Snapshot on carbapenemase-producing Pseudomonas aeruginosa and Acinetobacter baumannii in Bucharest hospitals reveals unusual clones and novel genetic surroundings for blaOXA-23

Objectives The present study was designed to provide a snapshot on carbapenemase-producing Pseudomonas aeruginosa (n = 11) and Acinetobacter baumannii (n = 7) isolates in hospitalized patients (November 2011, January–March 2012) from two main hospitals in Bucharest, south Romania. Methods Clonality among isolates was established by PFGE, MLST and Fourier transform infrared spectroscopy. Carbapenemases were screened by the Blue-Carba test, PCR and sequencing. Transferability of blaOXA-23 was tested by conjugation and plasmid typing (number, size and identity) was assessed by S1-PFGE, replicon typing, hybridization and PCR mapping. Results All P. aeruginosa isolates carried chromosomally located blaVIM-2, associated with a common class 1 integron (aacA7-blaVIM-2) or an atypical configuration (aacA7-blaVIM-2-dfrB5-tniC). These isolates belonged to unusual lineages; mostly ST233 disseminated in one hospital unit, with ST364 and ST1074 also being detected. A. baumannii isolates carried blaOXA-23 in Tn2008, which was found truncating a TnaphA6 transposon located in a common 60 kb GR6 (aci6) pABKp1-like conjugative plasmid in highly related CC92 clones (ST437, ST764 and ST765), where CC stands for clonal complex. Conclusions Our results show the spread of VIM-2-producing P. aeruginosa and OXA-23-producing A. baumannii clinical isolates in two hospitals from Bucharest and highlight a peculiar population structure in this Eastern European country. Also, we demonstrate the dissemination of a common and conjugative aci6 pABKp1-like plasmid scaffold in different A. baumannii clones and we report the first known identification of Tnaph6-carrying pACICU2-like plasmids in Europe.