Comparison of two molecular methods for detecting toxigenic Clostridium difficile.
BACKGROUND
Clostridium difficile is one of the most common causes of nosocomial diarrhea, and diagnostic methods for detecting C. difficile infection have shifted from conventional to more recent molecular techniques. This study aimed to compare the performance of two molecular assays (Meridian Illumigene™ and AdvanSure CD real-time PCR) in detecting C. difficile using a toxigenic culture as a reference standard.


METHODS
This study was conducted at Kyung Hee University Hospital, a tertiary university teaching hospital in Seoul, Korea, from July 2010 to February 2011. The study used 203 fresh diarrheal stools. All fecal specimens were immediately tested by culture and the VIDAS C. difficile toxin A & B assay using an automated VIDAS immunoanalyzer. The remainder was stored at -70°C until required for AdvanSure CD real-time polymerase chain reaction and Illumigene™. The alcohol shock procedure was then performed. Aliquots were inoculated directly on C. difficile-selective agar and blood agar and then incubated in an anaerobic jar for 48 h at 35°C. The Rapid ID 32 A test was used for specifying colonies on plates. The AdvanSure CD real-time PCR was used to detect the tcdA and tcdB gene, and PCR Illumigene™ kits were used to detect the tcdA gene of the pathogenicity locus (PaLoc) harboring toxigenic C. difficile.


RESULTS
Of 203 clinical samples, 197 showed identical results between the two molecular assays, with a concordance rate of 97.0%. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were as follows: Illumigene: 92.3, 99.4, 96.0, and 98.9, respectively; AdvanSure CD real-time PCR: 84.6, 98.3, 88.0, and 97.8, respectively.


CONCLUSIONS
Both molecular assays demonstrated good sensitivity and specificity. Additionally, both molecular assays showed comparable results to those of a toxigenic culture, albeit with a slight decrease in test sensitivity and specificity.
Department of Laboratory Medicine, School of Medicine, Kyung Hee University, 1 Hoegi-dong, Dongdaemun-gu, Seoul 130-702, Korea; phone: +82 2 958 8672 ; fax: +82 2 958 8609; e mail: leehejo@khmc.or.kr.
Yun Soo
YS
Soh
John Jeongseok
JJ
Yang
Eunkyoung
E
You
You
Y
La Jeon
Min Jin
MJ
Kim
You Sun
YS
Nam
Sun Young
SY
Cho
Tae Sung
TS
Park
Hee Joo
HJ
Lee
D001427:Bacterial Toxins / Q000302:isolation & purification*; D016360:Clostridioides difficile / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology; D006801:Humans; D025202:Molecular Diagnostic Techniques / Q000379:methods*
D001427:Bacterial Toxins