Characteristics of Salmonella enterica Serovar 4,[5],12:i:- as a Monophasic Variant of Serovar Typhimurium

Abstract

Salmonella enterica subspecies enterica serovar 4,[5],12:i:- (S. 4,[5]12:i:-) is believed to be a monophasic variant of S. enterica serovar Typhimurium (S. Typhimurium). This study was conducted to corroborate this hypothesis and to identify the molecular and phenotypic characteristics of the S. 4,[5]12:i:- isolates in Japan. A total of 51 S. 4,[5]12:i:- isolates derived from humans, cattle, swine, chickens, birds, meat (pork), and river water in 15 prefectures in Japan 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. Of the 51 S. 4,[5],12:i:- isolates, 39 (76.5%) harbored a 94-kb virulence plasmid, which is known to be specific for 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 and comparative genomic hybridization analysis 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 results of phenotypic analysis suggested that the S. 4,[5],12:i:- isolates in Japan consist of multiple distinct clones. This is the first detailed characterization of the S. 4,[5],12:i:- isolates derived from various sources across Japan.

Trends in the serovar and antimicrobial resistance in clinical isolates of Salmonella enterica from cattle and pigs between 2002 and 2016 in Japan

“…However, S. 4,[5],12:i:‐ has been rapidly increasing in prevalence in recent years. In Japan, Ido et al () detected S. 4,[5],12:i:‐ in isolates from humans and animals, including cattle and swine, from 2000 to 2010, and showed that these isolates consisted of multiple distinct clones that were predominantly pan‐susceptible, with the exception of swine‐derived isolates. Our present study showed that the incidence of S. 4,[5],12:i:‐ has been increasing, thereafter, in Japan in both cattle and swine, and that the resistance rates have also been increasing rapidly, particularly among the bovine isolates.…”

Horizontal Dissemination of Antimicrobial Resistance Determinants in Multiple Salmonella Serotypes following Isolation from the Commercial Swine Operation Environment after Manure Application

“…The pS24 plasmid isolated from S. enterica 4,12:i:Ϫ had a profile similar to that of S. Typhimurium plasmids, and the parent strain was also isolated from a different swine farm environment. During the last decade, S. enterica 1,4,12:i:Ϫ, 1,4, [5],12:i:Ϫ, and 4,12:i;Ϫ have emerged around the world and have frequently been isolated from human, animal, agricultural production, and environmental sources (37)(38)(39). These serotypes are believed to be a mosaic variant of S. Typhimurium and are related to plasmid-mediated colistin resistance encoded by the mcr-1 gene (37,39,81).…”

Phylogenetic Characterization of Salmonella enterica Serovar Typhimurium and Its Monophasic Variant Isolated from Food Animals in Japan Revealed Replacement of Major Epidemic Clones in the Last 4 Decades

“…Human infection by S. enterica serovar 4, [5],12:i:Ϫ (Salmonella 4, [5],12:i:Ϫ), which is believed to be a monophasic variant of Salmonella Typhimurium, has increased considerably since the mid-1990s. This serovar is currently one of the most common serovars in many countries (8)(9)(10)(11)(12) and is responsible for a number of outbreaks, including outbreaks in Luxembourg (13), Germany (14), France (15), and the United States (16). Many of these outbreaks were linked to the consumption of contaminated pork and other sources, such as cattle and poultry (17).…”

“…Many of these outbreaks were linked to the consumption of contaminated pork and other sources, such as cattle and poultry (17). Isolation of Salmonella 4, [5],12:i:Ϫ from humans and animals has also become common in Japan in recent years (10,18,19). However, the genetic relatedness between isolates in Japan and Western countries is not clear.…”