Multilocus sequence typing of IncI1 plasmids carrying extended-spectrum beta-lactamases in Escherichia coli and Salmonella of human and animal origin.
OBJECTIVE
Plasmids belonging to incompatibility group I1 (IncI1) are widespread in Enterobacteriaceae and are characterized by the presence of a cluster of genes encoding the type IV pili, contributing to the virulence of Shiga-toxigenic Escherichia coli. Recently, IncI1 plasmids were identified in E. coli and Salmonella strains of animal origin as responsible for the dissemination of beta-lactamase genes. Plasmid multilocus sequence typing (pMLST) was developed to discern naturally occurring IncI1 plasmids in homogeneous groups according to their allele assortment.


METHODS
pMLST was developed by selecting multiple target genes on the available complete IncI1 plasmid DNA sequences. Sixteen plasmids, all assigned to the IncI1 group by the PCR-based replicon typing method, were included in this study. They were analysed for beta-lactamase genes and typed by restriction fragment length polymorphism (RFLP) and pMLST.


RESULTS
Sixteen plasmids identified in E. coli and Salmonella isolated from animals and humans in different countries carried bla(CMY-2), bla(CTX-M-15), bla(CTX-M-1), bla(CTX-M-14), bla(TEM-52), bla(SHV-12) or bla(TEM-1) beta-lactamase genes. These plasmids were classified by RFLP in nine different groups corresponding to the nine sequence types determined by pMLST.


CONCLUSIONS
The pMLST method was suitable for rapid and easy subtyping of IncI1 plasmids. This study demonstrates that the pMLST method can contribute to the epidemiological description of circulation of specific resistance plasmids among beta-lactamase producers isolated from animals and humans.
García-Fernández
Aurora
A
Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Rome, Italy.
Chiaretto
Giuseppina
G
Bertini
Alessia
A
Villa
Laura
L
Fortini
Daniela
D
Ricci
Antonia
A
Carattoli
Alessandra
A
D000483:Alleles; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004285:Dogs; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D005838:Genotype; D006801:Humans; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D012150:Polymorphism, Restriction Fragment Length; D011200:Poultry; D011815:R Factors / Q000145:classification* / Q000302:isolation & purification; D012093:Replicon; D012475:Salmonella / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D018440:beta-Lactam Resistance / Q000235:genetics*; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics*; D047090:beta-Lactams / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D047090:beta-Lactams; D001618:beta-Lactamases