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Open AccessArticle

Discovery of Antibacterial Dietary Spices That Target Antibiotic-Resistant Bacteria

1
Department of Food Science & Technology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China
2
State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University, Hangzhou 310003, China
3
Department of Microbiology, Shanghai Municipal Center for Disease Control and Prevention, Shanghai 200336, China
4
Guangdong Provincial Key Laboratory of Food, Nutrition and Health, Guangdong Engineering Technology Research Center of Nutrition Translation, Department of Nutrition, School of Public Health, Sun Yat-Sen University, Guangzhou 510080, China
*
Authors to whom correspondence should be addressed.
Microorganisms 2019, 7(6), 157; https://doi.org/10.3390/microorganisms7060157
Received: 11 April 2019 / Revised: 20 May 2019 / Accepted: 28 May 2019 / Published: 29 May 2019
(This article belongs to the Special Issue Natural Alternatives against Bacterial Foodborne Pathogens)
Although spice extracts are well known to exhibit antibacterial properties, there is lack of a comprehensive evaluation of the antibacterial effect of spices against antibiotic-resistant bacteria. In the present study, ethanolic extracts from a total of 67 spices were comprehensively investigated for their in vitro antibacterial activities by agar well diffusion against two common food-borne bacteria, Staphylococcus aureus and Salmonella enteritidis, with multi-drug resistance. Results showed that S. aureus was generally more sensitive to spice extracts than S. enteritidis. Of the 67 spice extracts, 38 exhibited antibacterial activity against drug-resistant S. aureus, while only four samples were effective on drug-resistant S. enteritidis. In addition, 11 spice extracts with inhibition zones greater than 15 mm were further verified for their broad-spectrum antibacterial properties using another 10 drug-resistant S. aureus strains. It was found that five spice extracts, including galangal, fructus galangae, cinnamon, yellow mustard seed, and rosemary, exhibited the highest antibacterial capacity. Further cytotoxicity of these 11 spices was determined and LC50 values were found to be more than 100 μg/mL except for galangal, rosemary, and sage, whose LC50 values were 9.32 ± 0.83, 19.77 ± 2.17, and 50.54 ± 2.57, respectively. Moreover, the antioxidant activities (ferric-reducing antioxidant power (FRAP) and trolox equivalent antioxidant capacity (TEAC) values) and total phenolic content (TPC) of spice extracts were determined to establish possible correlations with the antibacterial activity. Although the antibacterial effect was positively correlated with the antioxidant activities and TPC, the correlation was weak (r < 0.5), indicating that the antibacterial activity could also be attributed to other components besides antioxidant polyphenols in the tested spice extracts. In conclusion, dietary spices are good natural sources of antibacterial agents to fight against antibiotic-resistant bacteria, with potential applications as natural food preservatives and natural alternatives to antibiotics in animal feeding. View Full-Text
Keywords: spice extracts; drug resistant bacteria; antibacterial activity; antioxidant activity; total phenolic content; correlation spice extracts; drug resistant bacteria; antibacterial activity; antioxidant activity; total phenolic content; correlation
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Zhang, D.; Gan, R.-Y.; Farha, A.K.; Kim, G.; Yang, Q.-Q.; Shi, X.-M.; Shi, C.-L.; Luo, Q.-X.; Xu, X.-B.; Li, H.-B.; Corke, H. Discovery of Antibacterial Dietary Spices That Target Antibiotic-Resistant Bacteria. Microorganisms 2019, 7, 157.

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