences and absence of neutralizing epitopes in the CTD of TcdB₀₂₇, a toxoid form of this toxin primed a strong protective response. These findings indicate TcdB₀₂₇ is a more potent toxin than TcdB₀₀₃ as measured by lethality assays and pathology, moreover the sequence differences between the two forms of TcdB alter antigenic epitopes and reduce cross-neutralization by antibodies targeting the CTD.

During the past decade, the C. difficile BI/NAP1/027 strain has emerged and in some settings predominated as the cause of C. difficile infection. Moreover, in some reports C. difficile BI/NAP1/027 has been associated with more severe disease. The reasons for association of this strain with more severe disease and relapse are poorly understood. We compared the toxicity and antigenic profiles of the major C. difficile virulence factor, TcdB, from a previously studied reference strain and a BI/NAP1/027 strain. The results indicate TcdB₀₂₇, the toxin from the BI/NAP1/027 strain, is more lethal and causes more extensive brain hemorrhaging than TcdB₀₀₃, the toxin produced by a reference strain of C. difficile. Furthermore, the results show that the antigenic carboxy-terminal domain (CTD) encodes at least 11 epitopes that differ between the two forms of TcdB. In line with this, experiments demonstrate that antiserum against the CTD does not cross-neutralize TcdB₀₀₃ and TcdB₀₂₇ toxicity against CHO cells, and TcdB₀₂₇ appears to be devoid of neutralizing epitopes in this domain. These findings indicate differences in TcdB₀₀₃ and TcdB₀₂₇ contribute to increased virulence of C. difficile BI/NAP1/027 and reduce the likelihood of acquired immunity providing cross-protection against infection by these strains.

[A case of Clostridium liver abscess with sepsis]

Clostridial septicemia usually occurrs in patients with immunocompromised diseases such as diabetes and malignancy. Clostridial liver abscess is very rare but highly fatal. We experienced a case of Clostridial septicemia due to liver abscess in a 73-year-old man. He was presented with fever and chills. On admission, abdominal CT scan showed about 35 mm sized hypoattenuated lesion with multiple central air-bubbles. After the diagnosis of liver abscess, the patient underwent prompt empirical antimicrobial therapy and percutaneous drainage. In spite of early therapy, the patient had gone into shock and death.

Systemic dissemination of Clostridium difficile toxins A and B is associated with severe, fatal disease in animal models

BACKGROUND

Clostridium difficile infection (CDI) can cause a wide range of disease, from mild diarrhea to fulminant systemic disease. The incidence of systemic CDI with fatal consequence has increased rapidly in recent years.

METHODS

Using an ultrasensitive cytotoxicity assay, we measured C. difficile toxin A (TcdA) and C. difficile toxin B (TcdB) in sera and body fluids of piglets and mice exposed to C. difficile to investigate the relationship between the presence of toxins in body fluids and systemic manifestations of CDI.

RESULTS

We found that both TcdA and TcdB disseminate systemically, with toxins present in the sera and body fluids of infected animals, and toxemia is significantly correlated with the development of systemic CDI. The systemic administration of neutralizing antibodies against both toxins blocked the development of systemic disease in mice. We measured cytokine concentrations in the sera of mice and piglets with systemic and nonsystemic CDI and found that proinflammatory mediators were considerably elevated in animals with systemic CDI.

CONCLUSION

Our study demonstrates the existence of a strong correlation between toxemia and the occurrence of systemic disease, supporting the hypothesis that systemic CDI is most likely due to the toxicity of TcdA and TcdB and the induction of proinflammatory cytokines by the toxins.

Mouse relapse model of Clostridium difficile infection

Clostridium difficile is the causative agent of primary and recurrent antibiotic-associated diarrhea and colitis in hospitalized patients. The disease is caused mainly by two exotoxins, TcdA and TcdB, produced by the bacteria. Recurrent C. difficile infection (CDI) constitutes one of the most significant clinical issues of this disease, occurs in more than 20% of patients after the first episode, and may be increasing in frequency. However, there is no well-established animal model of CDI relapse currently available for studying disease pathogenesis, prevention, and therapy. Here we report the establishment of a conventional mouse model of recurrence/relapse CDI. We found that the primary episode of CDI induced little or no protective antibody response against C. difficile toxins and mice continued shedding C. difficile spores. Antibiotic treatment of surviving mice induced a second episode of diarrhea, while a simultaneous reexposure of animals to C. difficile bacteria or spores elicited a full spectrum of CDI similar to that of the primary infection. Moreover, mice treated with immunosuppressive agents were prone to more severe and fulminant recurrent disease. Finally, utilizing this model, we demonstrated that vancomycin only delayed disease recurrence, whereas neutralizing polysera against both TcdA and TcdB completely protected mice against CDI relapse. In conclusion, we have established a mouse relapse CDI model that allows for future investigations of the role of the host immune response in the disease's pathogenesis and permits critical testing of new therapeutics targeting recurrent disease.

Bacteraemia and breast abscess: unusual extra-intestinal manifestations of Clostridium difficile infection

Extra-intestinal manifestations of Clostridium difficile infection are uncommon. Most cases are associated with gastrointestinal disease and often occur as a mixed infection with other gut flora. We report a case of breast abscess following monomicrobial C. difficile bacteraemia in a female with background chronic hepatitis C infection and alcoholic liver disease. No evidence of colitis was found. Our case shows that C. difficile is indeed capable of spreading from the gastrointestinal tract.

Unusual manifestations of Clostridium difficile infection

BACKGROUND

Clostridium difficile infection (CDI) is an increasing nosocomial problem. New, more-virulent strains of C. difficile have spread across North America and Europe. Health care institutions now face a greater incidence of disease, often with greater severity. A need for surgical management for control of infection is on the increase. The clinical appearance of CDI is changed.

METHODS

We report four unusual and severe cases of CDI in surgical patients with a review of the relevant literature.

RESULTS

One patient developed CDI and required a colectomy for a perforated viscus. He developed C. difficile ileitis 12 days later that responded to medical therapy. Another patient who underwent a colectomy for infrarenal aortic occlusion, later in his hospital course, developed C. difficile ileitis and died. The third patient was hospitalized for several months for hypertension and associated morbidities. Eventually he developed severe abdominal pain and was found to have a small bowel mural abscess that grew C. difficile on culture. A fourth patient, taking long-term antibiotics for a surgical site infection of the knee, developed unexplained leukocytosis without diarrhea. Colonoscopy revealed pseudomembranous colitis that advanced to toxic megacolon. She required a colectomy and ultimately died from the disease.

CONCLUSIONS

Patients are at high risk from CDI in this modern era. Disease manifestations may differ from the typical presentation. A heightened awareness for diagnosing this dangerous, evolving disease is paramount.

The enterotoxicity of Clostridium difficile toxins

The major virulence factors of Clostridium difficile infection (CDI) are two large exotoxins A (TcdA) and B (TcdB). However, our understanding of the specific roles of these toxins in CDI is still evolving. It is now accepted that both toxins are enterotoxic and proinflammatory in the human intestine. Both purified TcdA and TcdB are capable of inducing the pathophysiology of CDI, although most studies have focused on TcdA. C. difficile toxins exert a wide array of biological activities by acting directly on intestinal epithelial cells. Alternatively, the toxins may target immune cells and neurons once the intestinal epithelial barrier is disrupted. The toxins may also act indirectly by stimulating cells to produce chemokines, proinflammatory cytokines, neuropeptides and other neuroimmune signals. This review considers the mechanisms of TcdA- and TcdB-induced enterotoxicity, and recent developments in this field.

Piglet models of acute or chronic Clostridium difficile illness

We examined the piglet model of Clostridium difficile illness (CDI) in humans, because swine are naturally susceptible to C. difficile. The piglet is a reproducible model of acute or chronic CDI with characteristic pseudomembranous colitis. Germ-free piglets were consistently and extensively colonized after oral challenge with the human strain 027/BI/NAP1, establishing an infectious dose-age relationship. This allowed a demarcation between acute fatal and chronic models. The clinical manifestations of disease inclusive of gastrointestinal and systemic symptoms and characteristic mucosal lesions of the large bowel (including pseudomembranous colitis) are described. Additionally, we demonstrate the presence of toxins in feces, body fluids, and serum and a significant elevation in interleukin 8 levels in animals with severe disease. We conclude that piglets infected with C. difficile mimic many of the key characteristics observed in humans with CDI and are suitable animals in which to investigate the role played by virulence attributes, drug efficacy, and vaccine candidates.

Clostridium perfringens liver abscess after pancreatic resection

BACKGROUND

Liver abscess is a rare complication after pancreatectomy. Clostridium perfingens is a rare cause of intrahepatic infections.

CASE REPORT

A 65-year-old woman with pancreatic cancer underwent explorative laparotomy, during which encasement of the hepatic artery by the tumor was found. Neoadjuvant radiochemotherapy with capecitabine was started, which caused tumor regression, and duodenopancreatectomy was performed. The portal vein was occluded and infiltrated by cancer and therefore was resected and not reconstructed. After a slow recovery, the patient developed hemorrhage at the gastrojejunal anastomosis, which was controlled by fibrin injection. Within a few days, she presented with signs of sepsis, and blood cultures yielded Clostridium perfringens, Streptococcus oralis, Staphylococcus aureus, and Candida albicans. The source of the sepsis proved to be a 9-cm liver abscess, which was drained; cultures grew C. perfringens, Hafnia alvei, and Enterobacter cloacae. Despite antibiotic treatment, the patient died from sepsis and multiorgan failure 27 days after pancreatic surgery.

CONCLUSION

Such rare infections can follow pancreatic resection with neoadjuvant radiochemotherapy. Clostridium perfringens-associated liver abscess maintains a high mortality rate.

Antibody-enhanced, Fc gamma receptor-mediated endocytosis of Clostridium difficile toxin A

Toxin A (TcdA) and toxin B (TcdB) are major virulence factors of Clostridium difficile. These two toxins intoxicate cultured cells by similar mechanisms, and TcdB generally is more potent than TcdA in cultured cells. The exact reason for this difference is unclear. Here, we report that the cellular effects of TcdA can be substantially enhanced via an opsonizing antibody through Fc gamma receptor I (FcgammaRI)-mediated endocytosis. A TcdA-specific monoclonal antibody, A1H3, was found to significantly enhance the cytotoxicity of TcdA to macrophages and monocytes. The A1H3-dependent enhancement of glucosyltransferase activity, cytoskeleton disruption, and tumor necrosis factor alpha production induced by TcdA was further demonstrated using RAW 264.7 cells. Subsequent experiments indicated that the interaction of FcgammaRI with A1H3 underlays the antibody-dependent enhancement of the cellular effects of TcdA. While blocking FcgammaRII and FcgammaRIII with anti-CD16/32 antibodies did not affect the TcdA-mediated glucosylation of Rac1 in RAW 264.7 cells, presaturation of FcgammaRI with anti-CD64 antibodies in THP1 cells significantly reduced this activity. Incubation of a TcdA-A1H3 immune complex with recombinant mouse CD64 completely abrogated the A1H3-mediated enhancement of the glucosyltransferase activity of TcdA in RAW 264.7 cells. Moreover, expression of FcgammaRI in CHO cells strikingly enhanced the sensitivity of these cells to TcdA complexed with A1H3. We showed that the presence of A1H3 facilitated cell surface recruitment of TcdA, contributing to the antibody-dependent, FcgammaRI-mediated enhancement of TcdA activity. Finally, studies using chlorpromazine and endosomal acidification inhibitors revealed an important role of the endocytic pathway in the A1H3-dependent enhancement of TcdA activity.

Elucidating the in vivo targets of bacterial toxins

Many bacterial pathogens release soluble proteins, referred to as toxins, which damage host cells during disease. In the past, bacterial toxins have been studied extensively using cultured cells, and in vitro biochemical systems. However, little is known about the types of cells targeted by toxins during the disease process while within the host. This has limited our understanding of these important virulence factors. To address this problem, we have recently used transparent zebrafish embryos to follow toxin activity in a multiorgan system in real-time. Zebrafish provide many advantages over more traditional animal models, since major organs can be directly visualized by light microscopy. This allows one to follow toxin activity and organ damage as it occurs following intoxication. As proof-of-principle, we have recently exploited the zebrafish embryo to identify the activities of Clostridium difficile toxin B, an intracellular bacterial toxin. By using the zebrafish system we have been able to identify a major organ, the heart, targeted by this toxin.

Molecular characterization and antimicrobial susceptibilities of extra-intestinal Clostridium difficile isolates

Amongst 25 extra-intestinal clinical isolates of Clostridium difficile, A(+)B(+) (72%) and A(-)B(+) (4%) toxigenic phenotypes, as well as the non-toxigenic phenotype (A(-)B(-)) (24%), were identified. The A(-)B(-) isolates did not express toxin, yet carried part of the tcdA and tcdB gene and are of a previously unreported toxinotype. Six A(+)B(+) isolates also carried binary toxin genes. Resistance to erythromycin (20%), clindamycin (48%), tetracycline (16%), moxifloxacin (16%) and imipenem (11%) occurred but with no apparent correlation to phenotype. None of the strains was resistant to vancomycin or metronidazole. Imipenem-resistance decreased by EDTA, but susceptibility to meropenem suggests the presence of an imipenem specific metalloenzyme.

Identification of Clostridium difficile toxin B cardiotoxicity using a zebrafish embryo model of intoxication

Clostridium difficile toxin B (TcdB) has been studied extensively by using cell-free systems and tissue culture, but, like many bacterial toxins, the in vivo targets of TcdB are unknown and have been difficult to elucidate with traditional animal models. In the current study, the transparent Danio rerio (zebrafish) embryo was used as a model for imaging of in vivo TcdB localization and organ-specific damage in real time. At 24 h after treatment, TcdB was found to localize at the pericardial region, and zebrafish exhibited the first signs of cardiovascular damage, including a 90% reduction in systemic blood flow and a 20% reduction in heart rate. Within 72 h of exposure to TcdB, the ventricle chamber of the heart became deformed and was unable to contract or pump blood, and the fish exhibited extensive pericardial edema. In line with the observed defects in ventricle contraction, TcdB was found to directly disrupt coordinated contractility and rhythmicity in primary cardiomyocytes. Furthermore, using a caspase-3 inhibitor, we were able to block TcdB-related cardiovascular damage and prevent zebrafish death. These findings present an insight into the in vivo targets of TcdB, as well as demonstrate the strength of the zebrafish embryo as a tractable model for identification of in vivo targets of bacterial toxins and evaluation of novel candidate therapeutics.

Prevalence of Clostridium Difficile Colonization at Admission to Rehabilitation

OBJECTIVES

To assess the prevalence of intestinal colonization with Clostridium difficile (C. difficile) at admission to acute rehabilitation and to identify risk factors associated with colonization.

DESIGN

Case-control study.

PARTICIPANTS

Consecutive admissions to 2 rehabilitation units (spinal cord injury, brain injury and stroke).

SETTING

Free-standing acute rehabilitation facility.

INTERVENTIONS

Rectal swabs for culture for C. difficile were obtained at admission and cytotoxin assay performed on all culture positive specimens. Rates of colonization with cytotoxic C. difficile were calculated. Charts were reviewed for medical and demographic factors that may have predisposed patients to colonization, and for possible symptoms at the time of admission.

MAIN OUTCOME MEASURES

Percentage of patients with culture and cytotoxin assay positive for C. difficile. Frequency of specific patient characteristics that could predispose to C. difficile colonization.

RESULTS

Of admission stool samples, 16.4% tested positive for C. difficile; none of these patients had been identified as colonized before admission. No patients were discordant for C. difficile positivity on culture and presence of a toxigenic strain. No medical or demographic factors were associated with increased risk of colonization, including age (t(52)=-.748, P=.458, not significant [NS]), diarrhea within 24 hours of admission (chi(1)(2) test=.001, P=.973 [NS]), or use of oral or intravenous antibiotics at admission (chi(1)(2) test=.044, P=.834 [NS]).

CONCLUSIONS

Patients admitted to acute rehabilitation may have an elevated rate of intestinal colonization with C. difficile without having clinical symptoms. No medical or demographic characteristics were found to be predictive of colonization, however, most of the patients admitted had more than 1 factor that may have increased their susceptibility to infection with this organism. Inadvertent transfer of this organism within the rehabilitation setting may occur because asymptomatic colonization is not recognized.

Identification and characterization of a fibronectin-binding protein from Clostridium difficile

A 68 kDa fibronectin-binding protein (Fbp68) from Clostridium difficile displaying significant homology to several established or putative Fbps from other bacteria was identified. The one-copy gene is highly conserved in C. difficile isolates. Fbp68 was expressed in Escherichia coli in fusion with glutathione S-transferase; the fusion protein and the native Fbp68 were purified. Immunoblot analysis and cell fractionation experiments revealed that Fbp68 is present on the surface of the bacteria. Far-immuno dot-blotting demonstrated that Fbp68 was capable of fixing fibronectin. Indirect immunofluorescence and ELISA were employed to demonstrate that C. difficile could bind both soluble and immobilized fibronectin. With competitive adherence inhibition assays it was shown that antibodies raised against Fbp68 partially inhibited attachment of C. difficile to fibronectin and Vero cells. Furthermore, Vero cells could fix purified membrane-immobilized Fbp68. Thus Fbp68 appears to be one of the several adhesins identified to date in C. difficile.

Clostridium difficile

Clostridium difficile is the most commonly identified infective cause of antibiotic associated diarrhoea. Broad spectrum antibiotics, are most frequently incriminated, although short (<3 day) antibiotic courses cause fewer episodes. Gold standard cell-culture based cytotoxin assays have been compared to rapid immunoassays, which are less effective, especially since toxin A negative, toxin B positive strains have been shown to be truly virulent. Details of colonization and adherence mechanisms have been revealed, and clonal spread has been demonstrated. The mainstay of treatment of C. difficile infection remains metronidazole. Justified fears over resistance are leading to development of alternative therapeutic strategies. These include a toxin binding polymer and ongoing biotherapy research. An antibody rise to toxin A during an episode of C. difficile diarrhoea protects against recurrence, and trials are in progress to investigate immunization: a toxoid vaccine which is immunogenic and safe in healthy volunteers shows promise for the future.

Extra-intestinal infections caused by Clostridium difficile

The objective of this paper was to investigate the incidence of extra-intestinal infections caused by Clostridium difficile. During a 10-year period, the microbiology laboratory of our institution isolated 2034 isolates of C. difficile. Of the 2034 isolates, 21 (1.08%) were obtained from extra-intestinal sources. This represents an incidence of extra-intestinal isolation of four cases per 100 000 admissions. We were able to review the records of 17 patients for our study. The isolates in 12 patients were obtained from structures or fluids anatomically close to the colon and included the following infections: peritonitis in five cases (three primary and two secondary), intra-abdominal abscesses in three patients and abdominal wound infections in four cases. The infections in the other five patients were not in the anatomic vicinity of the colon. They included one case with a brain abscess, two episodes of bacteremia and two cases of foot infections (one chronic osteomyelitis). In all but one case, C. difficile isolation was obtained as part of a polymicrobial flora. The isolates were frequently non-toxigenic and the extra-intestinal infections occurred without concomitant diarrhea or prior anti-microbial therapy. Out of the 17 patients, eight died and nine survived. Death could not be directly attributed to C. difficile in any of the cases. The isolation of C. difficile outside the intestinal tract is very uncommon. Its clinical significance should be interpreted with caution.