[Evaluation of four rapid methods for the investigation of the toxigenic capacity of Clostridium difficile strains isolated in a selective medium].
BACKGROUND
Use of selective Clostridium difficile culture as a diagnostic method for C. difficile associated disease requires to prove the toxigenic ability of the isolates. Toxin B detection by cell culture assay after growing the microorganism in enriched broth is the standard method, but it delays the final diagnosis for 3-5 days. This study compares retrospectively four rapid techniques for detecting these toxigenic C. difficile strains.


METHODS
106 clinical isolates of C. difficile (72 toxigenic and 34 non-toxigenic), these and 16 clinical strains of other species of Clostridium were investigated. The four methods were performed directly from colonies growing on solid agar. They were: a) cytotoxin detection in cell culture; b) two PCR amplifications of toxin A and toxin B, respectively, and c) toxin A detection by an immunoenzymatic method (VIDAS CDA2). All these procedures were completed within a normal working day.


RESULTS
Only the 72 toxigenic C. difficile strains gave positive results by cell culture and PCR techniques (sensitivity and specificity: 100%). A total of 14 out of 49 toxigenic C. difficile strains showed negative results by the VIDAS assay in the first run, but all them were positive in repeated tests.


CONCLUSIONS
Although all methods performed well, the cytotoxicity assay done directly on colonies growing in CCFA is a simple and rapid technique, and appears to be well-suited for use in laboratories with access to cell cultures.
García
A
A
Servicio de Microbiología, Ciutat Sanitària i Universitària de Bellvitge, L'Hospitalet de Llobregat, Barcelona.
Pérez
J L
JL
Pulido
A
A
Niubó
J
J
Pérez
P
P
Martín
R
R
D000362:Agar; D001427:Bacterial Toxins / Q000032:analysis*; D001431:Bacteriological Techniques; D016360:Clostridioides difficile / Q000737:chemistry*; D003470:Culture Media; D016133:Polymerase Chain Reaction
D001427:Bacterial Toxins; D003470:Culture Media; D000362:Agar