<i>In vitro</i> activities of antibiotic combinations against mature biofilms of ventilator-associated pneumonia isolates.

<b>Background:</b> The authors aimed to determine the efficacy of frequently used antibiotics, alone or in combination, against biofilms of ventilator-associated pneumonia isolates. <b>Materials &amp; methods:</b> The authors determined the MICs, minimum biofilm inhibitory concentrations and minimum biofilm eradication concentrations of meropenem, ciprofloxacin and colistin as well as their combinations against planktonic forms and biofilms of <i>Pseudomonas aeruginosa</i>, <i>Klebsiella pneumoniae</i> and <i>Acinetobacter baumannii</i> clinical isolates. <b>Results:</b> Generally, the minimum biofilm inhibitory concentrations and minimum biofilm eradication concentrations of the antibiotics were 1000-fold higher than their MICs, and synergy was provided by different concentrations of meropenem-colistin and meropenem-ciprofloxacin combinations with checkerboard and time-kill curve methods. <b>Conclusion:</b> The combination of meropenem and ciprofloxacin seems to be a good candidate for the treatment of biofilm-associated infections; none of the concentrations obtained as a result of the synergy test were clinically significant.