Antimicrobial Resistance and Virulence Determinants in European Salmonella Genomic Island 1-Positive Salmonella enterica Isolates from Different Origins

Abstract

Salmonella genomic island 1 (SGI1) contains a multidrug resistance region conferring the ampicillinchloramphenicol-streptomycin-sulfamethoxazole-tetracycline resistance phenotype encoded by bla PSE-1 , floR, aadA2, sul1, and tet(G). Its increasing spread via interbacterial transfer and the emergence of new variants are important public health concerns. We investigated the molecular properties of SGI1-carrying Salmonella enterica serovars selected from a European strain collection. A total of 38 strains belonging to S. enterica serovar Agona, S. enterica serovar Albany, S. enterica serovar Derby, S. enterica serovar Kentucky, S. enterica Only minor serovar-specific differences among virulence patterns were detected. In conclusion, the SGI1 carriers exhibited pathogenetic backgrounds comparable to the ones published for susceptible isolates. However, because of their multidrug resistance, they may be more relevant in clinical settings.Salmonella genomic island 1 (SGI1) is a 43-kb mobilizable chromosomal region that is located in Salmonella enterica serovars between the genes thdF and yidY or between thdF and int2 in the retron sequence of S. enterica serovar Typhimurium (7). In 2008, an SGI1 secondary chromosomal attachment site for integration of the island between the sodB and purR genes was described (17). SGI1 contains an antimicrobial resistance gene cluster (7, 16) located on a 13-kb complex class 1 integron designated In104 (31), which confers pentaresistance (Penta-R) to ampicillin (bla PSE-1 ), chloramphenicol/florfenicol (floR), streptomycin/spectinomycin (aadA2), sulfamethoxazole (sul1), and tetracycline [tet(G)] (8). The genes bla PSE-1 and aadA2 are located on class 1 integrons, named InC and InD, with variable regions of 1.2 kb and 1.0 kb, respectively (3, 24). The five resistance determinants are characteristic of the pandemic S. Typhimurium definite phage type 104 (DT104), which was globally most predominant in causing infections in humans since the 1980s (16,21,38). SGI1 was first identified in 2000 in a Canadian multidrug-resistant S. Typhimurium DT104 strain with the Penta-R phenotype (7). Subsequently SGI1 and several variant SGI1 antimicrobial resistance gene clusters were detected worldwide in different Salmonella serovars and in Proteus mirabilis (1,2,15,31,39,40).Within the European Union (EU) Network of Excellence Med-Vet-Net, an investigation on the molecular epidemiology of SGI1 in enteric bacteria other than S. Typhimurium DT104 was conducted (http://www.medvetnet.org). For this study, a collection of 445 multidrug-resistant strains (S. enterica, 277; Escherichia coli, 116; Shigella spp., 43, and Proteus spp., 9), isolated from animals, food, and humans from eight European

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

“…The presence of resistance genes on plasmids of specific AMR Salmonella phenotypes was detected using PCR (31,74). Overall, genes encoding resistance to ampicillin and cephalosporin (bla PSE-1 , bla TEM , and bla CMY-2 ), chloramphenicol (cmlA), streptomycin (aadA1, aadA2, strA, and strB), sulfisoxazole (sul1 and sul2), and tetracycline [tet(A), tet(B), tet(C), and tet(G)] were tested.…”

Salmonella Pathogenicity and Host Adaptation in Chicken-Associated Serovars

“…This region is found in many Salmonella isolates and, as mentioned above, is mobilizable. This alone enables a multidrug resistance phenotype, but the carriage of additional plasmids by SGI-1-containing strains is common (157). Interestingly, some plasmids have also been shown to enhance excision and variant formation of Salmonella genomic islands, such as the enhanced excision of SGI-1 by plasmids belonging to the IncA/C type (158,159).…”

Antimicrobial Resistance and Virulence: a Successful or Deleterious Association in the Bacterial World?

“…The S. enterica serovar Typhimurium phage type DT104, carrying SGI1, is disseminated worldwide, like other major clones. Because of its virulence and resistance gene repertoires, isolates with an SGI1 variant are a risk for rapid dissemination (141,251,252). The OmpR-EnvZ operon system, which is encoded in Salmonella pathogenicity island 2, is also involved in the regulation of resistance and virulence.…”

“…Because of their repertory of resistance and virulence genes, these types of isolates may become clinically relevant (141).…”