Abstract
Background: cell-cell variation in expression of their gene in isogenic population is frequently observed in microbes, which is recognized as one of the reasons for phenotype heterogeneity. The aim of this study is to investigate the hetorogeneous resistance level in genetically identical cells which was origenated from cell-cell variation in expression of blaCTX-M-14.
Methods: The transcriptional region of CTX-M-14 with or without the entire coding sequence of CTX-M-14 which were amplified from clinic strain isolated from patients with lower respiratory tract infection were subcloned to upstream of green fluorescent protein (GFP) gene to regulate expression of GFP followed by standard method. Applying flow cytometry measurement (FCM) to analyze the expression pattern of blaCTX-M-14 in single cell using GFP as the report genes. The expression pattern of cells after cultured with different ceftriaxone concentrations ranging from 0μg/ml to 2048μg/ml was also analyzed. Using the E-test method to measure the MIC to ceftriaxone.
Results: Variation in GFP expression from cell to cell was seen (The fluorescence intensity of different cells vary largely, ranging from 102 to 105). The resistance level to ceftroaxone was positively correlated with the expression level, with increment of the extracellular ceftroaxone concentrations, the proportion of cells with more GFP abundance increasing. We also found the epigenetic resistance phenotype mediated by the heterogeneous expression was non-strictly inheritable and have a transient property.
Conclusions: Heterogeneous expression of antibiotic genes other than nucleotide alterations in genetically identical cells may be one of the reasons for diverse antibiotic resistance level.
- © 2012 ERS
