Salmonella 4,[5],12:i:- (S. 4,[5],12:i:-) is believed to be a monophasic variant of S. Typhimurium. This study was conducted to identify the molecular and phenotypic characteristics of the S. 4,[5],12:i:- isolates. Fifty-one S. 4,[5],12:i:- isolates obtained between 2000 and 2010 were analyzed. All the S. 4,[5],12:i:- isolates were identified as S. Typhimurium by two different polymerase chain reactions (PCR) for identification of S. Typhimurium. These data suggest that the S. 4,[5],12:i:- isolates are monophasic variants of S. Typhimurium. The flagellar phase variation is induced by three adjacent genes (fljA, fljB, and hin) in the chromosome. The results of PCR mapping of this region suggested that the deletion of the fljAB operon and its flanking region was the major genetic basis of the monophasic phenotype of S. 4,[5],12:i:-. The fljAB operon and hin gene were detectable in eight of the S. 4,[5],12:i:- isolates with common amino acid substitutions of A46T in FljA and R140L in Hin. The introduction of these mutations into S. Typhimurium isolates led to the loss of selectability of isolates expressing the phase 2 H antigen. These data suggested that a point mutation was the genetic basis, at least in part, of the S. 4,[5],12:i:- isolates. The information in this study can be used to identify the monophasic variant of S. Typhimurium by PCR and sequencing.
(Bacterial and Parasitic Disease Research Division)
References:
Ido N. et al (2014) PLoS ONE 9(8):e104380 (doi:10.1371/journal.pone.0104380)
