In vitro activities of erythromycin, tetracycline and levofloxacin alone and in dual combinations against ureaplasma spp.

Purpose: It was the aim of our study to evaluate the in vitro activities of tetracycline (TET), erythromycin (ERY) and levofloxacin (LVX) alone and in dual combinations against ureaplasmas.

Methods: The minimum inhibitory concentrations (MICs) of 51 ureaplasmal strains were determined by microdilution assay.

Results: TET was the most active when the antibiotics were used alone. The combinations resulted in significantly decreased MICs for every agent compared with the use of single antibiotics (p < 0.05, respectively), except for ERY in the ERY-LVX pair (p > 0.05), and decreased the MICs more significantly in the strains with an MIC ≥4 mg/l compared with MIC <4 mg/l, except for the TET-ERY pair. The ERY-LVX pair increased ERY MICs significantly in the MIC <4 mg/l group (p < 0.05). The combinations resulted in more beneficial MICs in strains where both agents had an MIC ≥4 mg/l compared with those where either had an MIC ≥4 mg/l, as well as in strains where either agent had an MIC <4 mg/l compared with those where both had an MIC <4 mg/l.

Conclusions: Drugs in dual combinations always give more beneficial MICs against ureaplasmas than one agent alone. Combinational benefits prefer strains with a higher initial MIC.