Clostridium difficile toxin

Immune responses to Clostridium difficile infection

Clostridium difficile is the causal agent of antibiotic-associated diarrhea and is a leading cause of hospital-acquired infections in the US. C. difficile has been known to cause severe diarrhea and colitis for more than 30 years, but the emergence of a newer, hypervirulent strain of C. difficile (BI/NAP1) has further compounded the problem, and recently both the number of cases and mortality associated with C. difficile-associated diarrhea have been increasing. One of the major drivers of disease pathogenesis is believed to be an excessive host inflammatory response. A better understanding of the host inflammation and immune mechanisms that modulate the course of disease and control host susceptibility to C. difficile could lead to novel (host-targeted) strategies for combating the challenges posed by this deadly infection. This review summarizes our current knowledge of the host inflammatory response during C. difficile infection.

Clostridium difficile: progress and challenges

There is a surge of new interest in C. difficile infection (CDI) reflecting substantial increases in cases and fatalities. The new challenges by this now old pathogen have brought renewed interest in all facets of the disease. Particularly important are the role of fluoroquinolones as inducing agents, the new polymerase chain reaction test to detect toxigenic strains in stools, the important role of the NAP-1 strain, recent evidence favoring oral vancomycin over metronidazole in seriously ill patients, and new guidelines for management.

Laparoscopic Management of Adhesive Small Bowel Obstruction

Adhesions from prior surgery are the most common cause of small bowel obstruction (SBO) in the Western world. Although laparoscopic adhesiolysis can be performed safely and effectively, the indications and contraindications to the use of laparoscopic techniques in SBO are not clearly defined. The goal of our study was to determine the outcomes of the laparoscopic approach to SBO and discuss patient considerations for its utilization. We retrospectively surveyed all patients undergoing laparoscopic or attempted laparoscopic adhesiolysis performed by the authors between July 1997 and March 2006. Data obtained included patient demographics, clinical and radiologic presentation, and intraoperative and postoperative course. Thirty-three patients underwent laparoscopic adhesiolysis secondary to a SBO. Mean age was 53.6 years (range, 29–84 years) and 64 per cent (21 of 33) were female. Mean body mass index was 30.0 kg/m2 (range, 22.6–46.1 kg/m2). Thirty-one patients (93.9%) had undergone between one and four abdominal surgeries and seven (21.2%) had a previous episode of SBO. There were no patients with peritonitis. Abdominal CT scan was performed preoperatively in 27 patients (81.8%). Laparoscopy diagnosed the site of obstruction in all patients. Twenty-nine patients (88%) were successfully treated laparoscopically. Conversion to laparotomy was required in four cases as a result of dense adhesions and/or a lack of working space. Mean procedural time was 101 minutes (range, 19–198 minutes). There was one intraoperative complication (enterotomy), which was repaired laparoscopically and did not require conversion. Conversion was associated with significantly increased procedural time (129 versus 93 minutes; P = 0.02), but not blood loss or complications. Average times to passage of flatus and first bowel movement were 2.3 days (range, 0.5–5 days) and 3.2 days (range, 1–6 days), respectively. Seven patients (21.2%) had postoperative complications, including wound infection, urinary tract infection, and acute renal insufficiency, all of which occurred in patients completed laparoscopically. One patient had a recurrent SBO 8 months postoperatively managed by repeat laparoscopic lysis of adhesions. Mean postoperative stay was 6 days (range, 1–19 days). There was no hospital mortality. Laparoscopy is safe and feasible in the management of acute SBO in selected patients. It is an excellent diagnostic tool and is therapeutic in most cases.

Host damage from bacterial toxins

Bacterial infection often involves toxin-mediated damage to the host. This can occur at mucosal epithelial surfaces, in subepithelial tissues (involving connective tissue, blood vessels and host defence cells), or at organ or tissue sites distant from the focus of infection. This paper deals with host damage at each of these levels and examples have been selected of toxins that have a well defined role in pathogenesis and for which evidence is less clear cut. Current views of mechanisms of host damage are presented along with summaries of mode of action at the molecular level where this is known. Certain unifying features of mechanisms of toxin action on host cells are emphasised. Modern genetic methods and gene cloning techniques should help in the assessment of the role of individual toxic factors where pathogenesis is multifactorial, and preliminary examples of this approach are mentioned. The search for new toxins continues and this is illustrated with reference to the toxins involved in the staphylococcal scalded skin syndrome and staphylococcal toxic shock syndrome. This overview is intended to convey an impression of the rapid development that has taken place in knowledge of the role of toxins in pathogenesis.

Studies on the resistance of Clostridium difficile to antimicrobial agents

The susceptibility of C. difficile isolated at the Department of Medical Microbiology of the University of Zurich to a wide selection of antibacterial, antimycobacterial and antifungal agents was tested in vitro. Great differences in susceptibility were found against chloramphenicol, clindamycin, erythromycin, rifamycin, and tetracycline. Resistance to clindamycin and erythromycin could always be transferred jointly to a susceptible C. difficile strain by mixed culture on filters at low frequencies (1 X 10(-8) to 4 X 10(-8) per donor cell). Transfer of tetracycline resistance occurred at frequencies of 3 X 10(-7) to 5 X 10(-7). Chloramphenicol and rifamycin resistance could not be transferred in the system used (frequencies less than 10(-8)). Although a total of 38,000 colonies was screened by various methods known to affect plasmid replication, resistance to chloramphenicol, clindamycin, erythromycin, rifamycin, and tetracycline could not be eliminated. No connection between plasmid DNA and antimicrobial resistance could be established. Especially, no plasmid DNA was involved in the transfer of resistance determinants from resistant to susceptible strains.

Diagnosis of Clostridium difficile-associated intestinal disease

Toxigenic Clostridium difficile is the major cause of antimicrobial agent-associated pseudomembranous colitis and is the etiological agent of approximately 30% of cases of nonspecific colitis and diarrhea (without colitis) induced by antimicrobial agents. In addition, C. difficile has been implicated in certain intestinal diseases not related to prior antimicrobial administration. C. difficile has been reported to be one of the most common enteropathogens isolated from stool specimens submitted to hospital laboratories. Thus, diagnosis of C. difficile-associated intestinal disease should now be routinely performed in diagnostic clinical laboratories. The diagnosis of C. difficile-associated intestinal disease relies on the demonstration of either the organism or the toxin(s) in stool specimens or antibody response in serum to the toxin(s). Several selective medium are available for the recovery of C. difficile from stool specimens. The toxin(s) of C. difficile can be demonstrated using a variety of techniques, including biological assays as well as immunological assays. This article will review the techniques currently available to aid in the diagnosis of C. difficile-associated intestinal disease.

Transferable resistance to clindamycin, erythromycin, and tetracycline in Clostridium difficile

Resistance to clindamycin, erythromycin, and streptogramins in Clostridium difficile could be transferred to a susceptible strain by mixed culture at low frequencies (1 x 10(-8) to 4 - 10(-8) per donor cell). Transfer of tetracycline resistance occurred at frequencies of 3 x 10(-7) to 5 x 10(-7). No plasmid DNA involved in these transfers could be detected.

Prospective study of gram-stained stool smears in diagnosis of Clostridium difficile colitis

Gram stains of stools from patients with diarrhea and control patients with no diarrhea were examined for a predominance of gram-positive rods and the presence of polymorphonuclear leukocytes. Results were compared with those from lower gastrointestinal endoscopy for pseudomembranes. Clostridium difficile culturing, and C. difficile toxin assay. The Gram stain was moderately difficult to interpret and was not useful in diagnosing diarrheal disease associated with C. difficile.

Interaction of Clostridium difficile toxins and mouse hepatic microsomes

Intraperitoneal administration of toxins of Clostridium difficile to mice resulted in loss of hepatic cytochrome P450 and peroxidation of microsomal lipids. Pretreatment with the microsomal enzyme inducer beta-naphthoflavone partially alleviated these effects and increased survival time of intoxicated animals.

Biochemical and pathological effects of Clostridium difficile toxins in mice

Toxins produced by Clostridium difficile are lethal to mice after i.p. administration. Among the alterations observed when mice were given a preparation containing both Toxin A and Toxin B were a 1.6 +/- 0.2 degrees C (mean +/- S.E., N = 7) depression of rectal body temperature, blood in the liver (318 +/- 13% of control levels) and a decrease in glutathione concentration (74 +/- 2% of control). Purified Toxin A and purified Toxin B were both able to alter these parameters. Toxin B, however, had a more profound effect on serum isocitrate dehydrogenase levels (raised to 198 +/- 18% of control) and liver O-demethylase activity (reduced to 64 +/- 8% of control), parameters sensitive to alteration in liver damage. The effects of Toxin B on these parameters were partially alleviated in mice pretreated with N-acetylcysteine (1.2 g/kg i.p.) and triamcinolone (120 mg/kg i.p.) and, although the percentage of survivors did not improve, survival time was increased from 3.0 +/- 0.1 hr to 4.6 +/- 0.5 and 5.7 +/- 1.3 hr, respectively, by these agents.