Clostridium difficile (CD) is a bacterium causing diarrhea and other intestinal problems linked to 14,000 annual deaths in the US. CDI is an antibiotic-associated infection as well as a health-care-associated infection. Current CDI diagnosis relies on CD toxins enzyme immunoassay (EIA) together with antigen (GDH) EIA. Although stool toxin EIA is specific and relatively fast (hours to 1 day), the sensitivity of toxinEIA is only 60%. Nucleic acid amplification test (NAAT) using quantitative real-time polymerase chain reaction (qPCR) or loop-mediated isothermal amplification (LAMP) to detect the toxin gene tcdB or tcdA is sensitive and specific. However, due to the emergence of hypervirulent strains, detecting tcdA or tcdB alone cannot tell the severity of CDI, and is not sufficient to hel physician make informed CDI treatment decisions. The 30-day mortality rate and recurrence rate for CDI caused by hypervirulent strains are higher and are linked to a third toxin, the binary toxin which is encoded by cdtB and cdtA. All CDI involve tcdB but not tcdA. Therefore, if there is a genetic CD test that can detect tcdB and cdtB simultaneously in one test it would be possible to not only diagnose CDI but also determine the severity and recurrence risk of the CDI to help physicians make treatment decisions. (PbMg1/3Nb2/3O3)0.65(PbTiO3)0.35 (PMN-PT) piezoelectric plate sensor (PEPS) is a unique sensor developed by Shih and Shih, which uses relative resonance frequency shift, Df/f to detect binding of a target to the receptor on the PEPS surface. What is unique about PMN-PT PEPS is that detection Df/f is enhanced by 1000 times due to the unique polarization switching mechanism within the PMN-PT layer. As a result, PEPS has demonstrated sensitivity similar to PCR in DNA detection but without the need of DNA extraction and DNA amplification. The goal of the study is to develop a rapid, accurate, and low-cost CDI test using a 3- PEPS array--one PEPS to detect tcdB, the second PEPS to detect cdtB, and the third PEPS to serve as a negative control with high sensitivity and specificity to help diagnose CDI and assessing CDI severity and recurrence risk. Encouraging preliminary results of detecting tcdB in 20 blinded patient stools showed that PEPS correctly identified 11/11 qPCR positive samples and 7/9 qPCR negative samples within 40 min using simple electrical means, indicating the sensitivity of the PEPS test. In addition, PEPS is easily multiplexed and the simple electrical detection makes the test low-cost and thus can be widely available.
Clostridium difficile infection (CDI) is a major healthcare-associated diarrhea causing 14,000 deaths and costing more than $3B to treat each year in the US. Genetic testing using nucleic acid amplification (NAA) is expensive and not widely available. The proposed low-cost, portable genetic CDI test can detect multiple genes of CD at point of care to help not only diagnose CDI but also assess CDI severity and recurrence risk to help physicians make timely and proper therapy decision at point of care to better combat CDI.
|Kirimli, Ceyhun E; Shih, Wei-Heng; Shih, Wan Y (2016) Amplification-free in situ KRAS point mutation detection at 60 copies per mL in urine in a background of 1000-fold wild type. Analyst 141:1421-33|
|Kirimli, Ceyhun E; Shih, Wei-Heng; Shih, Wan Y (2014) DNA hybridization detection with 100 zM sensitivity using piezoelectric plate sensors with an improved noise-reduction algorithm. Analyst 139:2754-63|