Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 10, 1997
Publication Date: N/A
Interpretive Summary: Salmonella pullorum (SP) is a bacterial pathogen which causes serious disease in poultry. Unlike the vast majority of other Salmonella species, SP was thought to lack the ability to propel itself through its environment primarily because it lacked whip-like fibers called flagella on its cell surface. The absence of flagella and motility have been accepted characteristics of SP for more than 60 years and called into question the role of these attributes in the ability of the organism to cause disease. However, we found that, under special conditions, SP was in fact motile and appeared to produce flagella. This movement was affected by a number of factors, including the sugar composition and agar concentration of the growth medium and the temperature in which the organism was grown. The motility property could be induced in 40/44 SP strains indicating that it is prevalent within this species. These results suggest that, contrary to long-held beliefs, SP does not differ from other salmonellae as much as was originally thought, and motility may indeed play an important role in the ability of the organism to cause disease.
Technical Abstract: Salmonella pullorum is a host-adapted pathogen of poultry. For the past 60 years S. pullorum has been described as nonmotile and nonflagellated. We discovered that motility can be induced in this organism under special growth conditions. Migration of S. pullorum occurred only on the surface of the media and not from a stab inoculation, indicating that the organism m can be induced only to a swarming but not swimming motility. The best motility at 37C occurred when media levels of dextrose were 0.5% to 0.75%. Optimum agar concentration for motility was 0.5%, and S. pullorum migration occurred under either aerobic or anaerobic conditions. A three- fold increase in migration distance at 24 hours was observed on plates incubated at 42C or in media where dextrose was replaced with mannitol. Motility could be induced in 25/44 and 39/44 S. pullorum isolates incubated at 37C and 42C, respectively. Flagellar stains and transmission n electron micrographs of the motile S. pullorum culture showed long fibrou appendages resembling flagella. Antisera to G flagellar antigens reacted strongly with the S. pullorum culture indicating the G epitopes were expressed on these cells. These results indicate that, contrary to the previous paradigm which held that S. pullorum was nonmotile and nonflagellated, a special motility could be induced in S. pullorum and that the organism appeared to have the capacity to produce flagella.