Detection of clostridium difficile toxin A and B genes from stool samples of diarrheal patients by polymerase chain reaction (PCR) technique

Abstract

The prevalence of Clostridium difficile isolated from stools of diarrheal Thai adults patients with suspected antibiotic-associated diarrhea during the 17 months of study (January 2000 to May 2001) were 18.64%. The C. difficile strains were found in 107 of 574 stool samples. Detection of C. difficile toxin A and B genes directly from stool samples by PCR were performed. It was found that 47 (43.93%) out of 107 stools with culture positive were positive for toxin A gene and 48 (44.86%) out of 107 stools with culture positive were positive for toxin B gene. Comparative results between the detection of toxin A and B genes directly from stools and C. difficile isolates by PCR technique were done. It was shown that 33 out of 107 stools with culture positive were positive and 41 samples were negative for both toxin A and B genes. The results were not concordance in 14 samples with positive genes in stool samples but negative in C. difficile isolates. Eighteen samples were toxin genes negative in stool samples but positive in C. difficile isolates. One of the stools was positive in C. difficile isolate but that stool was only toxin B gene positive. When the results from PCR technique were compared to those from EIA, 98 out of 107 stool samples gave the same results. One out of 50 stools with negative culture and negative EIA was both toxin A and B genes positive by PCR. In conclusion, sixty-nine out of 107 samples (64.49%) gave same results in all three methods, PCR detection in stool specimens directly, PCR detection in C. difficile isolates and EIA in stool specimens directly. However, the direct detection of toxin A and B genes from the stool samples provided similar results with the detection from C. difficile isolates in 74 stool samples (69.16%). Thus, this study indicated that PCR detection of C. difficile toxin A and B genes in stool samples directly seems to be appropriate method for the detection of C. difficile infection even though technique development such as the sensitivity of PCR assays or the elimination of inhibitory substances is needed in order to increase the sensitivity of the technique.