Bacteriology & Applied Microbiology

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 Istanbul University, Istanbul Faculty of Medicine’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 micro-broth dilution assay as described by the 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. Additionally, in the tests for dalbavancin, CAMHB

with 0.002% final concentration of polysorbate 80 was used. The inoculum of strain was adjusted to approximately 5×105 cfu/mL in the wells. The Minimum Ä°nhibitory Concentration (MIC) was defined as the lowest concentration of antibiotic giving complete inhibition of visible growth and interpreted in accordance with 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 the micro-broth checker board technique. The Fractional Ä°nhibitory Concentration (FIC) indexes were calculated using the following formula: FICI=FICA+FICB. The FICI was interpreted as synergism, FICI≤0.5; additive/indifference, FICI δ0.5-≤4; antagonism, FICIδ4.