Rapid solid-phase immunoassay for detection of methicillin-resistant Staphylococcus aureus using cycling probe technology.
A Cycling Probe Technology (CPT) assay with a lateral-flow device (strip) was developed for the detection of the mecA gene from methicillin-resistant Staphylococcus aureus (MRSA) cultures. The assay uses a mecA probe (DNA-RNA-DNA) labeled with fluorescein at the 5' terminus and biotin at the 3' terminus. The CPT reaction occurs at a constant temperature, which allows the probe to anneal to the target DNA. RNase H cuts the RNA portion of the probe, allowing the cleaved fragments to dissociate from the target DNA, making the target available for further cycling. The strip detection step uses a nitrocellulose membrane with streptavidin and immunoglobulin G antibody impregnated on the surface. In the absence of the mecA gene, the uncut probe is bound to an antifluorescein-gold conjugate and is then captured by the streptavidin to form a test line. In the presence of the mecA gene, the probe is cut and no test line is formed on the strip. A screen of 324 S. aureus clinical isolates by the CPT-strip assay showed a 99.4% sensitivity and a 100% specificity compared to the results of PCR for the detection of the mecA gene. Specificity testing showed that the CPT-strip assay did not exhibit any cross-reactivity with a panel of mecA-negative non-S. aureus isolates. The CPT-strip assay is simple and does not require sophisticated equipment. Furthermore, the assay takes 1.5 h starting from a primary culture to the time to detection of the mecA gene in S. aureus isolates.
Fong
W K
WK
ID Biomedical Corp., Bothell, Washington 98011, USA.
Modrusan
Z
Z
McNevin
J P
JP
Marostenmaki
J
J
Zin
B
B
Bekkaoui
F
F
D001426:Bacterial Proteins / Q000235:genetics; D001431:Bacteriological Techniques; D003470:Culture Media; D015342:DNA Probes; D006801:Humans; D007118:Immunoassay; D016106:Methicillin Resistance / Q000235:genetics*; D016133:Polymerase Chain Reaction; D015347:RNA Probes; D011934:Reagent Strips; D012680:Sensitivity and Specificity; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification*
D001426:Bacterial Proteins; D003470:Culture Media; D015342:DNA Probes; D015347:RNA Probes; D011934:Reagent Strips