Study of the inhibitory effect of gallium nitrate combined with antimicrobial agents on biofilm formation of Burkholderia cepacia

Abstract

Objective To study the inhibitory effects of gallium nitrate alone and combined with ceftazidime or meropenem on biofilm formation of Burkholderia cepacia. Methods Thirty-four strains of Burkholderia cepacia were isolated from January to December 2017. The minimal inhibitory concentration (MIC) of Burkholderia cepacia to gallium nitrate, ceftazidime, compound sulfamethoxazole, levofloxacin, piperacillin/tazobactam, tegacycline, meropenem, chloramphenicol, minocycline and cefoperazone/sulbactam were detected by broth dilution method. Crystal violet staining was used to quantitatively and qualitatively analyze the ability of biofilm formation of, Burkholderia cepacia and to compare the sensitivity of those strains with different ability of biofilm formation to gallium nitrate and the nine antimicrobial agents. The effects of gallium nitrate and ceftazidime and meropenem on biofilm formation were evaluated separately or jointly at 1.0×MIC. Results All the 34 strains could form stable biofilms after 48 hours culture. Among them, 10 were weak postive (29.4%) and 24 were strong positive (70.6%). There was a significant difference in the resistant rate of cefoperazone and sulbactam between the weak and strong positive strains with biofilm. There were significant differences in optical density (OD) values of biofilm formed by the strains before and after treated with gallium nitrate alone or combined with ceftazidime, but there was no significant difference in OD values between treated with gallium nitrate alone and meropenem alone. Conclusion Burkholderia cepacia have strong biofilm formation ability. Gallium nitrate alone or in combined with ceftazidime have obvious inhibitory effect on the biofilm formation. Key words: Burkholderia cepacia; Biofilm; Gallium nitrate; Inhibition