Effects of repeated cycles of acid challenge and growth on the phenotype and virulence of Salmonella enterica
Article first published online: 15 OCT 2008
© 2008 The Authors. Journal compilation © 2008 The Society for Applied Microbiology
Journal of Applied Microbiology
Volume 105, Issue 5, pages 1640–1648, November 2008
How to Cite
Karatzas, K.A.G., Hocking, P.M., Jørgensen, F., Mattick, K., Leach, S. and Humphrey, T.J. (2008), Effects of repeated cycles of acid challenge and growth on the phenotype and virulence of Salmonella enterica. Journal of Applied Microbiology, 105: 1640–1648. doi: 10.1111/j.1365-2672.2008.03909.x
- Issue published online: 15 OCT 2008
- Article first published online: 15 OCT 2008
- 2007/1898: received 24 November 2007, revised 2 May 2008 and accepted 4 May 2008
- acid cycling;
- acid resistance;
- stress resistance;
Aims: The aim of the study was to investigate how stresses like low pH, which may be encountered in farms or food preparation premises, shape populations of Salmonella enterica by the selection of stress-resistant variants.
Methods and Results: Stationary-phase cultures of S. enterica serovar Enteritidis and serovar Typhimurium (one strain of each) were exposed to pH 2·5 for up to 4 h, followed by growth at pH 7 for 48 h. This process was repeated 15 times in two separate experiments, which increased the acid resistance of the three out of four populations we obtained, by three- to fourfold. Sustainable variants derived from the populations showed changes in colony morphology, expression of SEF17 fimbriae, growth, increased heat resistance and reduced virulence.
Conclusions: The study demonstrates that low pH environments can select for populations of S. enterica with persistent phenotypic changes such as increased acid resistance and occasionally increased SEF17 expression and lower virulence.
Significance and Impact of the Study: There is a common belief that increased acid resistance coincides with increased virulence. This study demonstrates for the first time that increased acid resistance often impairs virulence and affects the general phenotype of S. enterica.