Results obtained from the disc diffusion method indicated that S.typhi and S. aureus were the most sensitive microorganisms showing the largest inhibition zones in April (spring). This result may be explained by the structural differences of the bacterial cell wall of Gram positive and Gram-negative bacteria. Gram-negative bacteria, apart from the cell membrane, possess an additional outer layer membrane, which consists of phospholipids, proteins and
lipopolysaccharides, and this membrane is impermeable to most molecules