Gulseren Aktas
Istanbul University, Turkey
Title: Activity of Vancomycin Combined with Linezolid and with Dalbavancin against Clinical VRE Strains
Biography
Biography: Gulseren Aktas
Abstract
A total of 30 randomly-selected clinical VRE strains were included in the study. Each strain was isolated from different patients who were admitted to the different clinics of the university’s hospital. Bacterial identifications of the strains were undertaken using conventional routine methods. The antibiotics used in the study were vancomycin, linezolid and dalbavancin. Resistance to agents tested was investigated by using microbroth dilution method as described by Clinical and Laboratory Standards Institute (CLSI). They were prepared in accordance with CLSI proposals. Cation adjusted Mueller-Hinton broth (CAMHB) was used for all experiments. Additionaly, in the tests for dalbavancin, CAMHB with 0.002% final concentration of polysorbate 80 was used. The inoculum of strain was adjusted to approximately 5x105 cfu/mL in the wells. The minimum inhibitory concentration (MIC) was defined as the lowest concentration of antibiotic giving complete inhibition of visible growth, and interpreted in accordance with the CLSI guidelines. Quality control of the test procedures was monitored via testing of the reference strains S. aureus ATCC 29213 and E. faecalis ATCC 29212.
In vitro activities of antibiotics in combination were assessed using a microbroth checkerboard. The fractional inhibitory concentration (FIC) indexes were calculated using the following formula: FICI=FICA + FICB. The FICI was interpreted as follows: synergism, FICI ≤0.5; additive / indifference, FICI ˃0.5-≤4; antagonism, FICI ˃ 4.