Diversity of Plasmids Encoding Virulence and Resistance Functions in Salmonella enterica subsp. enterica Serovar Typhimurium Monophasic Variant 4,[5],12:i:- Strains Circulating in Europe

Abstract

Plasmids encoding resistance and virulence properties in multidrug resistant (MDR) Salmonella enterica (S.) serovar Typhimurium monophasic variant 4,[5],12:i:- isolates recovered from pigs and humans (2006-2008) in Europe were characterised. The isolates were selected based on the detection by PCR-amplification of S. Typhimurium virulence plasmid pSLT genes and were analysed by multi-locus sequence typing (MLST). The resistance genes present in the isolates and the association of these genes with integrons, transposons and insertion sequences were characterised by PCR-sequencing, and their plasmid location was determined by alkaline lysis and by S1-nuclease pulsed-field gel electrophoresis (PFGE) Southern-blot hybridisation. Plasmids were further analysed by replicon typing, plasmid MLST and conjugation experiments. The 10 S. 4,[5],12,i:- selected isolates belonged to ST19. Each isolate carried a large plasmid in which MDR with pSLT-associated virulence genes were located. After analysis, eight different plasmids of three incompatibility groups (IncA/C, IncR and IncF) were detected. Two IncA/C plasmids represented novel variants within the plasmid family of the S. 4,[5],12:i:- Spanish clone, and carried an empty class 1 integron with a conventional qacEΔ1-sul1 3′ conserved segment or an In-sul3 type III with estX-psp-aadA2-cmlA1-aadA1-qacH variable region linked to tnpA440-sul3, part of Tn2, Tn21 and Tn1721 transposons, and ISCR2. Four newly described IncR plasmids contained the resistance genes within In-sul3 type I (dfrA12-orfF-aadA2-cmlA1-aadA1-qacH/tnpA440-sul3) and part of Tn10 [tet(B)]. Two pSLT-derivatives with FIIs-ST1+FIB-ST17 replicons carried cmlA1-[aadA1-aadA2]-sul3-dfrA12 and bla TEM-1 genes linked to an In-sul3 type I integron and to Tn2, respectively. In conclusion, three emerging European clones of S. 4,[5],12:i:- harboured MDR plasmids encoding additional virulence functions that could contribute significantly to their evolutionary success.

Supplementary feeding as a source of multiresistantSalmonellain endangered Egyptian vultures

“…The two Typhimurium serotypes recovered at the highest rates in the two vulture species were among the most frequently reported in fattening pigs in Spain (Arguello, Carvajal, Collazos, García‐Feliz, & Rubio, ; EFSA‐ECDC , ; García‐Feliz et al., , Vico et al., ) and other European countries (EFSA, , ; EFSA‐ECDC , ). In particular, the monophasic variant of S. typhimurium was initially characterized from pig samples in Spain, and today is considered an emerging pathogen associated with human and swine infections worldwide (Echeita, Aladueña, Cruchaga, & Usera, ; García et al., ; Hauser et al., ; Hopkins et al., ). This serotype was the most commonly shed by Egyptian vultures on the three sampling days, as well as by griffon vultures in a single sampling.…”

Characterization of the emerging clinically-relevant multidrug-resistant Salmonella enterica serotype 4,[5],12:i:- (monophasic variant of S. Typhimurium) clones

“…Moreover, all but three Southern European clone isolates presented the MDR pattern CSSuTTm associated with a genetic platform including an atypical sul3 class 1 integron, previously described in Portuguese isolates [19], and tet(B), both located on large non-transferable IncR plasmids. Identification of those features in few sporadic S. 4, [5],12:i:-Italian (human) and Spanish (swine) isolates [12] suggests that this clone might be spread in other countries. IncR plasmids have been described in different Enterobacteriaceae and associated with high-risk clones and/or clinically relevant genes (e.g.…”

“…S. Rissen in Portuguese piggeries) [8]. Simultaneous presence of resistance genes to different antibiotics and/or virulence [12] could contribute to successful persistence of IncR plasmids by diverse co-selection events and provide selective advantages for this emerging S. 4, [5],12:i:-clone. Its potential reservoir and transmission pathways (e.g., food and animal sources, travel outside European Union), however, remain unknown and require further studies.…”

“…Those S. 4, [5],12:i:-isolates present MDR profiles associated with particular widespread clonal lineages, designated European and Spanish clones [3,4]. However, few studies comprehensively analyse the genetic elements (genes, integrons, plasmids) spreading antibiotic resistance [10][11][12] and the fljAB genomic deletion patterns in S. 4, [5],12:i:- [13]. This serotype is currently targeted by EU actions to detect and control Salmonella serotypes of concern [14], requiring further surveillance and mitigation strategies, including its epidemiological success characterization.…”

Draft Genome Sequences of 19 Salmonella enterica Serovar Typhimurium [4,5:i:−] Strains Resistant to Nalidixic Acid from a Long-Term Outbreak in Italy

“…Even if few lineages have been detected, its antibiotic resistance pattern is very heterogeneous, spanning from multidrug-resistant to largely susceptible strains (1). According to Garcia et al (2), two major profiles circulate in Europe, the Spanish clone and the ASSuT clone. The ASSuT clone, which is common in Italy, harbors a genomic region that confers resistance to ampicillin, streptomycin, sulfonamides, and tetracycline (3).…”