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ABSTRACTThe aim of the study was to identify the plasmid-encoded factors contributing to the emergence and spread of epidemic IncI1-Iγ plasmids obtained from Escherichia coliand Salmonella entericaisolates from animal and human reservoirs. For this, 251 IncI1-Iγ plasmids carrying various extended-spectrum β-lactamase (ESBL) or AmpC β-lactamase genes were compared using plasmid multilocus sequence typing (pMLST). Thirty-two of these plasmids belonging to different pMLST types were sequenced using Roche 454 and Illumina platforms. Epidemic IncI1-Iγ plasmids could be assigned to various dominant clades, whereas rarely detected plasmids clustered together as a distinct clade. Similar phylogenetic trees were obtained using only the plasmid backbone sequences, showing that the differences observed between the plasmids belonging to distinct clades resulted mainly from differences between their backbone sequences. Plasmids belonging to the various clades differed particularly in the presence/absence of genes encoding partitioning and addiction systems, which contribute to stable inheritance during cell division and plasmid maintenance. Despite this, plasmids belonging to the various phylogenetic clades also showed marked resistance gene associations, indicating the circulation of successful plasmid-gene combinations. The variation in traYand excAgenes found in IncI1-Iγ plasmids is conserved within pMLST sequence types and plays a role in incompatibility, although functional study is needed to elucidate the role of these genes in plasmid epidemiology.

ABSTRACTThe sul3gene recently described in Escherichia coliwas found in 22 of 512 (4.3%) German Salmonellaisolates from different regions and sources and of different serotypes, antimicrobial resistance phenotypes, and genomic groups. This is the first report on the prevalence of sul3among Salmonellastrains, and the findings support the strong potential of this determinant to spread within bacterial populations.

ABSTRACTAn unusual self-transferable virulence-resistance plasmid (pUO-StVR2) was found in nine multidrug-resistant (ACSSuT phenotype) Salmonella entericaserotype Typhimurium clinical isolates that were assigned to four different phage types and a single and distinctive XbaI pulsed-field gel electrophoresis profile. pUO-StVR2 is an IncFII plasmid of about 140 kb in length carrying the spvA, spvB, and spvC(Salmonellaplasmid virulence) and rck(resistance to complement killing) genes. It also carries the oxa1/aadA1a(ampicillin resistance and streptomycin-spectinomycin resistance) gene cassette configuration located within a class 1 integron with qacEΔ1/sul1(ammonium antiseptics resistance and sulfadiazine resistance); the transposon genes merA, tnpA, and tnpR(mercury resistance, transposase, and resolvase of Tn21, respectively); and the catA1(chloramphenicol resistance) and tet(B) (tetracycline resistance) genes. The insertion of resistance genes into a Salmonellavirulence plasmid constitutes a new and interesting example of plasmid evolution and presents a serious public health problem.

ABSTRACTA multidrug-resistant Salmonella entericaserotype [4,5,12:i:−] clone carried a class 1 integron harboringdfrA12and aadA2gene cassettes andblaTEM-1, aac(3)-IV,cmlA1, and tetAgenes located in large plasmids of about 140 kb (carrying spv) or 120 kb (lackingspv). Several segregants, lacking multidrug resistance, contained a plasmid smaller than the parental one and no longer hybridized with probes for the lost resistances. The genes mediating resistance to ampicillin, chloramphenicol, and tetracycline in the [4,5,12:i:−] clone are different from those found in the pentadrug-resistant serotype Typhimurium DT104 clone.

In 2012, a carbapenemase-producing Salmonella entericaserovar Corvallis isolate carrying a blaNDM-1multiresistance IncA/C2plasmid, apart from IncHI2 and ColE-like plasmids, was detected in a wild bird in Germany. In a recent broiler chicken infection study, we observed transfer of this blaNDM-1-carrying IncA/C2plasmid to other Enterobacteriaceae.

ABSTRACTThe emergence and spread of carbapenemase-producing Enterobacteriaceae(CPE) in wildlife and livestock animals pose an important safety concern for public health. With our in vivobroiler chicken infection study, we investigated the transfer and experimental microevolution of the blaNDM-1-carrying IncA/C2plasmid (pRH-1238) introduced by avian native Salmonella entericasubsp. entericaserovar Corvallis without inducing antibiotic selection pressure. We evaluated the dependency of the time point of inoculation on donor (S. Corvallis [12-SA01738]) and plasmid-free Salmonellarecipient [d-tartrate-fermenting (d-Ta+) S. Paratyphi B (13-SA01617), referred to here as S. Paratyphi B (d-Ta+)] excretion by quantifying their excretion dynamics. Using plasmid profiling by S1 nuclease-restricted pulsed-field gel electrophoresis, we gained insight into the variability of the native plasmid content among S. Corvallis reisolates as well as plasmid acquisition in S. Paratyphi B (d-Ta+) and the enterobacterial gut microflora. Whole-genome sequencing enabled us to gain an in-depth insight into the microevolution of plasmid pRH-1238 in S. Corvallis and enterobacterial recipient isolates. Our study revealed that the fecal excretion of avian native carbapenemase-producing S. Corvallis is significantly higher than that of S. Paratyphi (d-Ta+) and is not hampered by S. Paratyphi (d-Ta+). Acquisition of pRH-1238 in other Enterobacteriaceaeand several events of plasmid pRH-1238 transfer to different Escherichia colisequence types and Klebsiella pneumoniaedemonstrated an interspecies broad host range. Regardless of the microevolutionary structural deletions in pRH-1238, the single carbapenem resistance marker blaNDM-1was maintained on pRH-1238 throughout the trial. Furthermore, we showed the importance of the gut E. colipopulation as a vector of pRH-1238. In a potential scenario of the introduction of NDM-1-producing S. Corvallis into a broiler flock, the pRH-1238 plasmid could persist and spread to a broad host range even in the absence of antibiotic pressure.