IncA/C plasmids mediate antimicrobial resistance linked to virulence genes in the Spanish clone of the emerging Salmonella enterica serotype 4,[5],12:i:−

Abstract

IncA/C plasmids are responsible for multidrug resistance in an increasing number of relevant human and animal bacterial pathogens, and hence are regarded as an important threat to public health. Those found in the Spanish clone of Salmonella 4,5,12:i:- constitute a relevant example of short-term evolution, and could have been involved in the successful adaptation of this pathogen.

Genetic Types, Gene Repertoire, and Evolution of Isolates of the Salmonella enterica Serovar 4,5,12:i:− Spanish Clone Assigned to Different Phage Types

“…The isolates were given designation consisting of LSP (for Laboratorio de Salud Pública) followed by a code number/year of isolation. Nineteen isolates had been previously investigated with regard to phage type, PFGE profile, plasmid content, and antimicrobial susceptibility and responsible genes (11). Two additional isolates (LSP 127/00 and LSP 148/ 00) were similarly characterized for the present study.…”

“…Mainly due to its connection with an increasing number of human cases of salmonellosis, a number of studies have focused on its emergence and evolution (1,2). It was shown that S. 4, [5],12:i:Ϫ is closely related to S. Typhimurium (3)(4)(5)(6)(7)(8)(9)(10)(11). The monophasic serovar does not express the second-phase flagellar antigen, and different mutations and/or deletions affecting the fljAB operon (encoding a negative regulator of the fliC gene for the first-phase flagellar antigen and the second-phase antigen, respectively) and surrounding genes have been detected (6,9,10,12,13).…”

“…The European clone, particularly common since 2000, harbors a chromosomal region responsible for resistance to ampicillin, streptomycin/spectinomycin, sulfonamides, and tetracycline (ASSuT type) (10,(14)(15)(16). The Spanish clone, first reported in Spain in 1997, displays plasmid-mediated resistance up to seven antimicrobial drugs: ampicillin, chloramphenicol, gentamicin, streptomycin/spectinomycin, sulfonamides, tetracyclines, and trimethoprim (ACGSSuTTp type) (3,11,17). The genes are carried by a family of IncA/C plasmids which harbor (pUOSTmRV1-like) or do not harbor (pUO-STmR1-like) genes of pSLT, the specific virulence plasmid of serovar Typhimurium (11,17).…”

“…The Spanish clone, first reported in Spain in 1997, displays plasmid-mediated resistance up to seven antimicrobial drugs: ampicillin, chloramphenicol, gentamicin, streptomycin/spectinomycin, sulfonamides, tetracyclines, and trimethoprim (ACGSSuTTp type) (3,11,17). The genes are carried by a family of IncA/C plasmids which harbor (pUOSTmRV1-like) or do not harbor (pUO-STmR1-like) genes of pSLT, the specific virulence plasmid of serovar Typhimurium (11,17). Multidrug-resistant S. 4,5,12:i:Ϫ isolates belonging to the Spanish clone and ascribed to phage type U302 have been shown to differ from S. Typhimurium LT2 by five major deletions, designated clusters I to V (6).…”

Salmonella Pathogenicity and Host Adaptation in Chicken-Associated Serovars

“…A more likely scenario based upon recent work is that an ancestral plasmid type possessed an IncFIIA/IncFIB backbone containing spv, prf, and pef and separated following the divergence of serogroups and that the plasmid lineages subsequently underwent recombination events, resulting in the current virulence plasmid profiles. Interestingly, there is little evidence of extensive transfer of virulence plasmids among the Salmonella serovars, even though their transfer in vivo has been documented (129). The horizontal transfer of these plasmids is likely a neutral trait in Salmonella, and thus, transfer between serovars is not strongly selected (130,131).…”