title: Horizontal Acquisition of a Multidrug-Resistance Module (R-type ASSuT) Is Responsible for the Monophasic Phenotype in a Widespread Clone of Salmonella Serovar 4,[5],12:i:.
abstract: Salmonella enterica serovar 4,[5],12:i:- is a monophasic variant of S. Typhimurium incapable of expressing the second-phase flagellar antigen (fljAB operon), and it is recognized to be one of the most prevalent serovars causing human infections. A clonal lineage characterized by phage type DT193, PulseNet PFGE profile STYMXB.0131 and multidrug resistance to ampicillin, streptomycin, sulphonamides and tetracycline (R-type ASSuT) is commonly circulating in Europe. In this study we determined the deletions affecting the fljAB operon and the resistance region responsible for the R-type ASSuT in a strain of Salmonella enterica serovar 4,5,12:i:- DT193/STYMXB.0131, through an approach based on PCRs and Southern blot hybridization of genomic DNA. Using a set of nine specific PCRs, the prevalence of the resistance region was assessed in a collection of 144 S. enterica serovar 4,[5],12:i:-/ASSuT/STYMXB.0131 strains isolated from Germany, Switzerland and Italy. A 28 kb-region is embedded between the loci STM2759 and iroB, replacing the DNA located in between, including the fljAB operon. It encompasses the genes bla TEM-1, strA-strB, sul2 and tet(B) responsible for the R-type ASSuT together with genes involved in plasmid replication and orfs of unknown function characteristically located on IncH1 plasmids. Its location and internal structure is fairly conserved in S. enterica serovar 4,[5],12:i:-/ASSuT/STYMXB.0131 strains regardless of the isolation source or country. Hence, in the S. enterica serovar 4,[5],12:i:-/ASSuT/STYMXB.0131 clonal lineage widespread in Germany, Switzerland and Italy, a resistance region derived from IncH1 plasmids has replaced the chromosomal region encoding the second flagellar phase and is an example of the stabilization of new plasmid-derived genetic material due to integration into the bacterial chromosome.
authors.affiliation: Department of Functional Biology, Area of Microbiology, University of Oviedo Oviedo, Spain.
authors.forename: Patricia
authors.initials: P
authors.lastname: García
authors.affiliation: Department of Biological Safety, Federal Institute for Risk Assessment Berlin, Germany.
authors.forename: Burkhard
authors.initials: B
authors.lastname: Malorny
authors.affiliation: Department of Functional Biology, Area of Microbiology, University of Oviedo Oviedo, Spain.
authors.forename: M Rosario
authors.initials: MR
authors.lastname: Rodicio
authors.affiliation: Vetsuisse Faculty, National Centre for Enteropathogenic Bacteria and Listeria, Institute for Food Safety and Hygiene, University of Zurich Zürich, Switzerland.
authors.forename: Roger
authors.initials: R
authors.lastname: Stephan
authors.affiliation: Vetsuisse Faculty, National Centre for Enteropathogenic Bacteria and Listeria, Institute for Food Safety and Hygiene, University of Zurich Zürich, Switzerland.
authors.forename: Herbert
authors.initials: H
authors.lastname: Hächler
authors.affiliation: Department of Biological Safety, Federal Institute for Risk Assessment Berlin, Germany.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Guerra
authors.affiliation: Department of Infectious, Parasitic and Immuno-Mediated Diseases, Istituto Superiore di SanitàRome, Italy; European Public Health Microbiology Training Programme, European Centre for Disease Prevention and ControlStockholm, Sweden.
authors.forename: Claudia
authors.initials: C
authors.lastname: Lucarelli
keywords: European clone; antimicrobial resistance; molecular epidemiology; monophasic Salmonella; plasmid origin