- Email: [email protected]
Antibacterial activity of vegetables and juices
REVIEW ARTICLE
Antibacterial Activity of Vegetables and Juices Yee-Lean Lee, PhD, Thomas Cesario, MD, Yang Wang, MB, Edward Shanbrom, MD, and Lauri Thrupp, MD From the University of California Irvine Medical Center, Orange, California, USA OBJECTIVE: We evaluated the antibacterial activities of various fruit and vegetable extracts on common potential pathogens including antibiotic-resistant strains. METHODS: Standardized bacterial inocula were added to serial dilutions of sterile vegetable and fruit extracts in broth, with final bacterial concentrations of 104 –5 cells/mL. After overnight incubation at 35°C, antibacterial activity was measured by minimum inhibitory and minimum bactericidal dilutions (for raw juices) or concentrations (for tea). RESULTS: Among the vegetable and fruit extracts tested, all green vegetables showed no antibacterial activity on Staphylococcus epidermidis and Klebsiella pneumoniae. All purple and red vegetable and fruit juices had antibacterial activities in dilutions ranging from 1:2 to 1:16. Garlic juice had significant activity, with bactericidal action in dilutions ranging up to 1:128 of the original juice. Tea also had significant activity, with bactericidal action in concentrations ranging up to 1.6 mg/mL, against a spectrum of pathogens including resistant strains such as methicillin- and ciprofloxacin-resistant staphylococci, vancomycin-resistant enterococci, and ciprofloxacin-resistant Pseudomonas aeruginosa. CONCLUSION: Tea and garlic have the potential for exploration of broader applications as antibacterial agents. Nutrition 2003;19:994 –996. ©Elsevier Inc. 2003 KEY WORDS: Antibacterial, vegetables, fruits, tea
INTRODUCTION In recent years, a number of studies have supported an association between high consumption of vegetables and fruits and low incidence of certain chronic diseases.1,2 There also have been reports of plants with an inhibitory effect on microorganisms.3,4 However, there is little information concerning the comparative antibacterial activity of common vegetables and fruits on common potential pathogens and resistant strains. We report on pilot studies screening the relative antibacterial activities of various fruit and vegetable extracts, garlic, and tea.
MATERIALS AND METHODS Various original raw juices from organically grown, common vegetables and fruits were prepared undiluted by direct squeezing in a commercial juicer. Tea broth was prepared by brewing 20 g of Japanese green tea (Camellia sinensis) leaves in 200 mL of boiling distilled water (10%). Garlic juice was extracted from raw and from cooked garlic cloves. Commercial garlic tablets (Nature Made, 5 g) were dissolved in 25 mL of distilled water. All the juices and tea broth were adjusted to a pH of 7 and filtered by a Nalgene filter with a pore size of 0.45 m. Equal amounts of each of these juices were mixed with double-strength trypticase soy (TS) broth. Then, a series of two-fold dilutions were made with single-strength TS broth. One hundred eighty microliters of each dilution was added to 96-well microtiter plates. Bacterial strains tested included American Type Culture Collection (Rockville, MD, USA) strains and discarded clinical isolates from the University of California Irvine Medical Center. From fresh overnight cultures on TS agar plates, several colonies were emulsified in saline to a turbidity of McFarland 0.5. A 1:100
Correspondence to: Lauri D. Thrupp, MD, Department of Medicine, Building 53, Room 220, UCI Medical Center, 101 The City Drive, Orange, CA 92868, USA. E-mail: [email protected] Nutrition 19:994 –996, 2003 ©Elsevier Inc., 2003. Printed in the United States. All rights reserved.
dilution of the McFarland standard in TS broth served as the inoculum. Twenty microliters of each inoculum was added to each juice dilution well and to the broth control wells. The final bacterial cell concentration approximated 104 –5/mL. Microtiter plates were incubated at 35°C overnight for 18 to 20 h. For the extracts of vegetables, fruits, and garlic, antibacterial activity was assessed by minimum inhibitory dilutions and minimum bactericidal dilutions. Minimum inhibitory dilutions were considered to be the last dilution wells remaining clear, analogous to standard minimum inhibitory concentration.5 Minimum bactericidal dilutions were considered to be the last dilution wells that demonstrated a 99.9% kill of the initial inoculum5 upon quantitative subculture at 24 h. For tea, the inhibitory and bactericidal activities were expressed by the concentration calculated from the original weight of tea leaves. For other juices, it was expressed by dilution of the original whole raw juice. Vegetables and fruits and tea broth were tested first on Staphylococcus epidermidis and Klebsiella pneumoniae. Those fruits and vegetable extracts that showed the highest antibacterial activity were tested further on other strains.
RESULTS Table I presents the antibacterial activities of different fruit and vegetable extracts that were screened against S. epidermidis and K. pneumoniae. The results showed that, among the vegetable and fruit juices tested, all the green vegetables, such as asparagus, bell pepper, broccoli, cucumber, and spinach, at 1:2 dilutions of the original raw juice showed no antibacterial activity against S. epidermidis and K. pneumoniae. All purple and red vegetable and fruit juices, such as beet, cherry, and cranberry, showed mild inhibitory antibacterial activity (1:2) against both strains. Red onion, red cabbage, and raspberry had mild activity (1:2) on S. epidermidis. Aronianberry, blackberry, and grape juice showed moderate activity (1:8 to 1:16) on K. pneumoniae. Pomegranates had moderate activity on both strains. Garlic and tea had the highest antibacterial activities (1:32 to 1:28) and were active against a spectrum of pathogens, including clinical antibiotic0899-9007/03/$30.00 doi:10.1016/j.nut.2003.08.003
Nutrition Volume 19, Numbers 11/12, 2003
Antibacterial Activity of Vegetables and Juices
TABLE I.
TABLE II.
ANTIBACTERIAL ACTIVITIES OF VEGETABLES AND FRUITS
ANTIBACTERIAL ACTIVITIES OF GARLIC JUICE
Vegetable and fruits juices
Staphylococcus epidermidis* (MID)
Klebsiella pneumoniae† (MID)
Aronianberry Asparagus Bell pepper Beet Blackberry Blueberry Broccoli Carrot Cucumber Cherry Cranberry Garlic Ginger Grape Red onion Red cabbage Rhubarb Rutabaga Raspberry Pomegranate Spinach Strawberry Green tea
ND UDT UDT 1:2 ND ND UDT UDT UDT 1:2 1:2 1:128 1:2 ND 1:2 1:2 1:4 UDT 1:2 1:16 UDT 1:2 3.12 mg/mL
1:8 UDT UDT 1:2 1:16 UDT UDT UDT UDT 1:2 1:2 1:128 1:2 1:4 1:4 UDT 1:4 UDT UDT 1:16 UDT 1:2 3.12 mg/mL
Dilutions of juice Bacterial strains
* Clinical isolate. † American Type Culture Collection 13883. MID, minimum inhibitory dilution; ND, not done; UDT, undetectable at 1:2 dilution
resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant S. epidermidis, vancomycinresistant enterococci, and ciprofloxacin-resistant Pseudomonas aeruginosa. Tables II and III present the results of expanded testing of garlic and tea against a variety of bacterial species. Cooked garlic and commercial garlic pills showed no activity in our study (data not shown). The antibacterial activity of fresh garlic juice remained stable upon weekly testing up to 3 wk and tea upon monthly testing up to 4 mo when stored at 4°C.
DISCUSSION With the emergence of antibiotic-resistant bacteria, it is reasonable to explore new sources of natural compounds with antibacterial activity. Edible plants have been proven to be harmless and are economical. Our study showed that the purple and red vegetables and fruits that we tested have mild antibacterial activity. Purple and red colors in plants have been identified to be anthocyanins, which have been reported to show antibacterial activity.6,7 Our results further supported the association of antibacterial activity and anthocyanins. We also demonstrated that tea and garlic have by far the highest antibacterial activity among the common vegetables and fruits that we tested; further, they are active against a spectrum of resistant strains. Garlic has long been known to have antibacterial activity from in vitro and in vivo studies.8 –10 It is effective against Helicobacter pylori,11 a bacteria associated with peptic ulcer disease and gastric cancer. It has synergistic effect with omeprazole against H.
995
Staphylococcus epidermidis CR S. epidermidis Staphylococcus aureus MRSA
Enterococcus faecalis VRE Escherichia coli 0157 H7 Pseudomonas aeruginosa CR P. aeruginosa P. aeruginosa S. marcescens Klebsiella pneumoniae K. pneumoniae, ESBL
Origin
MID
MBD
Clinical isolate Clinical isolate ATCC 29213 ATCC 33591 Clinical isolate 1 Clinical isolates 2–5 Clinical isolate 6 ATCC 29212 Clinical isolate 1 Clinical isolates 2–6 Clinical isolate ATCC 27853 Clinical isolate Clinical isolate Clinical isolate ATCC 13883 Clinical isolate
128 128 256 128 128 128 128 64 64 64 128 32 128 32 128 128 64
128 128 64 128 128 64 32 64 64 32 64 32 32 32 64 64 64
ATCC, American Type Culture Collection; CR, ciprofloxacin resistant; ESBL, extended-spectrum betalactamase producer; MBC, minimum bactericidal dilution; MIC, minimum inhibitory dilution; MRSA, methicillin-resistant Staphylococcus aureus; VRE, vancomycin-resistant Enterococcus faecium
pylori12 and with streptomycin or chloramphenicol against Mycobacterium tuberculosis.13 It has been shown to prevent the formation of Staphylococcus enterotoxin,14 which causes food poisoning. Garlic also has antifungal,15 antiviral, and antiparasitic properties.16 The mechanism responsible for all these activities is believed to be allicin and its chemical reaction with thiol groups of various enzymes.17 It is of interest that cooked garlic and commercially available garlic tablets lost the antibacterial effect found in raw garlic. Green tea has been studied extensively by Japanese investigators. In addition to its anticancer and anti-hypercholesterolic activities, it has antibacterial activity that includes inhibition of gram-positive cocci, gram-negative bacilli, and resistant strains vancomycin-resistant enterococci and MRSA.18 Further, it has been reported that green tea may tend to reverse resistance in MRSA.19 Green tea catechins are responsible for antibacterial properties; more specifically, it is epigallocatechin gallate, one of the components of catechin, which restores the effectiveness of -lactams against MRSA and suppresses the emergence of resistance.20 In vivo studies of green tea have shown inhibition against microflora in the human intestine, bacteria responsible for dental caries,21 and food-borne bacteria.22 A custom of drinking green tea might help to reduce the severity of Escherichia coli 057 infection even with antibiotic treatment.23 Further, the combination of green tea extract and levofloxacin has improved the therapeutic effect of antibiotic treatment of E. coli 0157 infection in a mouse model.23 Therapeutic application has shown that green tea solution is successful as nebulization therapy for subglottic tracheal stenosis due to MRSA.24 We confirmed that tea and garlic have antibacterial activity against a wide range of pathogens. We also showed that, in addition to vancomycin-resistant enterococci and MRSA, garlic and green tea inhibit ciprofloxacin-resistant MRSA, ciprofloxacin-
996
Lee et al.
Nutrition Volume 19, Numbers 11/12, 2003 TABLE III.
ANTIBACTERIAL ACTIVITIES OF GREEN TEA
Bacterial strains Staphylococcus epidermidis CR S. epidermidis Staphylococcus aureus MRSA Enterococcus faecalis VRE Escherichia coli E. coli 0157H7 Pseudomonas aeruginosa CR P. aeruginosa Serratia marcescens Salmonella enteritidis Klebsiella pneumoniae K. pneumoniae, ESBL
MIC (mg/mL)
MBC (mg/mL)
3.1
6.2
Clinical isolate ATCC 29213 ATCC 33591 Clinical isolates 1–6 ATCC 29212 Clinical isolate 1 Clinical isolates 2–5 ATCC 29522 Clinical isolate Clinical isolates 1–5
3.1 3.1 1.6 6.25 50 12.5 25 12.5 12.5 6.2
2.5 3.1 1.6 6.25 100 25 50 25 25 6.2
Clinical isolate Clinical isolate ATCC 14028 ATCC 13883 Clinical isolate
6.2 12.5 6.2 1.6 25
12.5 12.5 12.5 1.6 2.5
Origin Clinical isolate
ATCC, American Type Culture Collection; CR, ciprofloxacin resistant; ESBL, extended-spectrum betalactamase producer; MBC, minimum bactericidal dilution; MIC, minimum inhibitory dilution; MRSA, methicillin-resistant Staphylococcus aureus; VRE, vancomycin-resistant Enterococcus faecium
resistant MRSA, methicillin-resistant S. epidermidis, and ciprofloxacin-resistant P. aeruginosa. All of these resistant bacteria are increasing in long-term care facilities and acute care hospitals.25–28 It may be pertinent to explore the possibility of using green tea solution to decolonize nasal colonization with MRSA and methicillin-resistant S. epidermidis in nurses’ hands and intestinal carriage of vancomycin-resistant enterococci in long-term care facility patients. Another potential use of green tea might be for topical treatment of pressure ulcers, which are often superinfected with MRSA in nursing home patients. Green tea and garlic seem to be safe agents that have the potential for broader applications to take advantage of their antibacterial activities.
SUMMARY Among all plant juices tested, green vegetables showed little antibacterial activity, whereas red vegetables and fruit juices had mild activity. Garlic and tea had the highest antibacterial activity against a spectrum of pathogens including methicillin- and ciprofloxacin-resistant S. aureus, vancomycin-resistant enterococci, and ciprofloxacin-resistant P. aeruginosa.
REFERENCES 1. van’t Veer P, Jansen MC, Klerk M, Kok FJ. Fruits and vegetables in the prevention of cancer and cardiovascular disease. Public Health Nutr 2000;3(1): 103
2. Liu S, Manson JE, Lee IM, et al. Fruit and vegetable intake and risk of cardio vascular disease: the women’s health study. Am J Clin Nutr 2000;72:922 3. Cowan MM. Plant products as antimicrobial agents. Clin Microbiol Rev 1999; 12:564 4. Nascimento GF, Locatelli J, Freitas PC, Silva GL. Antibacterial activity of plant extracts and phytochemicals on antibiotic-resistant bacteria. Braz J Microbiol 2000;31:247 5. Murray PR, Baron EJ, Pfaller MA, Tenover FC, Yolken RH. Manual clinical microbiology, 6th ed. Washington, DC: ASM Press, 1995:1327 6. Rmarowicz R, Pegg RB, Bautista PA. Antibacterial activity of green tea polyphenols against E. coli K 12. Nahrung 2000;44:S60 7. Harborne JB, Williams CA. Advances in flavonoid research since 1992. Phytochemistry 2000;6:481 8. Ankri S, Mirelman D. Antimicrobial properties of allicin from garlic. Microbes Infect 1999;2:125 9. Uchida Y, Sato N. The characteristics of the antibacterial activity of garlic. Jpn J Antibiotics 1975;28:638 10. Chowdhury AK, Ahsan M, Islan SN, Ahmed ZU. Efficacy of aqueous extract of garlic and allicin in experimental shigellosis in rabbits. Indian J Med Res 1991;93:33 11. Sivam GP. Protection against Helicobacter pylori and other bacterial infections by garlic. J Nutr 2001;131(suppl 3):1106S 12. Jonkers D, van den Broek E, Dooren IV, et al. Antibacterial effect of garlic and omeprazole on Helicobacter pylori. J Antimicrob Chemother 1999;43:837 13. Gupta KC, Viswawnathan R. Combined action of streptomycin and chloramphenicol with plant antibiotics against tubercle bacilli. I. Streptomycin and chloramphenicol with cepharanthine. II. Streptomycin and allicin. Antibiot Chemother 1955;5:24 14. Gonzalez-Fandos E, Garcia-Lopez ML, Sierra MNL, Otero A. Staphylococcal growth and enterotoxins (A–D) and thermonuclease synthesis in the presence of dehydrated garlic. J Appl Bacteriol 1994;77:549 15. Yamada Y, Azuma K. Evaluation of the in vitro antifungal activity of allicin. Antimicrob Agents Chemother 1997;11:743 16. Tsai Y, Cole LL, Davis LE, Lockwood SJ, Simmons V, Wild GC. Antiviral properties of garlic: in vitro effects on influenza B, herpes simplex and coxsackie viruses. Planta Med 1985;5:460 17. Rabinkov A, Miron T, Konstantinovski L, Wilcheck M, Mirelman D, Weiner L. The mode of action of allicin: trapping of radicals and interaction with thiol containing proteins. Biochem Biophys Acta 1998;1379:233 18. Hamilton-Miller JMT. Antimicrobial properties of tea (Camellia sinensis). Antimicrob Agents Chemother 1995;39:2375 19. Yam TS, Hamiton-Miller JM, Shah S. The effect of a component of tea (Camellia sinensis) on methicillin resistance, PBP2⬘ synthesis, and beta-lactamase production in Staphylococcus aureus. J Antimicrob Chemother 1998;42:211 20. Shiota S, Shimizu M, Mizushima T, et al. Marked reduction in the minimum inhibitory concentration (MIC) of beta-lactams in methicillin-resistant Staphylococcus aureus produced by epicatechin gallate, an ingredient of green tea (Camellia sinensis). Biol Pharm Bull 1999;50:299 21. Hamilton-Miller JM. Anti-cariogenic properties of tea (Camellia sinensis). J Med Microbiol 2001;50:299 22. Ryu E. Prophylactic effect of tea on pathogenic microorganism infection to humans and animals. I J Zoonases 1980;7:164 23. Isogai E, Isogai H, Hirose K, Hayashi S, Oguma K. In vivo synergy between green tea extract and levofloxacin against enterohemorrhagic E. coli 0157 infection. Curr Microbiol 2001;42:248 24. Yamashita S, Yokoyama K, Matsumiya N, Yamaguchi H. Successful green tea nebulization therapy for subglottic tracheal stenosis due to MRSA infection. J Infect 2001;42:222 25. Lee YL, Gupta G, Cesario T, et al. Colonization by Staphylococcus aureus– resistant to methicillin and ciprofloxacin during 20 months surveillance in a private skilled nursing facility. Infect Control Hosp Epidemiol 1996;17:649 26. Lee YL, Cesario T, McCauley V, Pax A, Flionis L, Thrupp L. Low-level colonization and infection with ciprofloxacin resistant gram-negative bacilli in a skilled nursing facility. Am J Infect Control 1999;26:552 27. Parry MDF, Panzer KB, Yukna ME. Quinolone-resistance. Am J Med 1989; 87(suppl 5A):125 28. Lee YL, Cesario T, Lee R, et al. Colonization by Staphylococcus species resistant to mecillicin or quinolone on hands of medical personnel in a skilled-nursing facility. Am J Infect Control 1994;22:346
Antibacterial Activity of Vegetables and Juices Yee-Lean Lee, PhD, Thomas Cesario, MD, Yang Wang, MB, Edward Shanbrom, MD, and Lauri Thrupp, MD From the University of California Irvine Medical Center, Orange, California, USA OBJECTIVE: We evaluated the antibacterial activities of various fruit and vegetable extracts on common potential pathogens including antibiotic-resistant strains. METHODS: Standardized bacterial inocula were added to serial dilutions of sterile vegetable and fruit extracts in broth, with final bacterial concentrations of 104 –5 cells/mL. After overnight incubation at 35°C, antibacterial activity was measured by minimum inhibitory and minimum bactericidal dilutions (for raw juices) or concentrations (for tea). RESULTS: Among the vegetable and fruit extracts tested, all green vegetables showed no antibacterial activity on Staphylococcus epidermidis and Klebsiella pneumoniae. All purple and red vegetable and fruit juices had antibacterial activities in dilutions ranging from 1:2 to 1:16. Garlic juice had significant activity, with bactericidal action in dilutions ranging up to 1:128 of the original juice. Tea also had significant activity, with bactericidal action in concentrations ranging up to 1.6 mg/mL, against a spectrum of pathogens including resistant strains such as methicillin- and ciprofloxacin-resistant staphylococci, vancomycin-resistant enterococci, and ciprofloxacin-resistant Pseudomonas aeruginosa. CONCLUSION: Tea and garlic have the potential for exploration of broader applications as antibacterial agents. Nutrition 2003;19:994 –996. ©Elsevier Inc. 2003 KEY WORDS: Antibacterial, vegetables, fruits, tea
INTRODUCTION In recent years, a number of studies have supported an association between high consumption of vegetables and fruits and low incidence of certain chronic diseases.1,2 There also have been reports of plants with an inhibitory effect on microorganisms.3,4 However, there is little information concerning the comparative antibacterial activity of common vegetables and fruits on common potential pathogens and resistant strains. We report on pilot studies screening the relative antibacterial activities of various fruit and vegetable extracts, garlic, and tea.
MATERIALS AND METHODS Various original raw juices from organically grown, common vegetables and fruits were prepared undiluted by direct squeezing in a commercial juicer. Tea broth was prepared by brewing 20 g of Japanese green tea (Camellia sinensis) leaves in 200 mL of boiling distilled water (10%). Garlic juice was extracted from raw and from cooked garlic cloves. Commercial garlic tablets (Nature Made, 5 g) were dissolved in 25 mL of distilled water. All the juices and tea broth were adjusted to a pH of 7 and filtered by a Nalgene filter with a pore size of 0.45 m. Equal amounts of each of these juices were mixed with double-strength trypticase soy (TS) broth. Then, a series of two-fold dilutions were made with single-strength TS broth. One hundred eighty microliters of each dilution was added to 96-well microtiter plates. Bacterial strains tested included American Type Culture Collection (Rockville, MD, USA) strains and discarded clinical isolates from the University of California Irvine Medical Center. From fresh overnight cultures on TS agar plates, several colonies were emulsified in saline to a turbidity of McFarland 0.5. A 1:100
Correspondence to: Lauri D. Thrupp, MD, Department of Medicine, Building 53, Room 220, UCI Medical Center, 101 The City Drive, Orange, CA 92868, USA. E-mail: [email protected] Nutrition 19:994 –996, 2003 ©Elsevier Inc., 2003. Printed in the United States. All rights reserved.
dilution of the McFarland standard in TS broth served as the inoculum. Twenty microliters of each inoculum was added to each juice dilution well and to the broth control wells. The final bacterial cell concentration approximated 104 –5/mL. Microtiter plates were incubated at 35°C overnight for 18 to 20 h. For the extracts of vegetables, fruits, and garlic, antibacterial activity was assessed by minimum inhibitory dilutions and minimum bactericidal dilutions. Minimum inhibitory dilutions were considered to be the last dilution wells remaining clear, analogous to standard minimum inhibitory concentration.5 Minimum bactericidal dilutions were considered to be the last dilution wells that demonstrated a 99.9% kill of the initial inoculum5 upon quantitative subculture at 24 h. For tea, the inhibitory and bactericidal activities were expressed by the concentration calculated from the original weight of tea leaves. For other juices, it was expressed by dilution of the original whole raw juice. Vegetables and fruits and tea broth were tested first on Staphylococcus epidermidis and Klebsiella pneumoniae. Those fruits and vegetable extracts that showed the highest antibacterial activity were tested further on other strains.
RESULTS Table I presents the antibacterial activities of different fruit and vegetable extracts that were screened against S. epidermidis and K. pneumoniae. The results showed that, among the vegetable and fruit juices tested, all the green vegetables, such as asparagus, bell pepper, broccoli, cucumber, and spinach, at 1:2 dilutions of the original raw juice showed no antibacterial activity against S. epidermidis and K. pneumoniae. All purple and red vegetable and fruit juices, such as beet, cherry, and cranberry, showed mild inhibitory antibacterial activity (1:2) against both strains. Red onion, red cabbage, and raspberry had mild activity (1:2) on S. epidermidis. Aronianberry, blackberry, and grape juice showed moderate activity (1:8 to 1:16) on K. pneumoniae. Pomegranates had moderate activity on both strains. Garlic and tea had the highest antibacterial activities (1:32 to 1:28) and were active against a spectrum of pathogens, including clinical antibiotic0899-9007/03/$30.00 doi:10.1016/j.nut.2003.08.003
Nutrition Volume 19, Numbers 11/12, 2003
Antibacterial Activity of Vegetables and Juices
TABLE I.
TABLE II.
ANTIBACTERIAL ACTIVITIES OF VEGETABLES AND FRUITS
ANTIBACTERIAL ACTIVITIES OF GARLIC JUICE
Vegetable and fruits juices
Staphylococcus epidermidis* (MID)
Klebsiella pneumoniae† (MID)
Aronianberry Asparagus Bell pepper Beet Blackberry Blueberry Broccoli Carrot Cucumber Cherry Cranberry Garlic Ginger Grape Red onion Red cabbage Rhubarb Rutabaga Raspberry Pomegranate Spinach Strawberry Green tea
ND UDT UDT 1:2 ND ND UDT UDT UDT 1:2 1:2 1:128 1:2 ND 1:2 1:2 1:4 UDT 1:2 1:16 UDT 1:2 3.12 mg/mL
1:8 UDT UDT 1:2 1:16 UDT UDT UDT UDT 1:2 1:2 1:128 1:2 1:4 1:4 UDT 1:4 UDT UDT 1:16 UDT 1:2 3.12 mg/mL
Dilutions of juice Bacterial strains
* Clinical isolate. † American Type Culture Collection 13883. MID, minimum inhibitory dilution; ND, not done; UDT, undetectable at 1:2 dilution
resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant S. epidermidis, vancomycinresistant enterococci, and ciprofloxacin-resistant Pseudomonas aeruginosa. Tables II and III present the results of expanded testing of garlic and tea against a variety of bacterial species. Cooked garlic and commercial garlic pills showed no activity in our study (data not shown). The antibacterial activity of fresh garlic juice remained stable upon weekly testing up to 3 wk and tea upon monthly testing up to 4 mo when stored at 4°C.
DISCUSSION With the emergence of antibiotic-resistant bacteria, it is reasonable to explore new sources of natural compounds with antibacterial activity. Edible plants have been proven to be harmless and are economical. Our study showed that the purple and red vegetables and fruits that we tested have mild antibacterial activity. Purple and red colors in plants have been identified to be anthocyanins, which have been reported to show antibacterial activity.6,7 Our results further supported the association of antibacterial activity and anthocyanins. We also demonstrated that tea and garlic have by far the highest antibacterial activity among the common vegetables and fruits that we tested; further, they are active against a spectrum of resistant strains. Garlic has long been known to have antibacterial activity from in vitro and in vivo studies.8 –10 It is effective against Helicobacter pylori,11 a bacteria associated with peptic ulcer disease and gastric cancer. It has synergistic effect with omeprazole against H.
995
Staphylococcus epidermidis CR S. epidermidis Staphylococcus aureus MRSA
Enterococcus faecalis VRE Escherichia coli 0157 H7 Pseudomonas aeruginosa CR P. aeruginosa P. aeruginosa S. marcescens Klebsiella pneumoniae K. pneumoniae, ESBL
Origin
MID
MBD
Clinical isolate Clinical isolate ATCC 29213 ATCC 33591 Clinical isolate 1 Clinical isolates 2–5 Clinical isolate 6 ATCC 29212 Clinical isolate 1 Clinical isolates 2–6 Clinical isolate ATCC 27853 Clinical isolate Clinical isolate Clinical isolate ATCC 13883 Clinical isolate
128 128 256 128 128 128 128 64 64 64 128 32 128 32 128 128 64
128 128 64 128 128 64 32 64 64 32 64 32 32 32 64 64 64
ATCC, American Type Culture Collection; CR, ciprofloxacin resistant; ESBL, extended-spectrum betalactamase producer; MBC, minimum bactericidal dilution; MIC, minimum inhibitory dilution; MRSA, methicillin-resistant Staphylococcus aureus; VRE, vancomycin-resistant Enterococcus faecium
pylori12 and with streptomycin or chloramphenicol against Mycobacterium tuberculosis.13 It has been shown to prevent the formation of Staphylococcus enterotoxin,14 which causes food poisoning. Garlic also has antifungal,15 antiviral, and antiparasitic properties.16 The mechanism responsible for all these activities is believed to be allicin and its chemical reaction with thiol groups of various enzymes.17 It is of interest that cooked garlic and commercially available garlic tablets lost the antibacterial effect found in raw garlic. Green tea has been studied extensively by Japanese investigators. In addition to its anticancer and anti-hypercholesterolic activities, it has antibacterial activity that includes inhibition of gram-positive cocci, gram-negative bacilli, and resistant strains vancomycin-resistant enterococci and MRSA.18 Further, it has been reported that green tea may tend to reverse resistance in MRSA.19 Green tea catechins are responsible for antibacterial properties; more specifically, it is epigallocatechin gallate, one of the components of catechin, which restores the effectiveness of -lactams against MRSA and suppresses the emergence of resistance.20 In vivo studies of green tea have shown inhibition against microflora in the human intestine, bacteria responsible for dental caries,21 and food-borne bacteria.22 A custom of drinking green tea might help to reduce the severity of Escherichia coli 057 infection even with antibiotic treatment.23 Further, the combination of green tea extract and levofloxacin has improved the therapeutic effect of antibiotic treatment of E. coli 0157 infection in a mouse model.23 Therapeutic application has shown that green tea solution is successful as nebulization therapy for subglottic tracheal stenosis due to MRSA.24 We confirmed that tea and garlic have antibacterial activity against a wide range of pathogens. We also showed that, in addition to vancomycin-resistant enterococci and MRSA, garlic and green tea inhibit ciprofloxacin-resistant MRSA, ciprofloxacin-
996
Lee et al.
Nutrition Volume 19, Numbers 11/12, 2003 TABLE III.
ANTIBACTERIAL ACTIVITIES OF GREEN TEA
Bacterial strains Staphylococcus epidermidis CR S. epidermidis Staphylococcus aureus MRSA Enterococcus faecalis VRE Escherichia coli E. coli 0157H7 Pseudomonas aeruginosa CR P. aeruginosa Serratia marcescens Salmonella enteritidis Klebsiella pneumoniae K. pneumoniae, ESBL
MIC (mg/mL)
MBC (mg/mL)
3.1
6.2
Clinical isolate ATCC 29213 ATCC 33591 Clinical isolates 1–6 ATCC 29212 Clinical isolate 1 Clinical isolates 2–5 ATCC 29522 Clinical isolate Clinical isolates 1–5
3.1 3.1 1.6 6.25 50 12.5 25 12.5 12.5 6.2
2.5 3.1 1.6 6.25 100 25 50 25 25 6.2
Clinical isolate Clinical isolate ATCC 14028 ATCC 13883 Clinical isolate
6.2 12.5 6.2 1.6 25
12.5 12.5 12.5 1.6 2.5
Origin Clinical isolate
ATCC, American Type Culture Collection; CR, ciprofloxacin resistant; ESBL, extended-spectrum betalactamase producer; MBC, minimum bactericidal dilution; MIC, minimum inhibitory dilution; MRSA, methicillin-resistant Staphylococcus aureus; VRE, vancomycin-resistant Enterococcus faecium
resistant MRSA, methicillin-resistant S. epidermidis, and ciprofloxacin-resistant P. aeruginosa. All of these resistant bacteria are increasing in long-term care facilities and acute care hospitals.25–28 It may be pertinent to explore the possibility of using green tea solution to decolonize nasal colonization with MRSA and methicillin-resistant S. epidermidis in nurses’ hands and intestinal carriage of vancomycin-resistant enterococci in long-term care facility patients. Another potential use of green tea might be for topical treatment of pressure ulcers, which are often superinfected with MRSA in nursing home patients. Green tea and garlic seem to be safe agents that have the potential for broader applications to take advantage of their antibacterial activities.
SUMMARY Among all plant juices tested, green vegetables showed little antibacterial activity, whereas red vegetables and fruit juices had mild activity. Garlic and tea had the highest antibacterial activity against a spectrum of pathogens including methicillin- and ciprofloxacin-resistant S. aureus, vancomycin-resistant enterococci, and ciprofloxacin-resistant P. aeruginosa.
REFERENCES 1. van’t Veer P, Jansen MC, Klerk M, Kok FJ. Fruits and vegetables in the prevention of cancer and cardiovascular disease. Public Health Nutr 2000;3(1): 103
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