Development and validation of a lateral flow immunoassay for rapid detection of VanA-producing enterococci

Background: VRE are nosocomial pathogens with an increasing incidence in recent decades. Rapid detection is crucial to reduce their spread and prevent infections and outbreaks. Objectives: To evaluate a Lateral flow immunoassay (LFIA) (called NG-Test VanA) for the rapid and reliable detection of VanA-producing VRE (VanA-VRE) from colonies and broth. Methods: NG-Test VanA was validated on 135 well-characterized enterococcal isolates grown on Mueller-Hinton (MH) agar (including 40 VanA-VRE). Different agar plates and culture broths widely used in routine Laboratories for culture of enterococci were tested. Results: ALL 40 VanA-VRE clinical isolates were correctly detected in Less than 15 min irrespective of the species expressing the VanA Ligase and the medium used for bacterial growth. No cross-reaction was observed with any other clinically relevant Ligases (VanB, C1, C2, D, E, G, L, M and N). Overall, the sensitivity and specificity of the assay were 100% for VanA-VRE grown on MH agar plates. NG-Test VanA accurately detects VanA-VRE irrespective of the culture medium (agar and broth). Band intensity was increased when using bacteria grown on vancomycin-containing culture media or on MH close to the vancomycin disc as a consequence of VanA induction. The Limit of detection of the assay was 6.3x10(6) cfu per test with bacteria grown on MH plates and 4.9x10(5) cfu per test with bacteria grown on ChromlD (R) VRE plates. Conclusions: NG-Test VanA is efficient, rapid and easy to implement in the routine workflow of a clinical microbiology Laboratory for the confirmation of VanA-VRE.

Automated summary

NG-Test VanA is an efficient, rapid, and easy to implement lateral flow immunoassay for the detection of VanA-producing VRE. It has 100% sensitivity and specificity for VanA-VRE grown on MH agar plates, and can accurately detect VanA-VRE regardless of the culture medium used.