Several Salmonella enterica subsp. enterica Serotype 4,5,12:i:− Phage Types Isolated from Swine Samples Originate from Serotype Typhimurium DT U302

Abstract

Pulsed-field gel electrophoresis, plasmid profiling, and phage typing were used to characterize and determine possible genetic relationships between 48 Salmonella enterica subsp. enterica isolates of pig origin collected in Catalonia, Spain, from 1998 to 2000. The strains were grouped into 23 multidrug-resistant fljB-lacking S. enterica serovar 4,5,12:i:؊ isolates, 24 S. enterica serovar Typhimurium isolates, and 1 S. enterica serovar 4,5,12:؊:؊ isolate. After combining the XbaI and BlnI macrorestriction profiles (XB profile), we observed 29 distinct subtypes which were grouped into seven main patterns. All 23 of the 4,5,12:i:؊ serovar strains and 10 serovar Typhimurium isolates were found to have pattern AR, and similarities of >78% were detected among the subtypes. Three of the serovar Typhimurium DT U302 strains (strains T3, T4, and T8) were included in the same 4,5,12:i:؊ serovar cluster and shared a plasmid profile (profile I) and a pattern of multidrug resistance (resistance to ampicillin, chloramphenicol, streptomycin, sulfonamide, tetracycline, gentamicin, and trimethoprim-sulfamethoxazole) commonly found in monophasic isolates. This led us to the conclusion that strains of the S. enterica 4,5,12:i:؊ serovar might have originated from an S. enterica serovar Typhimurium DT U302 strain.

Detection of Multidrug-Resistant Salmonella enterica Serovar Typhimurium Phage Types DT102, DT104, and U302 by Multiplex PCR

“…All of these strains contained SGI1 (4,9,10,21). By using PCR to detect class 1 integron in the SGI1, we demonstrated that all ACSSuT-type serovar Typhimurium harbored SGI1.…”

“…The flagellar (H) antigen is expressed in the switching state between phase 1 and phase 2 antigens by the recombination event of an inverted repeat flanking the promoter region (27). Recently, monophasic H antigen expression (4,5,12:i:Ϫ) of serovar Typhimurium has been reported in phage type DT U302 (9). The mechanism that contributes to such expression change may be the inactivation of hin or one of the structural genes, fliC and fljB.…”

“…In addition to DT104, other serovar Typhimurium phage types, such as DT204b and U302, with the ACSSuT resistance phenotype, have also been isolated from animals, foods, and humans (20,24). Before phage typing, the identification of Salmonella serovars using H antisera is important; however, recent studies discovered a monophasic variant of serovar Typhimurium (4,5,12:1:Ϫ) from swine, the H antigen profile of which differs from the typical serovar Typhimurium U302 in that it has no phase switch (9). The situation prevents the rapid determination of serovar Typhimurium.…”

Pork Contaminated with Salmonella enterica Serovar 4,[5],12:i:−, an Emerging Health Risk for Humans

“…enterica serovar 4, [5],12:i:Ϫ is a worldwide emerging monophasic serovar (24). In Europe, especially, pork and its products contaminated with this serovar were identified as sources for human Salmonella infections (8,10,19). Several studies indicated that the serovar is a monophasic variant of S. enterica serovar Typhimurium lacking a genomic region that harbors the structural and regulating genes fljA, fljB, and hin encoding the second-phase flagellum (1,8,11,13,23).…”

Use of Biochemical Kinetic Data To Determine Strain Relatedness among Salmonella enterica subsp. enterica Isolates

“…This distribution is roughly representative of the serotypes isolated in our laboratory from 1997 to 2002. All isolates were epidemiologically unrelated and originated from different farms, and some had been used in previous studies (5,12).…”