The study aimed to test laser speckle contrast imaging for fast and non-invasive assessment of ultrasound induced bactericidal effect on C. albicans biofilm. Low frequency sonication applied at 1.1 MPa peak negative pressure for 1 min reduced the number of viable C. albicans cells. The bactericidal effect was related to the spectral contrast decrease resulting from the standard deviation decrease within the speckle pattern as compared to the unchanged mean intensity. C. albicans biofilm recovered completely within 41 h after sonication. The recovery of biofilm was represented by increase of speckle contrast parameter. We foresee that speckle-based technique would be helpful for the efficacy assay of microbial biofilm inactivation.
Photosensitization based antibacterial treatment is efficient against a broad range of pathogens but it utilizes suboptimal dosimetry with an explicit (and very broad range) determination of sensitizer concentration, light dose and fluence rates. In this study we verified the implicit dosimetry approach for pathogen photodynamic treatment, employing protoporphyrin IX (ppIX) photobleaching to assess the killing efficacy against Staphylococcus aureus and Candida albicans cells. The results show that there was an increased kill of S. aureus and C. albicans at higher degree of ppIX fluorescence decay. Therefore ppIX photobleaching can be incorporated into the PDI dose metric offering to predict the pathogen killing efficacy during photodynamic treatment.
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