ABSTRACT
Background & objectives: The pathogenicity of the nosocomial pathogens, Pseudomonas aeruginosa and Acinetobacter baumannii is regulated by their quorum sensing (QS) systems. The objective of the present study was to examine the effect of the cold ethyl acetate extract of Tinospora cordifolia stem on virulence and biofilm development in the wild type and clinical strains of P. aeruginosa and A. baumannii. The study was further aimed to identify the probable active constituents in the plant extract. Methods: P. aeruginosa virulence factors viz., LasA protease, LasB elastase and pyocyanin production were analyzed spectrophotometrically. Biofilm formation was studied using crystal violet staining-microtitre plate assay. The plant extract was fractionated using silica gel column chromatography and the most active fraction was derivatized using silylation and analyzed by gas chromatography-mass spectrometry (GC-MS). In silico testing of the molecules identified in GC-MS was performed, for binding to the P. aeruginosa LasI and LasR proteins, to predict the QS inhibitory molecules. Results: The plant extract inhibited three major virulence factors in P. aeruginosa; it exhibited enhanced biofilm formation in P. aeruginosa while decreased biofilm development in A. baumannii. The most active fraction obtained from column chromatography, exhibited suppression of virulence as well as biofilm in both the organisms. Docking scores were calculated for all the molecules identified in GC-MS, and high docking scores were obtained for 2,3,4-triacetyloxybutyl acetate, methyl 16-methyl heptadecanoate, 2-(5-ethenyl-5-methyloxolan-2-yl)propan-2-ol, methyl hexadecanoate and 2-methoxy-4-vinyl phenol. Interpretation & conclusions: The compounds showing high docking scores could probably be the QS inhibitors. These molecules can be screened further for the development of new anti-infective drugs.
ABSTRACT
To construct a pUCP18/lasRantisense plasmid carrying the reversed gene and analyze its effect on the virulence of Pseudomonas aeruginosus, LasR gene was amplified from the genome of Pseudomonas aeruginosus by PCR and reversely recombined with plasmid pUCP18. The recombinant pUCP18/lasRantisense was verified by enzyme digestion, PCR and sequencing. The biological effects of pUCP18/lasRantisense were examined by using RT-PCR, NAD method and the assay of pyocyanin. Our results showed that the expected full length lasR fragment (721 bp) was extended from Pseudomonas aeruginosus gene with PCR. And it is consistent with LasR gene of Pseudomonas aeruginosa in GenBank (No. NC_002516). The recombinant plasmid was successfully constructed and transferred into Pseudomonas aeruginosus. The antisense nucleic acid of LasR gene could reduce the virulence of Pseudomonas aeruginosus and might serve as a new target site for treatment purpose.
ABSTRACT
The LasR gene was amplified from the genome of Pseudomonas aeruginosus by PCR and recombined with plasmid pUCP18 reversely. The recombinant pUCP18/lasRantisense was verified with restriction analysis, PCR and sequence and was transformed in Pseudomonas aeruginosus. The biological effect of pUCP18/lasRantisense was detected by RT-PCR, NAD method and the assay of pyocyanin. The air tubes of rats were infected by pUCP18/lasRantisense strain and then carried on histopathologic slide check. Expected full length LasR fragment (721bp) can be extended from Pseudomonas aeruginosus gene with PCR technology. And it is consistent with LasR gene of Pseudomonas aeruginosa covered in GenBank (NO. NC_002516). The recombinant plasmid was constructed and transformed into Pseudomonas aeruginosus sucessfully. Compared with the rats which were infected by standard strain, the bronchitis of the rats which were infected by pUCP18/lasRantisense strain was obviously eased. It can be concluded that the antisensenucleic acid of LasR gene can depress the virulence of Pseudomonas aeruginosus and reveal a new target site for treatment.
ABSTRACT
Photorefractive keratectomy(PRK) was performed on 60 rabbit eyes, and synthetic inhibitor of metalloproteinase(SIMP) and cyclosporin A(CsA) was topically administered and their effects on coreneal haze were evaluated. They were randeomized to one of four groups: group A received topical SIMP, group B received topical CsA, group C received both SIMP and CsA, and group D received vehicles. At one, two, four, and six weeks after surgery, slit lamp examination was performed, and haze gradings were recorded. Light microscopy, together with immunohistochemistry using antibodies against collagen types III, IV, and VI were performed in corneas from all groups. Slit lamp examination and light microscopy revealed that SIMP significantly reduced corneal haze after PRK and subepithelial deposition of newly synthesized extracellular matrix, but CsA did not. By immunohistochemistry, deposition of types III and IV collagen was noted in ablated area of all groups. Positive staining for type III collagen was less frequent in groups treated with SIMP than in groups not treated with SIMP. In conclusion, SIMP significantly reduced the synthesis of type III collagen in treated area as well as corneal haze after excimer laser PRK in rabbits.