title: Invasive strains of Pseudomonas aeruginosa are able to cause epithelial cell cytotoxicity that is dependent on bacterial cell density.
abstract: The purpose of this study was to investigate the hypothesis that quorum-sensing systems are involved in the ability of invasive Pseudomonas aeruginosa strains to cause corneal epithelial cell death. Two invasive strains, 6294 and PAOI, were co-cultured with human corneal epithelial cells at different bacterial concentrations (10(5), 10(7) and 10(9) CFU/mL). Cytotoxicity was measured using a cytotoxicity assay kit. The levels of autoinducer in the supernatant were examined using a reporter strain of Agrobacterium tumefaciens (A136). Protease production was also monitored. Cytotoxicity of both strains was dependent on bacterial density; a moderate to high concentration of bacterial cells (10(7) and 10(9) CFU/mL) caused 70% to 94% loss of cell variability. Cytotoxicity was significantly correlated with enhanced autoinducer and protease production (r>0.95, P<0.05). These results indicate that the invasive strains regulate the production of virulence factors and, in turn, induce chronic dose-related cytotoxicity.
authors.affiliation: Cooperative Research Center for Eye Research and Technology, University of New South Wales, Sydney, Australia. hzhu@cclru.unsw.edu.au
authors.forename: H
authors.initials: H
authors.lastname: Zhu
authors.forename: S J
authors.initials: SJ
authors.lastname: Thuruthyil
authors.forename: M D
authors.initials: MD
authors.lastname: Willcox
mesh_terms: D016960:Agrobacterium tumefaciens / Q000201:enzymology / Q000472:pathogenicity; D016923:Cell Death; D002460:Cell Line; D018920:Coculture Techniques; D015169:Colony Count, Microbial; D004591:Electrophoresis, Polyacrylamide Gel; D019573:Epithelium, Corneal / Q000382:microbiology* / Q000473:pathology; D020689:Exopeptidases / Q000378:metabolism; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000201:enzymology / Q000472:pathogenicity*
chemical_list: D007770:L-Lactate Dehydrogenase; D020689:Exopeptidases