Inhibitory activity of Thai condiments on pandemic strain of Vibrio parahaemolyticus.
Antibacterial activity of 13 condiments used in Thai cooking was investigated with a pandemic strain of Vibrio parahaemolyticus. Using a disk diffusion technique, freshly squeezed extracts from galangal, garlic and lemon, at a concentration of 10 microl/disk produced a clear zone of 13.6+/-0.5, 11.6+/-0.5 and 8.6+/-1.2mm, respectively. The inhibitory activity of these 3 condiments on pandemic strains was not significantly different from that on non-pandemic strains of V. parahaemolyticus. Because of its popularity in seafood cooking, galangal was subjected to further investigation. Only a chloroform extract of galangal inhibited growth of V. parahaemolyticus producing a clear zone of 9.5+/-0.5, 12.0+/-0 and 13.5+/-0.5mm diameter at concentrations of 25, 50 and 100 microg/disk, respectively. One active component is identified as 1'-acetoxychavicol acetate. The activity of galangal was not reduced at pH 3 or in the presence of 0.15% bile salt but was reduced by freeze and spray drying. Heating a fresh preparation of galangal to 100 degrees C but not 50 degrees C for 30 min also reduced growth inhibition. Therefore, using fresh galangal in cooking was recommended. The MIC and MBC of a freshly squeezed preparation of galangal were 1:16 and 1:16, respectively. This is the first report of an inhibitory activity of a Thai medicinal plant, galangal that is used in Thai cooking, on the pandemic strain of V. parahaemolyticus.
Vuddhakul
Varaporn
V
Department of Microbiology, Faculty of Science, Prince of Songkla University, Hat-yai, Thailand. varaporn.v@psu.ac.th
Bhoopong
Phuangthip
P
Hayeebilan
Fadeeya
F
Subhadhirasakul
Sanan
S
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015169:Colony Count, Microbial; D003212:Condiments; D003257:Consumer Product Safety; D003296:Cooking / Q000379:methods; D004305:Dose-Response Relationship, Drug; D005511:Food Handling / Q000379:methods*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D013696:Temperature; D013785:Thailand; D014736:Vibrio parahaemolyticus / Q000187:drug effects*
D000900:Anti-Bacterial Agents