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Resistance determinants in strains of Clostridium difficile from two geographically distinct populations.

Ninety-three clinical isolates of Clostridium difficile, comprising 65 from Royal Gwent Hospital, Newport and 28 from Southmead Hospital, Bristol were examined to determine the prevalence of genes coding for macrolide resistance and to explore differences in susceptibility patterns. Antibiogram testing produced similar results for both sets of strains with respect to amoxicillin, tetracycline, erythromycin and cefotaxime. Results differed for rifampicin, where 53% of the Bristol isolates were resistant, compared with 3% of the Newport isolates. Clindamycin disc susceptibility testing produced similar resistance rates. However, clindamycin MIC determinations revealed that 53% of the Bristol strains exhibited high-level resistance (MIC > 256 mg/L), whereas strains from Newport had clindamycin MICs ranging from 0.25 to 3mg/L. erm (B) was present in 15 of the strains from Bristol and in none of the Newport strains. erm (F) and erm (Q) were not detected in either population. The two geographically distinct populations of C. difficile differed considerably in their susceptibility to antibiotics. The possibility that C. difficile may serve as a conservator for resistant determinants subsequent to exposure to antimicrobial agents, has important implications for infection control.

Bacterial Proteins↗

Toxigenic C. difficile induced inflammatory marker expression by human intestinal epithelial cells is asymmetrical.

Clostridium difficile infection of the intestinal epithelium and consequent pseudomembranous colitis is an important cause of morbidity and mortality. Pathogenesis has been ascribed exclusively to toxin production. Using in vitro models of human intestinal epithelial layers, we show that exposure to toxigenic C. difficile upregulates epithelial expression of IL-8 and ICAM-1, two molecules important in neutrophil chemoattraction and adhesion and subsequent inflammation. IL-8 production was also stimulated by toxin-containing supernatants. C difficile induced IL-8 release was inhibited by specific antiserum. Increased ICAM-1 expression only occurred after basolateral exposure to C. difficile while apical exposure had no effect on ICAM-1 expression. However, transepithelial electrical resistance was impaired by apical exposure to bacterial suspensions. We suggest that apical exposure to C. difficile induces changes in epithelial layer integrity which allows the bacteria and/or the toxin access to the basolateral compartment where pathogenic inflammatory mechanisms are activated.

Antibodies, Blocking↗

Clonal dissemination of a toxin-A-negative/toxin-B-positive Clostridium difficile strain from patients with antibiotic-associated diarrhea in Poland.

OBJECTIVE: To determine the incidence of toxin-A-negative/toxin-B-positive Clostridium difficile strains and their genetic relatedness in the feces of patients suffering from antibiotic-associated diarrhea (AAD) in Polish hospitals. METHODS: C. difficile strains were cultured from patients' stool samples. The present study characterises these strains with respect to their cytopathogenicity on McCoy cells and the absence of toxin A despite a functional toxin B as determined with commercial test kits (Culturette Brand Toxin CD-TCD toxin A test and C. difficile Tox A/B test). In addition, PCR using different primer pairs aiming at non-repeating or repeating regions of the toxin A and B genes were used to confirm the findings. All toxin A(-)B(+) strains were genetically characterised by random amplification of polymorphic DNA (RAPD) analysis, PCR ribotyping and, in part, pulsed-field gel electrophoresis (PFGE) of DNA macrorestriction fragments. RESULTS: We here present the presence of 17 toxin A(-)B(+) strains among 159 C. difficile strains (11%) isolated from fecal samples from 413 patients with antibiotic-associated diarrhea. All 17 strains possessed the toxin B gene, demonstrated a cytopathogenic effect on the McCoy cells, and were positive in the Tox A/B test. Molecular typing of these 17 C. difficile strains revealed that 7 of 17 (41%) toxin A(-)/B(+) C. difficile strains could not be discriminated. It appeared that these strains had a genotype that could not be distinguished from that of a Japanese control strain. CONCLUSION: Our observations imply that a particular genotype of toxin A(-)B(+) C. difficile has spread extensively, not only in Poland but possibly even worldwide.

Anti-Bacterial Agents↗

Cytotoxic effects of children's faeces: relation to diarrhoea due to Clostridium difficile and other enteric pathogens.

Cytotoxicity of faecal extracts was demonstrated in 47 of 88 children (54%) referred for microbiological investigation of stools. Cytotoxic Clostridium difficile and vertotoxigenic Escherichia coli (VTEC) were the pathogens identified most commonly but cytotoxicity was also found in association with Campylobacter jejuni, Salmonella spp, Shigella sonnei, Giardia lamblia, rotavirus, adenovirus and poliovirus type 1 which had been acquired by oral immunization. In two patients, one of whom had cystic fibrosis, cytotoxicity of faecal extracts was associated with isolation of Pseudomonas aeruginosa. In five of 13 patients with diarrhoea and cytotoxic C. difficile, other pathogens were also present, in agreement with the view that C. difficile are more readily recovered when the intestinal flora have been altered by colonization with other micro-organisms. There was no correlation between previous treatment with antibiotics and isolation of C. difficile. Cytotoxicity neutralized by antitoxin, usually to C. sordellii, is used to detect cytotoxic C. difficile. We suggest that cytotoxicity not neutralized in this way should be an indication for further investigation of stools for the presence of other pathogens such as VTEC or viruses.

Adolescent↗

Binary toxin-producing, large clostridial toxin-negative Clostridium difficile strains are enterotoxic but do not cause disease in hamsters.

Binary toxin CDT or its genes have been identified in some strains of Clostridium difficile that also produce the large clostridial toxins, toxins A and B (A+B+CDT+), including a newly recognized epidemic strain in the United States and Canada. To study the effects of binary toxin alone, we characterized 4 binary toxin CDT-positive only (A-B-CDT+) C. difficile strains. Unlike other clostridial binary toxins, binary toxin CDT required exogenous trypsin for activation. Supernatants from all A-B-CDT+ strains caused marked fluid accumulation in the rabbit ileal loop assay after concentration and trypsinization. In addition, the ileal loop response was neutralized by antisera raised against other binary toxin-producing clostridia. Challenge of clindamycin-treated hamsters with these strains resulted in colonization but not diarrhea or death. Binary toxin CDT may play an adjunctive role to toxins A and B in the pathogenesis of C. difficile-associated disease but by itself may not be sufficient to cause disease.

Animals↗

Multicenter typing comparison of sporadic and outbreak Clostridium difficile isolates from geographically diverse hospitals.

In a collaborative study by three laboratories, arbitrarily primed polymerase chain reaction (AP-PCR), HindIII restriction enzyme analysis (REA), and pulsed-field gel electrophoresis (PFGE) using SmaI were compared for typing of Clostridium difficile. The study included 30 isolates from nosocomial outbreaks in six geographically disparate hospitals and 15 isolates from sporadic cases of C. difficile diarrhea. REA distinguished a total of 23 types representing 10 groups; AP-PCR performed at Deaconess Hospital resolved 19 types; AP-PCR performed at the Centers for Disease Control resolved 15 types. Thirty isolates exhibited degradation of larger sized fragments during processing and therefore were nontypeable by PFGE; among the remaining 15 isolates, PFGE resolved 11 types. Outbreak isolates in five different hospitals represented REA group J and constituted a single AP-PCR strain. In summary, nosocomial outbreaks of C. difficile diarrhea in five hospitals were associated with a single genetic lineage as resolved by multiple strain typing systems.

Bacterial Typing Techniques↗

Nosocomial infection with Clostridium difficile investigated by pyrolysis mass spectrometry.

Fifty-eight isolates of Clostridium difficile from two distinct outbreaks were examined for inter-strain similarity by pyrolysis mass spectrometry (PMS). The first outbreak began on a geriatric acute unit and spread to a long stay geriatric facility. PMS analysis showed that most isolates from both sites were indistinguishable. Isolates obtained in the preceding year from the long stay facility were found to be closely similar to these outbreak isolates. In the second, smaller outbreak on a female medical ward in another general hospital, PMS again showed that a single strain was probably responsible. Representative isolates from these two different outbreaks were shown to be distinct. The ability to compare rapidly large numbers of isolates of C. difficile makes PMS attractive for initial screening in suspected outbreaks, providing important information for outbreak management and allowing conventional typing methods to be concentrated on relevant isolates.

Aged↗

Growth inhibition of Clostridium difficile by intestinal flora of infant faeces in continuous flow culture.

Growth of Clostridium difficile was inhibited more strongly in continuous flow (CF) culture with C. difficile-negative faeces of infants than with C. difficile-positive faeces. Culture of faecal flora of infants yielded a greater variety of bacterial species in C. difficile-negative than in C. difficile-positive faeces. In the mixed CF culture of C. difficile with Enterococcus avium, Bacteroides distasonis, Eubacterium lentum, C. ramosum, C. perfringens and either Escherichia coli or Klebsiella pneumoniae isolated from C. difficile-negative faeces, inhibition of growth of C. difficile was demonstrated when the pH of the culture medium was decreased. Amino-acid analysis of CF cultures showed considerable utilisation of aspartic acid, serine, threonine, arginine and asparagine. A marked increase in concentrations of citrulline and ornithine was found in the culture that inhibited growth of C. difficile. The addition of citrulline and ornithine into a Gifu anaerobic medium (GAM) broth produced no inhibition of growth of C. difficile. The addition of the mixture of the depleted amino acids (aspartic acid, serine, threonine, arginine and asparagine) to the culture filtrate or adjustment of the pH of the culture filtrate induced considerable growth of C. difficile. These results suggest that the inhibition of growth of C. difficile may be due to consumption of amino acids by intestinal flora, and not to the presence of inhibitors produced by the intestinal flora.

Amino Acids↗

Inhibition of Clostridium difficile strains by intestinal Lactobacillus species.

Indigenous intestinal microflora (including lactobacilli) has an important role in protection against Clostridium difficile infection. To assess in vitro interaction between lactobacilli and C. difficile, antagonistic activity of 50 intestinal Lactobacillus spp. strains against 23 pathogenic C. difficile strains was determined. Phenotypic properties of C. difficile strains [production of short-chain fatty acids (SCFAs) and toxin A, and antimicrobial susceptibility] and lactobacilli (production of SCFAs and H(2)O(2)) were investigated. Five lactobacilli (Lactobacillus paracasei and Lactobacillus plantarum species) were antagonistic to all C. difficile strains, 18 were antagonistic to some C. difficile strains and 27 showed no antagonistic activity. This antagonistic activity was strain-specific and seemed to correlate with H(2)O(2) and lactic acid production. C. difficile strains that were more sensitive to lactobacilli (n = 9) usually produced higher toxin levels and more SCFAs, and were more resistant to antibiotics, than strains that were resistant to lactobacilli (n = 14). Compatibility of C. difficile strain properties (resistance to lactobacilli or antibiotics) with intestinal microecological conditions (e.g. presence of antagonistic lactobacilli, concentration of antibiotics) may determine expression of disease.

Anti-Bacterial Agents↗

Prevalence and association of PCR ribotypes of Clostridium difficile isolated from symptomatic patients from Warsaw with macrolide-lincosamide-streptogramin B (MLSB) type resistance.

Isolates (79 in total) of Clostridium difficile obtained over a 2 year period from 785 patients suspected of having C. difficile-associated diarrhoea (CDAD) and being hospitalized in the University Hospital in Warsaw were characterized by toxigenicity profile and PCR ribotyping. Furthermore, their susceptibility to clindamycin and erythromycin was determined. Among the 79 C. difficile isolates, 35 were classified as (A+)B+, 1 as (A+)(B+)CDT+, 36 as (A-)B+ and 7 as (A-)B-. A total of 21 different PCR ribotypes was detected. Two main (A+)B+ strains circulated in our hospital: ribotype 014 and ribotype 046. Unexpectedly, the predominant PCR ribotype was type 017, a known (A-)B+ strain, and this accounted for about 45.5 % of all isolates cultured from patients with CDAD. Isolates belonging to PCR ribotype 017 were found in cases from epidemics of antibiotic-associated diarrhoea in the internal and surgery units. High-level resistance (MIC > or = 256 mg l(-1)) to clindamycin and erythromycin was found in 39 (49 %) of the C. difficile isolates. Interestingly, 34 (94 %) of macrolide-lincosamide-streptogramin B (MLSB) type resistance strains did not produce toxin A, but produced toxin B and were (A-)B+ ribotype 017. Thirty-seven of the high-level resistance strains harboured the erythromycin-resistance methylase gene (ermB). C. difficile isolates (2/29) that had high-level clindamycin and erythromycin resistance, and belonged to PCR ribotype 046, were ermB negative. These investigations revealed that the predominant C. difficile strain isolated from symptomatic patients hospitalized in University Hospital in Warsaw was MLSB-positive clindamycin/erythromycin-resistant PCR ribotype 017.

Anti-Bacterial Agents↗

Clinical manifestations, treatment and control of infections caused by Clostridium difficile.

Clostridium difficile should be suspected in patients who present with nosocomial diarrhoea. It is more common in the elderly or in patients with a debilitating underlying condition who have received antimicrobial agents, and up to 20-25% of patients may experience a relapse. The reference method for diagnosis is the cell culture cytotoxin test which detects the presence of toxin B in a cellular culture of human fibroblasts, but recovering C. difficile in culture allows the performance of a ''second-look" cell culture assay that enhances the potential for diagnosis. Oral metronidazole (500 mg tid or 250 mg every 6 hrs) and oral vancomycin (125 mg every 6 hrs) administered for 1014 days have similar therapeutic efficacy, with response rates near 90-97%. C. difficile strains resistant to metronidazole and with intermediate resistance to vancomycin have been described. The administration of probiotics such as Saccharomyces boulardii, Lactobacillus sp. or brewer's yeast for prophylaxis of CDAD remains controversial.

Anti-Bacterial Agents↗

International typing study of toxin A-negative, toxin B-positive Clostridium difficile variants.

Clinically important strains of Clostridium difficile that do not produce toxin A but produce toxin B and are cytotoxic (A(-)/B(+)) have been reported from multiple countries. In order to compare the relatedness of these strains, we typed 23 A(-)/B(+) C. difficile isolates from the United Kingdom (6 isolates), Belgium (11 isolates), and the United States (6 isolates) by three well-described typing methods. Restriction endonuclease analysis (REA), PCR ribotyping, and serogrouping differentiated 11, 4, and 3 different strain types, respectively. Twenty-one of the 23 A(-)/B(+) variants had a 1.8-kb truncation of the toxin A gene characteristic of toxinotype VIII strains; 20 of the 21 toxinotype VIII-like strains were PCR type 17. PCR type 17 isolates could be differentiated into two separate strain groups by serogrouping and by REA. REA further discriminated these isolates into eight subgroups (REA types). PCR type 17-serogroup F-REA group CF isolates were recovered from all three countries, and one specific REA type, CF4, was recovered from patients with C. difficile disease in the United Kingdom and the United States. C. difficile A(-)/B(+) variants of apparent clonal origin are widely distributed in Europe and North America.

Adult↗

Clonal spread of a Clostridium difficile strain with a complete set of toxin A, toxin B, and binary toxin genes among Polish patients with Clostridium difficile-associated diarrhea.

Clinically relevant Clostridium difficile strains usually produce toxins A and B. Some C. difficile strains can produce an additional binary toxin. We report clonality among five strains carrying all toxin genes from Polish patients with C. difficile-associated diarrhea. In another strain, possible recombination between binary toxin genes is documented.

Adolescent↗

Preparation of antibacterial and antitoxic Clostridium difficile sera.

Preparation of Clostridium difficile antibacterial and antitoxic sera is presented. Fifty one strains (72%) were typeable within Delmee scheme. Twenty strains (28%) belonged to new Polish serogroups designated 18, 27, 70, 71, 72, 88, 89 and NICH. Supernatants of all toxigenic Clostridium difficile strains were neutralized by gamma-globulin fraction of goat Clostridium difficile antitoxin in neutralization assay when it was performed on McCoy cell line. Only 8 toxigenic strains (21%) were positive in counterimmunoelectrophoresis.

Animals↗

The chemotactic response of human granulocytes to Clostridium difficile toxin A is age dependent.

Elderly patients are at high risk for developing diarrhea and colitis as a complication of antimicrobial therapy. Clostridium difficile, the causative agent of antibiotic-associated diarrhea and colitis produces an enterotoxin (toxin A) and a cytotoxin (toxin B). Of these two exotoxins, toxin A appears to be largely responsible for the inflammatory phenomena of C. difficile colitis, because it produces secretion, pronounced granulocytic infiltration, and epithelial cell necrosis and ulceration in ligated ileal loops of experimental animals. We have recently demonstrated that the inflammatory effects of C. difficile toxin A in the intestine may be related to its ability to mobilize intracellular calcium and elicit a chemotactic response by human granulocytes. In this study, in order to explain why the elderly are at greater risk for developing antibiotic-associated colitis, we investigated the effects of toxin A on activation of granulocytes from healthy elderly and young subjects. Highly purified toxin A and the chemotactic factor N-formyl-Met-Leu-Phe (FMLP) at concentrations of 10(-7) M both elicited a significant (p less than 0.001) and comparable chemotactic and chemokinetic response in human granulocytes from both age groups. A significantly (p less than 0.001) increased chemotactic effect in elderly subjects compared with young subjects was elicited by toxin A and not by FMLP. These findings suggest that the enhanced intestinal inflammatory effects of C. difficile in the elderly, compared with the young, may be related to the ability of its enterotoxin to elicit a more pronounced chemotactic response by granulocytes.

Adult↗

Clostridium difficile toxins may augment bacterial penetration of intestinal epithelium.

BACKGROUND: Clostridium difficile can be recovered from many high-risk hospitalized patients receiving broad-spectrum antibiotic therapy. Clostridium difficile toxins A and B have been associated with increased intestinal permeability in vitro and there is growing evidence that increased intestinal permeability may be a common mechanism whereby enteric bacteria penetrate the intestinal epithelium. HYPOTHESIS: Clostridium difficile-induced alterations in the intestinal barrier facilitate microbial penetration of the intestinal epithelium, which in turn facilitates the translocation of intestinal bacteria. DESIGN: Mature Caco-2 enterocytes were pretreated with varying concentrations of toxin A or toxin B followed by 1 hour of incubation with pure cultures of either Salmonella typhimurium, Escherichia coli, or Proteus mirabilis. The effects of toxins A and B on enterocyte viability, cytoskeletal actin, and ultrastructural topography were assessed using vital dyes, fluorescein-labeled phalloidin, and scanning electron microscopy, respectively. The toxins' effects on bacterial adherence and bacterial internalization by cultured enterocytes were assessed using enzyme-linked immunosorbent assay and quantitative culture, respectively. Epithelial permeability was assessed by changes in transepithelial electrical resistance and by quantifying paracellular bacterial movement through Caco-2 enterocytes cultivated on permeable supports. RESULTS: Neither toxin A nor toxin B had a measurable effect on the numbers of enteric bacteria internalized by Caco-2 enterocytes; however, both toxins were associated with alterations in enterocyte actin, decreased transepithelial electrical resistance, and increased bacterial adherence and paracellular transmigration. CONCLUSION: Clostridium difficile toxins A or B may facilitate bacterial adherence and penetration of the intestinal epithelial barrier.

Bacterial Adhesion↗

Clostridium difficile-associated diarrhoea after internal fixation of intertrochanteric femoral fractures.

The aim of the study presented here was to record the incidence and outcome of Clostridium difficile-associated diarrhoea in patients undergoing surgery for intertrochanteric femoral fractures. Between January 2000 and June 2001, a total of 239 patients who underwent surgery after sustaining an intertrochanteric femoral fracture were included in the study. Seventeen patients developed Clostridium difficile-associated diarrhoea (incidence risk, 7.1%), and six patients died after developing the condition (case fatality rate, 35%). Thus, Clostridium difficile-associated diarrhoea was found to cause significant morbidity and mortality after surgery for intertrochanteric femoral fractures, and antibiotics should be used judiciously in this group of patients.

Age Distribution↗

Clostridium difficile infection of a prosthetic joint presenting 12 months after antibiotic-associated diarrhoea.

Clostridium difficile is a common cause of antibiotic-associated diarrhoea, but it rarely causes extra-colonic disease. An 83-year-old woman who developed culture-positive C. difficile-associated diarrhoea following pneumonia and a total hip replacement was treated successfully with oral metronidazole therapy. She was readmitted 12 months later for revision of the hip prosthesis because of increasing pain. At surgery an abscess associated with the prosthesis was discovered. Culture of the pus grew C. difficile. When the surgical isolate and the cryopreserved faecal isolates were compared using Pulsed Field Gel Electrophoresis (PFGE), an identical banding pattern was observed. This case extends the clinical spectrum of C. difficile infection by documenting a prolonged interval between the initial infection, and diagnosis of the prosthetic joint infection. The importance of molecular typing to show strain relatedness is demonstrated.

Aged↗