Two-tier approach combining molecular and culture-based techniques for optimized detection of vancomycin-resistant...

Area of Science:

• Clinical Microbiology
• Infectious Diseases
• Molecular Diagnostics

Background:

• Rising incidences of vancomycin-resistant enterococci (VRE) colonization and infection necessitate rapid identification methods.
• Accurate VRE carrier detection is crucial in high-risk patient populations to prevent transmission.

Purpose of the Study:

• To evaluate a two-tier VRE detection strategy combining PCR screening with cultural confirmation.
• To compare the time efficiency and accuracy of the two-tier approach against conventional culture-based methods.

Main Methods:

• A two-tier approach using PCR-based screening followed by selective culture for positive results was implemented.
• This strategy was compared to the conventional method relying solely on selective culture.
• Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for PCR assays.

Main Results:

• The two-tier strategy demonstrated high consistency with conventional methods, showing 93.1% sensitivity and 100% specificity.
• A significant reduction in median time to result by 44.3 hours was observed with the PCR-based approach.
• Positive vanA PCR results showed high consistency with culture (PPV: 92.0%, NPV: 99.6%), allowing preliminary reporting, unlike vanB PCR (PPV: 58.5%).

Conclusions:

• A molecular assay for rapid VRE detection from rectal swabs, coupled with cultural confirmation, is reliable and time-saving.
• This approach is particularly effective in settings with low VRE prevalence and a predominance of vanA-positive strains.
• The two-tier strategy significantly improves the speed of VRE carrier identification in clinical microbiology.