Real-time cellular analysis coupled with a specimen enrichment accurately detects and quantifies Clostridium difficile toxins in stool.
We describe here the use of an immunomagnetic separation enrichment process coupled with a modified real-time cellular analysis (RTCA) system (RTCA version 2) for the detection of C. difficile toxin (CDT) in stool. The limit of CDT detection by RTCA version 2 was 0.12 ng/ml. Among the consecutively collected 401 diarrheal stool specimens, 53 (13.2%) were toxin-producing C. difficile strains by quantitative toxigenic culture (qTC); bacterial loads ranged from 3.00 × 10(1) to 3.69 × 10(6) CFU/ml. The RTCA version 2 method detected CDT in 51 samples, resulting in a sensitivity of 96.2%, a specificity of 99.7%, and positive and negative predictive values of 98.1% and 99.4%, respectively. The positive step time ranged from 1.43 to 35.85 h, with <24 h for 80% of the samples. The CDT concentrations in stool samples determined by RTCA version 2 correlated with toxigenic C. difficile bacterial load (R(2) = 0.554, P = 0.00002) by qTC as well as the threshold cycle (R(2) = 0.343, P = 0.014) by real-time PCR. A statistically significant correlation between the CDT concentrations and the clinical severity of CDI was observed (P = 0.015). The sensitivity of the RTCA version 2 assay for the detection of functional toxins in stool specimens was significantly improved when the immunomagnetic separation enrichment process was incorporated. More than 80% positive results can be obtained within 24 h. The stool specimen CDT concentration derived using the RTCA version 2 assay correlates with clinical severity and may be used as a marker for monitoring the status of CDI.
Department of Laboratory Medicine, First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.
Bin
B
Huang
Dazhi
D
Jin
Jing
J
Zhang
Janet Y
JY
Sun
Xiaobo
X
Wang
Jeffrey
J
Stiles
Xiao
X
Xu
Mini
M
Kamboj
N Esther
NE
Babady
Yi-Wei
YW
Tang
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001427:Bacterial Toxins / Q000032:analysis*; D002648:Child; D002675:Child, Preschool; D016360:Clostridioides difficile / Q000302:isolation & purification; D003015:Clostridium Infections / Q000175:diagnosis* / Q000382:microbiology; D005243:Feces / Q000737:chemistry*; D005260:Female; D006801:Humans; D018189:Immunomagnetic Separation / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013997:Time Factors; D055815:Young Adult
D001427:Bacterial Toxins