Abstract
The data presented here demonstrate that Salmonella typhi is capable of expressing an acid tolerance response (ATR) and that effective induction of this response (in nutrient-rich medium) occurs at pH 5.0 in anaerobic conditions. The candidate live oral S. typhi vaccine strains made by precise genetic methods and which carry auxotrophic mutations were CVD 906 (carries defined attenuating deletion mutations: delta aroC, delta aroD), CVD 908 (carries defined attenuating deletion mutations: delta aroC, delta aroD), 541Ty (carries attenuating deletion mutations: aroA, purA), and galE, Vi-negative (via) strain EX462. All generate an effective ATR. In contrast, nitrosoguanidine-derived live oral typhoid vaccine strain Ty21a only weakly expresses acid tolerance. This further demonstrates that the non-specific mutagenesis process used to produce Ty21a affects genetic loci outside the intended target genes for mutagenesis, galE and via, and further emphasizes the importance of using precise genetic techniques when developing live oral S. typhi vaccines.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
