Effect of fluoroquinolones on the biofilm produced by Haemophilus influenzae

Objective To observe the formation of bacterial biofilm by H.influenzae and determine the in vitro inhibitory effect of antibiotics on the biofilm.MethodsTwelve strains of H.influenzae were isolated from sputum in patients with acute exacerbation of chronic obstructive pulmonary diseases.Formation of bacterial biofilm was examined by crystal violet assay and scanning electron microscope.Alteration of biofilm was measured under varying concentrations of fluoroquinolones.ResultsSignificant differences were observed among strains with regard to the ability to form biofilm.Typical membrane-like structure formed by bacterial cells and extracellular matrix was detected.Initial biofilm synthesis was inhibited by fluoroquinolones at concentrations higher than two times of minimal inhibitory concentration.Disruption of mature biofilm could be achieved at relatively higher concentration.Ciprofloxacin displayed more potent inhibitory effect on biofilm formation.ConclusionsH.influenzae is able to form stable biofilm in vitro.Sufficient dose of fluoroquinolones may control early formation of bacterial biofilm.Ciprofloxacin exerts better effect than other fluoroquinolones in terms of biofilm disruption.