ABSTRACT
Salmonella enterica is one of the most important food-borne pathogens, causing a variety of diseases in humansand animals. This study aimed to detect the virulence genes in 33 S. enterica strains isolated from patients andto investigate the immunogenicity of the outer membrane proteins (OMPs) of S. enterica serovar Typhimurium.The aggregative fimbriae (agfA) gene was detected in all S. enterica isolates except one strain, SalmonellaParatyphi C strain SA7. In addition, 81.8% of the isolates harbored the sefC gene (fimbrial protein). However,all of the tested S. enterica isolates possessed the fimA, hilA, invA, stn, and misL virulence genes, regardless ofserovar. The predominant OMPs of S. enterica Typhimurium SA3 identified by 12% sodium dodecyl sulfatePolyacrylamide Gel Electrophoresis (PAGE) were used as eliciting antigens in the experimental mice. Theresults of the protection studies indicated that the selected OMPs conferred varying degrees of protection.However, the highest protection was observed using the 38-kDa OMP, which provided 100% protection tomice challenged with 50× LD50 of Salmonella Typhimurium SA3 and 75% protection to mice subjected toan even higher bacterial challenge of 100× LD50. The humoral response in mice caused by the 38-kDa OMPwas confirmed using an immunodiffusion assay. This 38-kDa OMP is a promising candidate for the vaccinedevelopment against S. enterica Typhimurium. Further research on the protein structure was recommended.
ABSTRACT
The main goal of this work was to investigate the biosynthetic origin of diterpenes in gorgorian Pseudopterogorgia acerosa and to investigate the possibility of diterpenes production by the coral associated bacteria. Live coral Pseudopterogorgia acerosa was treated with different antibiotics, specific for different bacterial groups. The treated coral homogenate was prepared and assayed for conversion of radiolabeled terpenes precursor geranyl genranyl diphosphate [3H-GGPP] into radiolabled diterpenes. Mixed bacterial cultures were started from different coral tissues. Cell free extract were prepared from the isolated mixed culture and assayed for radiolabeled diterpenes biosynthesis. Production of diterpenes by the mixed bacterial cultures was investigated using LC-MS analysis. Investigation of the effect of different antibiotics on live coral demonstrated that the biosynthetic capability of diterpenes by the coral homogenate, from 3H-GGPP, was reduced by the effect of antibiotics mixture which suggested bacterial origin of this diterpene in P. acerosa. Furthermore, coral treated with nalidixic acid [gram negative bacterial inhibitor] resulted in about three fold increase of the biosynthesis of the radiolabled diterpes by the coral homogenate which suggested that the diterpenes producer may be gram positive bacteria. The cell free extract of mixed bacterial cultures isolated from the coral tissues was able to convert the radiolabled diterpenes precursor, 3H-GGPP, into pseudopterolide. Furthermore, mixed bacterial culture, isolated from the coral, showed low level production of diterpenes using diluted marine broth medium The results provided strong evidences that the diterpenes biosynthesis in P. acerosa is due to bacterial symbionts rather than the coral tissues