Comparative study of effect garlic and anion extract on the growth of some gram negative bacteria

During this study, a comparison of antimicrobial effects of garlic and onion extract on some gram negative bacteria were assayed in vitro. Primarily, each of these microorganisms including Escherichia coli, Salmonella typhi, Klebsiella pneumonia and Pseudomonas aeruginosa were isolated and diagnosed from patients suffering from different infection cases. This step was followed by preparation of aqueous extracts from onion and garlic. Furthermore, the activity of the two extracts on those microorganisms was tested by using different garlic extract concentrations, and application cup–plate diffusion and total count methods. It was noticed that increasing garlic aqueous extract concentration, would lead to a notable increase in inhibition zone diameter, compared with control. However the inhibition zone diameter was about 28 mm for Salmonella typhi, at concentration of 500mg/0.5ml of garlic extract was used; while the diameter was about 26–30–16 mm for the same concentration for each of K. pneumonia, Escherichia coli and P. aeruginosa respectively. Moreover a comparison was done between these results and that obtained when using onion aqueous extract. It was observed that the activity of garlic was more than onion which gave inhibitory zone diameter of about 25–16–17 mm to each of S. typhi, K. pneumonia and E. coli respectively , at concentration of 500mg/0.5ml; but the P. aeruginosa was unaffected. Other observation was show that there is adecrease in number of isolated microbial cells by increasing both extract concentrations, hence when treating the bacteria with garlic extract of 500mg/0.5ml concentration, the number of cells forming colonies were 6210 2 , 7110 2 , 1210 3 and 1310 3 cell/ml for each of S. typhi, K. pneumonia, E. coli and P. aeruginosa respectively. In the other hand, the number of colony forming unit for the same bacteria were 16 10 4 , 3110 3 , 110 5 and 810 6 cell/ml when using onion extract of 500mg/0.5ml concentration