The sensitivity of pure cultures of Staphylococcus epidermidis and Klebsiella pneumoniae towards arsenic was studied with particular reference to biochemical changes induced by the heavy metal in these organisms. Arsenic strongly inhibited the growth and viability of both the organisms. Addition of arsenic prolonged the lag phase and this was found to be the concentration dependent phenomenon. The Minimum inhibitory concentration (MIC) determined was 200 ppm and 20 ppm in S. epidermidis and K. pneumoniae respectively that inhibited growth, synthesis of protein, DNA, RNA completely and activity of dehydrogenases of the TCA cycle. In S. epidermidis and K. pneumoniae, cell wall, membrane and cytoplasm 24.5%, 32.5%, 43% and 20%, 35%, 45% arsenic respectively got incorporated. As the activity of dehydrogenases was inhibited by arsenic, cells were incapable of oxidizing substrate. It resulted in limited supply of energy rich compounds such as ATP that affected the synthesis of macromolecules. Ultimately multiplication and growth of the organism got ceased.
The inhibitory action of Sulphaphenazole on pure culture of Klebsiella aerogenes was studied with emphasis on the mode of action of the drug. Sensitivity was studied by broth dilution method and by Hi-Comb Method. The Minimum Inhibitory Concentration (MIC) of Sulphaphenazole determined by broth dilution method and Hi-Comb Method against Klebsiella aerogenes was 30 µg/ml. Sulphaphenazole induced changes in bacteria which interfered with cell wall synthesis revealing morphological alterations that was shown by Scanning Electron Microscopy (SEM). The present studies were undertaken to investigate the presence and characteristic alterations in surface morphology of cells resulting from the action of Sulphaphenazole known to interfere with intracellular protein synthesis. The morphological abnormalities observed may be surface reflections of specific abnormalities of intracellular protein synthesis or may represent a final common pathway of drug-induced injury at many sites within or on bacterial cells. As the activity of dehydrogenases was inhibited by Sulphaphenazole, cells were incapable of oxidizing substrate. It resulted in limited supply of energy rich compounds such as ATP that affected the synthesis of macromolecules. Ultimately multiplication and growth of the organism got ceased.
Oxazolidinone, a new class of antimicrobial agents is active against various Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus epidermidis (MRSE), penicillin-resistant Streptococcus pneumoniae (PRSP) and vancomycin-resistant Enterococci (VRE). Sensitivity of Oxazolidinone Linezolid was studied against pathogenic microorganism Listeria ivanovii and Minimum Inhibitory Concentration (MIC) determined by broth dilution method and Hi-Comb method was 10 µg/ml. Morphological alterations on Listeria ivanovii cell surface were seen by Scanning Electron Microscopy (SEM) after treatment with Linezolid. Inhibition on the activity of dehydrogenases of organism by Linezolid was also studied in the present study.
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