Individual or combined effects of meropenem, imipenem, sulbactam, colistin, and tigecycline on biofilm-embedded Acinetobacter baumannii and biofilm architecture

摘要

[[abstract]]Acinetobacter baumannii biofilms are difficult to eradicate. We investigated the effects of meropenem (2 mg/L), imipenem (2 mg/L), sulbactam (4 mg/L), colistin (2 mg/L), and tigecycline (2 mg/L), alone or in combination, on biofilm-embedded carbapenem-resistant and carbapenem-susceptible A. baumannii (CRAb and CSAb, respectively) as well as on the architecture of the biofilms. A. baumannii ATCC 15151(Ab15151), and its OXA-82 overproducing transformant, along with two clinical CSAb and two clinical CRAb isolates of differing clonalities were used. The minimal bactericidal concentrations for biofilm-embedded cell of the six tested isolates were more than 50-fold that for their planktonic cells. When used individually, meropenem exhibited higher killing effect than the other four antimicrobials on biofilm-embedded CSAb in the colony biofilm assay. For two clinical CRAb isolates, meropenem plus sulbactam or sulbactam plus tigecycline showed more than 100-fold the bactericidal effect exhibited by these agents used alone after 48 hours treatment. The effect of antimicrobials on the architecture of Ab15151 biofilm emitting green fluorescence was determined by confocal laser scanning microscopy using COMSTAT software. Significant decreases in the maximum biofilm thickness were observed after exposure to meropenem and imipenem. Meropenem plus sulbactam caused significantly changes in biomass, mean thickness and roughness coefficient of biofilm, but sulbactam plus tigecycline caused changes only in maximum and mean biofilm thickness than did any of these agents used alone. Meropenem was active against biofilm-embedded CSAb, whereas meropenem plus sulbactam exhibited synergism against biofilm-embedded CRAb and caused significantly more damage to biofilm architecture than any of the agents used alone.