Activity of ciprofloxacin and azithromycin on biofilms produced in vitro by Haemophilus influenzae.
BACKGROUND
It is recognized that Haemophilus influenzae isolated from patients with otitis media forms biofilms both in vitro and in vivo, suggesting that biofilm formation in vivo might play an important role in the pathogenesis and chronicity of otitis media, but the effect of antibiotics on biofilm has not been well studied. We investigated the impact of ciprofloxacin and azithromycin on bacterial biofilms formed by Haemophilus influenzae in vitro in this study.


METHODS
Eleven strains of Haemophilus influenzae were isolated from sputum specimens collected from patients with acute exacerbation of chronic obstructive pulmonary diseases. Formation of bacterial biofilm was examined by crystal violet assay and a scanning electron microscope. Alterations of biofilms were measured under varying concentrations of azithromycin and ciprofloxacin.


RESULTS
Striking 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 azithromycin and ciprofloxacin at concentrations higher than two-fold minimal inhibitory concentration. Disruption of mature biofilms could be achieved at relatively higher concentration, and ciprofloxacin displayed more powerful activity.


CONCLUSIONS
Haemophilus influenzae is capable of forming biofilm in vitro. Sufficient dosage might control early formation of biofilms. Ciprofloxacin exerts better effects on breakdown of biofilm than azithromycin at conventional concentration in clinics.
Wang
Dong
D
Department of Respiratory Diseases, Airforce General Hospital, Beijing 100036, China.
Wang
Ying
Y
Liu
You-ning
YN
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017963:Azithromycin / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D002939:Ciprofloxacin / Q000494:pharmacology*; D006193:Haemophilus influenzae / Q000187:drug effects* / Q000302:isolation & purification; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D008855:Microscopy, Electron, Scanning
D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D017963:Azithromycin