Impact of material and manufacturing method on the efficacy of NIR spectroscopy to detect Staphylococcus aureus biofilms

<h2>Abstract</h2> The formation of biofilms on surfaces from clinical and food industry settings represents a significant risk to human health due to their resistance to traditional antimicrobial agents. The development of rapid and effective detection methods would help to improve cleaning and disinfection, and to prevent the dispersion of pathogens. This study evaluates the ability of near-infrared (NIR) spectroscopy to identify <i>Staphylococcus aureus</i> biofilms on different surfaces commonly used in these settings. Moreover, we also tested this technique on biofilms formed on newly emerging composites, and assessed the influence of the material manufacturing method on detection accuracy. Indeed, we analyzed biofilm samples grown on nylon, ABS, onyx, stainless steel, and PVC manufactured by laser cutting or fused deposition modeling (FDM). The generated spectral data were analyzed using partial least squares discriminant analysis (PLSDA) and sparse PLSDA (sPLSDA) to classify samples into contaminated and non-contaminated groups. The results demonstrated that NIR spectroscopy can successfully discriminate the presence of biofilms in most of the materials studied. however, classification accuracy varied depending on the material and manufacturing method. Samples manufactured by FDM, characterized by higher surface porosity, showed significantly higher classification accuracy compared to those manufactured by laser cutting (FDM-ABS reached 70.59 % accuracy, whereas laser-cut ABS samples reached 57.14 % accuracy). This finding suggests that surface porosity plays a crucial role in the interaction between the NIR signal and the presence of biofilms. The study confirms the effectiveness of NIR spectroscopy as a fast and accurate technique for detecting biofilms on different surfaces, and it is particularly promising for the early identification of contamination in materials with higher surface porosity, such as those manufactured by FDM.