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Acid Resistance in Francisella tularensis
Adcock, N. J., B. J. Morris, AND E. W. Rice. Acid Resistance in Francisella tularensis. MicrobiologyOpen. Wiley-Blackwell Publishing, Hoboken, NJ, 3(1):133-138, (2014).
Francisella tularensis, the etiologic agent of tularemia, can survive under acidic conditions. Tularemia can be acquired by several routes, including by ingestion of contaminated food or water. While acid resistance is usually associated with a low oral infective dose, the infective dose for gastrointestinal illness is quite high. In this study, four strains of F. tularensis ssp. tularensis (type A) and four strains of F. tularensis ssp. holarctica (type B) were examined for innate acid resistance and the ability to survive in synthetic gastric fluid under in vitro conditions similar to passage through the human stomach. Survival for all strains was significantly less in pH 2.5 synthetic gastric fluid than in pH 2.5 phosphate buffered saline and pH 4.0 synthetic gastric fluid. Attenuated strains were consistently less resistant. Type B strains are most often associated with waterborne outbreaks and were examined after storage in natural water. Low nutrient pre-adaptation resulted in increased resistance. Although F. tularensis can persist under certain acidic conditions, it is sensitive to conditions replicating the fasting human stomach. This may help explain the high infective dose required for gastrointestinal infections.
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL HOMELAND SECURITY RESEARCH CENTER
WATER INFRASTRUCTURE PROTECTION DIVISION