Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/27/2007
Publication Date: 11/1/2007
Citation: Hoque, M.M., Inatsu, M.B., Juneja, V.K., Kawamoto, S. 2007. Antibacterial activity of guava (psidium guajava l.) and neem (azadirachta indica a. juss.)extracts against food borne pathogens and spoilage bacteria. Foodborne Pathogens & Disease. 4:481-488. Interpretive Summary: Consumers have expressed concerns on the use of chemical preservatives in processed foods. Accordingly, there is a need to explore the potential use of natural compounds in foods as preservatives. We investigated the antibacterial properties of extracts of guava (Psidium guajava) and neem (Azadirachta indica) against a number of common food borne pathogens and spoilage bacteria. Guava and neem extracts exhibited higher antibacterial activity against Gram-positive bacteria than Gram-negative bacteria, except for V. parahaemolyticus, Pseudomonas aeroginosa and Aeromonas hydrophila. None of the extracts showed activity against Escherichia coli O157:H7 and Salmonella Enteritidis. Use of guava and neem can guard against some of the foodborne pathogens and spoilage organisms in processed foods.
Technical Abstract: The objective of this study was to investigate the antibacterial properties of guava (Psidium guajava) and neem (Azadirachta indica) extracts against a number of common food borne pathogens and spoilage bacteria. Screening for antibacterial activity was determined by disc diffusion assay against 21 strains of food borne pathogens: Listeria monocytogenes (5 strains), Staphylococcus aureus (4 strains), Escherichia coli O157:H7 (6 strains), Salmonella Enteritidis (4 strains), Vibrio parahaemolyticus and Bacillus cereus, and 5 food spoilage bacteria: Pseudomonas aeroginosa, P. putida, Alcaligenes faecalis, and Aeromonas hydrophila (2 strains). The Minimum inhibitory concentration (MIC) of the extracts was determined using the micro dilution method. The results indicated that ethanol extracts of guava inhibited all L. monocytogenes and S. aureus strains, and V. parahaemolyticus IFO 12711, B. cereus IFO 3457, P. aeroginosa PA 01, A. faecalis IFO 12669, and two A. hydrophila strains, NFRI 8282 and NFRI 8283. On the other hand, aqueous extracts of guava inhibited all S. aureus strains, V. parahaemolyticus IFO 12711, A. faecalis IFO 12669 and the two A. hydrophila strains. The MIC of ethanol extracts of guava showed the highest inhibition for L. monocytogenes JCM 7676 (0.1 mg/ml), S. aureus JCM 2151 (0.1 mg/ml), S. aureus JCM 2179 (0.1 mg/ml) and V. parahaemolyticus IFO 12711 (0.1 mg/ml) and the lowest inhibition for A. faecalis IFO 12669 and the two A. hydrophila strains (4.0 mg/ml). The MIC of chloroform extracts of neem showed similar inhibition (4.0 mg/ml) for L. monocytogenes ATCC 43256 and L. monocytogenes ATCC 49594. However, ethanol extracts of neem showed higher inhibition (4.5 mg/ml) for S. aureus JCM 2151 and S. aureus IFO 13276, and the lower inhibition (6.5 mg/ml) for other microorganisms. No significant effects of temperature and pH were found on guava and neem extracts against cocktails of L. monocytogenes, and S. aureus. Guava and neem extracts showed higher antimicrobial activity against Gram-positive bacteria compared to Gram-negative bacteria except for V. parahaemolyticus, Pseudomonas aeroginosa, and Aeromonas hydrophila. None of the extracts showed antimicrobial activity against E. coli O157:H7 and S. Enteritidis. The results of the present study suggest that guava and neem extracts possess compounds containing antibacterial properties that can potentially be useful to control food-borne pathogens and spoilage organisms.