Effects of vancomycin and ceftazidime on biofilm formation in Elizabethkingia

Elizabethkingia infections are associated with high mortality rates which is due in part to the antibiotic resistance expressed by all Gram-negative Elizabethkingia species. Biofilm formation by Elizabethkingia provides the bacteria with further defense against the action of antibiotics. Vancomycin is an unusual drug used to treat Elizabethkingia infections, but its use is controversial, since it is normally only used to treat Gram-positive infections. Our study tests the effect of vancomycin and ceftazidime on biofilm formation for all known species of Elizabethkingia. Biofilm formation was measured at 24, 48, and 72-hour timepoints using a crystal violet biofilm assay. Biofilm formation occurred in all positive control wells for all three timepoints for all species. The biofilms of Elizabethkingia meningoseptica in the presence of subinhibitory vancomycin concentrations, and Elizabethkingia ursingii in the presence of inhibitory ceftazidime concentrations, were reduced compared to the controls. This suggests that both drugs can inhibit biofilm formation in a species-specific manner.Howard Hughes Medical Institute Science Education ProgramBiochemistry and Molecular Biolog