Evaluation of the BD GeneOhm StaphSR Assay for Detection of Methicillin-Resistant and Methicillin-Susceptible Staphylococcus aureus Isolates from Spiked Positive Blood Culture Bottles

Abstract

To improve the clinical outcome of Staphylococcus aureus septicemia, the early selection of appropriate antibiotic treatment is crucial. Molecular diagnostics represents an attractive approach for the rapid identification of S. aureus and the determination of its methicillin (meticillin) resistance. In direct comparison to other molecular assays (sa442 and mecA real-time PCRs) and standard laboratory procedures, we evaluated the BD GeneOhm StaphSR assay for its use in the detection of S. aureus and methicillin-resistant S. aureus (MRSA) from spiked blood culture bottles (n ‫؍‬ 134). In the case of detecting S. aureus (n ‫؍‬ 90; for methicillin-susceptible S. aureus, n ‫؍‬ 45; for MRSA, n ‫؍‬ 45), the BD GeneOhm StaphSR assay had a sensitivity and a specificity of 100% each (95% confidence intervals [CIs], 96.0 to 100% and 82.4 to 100%, respectively). For MRSA (n ‫؍‬ 45), the test was 95.6% (95% CI, 84.9 to 99.5%) sensitive and 95.3% (95% CI, 86.9 to 99.0%) specific. Overall, five discrepant results arose with this assay due to the presence of methicillin-susceptible, revertant MRSA strains (3/45) and MRSA strains that were not detected by the BD GeneOhm StaphSR assay (2/45). Compared to other real-time PCR-based molecular approaches and to conventional standard laboratory methods, the BD GeneOhm StaphSR turned out to be an appropriate diagnostic tool for a rapid (ϳ1.5 h), preliminary identification of S. aureus and MRSA from blood cultures.

Same-day Detection of Methicillin Resistance in Staphylococcus aureus Isolates by StaResMet® Kit

“…The commonly used commercial kits based on molecular methods include the BD GeneOhmTM MRSA ACP assay, the GeneXpert® MRSA assay, the Hyplex Staphylo Resist test system, and the BD GeneOhmTM StaphSR assay (5,7,20). However, these molecular methods cannot be used in most clinical microbiology laboratories in Turkey due to their high costs and lack of required technical equipment.…”

Resazurin Microplate Assay: Rapid Assay for Detection of Methicillin Resistant Staphylococcus aureus

“…The early detection of MRSA allows for the early initiation of the appropriate antibiotic therapy which, in turn, reduces mortality, the length of hospitalization, and costs associated with MRSA infections (Grobner et al, 2009).…”

Rapid Antimicrobial Susceptibility Testing Using Forward Laser Light Scatter Technology

“…For example, methicillin resistance by genotyping does not always indicate phenotypic resistance. This is evidenced by the finding of "mecA dropout" or "empty cassette" strains (17,18).…”

“…These assays may provide results in less than 2 h (15)(16)(17). However, molecular detection of the gene targets is far from a perfect solution, targeting only select genetic loci, typically responsible for only a fraction of important resistance patterns.…”