Abstract
Ultrasound imaging is proving to be an important tool for medical diagnosis of dermatological disease. Backscatter spectral profiles using high-frequency ultrasound (HFUS, 10–100 MHz) are sensitive to subtle changes in eukaryotic cellular morphology and mechanical properties that are indicative of early apoptosis, the main type of cell death induced following photodynamic therapy (PDT). We performed experiments to study whether HFUS could also be used to discern changes in bacteria following PDT treatment. Pellets of planktonic Staphylococcus aureus were treated with different PDT protocols and subsequently interrogated with HFUS. Changes in ultrasound backscatter response were found to correlate with antimicrobial effect. Despite their small size, distinct changes in bacterial morphology that are indicative of cell damage or death are detectable by altered backscatter spectra from bacterial ensembles using HFUS. This highlights the potential for HFUS in rapidly and non-invasively assessing the structural changes related to antimicrobial response.
Keywords: Antimicrobial photodynamic therapy, Cell death, High-frequency ultrasound, Ultrasound backscatter
References
- 1.Maisch, T., Szeimies, R.M., Jori, G., et al.: Antibacterial photodynamic therapy in dermatology. Photochem. Photobiol. Sci. 3, 907–917 (2004) [DOI] [PubMed]
- 2.Demidova, T.N., Hamblin, M.R.: Photodynamic therapy targeted to pathogens. Int. J. Immunopathol. Pharmacol. 17, 245–254 (2004) [DOI] [PMC free article] [PubMed]
- 3.Czarnota, G.J., Kolios, M.C., Abraham, J., et al.: Ultrasound imaging of apoptosis: High-resolution non-invasive monitoring of programmed cell death in vitro, in situ and in vivo. Brit. J. Cancer 81, 520–527 (1999) [DOI] [PMC free article] [PubMed]
- 4.Hacker, G.: The morphology of apoptosis. Cell Tissue Res. 301, 5–17 (2000) [DOI] [PubMed]
- 5.Aldsworth, T.G., Sharman, R.L., Dodd, C.E.R.: Bacterial suicide through stress. Cell. Mol. Life Sci. 56, 378–383 (1999) [DOI] [PMC free article] [PubMed]
- 6.Nitzan, Y., Salmon-Divon, M., Shporen, E., et al.: ALA induced photodynamic effects on Gram positive and negative bacteria. Photochem. Photobiol. Sci. 3, 430–435 (2004) [DOI] [PubMed]
- 7.Hamblin, M.R., Hasan, T.: Photodynamic therapy: A new antimicrobial approach to infectious disease? Photochem. Photobiol. Sci. 3, 436–450 (2004) [DOI] [PMC free article] [PubMed]
- 8.Bisland, S.K., Chien, C., Wilson, B.C., et al.: Pre-clinical in vitro and in vivo studies to examine the potential use of photodynamic therapy in the treatment of osteomyelitis. Photochem. Photobiol. Sci. 5, 31–38 (2006) [DOI] [PubMed]
- 9.Liu, X., Wang, S., Sendi, L., et al.: High-throughput imaging of bacterial colonies grown on filter plates with application to serum bactericidal assays. J. Immunol. Methods 292, 187–193 (2004) [DOI] [PubMed]
- 10.Strutt, J.W.: Investigation of the disturbance produced by a spherical obstacle on the waves of sound. Proc. London Math. Soc. 4, 233–283 (1872)
- 11.Lizzi, F.L., Astor, M., Liu, T., et al.: Ultrasonic spectrum analysis for tissue assays and therapy evaluation. Int. J. Imaging Syst. Technol. 8, 3–10 (1997) [DOI]