Authors : M.S. Ambatkar
Page Nos : 71-83
Description :
Medicinal plant oils of Cinnamon cassia, Thymus vulgaris and Zingiber officinale traditionally used in India for treating conditions likely to be associated with microorganisms were screened for antibacterial activity against some fish pathogens viz Aeromonas hydrophila, Pseudomonas aeruginosa, Staphylococus aureus, and Bacillus species using broth microdilution method. Among the essential oils tested thyme and cinnamon showed the most promising antibacterial properties as compared to ginger oil inhibiting all the strains tested with minimum inhibitory concentrations (MICs) ranging from 0.0625 % to 0.25% for thyme oil whereas in case of cinnamon oil MICs were in the range of 0.09375% to 0.1875 %. Among these bacteria Aeromonas hydrophila being the common fish pathogen was selected for TEM study. Electron microscopy results demonstrates that thyme and cinnamon oils changes the ultrastructure of A. hydrophila. The cytological changes induced in the morphology of Aeromonas hydrophila shows the break in a multilayered cell wall when treated with cinnamon oil in an 18 hrs extract-treated culture. This may be due to injury of the cell wall and alterations in the cytoplasmic membrane permeability, resulting in the loss of cytosol and finally in cell death. In case of thyme oil spheroplast was obtained indicating the total disintegration of the cell wall. The test results shows that the essential oils are effective against fish pathogens and would justify its further investigation for alternative to antibiotics.
