Rapid molecular testing economical, improved antibiotic therapy

October 14, 2013

SAN FRANCISCO — A molecular-based technique for identifying gram-positive organisms in blood cultures produced rapid results, leading to improved antibiotic therapy, according to recent study results presented at ID Week 2013. The method also was more cost-effective than conventional methods.

“Compared to the conventional workup — which is what most hospitals are using — we found that, on average, this system saved 42 hours in reporting the identification of the organism in cases of methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci (VRE),” Felix Roth, PhD, a molecular pathologist at Sanford Health in Fargo, N.D., told Infectious Disease News. “At the same time, we were able to prevent patients from being admitted mostly for coagulase-negative staphylococci cases.”

Roth and colleagues evaluated the economic impact of using the Verigene gram-positive blood culture nucleic acid test (Nanosphere Inc.) compared with the conventional approach of identifying gram-positive organisms in blood cultures, which typically produces results within 1 to 3 days. The study included 45 positive blood cultures harboring a gram-positive organism. The researchers compared costs associated with antimicrobial therapy, drug-level monitoring and hospital admissions.

Results from the Verigene test were available 42 hours before those of the convention method (P<.001). Use of rapid molecular testing allowed seven patients to avoid vancomycin therapy and three patients to discontinue the antibiotic, the researchers said. Among patients in which S. aureus was identified, four patients had methicillin-sensitive S. aureus, three patients switched from vancomycin to another agent, and one patient avoided the institution of vancomycin therapy altogether. In one case, the researchers identified a single isolate of group B streptococcus, and vancomycin was replaced with another antibiotic as a result. Use of the Verigene test also helped two patients with a history of VRE avoid daptomycin therapy, and one patient had linezolid discontinued after S. pneumoniae was identified.

According to Roth, the Verigene test was more cost-effective across all three endpoints: antimicrobial therapy, drug-level monitoring and hospital admission.

“We tested 45 cases and saved $12,000,” Roth said.