title: Mechanistic aspects of the photodynamic inactivation of vancomycin-resistant Enterococci mediated by 5-aminolevulinic acid and 5-aminolevulinic acid methyl ester.
abstract: Vancomycin-resistant Enterococci (VRE) is a serious concern for public health. Serious infections with VRE have very limited effective antimicrobial therapy, and alternative treatment approaches are highly desirable. One promising approach might be the photodynamic antimicrobial chemotherapy. In the present study, we investigated the photodynamic inactivation (PDI) of two VRE strains mediated by 5-aminolevulinic acid (5-ALA) and its derivative 5-ALA methyl ester (MAL). The photodynamic damages to bacteria on the level of genomic DNA, the leakage of cell components, and the changes of membrane structure were investigated. After treated with 10 mM 5-ALA and irradiated by the 633 ± 10 nm LED for 60 min, 5.37 and 5.22 log10 reductions in bacterial survival were achieved for the clinical isolate of VRE and E. faecalis (ATCC 51299), respectively. After treated with 10 mM MAL and irradiated by the LED for 60 min, 5.02 and 4.91 log10 reductions in bacterial survival were observed for the two VRE strains, respectively. In addition, the photocleavage on genomic DNA and the rapid release of intracellular biopolymers were detected in PDI-treated bacteria. The intensely denatured cytoplasm and the aggregated ribosomes were also found in PDI-treated bacteria by transmission electron microscopy. Although 5-ALA and MAL-mediated PDI could induce the photocleavage on genomic DNA, the PDI of the two VRE strains might be predominantly attributed to the envelope injury, the intracellular biopolymers leakage, and the cytoplasm denature.
authors.affiliation: Department of Immunology and Pathogenic Biology, College of Medicine, Xi'an Jiaotong University, 76 West Yanta Road, Xi'an, 710061, People's Republic of China.
authors.forename: Chengcheng
authors.initials: C
authors.lastname: Liu
authors.forename: Yingli
authors.initials: Y
authors.lastname: Zhou
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Lei
authors.initials: L
authors.lastname: Han
authors.forename: Jin'e
authors.initials: J
authors.lastname: Lei
authors.forename: Hafiz Muhammad
authors.initials: HM
authors.lastname: Ishaq
authors.forename: Jiru
authors.initials: J
authors.lastname: Xu
mesh_terms: D000622:Aminolevulinic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000528:radiation effects; D003593:Cytoplasm / Q000187:drug effects / Q000528:radiation effects / Q000648:ultrastructure; D004269:DNA, Bacterial / Q000187:drug effects; D050296:Microbial Viability / Q000187:drug effects*; D046529:Microscopy, Electron, Transmission; D010539:Permeability / Q000187:drug effects / Q000528:radiation effects; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011489:Protein Denaturation; D012270:Ribosomes / Q000187:drug effects / Q000528:radiation effects / Q000648:ultrastructure; D065507:Vancomycin-Resistant Enterococci / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects* / Q000648:ultrastructure
chemical_list: D004269:DNA, Bacterial; D017319:Photosensitizing Agents; C114767:delta-aminolevulinic acid methyl ester; D000622:Aminolevulinic Acid