Modifications of Commercial Toxigenic Clostridium difficile PCR Resulting in Improved Economy and Workflow Efficiency

Abstract

Expense inherent to molecular diagnostics may prevent laboratories from utilizing real-time PCR for Clostridium difficile infection. Frozen master mix and overnight aliquot modifications of the BD GeneOhm Cdiff assay failed to impact performance indices compared to the package insert protocol (P > 0.31), provided accurate results, and decreased reagent expenditure.Traditional laboratory methods detecting toxigenic Clostridium difficile to confirm Clostridium difficile infection (CDI) suffer from deficiencies in analytical sensitivity and/or time to final result (14). Recent consensus clinical practice guidelines for CDI developed by the Society for Healthcare Epidemiology of America (SHEA) and Infectious Diseases Society of America (IDSA) suggest that molecular testing for toxigenic C. difficile may ultimately address laboratory diagnostic concerns (3). In spite of this, some clinical microbiology laboratories may not adopt rapid, molecular biology-based methods due to financial considerations (17, 21) or reservations about intricate processing protocols (particularly with specimens possessing nucleic acid amplification inhibitors [9]). The real-time BD GeneOhm Cdiff assay (BD Diagnostics, Sainte-Foy, Quebec, Canada) has demonstrated high levels of clinical sensitivity for detection of tcdB from primary clinical specimens (1,4,8,15,19,20). In this report, we demonstrate the economical and logistical impact of two protocol modifications on this assay.(Part of this work was presented at the 110th General Meeting of the American Society for Microbiology, San Diego, CA, 23 to 27 May 2010 [2,11].)In an institutional review board (IRB)-approved protocol, 251 consecutive unpreserved liquid fecal specimens from patients symptomatic for CDI were processed to a lysate form for the BD GeneOhm Cdiff assay per the manufacturer's specifications (same-day aliquot). Specimen aliquots were also transferred into kit-provided buffer tubes 1 day prior to lysate generation and stored at 2 to 8°C (overnight aliquot). Freshly reconstituted and frozen master mix were prepared and analyzed as previously described (10,12). tcdB (positive)-and buffer (negative)-based control material was prepared and analyzed analogous to previously described methods (12). A prospective clinical study analyzed 502 lysates in tandem using freshly reconstituted master mix and master mix that had been frozen for 1 week.Primary specimen aliquots were transferred to kit-provided diluent for the ProSpecT C. difficile toxin A/B microplate assay (Remel, Lenexa, KS). Spectrophotometric optical density (OD) values Ն 0.080 were interpreted as positive results. All components of enzyme immunoassay (EIA) and PCR testing, including specimen aliquoting, were timed for workflow analysis. Consensus positive and negative results generated by both EIA and PCR constituted reference results. Discrepancies were resolved upon utilization of the toxigenic culture reference standard (P. Riska; Montefiore Medical Center, Bronx, NY [8]). Toxigenic culture, following a 30-min 100% a...

Molecular methods in the diagnosis ofClostridium difficileinfections: an update

“…The use of frozen master mix reduces hands-on time by 15%, even if it is not recommended by the manufacturer. Sensitivity, specificity and inhibitor rates are similar with frozen or freshly reconstituted master mix [28].…”

Evaluation and utilization of preassembled frozen commercial fast real‐time qPCR master mixes for detection of cytomegalovirus and BK virus

“…However, lyophilization is a multistep process requiring specialized equipment. An alternative approach to the reduction of molecular assay setup times is the utilization of preassembled frozen master mixes [Kofler and Klausegger, 1999;West and Sawyer, 2006;Munson et al, 2010Munson et al, , 2011]. Previous reports have described the successful ability of preassembled conventional and real-time PCR master mixes to maintain performance following freezing [Kofler and Klausegger, 1999;West and Sawyer, 2006].…”

Infectious Disease Management through Point-of-Care Personalized Medicine Molecular Diagnostic Technologies

“…In the clinical microbiology market, this real-time polymerase chain reaction (rtPCR) assay was followed by several other BD GeneOhm™ tests, initially developed by our group, for the rapid diagnostics of hospital-acquired infections associated to methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and Clostridium difficile . It has been shown that these tests have saved lives, decreased the spread of these infections, and reduced healthcare costs [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ].…”