Determination of Piperacillin/Tazobactam and Ticarcillin/Clavulanate
Susceptibilities in Pseudomonas aeruginosa Isolates in Hospitalised Patients by E-test Gradient Method and Comparison of Results with Disk Diffusion Tests

Pseudomonas aeruginosa is an important opportunistic pathogen in human infections. P. aeruginosa is naturally resistant to many antibiotics and mutations can result in resistance development during treatment as well. Piperacillin/tazobactam and Ticarcillin/clavulanate are β-lactam/β-lactamase inhibitor combination with a wide spectrum of antibacterial activity. In this study was aimed to determine the susceptibility of P. aeruginosa isolates to Piperacillin/tazobactam and Ticarcillin/clavulanate antibiotics by Epsilometer test in the patients in intensive care units of Giresun State Hospital and to compare PIP/TZP results by Disk Diffusion method. Sensitivities of PIP/TZP were determined via Kirby Bauer disk diffusion method and MIC values of the isolates against PIP/TZP and TIC/CLA were determined by E-test. By using E-test method and in accordance with the CLSI standards, 43 (64%) isolates were found to be susceptible and 24 (36%) isolates were found to be resistant to TIC/CLA. For the PIP/TZP, 49 of the 67 isolates were susceptible, three were intermediate and 15 were resistant by using disk diffusion method. On the other hand, according to the E-test results, 63 isolates were susceptible and four isolates were resistant. When compared to eleven isolate E-test methods, the disk diffusion method was incorrectly determined to be resistant. The results of our study suggest that it would be more appropriate to use E-test method to confirm the results of the isolates which were found to be resistant against PIP/TZP by disk diffusion method.