The burden of healthcare-associated infections and antibiotic-resistance: investigation of novel strategies to reduce bacterial load in healthcare settings

INTRODUCTION Hospital-acquired infections (HAIs) represent an important clinical and economic burden, with pathogens such as Escherichia coli, Acinetobacter baumannii, and Clostridium difficile contributing to high rates of morbidity and mortality. Traditional cleaning methods often result as insufficient, especially in high-risk hospital environments: there is, in fact, an increasing need to identify eco-sustainable detergents as alternatives to conventional chemical disinfectants, particularly in healthcare settings. At the same time, advances in nanotechnology have enabled the development of nanoparticle-based antimicrobials with strong bactericidal properties. The aim of this thesis project is to investigate innovative strategies to enhance surface decontamination, to reduce infection risk. Firstly, we evaluated the effectiveness of the SMEG BPW1260 bedpan washer-disinfector, a device designed for the thermal disinfection of human waste containers. Afterwards, we aimed at assessing the efficacy of a new methyl-ester sulphonate ecological detergent in combination with silver-derivatized magnetic nanoparticles against bacteria commonly found in hospital infections. Finally, we focused on the infection risk associated with items commonly used to transport patients inside the hospitals, such as wheelchairs: to this aim, we tested the SAFE-HUG Wheelchair Cover, a disposable non-woven barrier designed to minimize patient exposure to potentially contaminated wheelchairs. MATERIALS AND METHODS To assess residual contamination of human waste containers after the washing process with the SMEG BPW1260 bedpan washer-disinfector, molecular techniques such as spectrophotometry, cell counting and DNA quantification were employed. Similarly, the efficacy of the wheelchair cover in reducing bacteria transmission was evaluated through the same methods. The methyl-ester sulphonate detergent and the magnetic nanoparticles were then tested on 30 Escherichia coli and 30 Acinetobacter baumannii strains, which exhibited various resistance profiles, assessing their effects through minimum inhibitory concentration (MIC50 and MIC90) and minimum bactericidal concentration (MBC50 and MBC90) tests. Two types of nanoparticles were tested: silver-derivatized magnetic nanoparticles (MNPs) and silver-derivatized biomimetic magnetic nanoparticles (BMNPs). RESULTS The results of colony-forming units (CFUs) count before and after the thermal disinfection treatment demonstrated a reduction of Clostridium difficile and Escherichia coli contamination by >99.9% (>3 log reduction). The significative decrease in bacterial load was further confirmed through molecular techniques: in particular, Clostridium difficile showed a reduction of roughly 89% in both cell count (cells/ml) and optical density (OD); in the case of Escherichia coli, a reduction of approximately 82% in OD was observed, with an even more marked decrease in cell count, reaching almost 99.3%. DNA quantification resulted below detectable levels for both microorganisms. Additionally, we lowered power consumption by 45% when compared to standard protocols by optimizing the disinfection cycle's energy efficiency, maintaining unchanged the efficacy in reducing bacterial contamination. The methyl-ester sulphonate detergent showed its strongest effect in lowering detectable contamination when used in combination with nanoparticles, exhibiting both inhibitory and bactericidal activity; in particular, the two types of silver-derivatized magnetic nanoparticles showed comparable antimicrobial efficacy. Finally, the significative barrier effect of the wheelchair cover was demonstrated by optical density and bacterial DNA quantification, which resulted undetectable after both one and 24 hours. CONCLUSION Overall, the approaches presented in this project - thermal disinfection, eco-friendly detergent enriched with nanoparticles, and protective transport barriers – are proposed as effective solutions to the urgent need for efficacious and sustainable infection control in healthcare facilities. These findings demonstrate the potential of these systems to counteract microbial contamination while minimizing environmental impact, offering promising solutions for the future of infection prevention in healthcare settings.