This study aimed to determine the antimicrobial activities of sumac (Rhus coriaria L.) water extract (8.0 %, wt/vol), thyme (Thymus vulgaris L.) water (commercial hydrosol) and ½ thyme water (1:1, commercial hydrosol / distilled water, vol/vol) in vitro in comparison with lactic acid (1.0 %, vol/vol), against the foodborne pathogenic bacteria Escherichia coli O157:H7, Listeria monocytogenes 4b, Staphylococcus aureus and Yersinia enterocolitica O3. The test microorganisms were inoculated to the treatment solution tubes. All the inoculated tubes were kept at 20 ± 2°C for 60 minutes. The numbers of the four test bacteria decreased to an uncountable level (<1 cfu/ml) in 1 min in the thyme water. The counts of all the pathogens, with the exception of L. monocytogenes 4b, were lower than the countable level after 1 min in the lactic acid. Both lactic acid and ½ thyme water reduced the test bacteria counts to the uncountable level in 10 min. In the sumac extract, the reduction time periods were 10 min for E. coli O157:H7, 30 min for Staph. aureus and 60 min for L. monocytogenes 4b and Y. enterocolitica O3. However, when enriched after treatment, E. coli O157:H7 and Staph. aureus were grown in lactic acid, S. aureus was grown in ½ thyme water and E. coli O157:H7, Staph. aureus, and L. monocytogenes 4b were grown in sumac extract. Thyme water had the strongest antibacterial activity against both the Gram negative and the Gram positive bacteria tested, followed by lactic acid, ½ thyme water and sumac extract.
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