Study of Alterations of Bacterial Membrane Proteins involved in ?-Lactam Sensitivity

Abstract

The selective nature of organisms to prevailing stress– ?-lactam antibiotics is obviously concerned with the architecture of outer membrane. Bacillus subtilis Gram-positive bacteria advocates variation in achieving cellular morphogenetic dimensions. In the present study more protonated species of ?-lactam i.e. Ceftriaxone proved to be more effective in contrast to cefazolin as far as sensitivity of Bacillus subtilis is concerned. The MIC₅₀ for ceftriaxone (CT) was observed to be 1.5 ppm in contrast to first generation ?-lactam antibiotic i.e. cefazolin with MIC₅₀ 18 ppm concentration. The relative sensitivity of bacterial cells to both the cephalosporins was more positively inclined to third generation species. The role of modified cephalosporin was observed under various physiological situations under laboratory conditions such as pH, Temp, chelating agent and Mg²⁺ ion concentrations. The sensitivity of Bacillus subtilis to ?-lactam was more potentiated at acidic pH than at alkaline pH. At alkaline pH only 16% inhibition of growth of Bacillus subtilis in Dye’s minimal media at 37±1⁰C was seen in contrast to 60% inhibition of growth in the presence of CZ. The growth was enhanced / potentiated in the presence of chelating agent – EDTA at 0.25 mM concentration in combination with MIC₅₀ of CT and CZ 84% inhibition of growth was recorded in the presence of CT (MIC₅₀) in contrast to 82% inhibition in the presence of CZ (MIC₅₀). The growth inhibition with 0.25 mM EDTA alone was also seen to be 82%.

Keywords: ?-lactam, EDTA, MIC_50, Ceftriaxone sodium, Cefazolin sodium