title: Cost-effective frozen master mix modification of a commercial methicillin-resistant Staphylococcus aureus PCR assay.
abstract: The expense inherent to molecular diagnostics may be an overriding concern for a variety of clinical laboratories in the development of PCR-based methicillin-resistant Staphylococcus aureus (MRSA) active surveillance programs. BD GeneOhm MRSA assay master mix was reconstituted, aliquoted into SmartCycler tubes in 25-microl volumes, and frozen at -70 degrees C. One hundred percent of archival nasal swab lysates yielded the expected PCR results when incubated in master mix frozen for 1, 2, 3, and 4 weeks. A 98.8% concordance of the final result was observed upon prospective PCR analysis of 320 clinical lysates utilizing freshly reconstituted master mix and 2-week-frozen master mix. Initial unresolved rates generated by frozen master mix and freshly reconstituted master mix differed by 1.6% (P = 0.16). Of 50 MRSA-positive lysates, the titers of 32 (64%) were determined to the same value upon initial tandem frozen master mix and freshly reconstituted master mix utilization; the titers of an additional 14 were determined to the same value upon repeat testing. Frozen master mix maintains potency for at least 4 weeks, facilitating detection of MRSA from nasal swab lysates, and may decrease the amount of unused reagent up to an average of 33%.
authors.affiliation: Wheaton Franciscan Laboratory, 11020 West Plank Court, Suite 100, Wauwatosa, WI 53226, USA. Erik.Munson@wfhc.org
authors.forename: Erik
authors.initials: E
authors.lastname: Munson
authors.forename: Timothy
authors.initials: T
authors.lastname: Block
authors.forename: Janet T
authors.initials: JT
authors.lastname: Voegeli
authors.forename: Jeanne E
authors.initials: JE
authors.lastname: Hryciuk
authors.forename: Ronald F
authors.initials: RF
authors.lastname: Schell
mesh_terms: D002353:Carrier State / Q000175:diagnosis*; D005615:Freezing; D006801:Humans; D008403:Mass Screening / Q000191:economics / Q000379:methods*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification*; D025202:Molecular Diagnostic Techniques / Q000191:economics / Q000379:methods*; D016133:Polymerase Chain Reaction / Q000191:economics / Q000379:methods*; D011933:Reagent Kits, Diagnostic / Q000191:economics*; D012680:Sensitivity and Specificity; D013203:Staphylococcal Infections / Q000175:diagnosis*
chemical_list: D011933:Reagent Kits, Diagnostic