Non-Contact Real-Time Detection and Monitoring of Microbial Contaminants on Solid Surfaces Using Medium-(BC-Sense) and Short-Distance (H2B-Spectral) Range Sensors

Real-time detection and monitoring (RTDM) of microbial contamination on solid surfaces is mandatory in a range of security, safety, and biomedical applications where surfaces are exposed to natural, accidental or intentional microbial contamination. This work presents the RTDM results obtained with two new devices, i.e. the BC-Sense and the H2B-Spectral sensors. Both tools allow a rapid and user-friendly RTDM of microbial contamination on various surfaces while assessing the decontamination kinetics and degree of cleanliness.

The BC-Sense is a stand-off LIDAR (Light Detection And Ranging) device using the Light-Induced Fluorescence (LIF) method based on dual-wavelength sensing with a multispectral pattern recognition system to rapidly detect and classify microbial contamination on a solid surface at medium-distance range. In contrast, the H2B-Spectral is a compact sensor using the LIF method with dual-wavelength sensing in non-contact mode at short distances. Both devices allow real-time control of the surface contamination before, during, and after the decontamination procedure.

Accordingly, their performance was evaluated in operator-induced contamination experiments, using microbial simulants (bacteria, bacterial spores, fungal conidia, and viruses) spread on various solid surfaces. The limit of detection (LoD) of E. coli and MS2 virus were 2.9 x104 and 9.5 x 104 PFU and CFU/cm2, respectively. The LoD of bacteria detection with H2B-Spectral was as little as 2 x 103 CFU/cm2.

Random samples (n=200) tested against a training dataset (n=800) were optimally discriminated for contamination versus background with a threshold of predicted response (PR) > 0.55 and < 0.4, respectively with BC-Sense. The kinetics of decontamination by vaporized hydrogen peroxide (VHP) of the spores of Bacillus atrophaeus (BA) measured with the H2BSpectral device revealed the bi-exponential fluorescence quenching function of the fluorescence intensity and the VHP decontamination agent concentration, backed with a model of underlying processes.

This paper provides evidence of the validity of the LIF method realised in the stand-off and non-contact modes and its feasibility for the RTDM application for medium- (BC-Sense) and short-distance (H2B-Spectral) ranges.