title: Characterization and PCR-based replicon typing of resistance plasmids in Acinetobacter baumannii.
abstract: Acinetobacter baumannii is an opportunistic pathogen, especially in intensive care units, and multidrug-resistant isolates have increasingly been reported during the last decade. Despite recent progress in knowledge of antibiotic resistance mechanisms in A. baumannii, little is known about the genetic factors driving isolates toward multidrug resistance. In the present study, the A. baumannii plasmids were investigated through the analysis and classification of plasmid replication systems and the identification of A. baumannii-specific mobilization and addiction systems. Twenty-two replicons were identified by in silico analysis, and five other replicons were identified and cloned from previously uncharacterized A. baumannii resistance plasmids carrying the OXA-58 carbapenem-hydrolyzing oxacillinase. Replicons were classified into homology groups on the basis of their nucleotide homology. A novel PCR-based replicon typing scheme (the A. baumannii PCR-based replicon typing [AB-PBRT] method) was devised to categorize the A. baumannii plasmids into homogeneous groups on the basis of the nucleotide homology of their respective replicase genes. The AB-PBRT technique was applied to a collection of multidrug-resistant A. baumannii clinical isolates carrying the bla(OXA-58) or bla(OXA-23) carbapenemase gene. A putative complete conjugative apparatus was identified on one plasmid whose self-conjugative ability was demonstrated in vitro. We showed that this conjugative plasmid type was widely diffused in our collection, likely representing the most important vehicle promoting the horizontal transmission of A. baumannii resistance plasmids.
authors.affiliation: Department of Infectious, Parasitic and Immuno-Mediated Diseases, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Alessia
authors.initials: A
authors.lastname: Bertini
authors.forename: Laurent
authors.initials: L
authors.lastname: Poirel
authors.forename: Pauline D
authors.initials: PD
authors.lastname: Mugnier
authors.forename: Laura
authors.initials: L
authors.lastname: Villa
authors.forename: Patrice
authors.initials: P
authors.lastname: Nordmann
authors.forename: Alessandra
authors.initials: A
authors.lastname: Carattoli
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015780:Carbapenems / Q000378:metabolism*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D010957:Plasmids / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods*; D012093:Replicon / Q000235:genetics / Q000502:physiology*; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D001618:beta-Lactamases; C108449:oxacillinase