The investigaton of the antibiotic resistance, inducible beta lactamase, metallo beta lactames ratios and in vitro efficacy of some antibiotic combinations in pseudomonas aeruginosa strains isolated from inpatients

Pseudomonas aeruginosa is one of the most common agents of nosocomical infections and it causes problems in treatment due to their resistance mechanisms. Chromosomal Amp-C beta lactamases are also known as inducible beta lactamases (IBL) and refers to the resistance to all beta-lactam antibiotics except 4th generation cephalosporins. Metallo-beta-lactamases (MBL) are enzymes which have an important role in carbapenem resistance. This study was conducted with the aim of the detection of antibiotic sensitivity, IBL and MBL rates and in vitro tested the combination effect of ceftazidime and imipenem with amikacin, levofloxacin and colistin in Pseudomonas isolates recovered from various clinical samples. This study was carried out with 60 P. aeruginosa isolates from different clinical samples. Disc diffusion method in the accordance with the recommendations of Clinical and Laboratory Standards Institute (CLSI) was used to determine the antibiotic sensitivity of the strains. IBL activity was investigated by disc induction test and MBL activity of 21 imipenem resistant strains was investigated with combine disc test. Antibiotic combination studies were carried out with E test. As a result of this study it is detected that colistin is the most effective drug (100%) to P. aeruginosa and amikacin is the second (93.3%). IBL positivity was detected in 42 of the isolates (70%) and MBL positivity was detected in 18 of the 21 imipenem resistant strains (85.7%). In the study it was determined that amikacin-ceftazidime combination has the highest synergy rate (15%). As a result of the data obtained from this study, it was concluded that the determination of Amp-C beta-lactamase and of strains synthesizing MBL play an important role in the selection of the antibiotics for treatment. It is concluded that amikacin-ceftazidime combination can be used in P. aeruginosa infections to reduce the possibility of resistance development and to enhance the effectiveness of the treatment. Key words: P. aeruginosa, Amp-C-beta-lactamase, metallo-beta-lactamase, synergy test