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Jeganathan lakshmi priya, Rajapandian Sivaganesa Karthikeyan, Namperumalsamy Venkatesh Prajna, Eric Pearlman, Arne Rietsch, Prajna Lalitha; Characterization Of Pseudomonas Aeruginosa Type Three Secretory System (TTSS) Effector Molecules (Exo U/S/T) From Human Corneal Ulcer. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6135.
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Bacterial corneal infections is an important cause of keratitis, which constitutes 34% in South India, among which Pseudomonas aeruginosa (75%) is the predominant causative agent in the gram negative bacteria. Type III secretory system is one of the most important virulence determinants, which can modulate the host cells directly by injection of their toxins. The purpose of this study is to characterize the effector molecules (Exo U/S/T) in Type III Secretory System of Pseudomonas aeruginosa from human corneal ulcer.
Pseudomonas aeruginosa isolates from patients with corneal ulcer were used for this study. The organisms were confirmed by sequencing of 16s rRNA gene. The genotypic variation was identified by performing Colony PCR using gene specific primers. The isolates were grown in modified LB Broth with high salt under depleted calcium condition to stimulate the production of effector molecules. Proteins from the cell pellet and culture supernatant after TCA precipitation were resolved in poly acrylamide gel and western blot was done using specific antibodies and detected using the chemiluminense kit.
Among the 50 Pseudomonas aeruginosa isolates tested 92% of them are having any one of the effector genes, but only 82% of them are expressing it. 32 % of the isolates expressing ExoS/T and 14 % of them are positive to ExoU/T, 34 % of the isolates found to carrying any one of the effector molecules tested. We also identified seven of them are having all the three effector genes.
Effector molecules of the TTSS were present in majority of the clinical isolates causing keratitis signifies its obligate necessity for this organism. Majority of the isolates possesses the effector ExoS/T which is required for the invasiveness of this pathogen. Better understanding of virulence factors may lead to the development of new therapeutic target for treating this disease.
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