Abstract—Extract of Quercus infectoria galls was evaluated for its antimicrobial activity against a wide variety of pathogenic bacteria such as Escheria coli ATCC 25922, Staphylococus aurus ATCC 25923 and Bacillus subtilis ATCC 6633. The antimicrobial activities of Q. infectoria extracts prepared from different solvents of varying polarity were examined and their efficacies were then compared by the disc diffusion method. Crude extracts of the solvents exhibited the anitmicrobial effect to a different extent as seen in the varying diameters of the zones of inhibition. The antimicrobial activity of the methanol extract was found to be superior to all other extracts. Ethanol and aqueous extracts showed a strong though lower antimicrobial effect against all the tested organisms while chloroform and hexane extracts of Q. infactoria were found to be least active. Compared to the commercial antibiotics, all the extracts exhibited a good antimicrobial activity. All the gram-positive bacteria and gram-negative bacteria tested were susceptible to all aqueous and solvent extracts of Q. infectoria galls. The methanol extracts at different concentrations were then incubated with the three bacteria strains, and the minimum inhibitory concentrations (MICs) of each bacterial strain were determined. The MIC values of methanol extracts for E. coli ATCC 25922, S. aureus ATCC 25923 and B. subtilis ATCC 6633 are 2.500, 1.25 and 0.625 mg ml^{–1 respectively. Microscopic observation under scanning electron microscopy (SEM) revealed a sharp decline in bacterial population density for all three bacterial strains. The bacterial morphology of all the strains became more irregular in shape differing from their respective originally homogeneous forms.}

Index Terms—antimicrobial activity, Quercus infectoria galls, pathogenic bacteria, the extracts

C. Satirapipathkul is with the Chemical Engineering Department, Faculty of Engineering, Chulalongkorn University, Bangkok 10330 Thailand (corresponding author to provide phone: 662-218-6876; fax: 662-218-6877; e-mail: Chutimon.s@chula.ac.th).
T. Leela is with is with the Chemical Engineering Department, Faculty of Engineering, Chulalongkorn University, Bangkok 10330 Thailand (e-mail: Tossaporn.Lee@gmail.com).

Cite: C. Satirapathkul and T. Leela, "Growth Inhibition of Pathogenic Bacteria by Extract of Quercus Infectoria Galls," International Journal of Bioscience, Biochemistry and Bioinformatics vol. 1, no. 1, pp. 26-31, 2011.