At the detection line the biotin on the dual-labeled DNA products bound to streptavidin on the detection strip

At the detection line the biotin on the dual-labeled DNA products bound to streptavidin on the detection strip. burden of diarrheal illness. 1Although recently there has been conflicting evidence as to exactly how significantGiardia’s Amisulpride hydrochloride contribution is to the diarrheal burden, Giardiais nonetheless a highly infectious parasite with an infectious dose as small as 1025 cysts. 2, 3Symptoms ofGiardiainfection (known as giardiasis) include watery diarrhea, epigastric pain, nausea, vomiting, and weight loss and these symptoms tend to disproportionately affect children and immune-compromised individuals. 46 Diagnosis ofGiardiainfection is usually based on identification of the cyst or trophozoite form of the parasite by stool smear microscopy. 7Although highly specific, microscopic identification ofGiardiatends to have poor sensitivity with low levels of parasitic infection and can require up to three separate stool samples. 8Microscopy requires sample processing with specialized stains and trained microscopists; thus, it is usually performed in a centralized laboratory facility. A number of nucleic acid-based and antigen-based diagnostic assays for stool sample detection ofGiardiaat the point-of-care are available and have shown impressive reliability. 911Traditional nucleic acid diagnostics such as polymerase chain reaction (PCR), however , require the use of expensive thermal cycling equipment, limiting their use to central laboratories. Recently, a number of nucleic acid amplification techniques have been developed that do not require the use of thermal cycling equipment. 1216Among these isothermal amplification platforms, recombinase polymerase amplification (RPA) has a number of advantages. The RPA can be performed at body temperature, theoretically alleviating the need for external heating equipment if body heat were to be harnessed to Rabbit Polyclonal to CHRM4 incubate reactions. The RPA amplifies target to detectable limits in as few as 15 minutes. 16, 17The RPA enzymes are supplied in a lyophilized pellet allowing for short-term storage and transport at ambient temperatures, reducing the need for refrigeration and cold chain storage. 18Additionally, RPA results can be read visually using simple lateral flow strips. Here, we report the use of RPA technology to develop aGiardiaassay (recombinase polymerase amplification-basedGiardia[RPAG] assay) that is capable of detecting the presence ofGiardiain nucleic acids extracted from stool samples. We initially developed the assay on the bench top, where it showed performance similar to that of Amisulpride hydrochloride the gold standard, PCR. We went on to test the RPAG assay on 104 clinical stool samples suspected of containingGiardia. Clinical results show 73% sensitivity and 95% specificity compared with a PCR and microscopy composite gold standard. The RPAG assay has the potential to be of use for giardiasis diagnosis in locations where thermal cyclers are unavailable. == Materials and Methods == == Ethics statement. == For bench top characterization of the RPAG assay stool samples were collected from normal, healthy volunteers according to Rice University Institutional Review Board (IRB) approved protocol 11-101E. Informed, written consent was given by all volunteers. Clinical samples were collected from children 312 years of age whose parents provided verbal consent in accordance with the UTMB IRB approved protocol 07-285. == DNA extraction of stool samples. == For bench top development of the RPAG assay fresh stool samples were collected from healthy volunteers and stored with equal parts stool and phosphate buffered saline (PBS) according to IRB approved protocol number 11-101E. Stool samples were stored at 4C until use (up to 48 hours). Aliquots of 250 L of the stool-PBS mixture were spiked with 10 L PBS containing purifiedGiardiacysts at various concentrations. Giardia duodenaliscysts (genotype assemblage B) were purchased from Waterborne Inc. (P101, Waterborne, New Orleans, LA). One hundred and four stool samples were collected from children 3 to 12 years of age in six rural communities from Cuzco, Peru (altitude 3, 800 m) for epidemiologic studies on intestinal parasites. Freshly collected stool was aliquoted into a container with 10% formalin and into a separate container with 70% ethanol in the field. Formalin preserved stools were evaluated with microscopy by direct, Kato Katz, rapid sedimentation Amisulpride hydrochloride in slide, and rapid sedimentation in plate tests to identify protozoan and helminths. 19A specimen was considered positive by microscopy if at least one protozoa was identified in any of the four tests. Stools preserved in alcohol were de-identified and stored at 4C for 812 months Amisulpride hydrochloride until use. Stool collection studies and storage of de-identified specimens for future use were approved by the University of Texas Medical Branch Institutional Review Board. Parents and children provided verbal informed consent and assent, respectively. The DNA was extracted from stool samples preserved in ethanol using Qiagen DNA Mini Kits (no. 51304, Qiagen, Valencia, CA).