Phenotypic and genotypic determination of beta lactamases causing carbapenem resistance in hospital acquired pseudomonas aeruginosa and acinetobacter baumannii

Carbapenems are important antibiotics for the treatment of infections due to multiple resistant Gram-negative bacteria and the dissemination of carbapenemases became more important last years. In the present study presence of carbapenem resistance genes among P. aeruginosa and A. baumannii isolated from inpatients of Fırat University hospital was studied. A total of 50 P. aeruginosa, and 50 A. baumannii isolated from various clinical samples from March 2011 to March 2012 included to the study. Identification of bacteria at specie level was done using classical method and confirmed with BD Phoneix bacteria identification system. Imipenem sysceptibility was tested by disk diffusion test and presence of carbapenemases was tested by combined disk, double disk synergy test and modified Hodge test. All imipenem resistance isolates were tested for the presence of blaOXA-51, blaOXA23, blaOXA24, blaOXA58, blaKPC, blaIMP and blaVIM by PCR. The results showed that blaOXA-51 were positive in 98% of A. baumannii, blaOXA-58 14%, blaOXA-23 14% and blaKPC 8%. All of the A. baumannii were negative for the genes encoding for OXA-24, VIM and IMP enzymes. All P. aeruginosa isolates were negative for the genes studied. The sequence analysis of the amplicons were done and compared with the sequences in genebank. Phylogenic analysis of the sequences and the differences were calculated by 0.75. The homology of the amplicons and genebank sequences were determined using BLAST program. Homology of 5 OXA-23 amplicons were 97-99%, 8 OXA-51 were 95-98%, 7 OXA-58 were 99-100%. This is the first carbapenemase gene detection study in our region and presence of carbapenemase genes found to be common. Studies on dissemination resistance genes and resistance mechanisms are important to have epidemiologic data and to guide treatment of patients infected with resistant bacteria. Keywords: A. baumannii, P. aeruginosa, OXA-51, OXA-58, OXA-23, OXA-24, VIM, IMP.