Proteus mirabilis causes urinary tract infections (UTIs) in individuals requiring long-term indwelling catheterization. The pathogenesis of this uropathogen is mediated by a number of virulence factors and the formation of crystalline biofilms. Numerous studies have demonstrated that biofilms have a greater antibiotic resistance than the planktonic populations of the same organism. The CYC biofilm assay can be critical evaluation of the effectiveness of antibiotics against biofilms. In addition, micro-organisms have evolved complex systems for the acquisition of nutrients, including the chemotaxis and motility which has been shown to be important in biofilm of drug resistance. In our study, we have used six kinds of antibiotics to evaluate the relationship between drug resistance and biofilms. The biofilm formed by the P. mirabilis was proved to be significantly more resistant to antibiotics than a planktonic culture. Minimal penetrable concentration (MPC) assays found that every antibiotic can not inhibit the growth of P. mirabilis in 4096 μ g/mLs. We also observe the growth time course of P. mirabilis to determine the formation of the biofilm. In clinical diagnosis and treatment of P. mirabilis, it is no effective to use minimal inhibitory concentration (MIC) assays only. We suggest MPC assay is better than MIC assay.
