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Medline ® Abstracts for References 75-79

of 'Clostridium difficile infection in adults: Clinical manifestations and diagnosis'

75
TI
Pseudomembranous colitis caused by a toxin A(-) B(+) strain of Clostridium difficile.
AU
Limaye AP, Turgeon DK, Cookson BT, Fritsche TR
SO
J Clin Microbiol. 2000;38(4):1696.
 
We report a case of severe pseudomembranous colitis due to a toxin A(-) B(+) strain of Clostridium difficile in an immunosuppressed patient and discuss the implications for diagnostic testing in suspected C. difficile-associated diarrhea.
AD
Department of Laboratory Medicine, University of Washington, Seattle, Washington 98195, USA. limaye@u.washington.edu
PMID
76
TI
Prevalence and genetic characterization of toxin A variant strains of Clostridium difficile among adults and children with diarrhea in France.
AU
Barbut F, Lalande V, Burghoffer B, Thien HV, Grimprel E, Petit JC
SO
J Clin Microbiol. 2002;40(6):2079.
 
Toxin A variant strains (toxin A-negative, toxin B-positive strains) of Clostridium difficile have been reported to be responsible for diarrhea or pseudomembranous colitis in humans. These strains lack parts of the repeating sequences of the toxin A gene (tcdA) and are toxin A negative by commercial enzyme immunoassays (EIA). Here, we report the prevalence of the toxin A variant strains in 334 patients with C. difficile-associated diarrhea in France. The repeating segment of the tcdA gene (1,200 bp) was amplified by PCR using the primers NK9 and NK11 (H. Kato et al., J. Clin. Microbiol. 36:2178-2182, 1998). In the case of amplified fragments of unexpected size, the entire tcdA gene was studied by PCRs A1, A2, and A3 (Rupnik et al., J. Clin. Microbiol. 36:2240-2247, 1998), and strains were characterized by serotyping, pulsed-field gel electrophoresis and PCR ribotyping. By PCR with primers NK9 and NK11, C. difficile variant strains were detected in 2.7% of patients. Several variant types were found. A deletion of approximately 1,700 bp was observed in six strains from five patients. These strains belonged to serotype F and were characterized by the same pulsotype and the same PCR ribotype. They were toxin A negative by EIA and exhibited an atypical cytopathic effect on MRC-5 cells. Two other tcdA variant types that exhibited a positive result for toxin A by EIA were identified: one from serotype H with a longer amplified fragment (insertion of 200 bp) and one with a deletion of 600 bp. Diagnosis of C. difficile-associated diseases would have been missed in five patients (1.5%) by laboratories that screen the stools only for the presence of toxin A. This result underlines the need for testing stool by the cytotoxicity assay in patients with a high suspicion of C. difficile-associated diarrhea but a negative immunoassay for toxin A.
AD
Research Group on Clostridium difficile, Centre Hospitalo-Universitaire Saint-Antoine, Assistance Publique-Hôpitaux de Paris, UniversitéPierre et Marie Curie, Paris, France. frederic.barbut@sat.ap-hop-paris.fr
PMID
77
TI
Fatal pseudomembranous colitis associated with a variant clostridium difficile strain not detected by toxin A immunoassay.
AU
Johnson S, Kent SA, O'Leary KJ, Merrigan MM, Sambol SP, Peterson LR, Gerding DN
SO
Ann Intern Med. 2001;135(6):434.
 
BACKGROUND: Many clinical laboratories use toxin A immunoassays to test for Clostridium difficile.
OBJECTIVE: To describe the clinical course of a patient infected with a toxin variant strain of C. difficile that was not detected by toxin A immunoassay; to genetically characterize this strain; and to estimate the number of laboratories that use only toxin A immunoassays.
DESIGN: Case report, molecular investigation, and laboratory survey.
SETTING: Tertiary care hospital in Chicago, Illinois.
PATIENT: An 86-year-old man.
MEASUREMENTS: Restriction endonuclease analysis, polymerase chain reaction, and survey of regional clinical laboratories.
RESULTS: An elderly hospitalized man died of advanced pseudomembranous colitis. Four stool specimens submitted over a 2-month period had tested negative on toxin A immunoassay, but a strain of C. difficile with a 1.8-kb deletion of the toxin A gene was recovered from each specimen. This strain, identified as restriction endonuclease analysis type CF4, is closely related to a widely disseminated variant, toxinotype VIII. Toxin A immunoassay was the only test being performed for detection of C. difficile at 31 of 67 (46%) regional clinical laboratories.
CONCLUSIONS: Toxin A variant strains of C. difficile cause serious disease and are undetectable in clinical laboratories that use only toxin A immunoassays for C. difficile testing.
AD
Medical Service, Veterans Affairs Chicago Health Care System-Lakeside, 333 East Huron Street, Chicago, IL 60611, USA.
PMID
78
TI
Comparison of vidas Clostridium difficile toxin-A assay and premier C. difficile toxin-A assay to cytotoxin-B tissue culture assay for the detection of toxins of C. difficile.
AU
Knapp CC, Sandin RL, Hall GS, Ludwig MD, Rutherford I, Washington JA
SO
Diagn Microbiol Infect Dis. 1993;17(1):7.
 
Damage to the intestinal mucosa by Clostridium difficile (CD) is toxin mediated. Two enzyme immunoassays (EIAs) for toxin-A detection, the automated Vitek immunodiagnostic assay system CDA (Vidas CDA), and the Premier toxin A (Premier) were tested for their ability to detect toxin A in 301 stool samples and compared with an in-house tissue culture assay for toxin B (TCA). Of these 301 samples, 49 were TCA positive and 252 were TCA negative. Agreement between Vidas CDA and TCA on the initial run was 85% (255 of 301) and increased to 94% (278 of 296) when discordant samples were retested from available frozen specimens. Corresponding levels of agreement for Premier were 91% (272 of 301) and 98% (284 of 288), respectively. If tissue culture positivity at any titer was used as the sole criterion for positivity of the specimen, agreement with positive TCA before and after repeat testing was 57% (26 of 49) and 74% (34 of 46) for Vidas CDA and 65% (32 of 49) and 95% (36 of 38) for Premier. Agreement with negative TCA titers was good: 90% for Vidas CDA and 95% for Premier, and 98% for Vidas CDA and 99% for Premier after repeat testing. Predictive values positive and negative after repeat testing were, respectively, 88% and 96% for Vidas CDA, and 95% and 99% for Premier. Results for the automated and manual EIA methods for detection of C. difficile toxin A were obtained in 2.5 h as compared with 36-48 h for tissue culture.
AD
Department of Microbiology, Cleveland Clinic Foundation, OH 44195.
PMID
79
TI
Toxin B is essential for virulence of Clostridium difficile.
AU
Lyras D, O'Connor JR, Howarth PM, Sambol SP, Carter GP, Phumoonna T, Poon R, Adams V, Vedantam G, Johnson S, Gerding DN, Rood JI
SO
Nature. 2009;458(7242):1176. Epub 2009 Mar 1.
 
Clostridium difficile is the leading cause of infectious diarrhoea in hospitals worldwide, because of its virulence, spore-forming ability and persistence. C. difficile-associated diseases are induced by antibiotic treatment or disruption of the normal gastrointestinal flora. Recently, morbidity and mortality resulting from C. difficile-associated diseases have increased significantly due to changes in the virulence of the causative strains and antibiotic usage patterns. Since 2002, epidemic toxinotype III NAP1/027 strains, which produce high levels of the major virulence factors, toxin A and toxin B, have emerged. These toxins have 63% amino acid sequence similarity and are members of the large clostridial glucosylating toxin family, which are monoglucosyltransferases that are pro-inflammatory, cytotoxic and enterotoxic in the human colon. Inside host cells, both toxins catalyse the transfer of glucose onto the Rho family of GTPases, leading to cell death. However, the role of these toxins in the context of a C. difficile infection is unknown. Here we describe the construction of isogenic tcdA and tcdB (encoding toxin A and B, respectively) mutants of a virulent C. difficile strain and their use in the hamster disease model to show that toxin B is a key virulence determinant. Previous studies showed that purified toxinA alone can induce most of the pathology observed after infection of hamsters with C. difficile and that toxin B is not toxic in animals unless it is co-administered with toxin A, suggesting that the toxins act synergistically. Our work provides evidence that toxin B, not toxin A, is essential for virulence. Furthermore, it is clear that the importance of these toxins in the context of infection cannot be predicted exclusively from studies using purified toxins, reinforcing the importance of using the natural infection process to dissect the role of toxins in disease.
AD
Australian Bacterial Pathogenesis Program, Department of Microbiology, Monash University, Victoria 3800, Australia.
PMID