SEQUENCE ANALYSIS OF A NOVEL PLASMID CARRYING blaOXA-58 ISOLATED FROM A LOCAL Acinetobacter baumannii CLINICAL STRAIN

CAMERANESI MM; MORAN BARRIO J; VIALE AM; LIMANSKY AS

Congreso; X Congreso de Microbiología General - SAMIGE 2014; 2014

Sociedad Argentina de Microbiología

The emergence of carbapenem resistance in Acinetobacter baumannii has been reported worldwide and correlated with the acquisition of carbapenem-hydrolyzing oxacillinases. Dissemination of blaOXA-58 genes by plasmids may explain the wide propagation of these genes among nosocomial A. baumannii strains. We reported previously the presence of blaOXA-58-expressing plasmids in local clinical strains of this opportunistic pathogen. Still, little is known about the replicon types of blaOXA-58-carrying plasmids in A. baumannii strains from Argentina. We present here the sequence analysis and characterization of a plasmid isolated from a multiresistant (MDR) A. baumannii clinical strain (Ab242) from a Rosario hospital and carrying the ISAba825-blaOXA-58 arrangement that we described previously. The complete Ab242 sequence was done by pyrosequencing (INDEAR-Rosario). Exhaustive analysis of its whole genome allowed the identification of four plasmids, one of them harboring the ISAba825-blaOXA-58 arrangement and designed as pAb242. pAb242 contigs were manually gathered in a 22.8 kbp circular construct, and this assembly validated by PCR. The plasmid was further classified on the basis of its replication systems. Phylogenetic analysis employing the plasmid-borne replicase genes including representative Rep groups could classify pAb242 as a multireplicon plasmid showing homology with both p11921 Rep Aci8 and pACICU1 Rep AciX, both isolated from clinical A. baumannii strains in Italy. Remarkably, pAb242 represents a chimera of these two replicons. Further sequence analysis shows that pAb242 is composed of different modules responsible of replication, maintenance, adaptability, and mobility. The replication and maintenance modules are closely related to those of pACICU1, which also carries blaOXA-58 but lacks ISAba825. The adaptability module comprises a backbone region containing a ISAba3 located immediately upstream blaOXA-58 and a araC1 and lysE downstream of this gene. Comparative sequence analysis showed that this adaptability module has unique features: i) the presence of ISAba825 inserted within ISAba3 generating a hybrid promoter overexpressing blaOXA-58; ii) an ISAba125 interrupting the lysE gene. In turn, the pAb242 mobility module showed no detectable homology to other plasmids harboring blaOXA-58 genes. The pAb242 adaptability module showed similar backbone regions than other plasmids isolated from other A. baumannii strains as well as A. pittii and A. nosocomialis, thus suggesting the dissemination of this region among the A. calcoaceticus-baumannii (ACB) complex. Still, pAb242 represents a novel plasmid exhibiting distinctive characteristics, including its adaptability module, an unusual multireplicon, and a mobility module. Genetic platforms such as pAb242 may be responsible for the wide dissemination of blaOXA-58 genes among strains of the ACB complex.