Objective ： To construct plant transformation vector containing Escherichia coli heat-labile enterotoxin B subunit （LT-B） gene and generate LT-B transgenic tobacco plants. Methods： The LT-B coding sequence was amp...Objective ： To construct plant transformation vector containing Escherichia coli heat-labile enterotoxin B subunit （LT-B） gene and generate LT-B transgenic tobacco plants. Methods： The LT-B coding sequence was amplified from pMMB68 by PCR, subcloned into middle vector pUCmT and binary vector pBI121 to obtain plant expression vector pBI-LTB, in which LT-B expression was controlled under the Cauliflower mosaic virus （CaMV） 35S promoter. The tobacco plants （Nicotiana tobacum L. Cuttivar Xanthi） were transformed by co-cultivating leaf discs method via Agrobacterium tumefaciens LBA4404 harboring the plant expression vector. The regenerated transgenic tobacco plants were selected by kanamycin and confirmed by PCR, Southern blot, Western blot and ELISA. Resuits： LT-B gene integrated in the tobacco genomic DNA and were expressed in 9 strains of transgenic tobacco plants. The yield was varied from 3. 36-10. 56 ng/mg total soluble tobacco leaf protein. Conclusion： The plant binary expression vector pBI-LTB was constructed successfully, and transgenic LT-B tobacco plants was generated, and confirmed by Southern blot. The protein LT-B expressed by engineered plants was identified by Western blot analysis and had the expected molecular weight of LT-B pentamer protein. This result is an important step close to developing an edible vaccine and supplying a mucasal immunoajuvant, which will contribute to the preven- tion of mucosaroute evading pathogen.展开更多
Aim: The present study aims to evaluate the occurrence and characterize E. coli in meat and meat products marketed in Egypt based on their antimicrobial-resistance pattern and production of enterotoxins. Methods: A to...Aim: The present study aims to evaluate the occurrence and characterize E. coli in meat and meat products marketed in Egypt based on their antimicrobial-resistance pattern and production of enterotoxins. Methods: A total of 250 meat samples, categorized as 80 fresh beef, 85 ground beef and 85 beef burger purchased from supermarkets and butchers’ shops were used for isolation of E. coli. All isolates were screened for antimicrobial susceptibility. Plasmid profile analyses were done. Polymerase chain reactions were performed for detection of enterotoxin-encoding genes (astA, eaeA, stx1 and stx2). Results: Twenty-five samples were isolated and identified as E. coli. 14 isolates were multidrug resistant. Plasmids isolation from all isolates revealed that 76% of these isolates harbored plasmids. astA gene was amplified in 7 isolates (28%). Eight (32%) isolates harbored eaeA gene. However, none of the isolates harbored stx1 or stx2 genes. Analysis of multiple drug resistant isolates revealed a significant relation between multiple drug resistance and both astA and eaeA. Conclusion: The study confirmed the prevalence of enterotoxin genes (astA and eaeA) in E. coli isolated from meat product and the association between the presence of these genes and multiple drug resistant phenomena.展开更多
基金Supported by the National Natural Science Foundation ofChina (No. 30070848)
文摘Objective ： To construct plant transformation vector containing Escherichia coli heat-labile enterotoxin B subunit （LT-B） gene and generate LT-B transgenic tobacco plants. Methods： The LT-B coding sequence was amplified from pMMB68 by PCR, subcloned into middle vector pUCmT and binary vector pBI121 to obtain plant expression vector pBI-LTB, in which LT-B expression was controlled under the Cauliflower mosaic virus （CaMV） 35S promoter. The tobacco plants （Nicotiana tobacum L. Cuttivar Xanthi） were transformed by co-cultivating leaf discs method via Agrobacterium tumefaciens LBA4404 harboring the plant expression vector. The regenerated transgenic tobacco plants were selected by kanamycin and confirmed by PCR, Southern blot, Western blot and ELISA. Resuits： LT-B gene integrated in the tobacco genomic DNA and were expressed in 9 strains of transgenic tobacco plants. The yield was varied from 3. 36-10. 56 ng/mg total soluble tobacco leaf protein. Conclusion： The plant binary expression vector pBI-LTB was constructed successfully, and transgenic LT-B tobacco plants was generated, and confirmed by Southern blot. The protein LT-B expressed by engineered plants was identified by Western blot analysis and had the expected molecular weight of LT-B pentamer protein. This result is an important step close to developing an edible vaccine and supplying a mucasal immunoajuvant, which will contribute to the preven- tion of mucosaroute evading pathogen.
文摘Aim: The present study aims to evaluate the occurrence and characterize E. coli in meat and meat products marketed in Egypt based on their antimicrobial-resistance pattern and production of enterotoxins. Methods: A total of 250 meat samples, categorized as 80 fresh beef, 85 ground beef and 85 beef burger purchased from supermarkets and butchers’ shops were used for isolation of E. coli. All isolates were screened for antimicrobial susceptibility. Plasmid profile analyses were done. Polymerase chain reactions were performed for detection of enterotoxin-encoding genes (astA, eaeA, stx1 and stx2). Results: Twenty-five samples were isolated and identified as E. coli. 14 isolates were multidrug resistant. Plasmids isolation from all isolates revealed that 76% of these isolates harbored plasmids. astA gene was amplified in 7 isolates (28%). Eight (32%) isolates harbored eaeA gene. However, none of the isolates harbored stx1 or stx2 genes. Analysis of multiple drug resistant isolates revealed a significant relation between multiple drug resistance and both astA and eaeA. Conclusion: The study confirmed the prevalence of enterotoxin genes (astA and eaeA) in E. coli isolated from meat product and the association between the presence of these genes and multiple drug resistant phenomena.
