The photodynamic effects of photosensitizers on Acinetobacter baumannii were studied. These Gram negative bacteria have recently been implicated in various infections, mainly acquired in hospitals. They have outstanding characteristics of multidrug high resistance to antimicrobial agents. The best photodynamic effect was obtained when A. baumannii cultures were treated with light activated deuteroporphyrin (Dp) at a concentration of 34 μmoles l-1 and polymyxin nonapeptide (PMNP) at a concentration of 200 μmoles l-1. At these concentrations the culture in brain heart infusion (BHI) broth was found to be sterile after 1 h of treatment. Some inhibition was also obtained under the same conditions with Cd-texaphyrin (Cd-Tx) in the presence of PMNP. Treatment with various other photosensitizers in the presence of PMNP exhibited only marginal antibacterial activity. The cationic photosensitizer tetra-methylpyridyl porphine (TMPyP) did not exhibit any photodynamic effect on A. baumannii when illuminated during its growth in BHI broth. Bacteria grown in nutrient broth or suspended in saline and trrated by TMPyP resulted in a significant photoinactivation by the sensitizer alone even in the absence of PMNP. It was found that a high concentration of the proteins present in BHI or in serum prevent TMPyP from acting as a photosensitizer against A. baumannii. Bovine serum albumin at the same high protein concentration prevents Dp (in the presence of PMNP) to act as a photosensitizer. The amionic photosensitizer tetra-sulfonatopheny] porphine (TPPS4) did not show any photodynamic effect in high or low protein media. In this study it was found that despite the high resistance of the Acinetobacter baumannii to antibiotics, these bacteria can be significantly photoinactivated by treatment with either Dp + PMNP or TMPyP in low protein content environments. When the protein concentration is high, photoinactivation efficiency depends on the type of protein present in the medium.
|Number of pages||8|
|Journal||Journal of Photochemistry and Photobiology B: Biology|
|State||Published - Mar 1998|
Bibliographical noteFunding Information:
The authors would like to thank Mrs R. Dror for excellent technical assistance. This work was supported in part by a grant from the Health Sciences Research Center Funds (to Y.N.).
- Cationic porphyrins
- Gram-negative bacteria
- Polymyxin nonapeptide