Effects of crp deletion in Salmonella enterica serotype Gallinarum.
BACKGROUND
Salmonella enterica serotype Gallinarum (S. Gallinarum) remains an important pathogen of poultry, especially in developing countries. There is a need to develop effective and safe vaccines. In the current study, the effect of crp deletion was investigated with respect to virulence and biochemical properties and the possible use of a deletion mutant as vaccine candidate was preliminarily tested.


METHODS
Mutants were constructed in S. Gallinarum by P22 transduction from Salmonella Typhimurium (S. Typhimurium) with deletion of the crp gene. The effect was characterized by measuring biochemical properties and by testing of invasion in a chicken loop model and by challenge of six-day-old chickens. Further, birds were immunized with the deleted strain and challenged with the wild type isolate.


RESULTS
The crp deletions caused complete attenuation of S. Gallinarum. This was shown by ileal loop experiments not to be due to significantly reduced invasion. Strains with such deletions may have vaccine potential, since oral inoculatoin with S. Gallinarum Deltacrp completely protected against challenge with the same dose of wild type S. Gallinarum ten days post immunization. Interestingly, the mutations did not cause the same biochemical and growth changes to the two biotypes of S. Gallinarum. All biochemical effects but not virulence could be complemented by providing an intact crp-gene from S. Typhimurium on the plasmid pSD110.


CONCLUSIONS
Transduction of a Tn10 disrupted crp gene from S. Typhimurium caused attenuation in S. Gallinarum and mutated strains are possible candidates for live vaccines against fowl typhoid.
Rosu
Valentina
V
Department of Biomedical Science, University of Sassari, Viale San Pietro 43B, 07100 Sassari, Italy. v_rosu@hotmail.com <v_rosu@hotmail.com>
Chadfield
Mark S
MS
Santona
Antonella
A
Christensen
Jens P
JP
Thomsen
Line E
LE
Rubino
Salvatore
S
Olsen
John E
JE
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001681:Biological Assay / Q000662:veterinary; D002645:Chickens; D002373:Cyclic AMP Receptor Protein / Q000235:genetics* / Q000502:physiology; D005260:Female; D017353:Gene Deletion; D008969:Molecular Sequence Data; D012329:RNA, Bacterial / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D012481:Salmonella Infections, Animal / Q000517:prevention & control*; D022562:Salmonella Vaccines / Q000276:immunology; D019779:Salmonella enterica / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity; D012486:Salmonella typhimurium / Q000235:genetics; D016415:Sequence Alignment; D014161:Transduction, Genetic / Q000379:methods / Q000662:veterinary; D014613:Vaccines, Attenuated / Q000276:immunology; D037521:Virulence Factors / Q000235:genetics
D002373:Cyclic AMP Receptor Protein; D012329:RNA, Bacterial; D022562:Salmonella Vaccines; D014613:Vaccines, Attenuated; D037521:Virulence Factors