Induction of L1 and L2 ?-lactamase by common antimicrobial agents and their modulation / 解放军医学杂志

ABSTRACT

Objective To compare the induction of L1 and L2 ?-lactamase stenotraphomonas maltoptilia by common antimicrobial agents, including imipenem, meropenem, cefotaxime and ceftazidime, and to survey the modulation of L1 and L2 ?-lactamase expression. Methods One clinical strain of S. maltophilia was isolated and identified with VITEK automatic microbic system. L1 and L2 ?-lactamase genes were amplified, cloned and sequenced by PCR method. Minimal inhibitory concentrations (MICs) of four antimicrobial agents against the clinical isolates were determined by agar dilution method. Two hours after being induced by different concentrations of four antimicrobial agents, total RNA was extracted, and RT-PCR method was used to determine the induction of L1 and L2 ?-lactamase by different concentrations (0.25, 1 or 4?MIC) of common antimicrobial agents. Electrophoresis strips of L1 and L2 ?-lactamase were quantified by Image J software. Results The clinical isolates of S. maltophilia with simultaneous production of L1 and L2 ?-lactamse were identified. When different concentrations of four antimicrobial agents were used as inductors, electrophoresis strips of L1 and L2 amplicons were not found in strains of blank control and those in which imipenem, meropenem or cefotaxime (4?MIC) was added to the culture mediam, while light electrophoresis strips were exhibited by the isolates with ceftazidime (0.25, 1 or 4?MIC) or cefotaxime (0.25?MIC) added to the medium. The strongest electrophoresis strips and the strongest expression were found in the isolates with cefotaxime (1?MIC) added to the medium. Conclusions Clinical common antimicrobial agents, e.g. ceftazidime and cefotaxime, are able to induce production of L1 and L2 ?-lactamase, and cefotaxime (1?MIC) is the strongest inductor. Cefotaxime can exert an effect on transcription of L1, L2 genes simultaneously, implying that a significant overlap might exist between the mechanism of modulation of two ?-lactamases.