Salmonella Typhi (S. Typhi) is the causative agent of typhoid fever, a serious health threat resulting in some 22 million new cases yearly and approximately 217,000 fatalities. A number of novel vaccine candidates using live attenuated strains of Salmonella are being developed, but care must be taken to ensure the bacteria are not excreted into the environment following vaccination.
Karen Brenneman and her colleagues at Arizona State University's Biodesign Institute have been examining ways to detect the presence of S. Typhi in stool following inoculation with various vaccine strains. Their results recently appeared in the Journal of Microbiological Methods.
The group, overseen by Roy Curtiss III, who directs Biodesign's Center for Infectious Diseases and Vaccinology, applied a test known as RapidChek SELECTTM Salmonella to detect the shedding of S. Typhi in stool, demonstrating a 10-fold to 1000-fold improvement in detection of attenuated strains compared with conventional methods.
"This technology is of critical value to help us assess the degree and duration of shedding that occurs after immunization with any live vaccine. We have an ethical responsibility to make sure we understand the effects of vaccination not only on the individual that receives the vaccine, but also on those around him/her in the community," Brenneman says.
Shedding of Salmonella species in stool following infection typically lasts 3-5 weeks, although typhoid fever infection often results in shedding of bacteria for up to 3 months and typhoid carriers can shed the pathogen indefinitely.
New vaccines using attenuated versions of S. Typhi are able to confer protection against typhoid fever, triggering a robust, system-wide immune response. Further, the current research (combined with data from clinical trials) demonstrates that attenuated forms of the bacteria are shed for a much shorter time period
|Contact: Joseph Caspermeyer|
Arizona State University