Antibacterial activity of vegetables and juices

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Review article

Nutrition Vol: 19 Issue: 11-12, November - December, 2003 pp: 994-996

Article Full Text

 

Antibacterial activity of vegetables and juices

Yee-Lean Lee PhDa, Thomas Cesario MDa, Yang Wang MBa, Edward Shanbrom MDa,

Lauri Thrupp MD, a, ,

a. University of California Irvine Medical Center, Orange, California , USA

 

 

Article Outline:

1. Objective

2. Methods

3. Results

4. Conclusion

1. Introduction

2. Materials and methods

3. Results

4. Discussion

5. Summary

References

 

Abstract

1. Objective

We evaluated the antibacterial activities of various fruit and vegetable

extracts on common potential pathogens including antibiotic-resistant strains.

 

2. 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).

 

3. 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.

 

4. Conclusion

Tea and garlic have the potential for exploration of broader applications

as antibacterial agents.

 

 

Keywords: Antibacterial; vegetables; fruits and tea.

1. 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.

 

2. 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 mm. 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 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 inoculum[ 5 ] 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.

 

3. Results

- Table: [ 1]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 antibiotic-resistant strains such as methicillin-resistant

Staphylococcus aureus (MRSA), methicillin-resistant S. epidermidis,

vancomycin-resistant enterococci, and ciprofloxacin-resistant Pseudomonas

aeruginosa. - Tables: [ 2, 3]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.

 

 

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TABLE S: ANTIBACTERIAL ACTIVITIES OF VEGEAND FRUITS

 

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TABLE II: ANTIBACTERIAL ACTIVITIES OF GARLIC JUICE

 

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Table III: Antibacterial activities of Green Tea

 

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4. 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, 9, 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. pylori[ 12 ]

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 b-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-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, 26, 27, 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.

 

5. 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 M.C., Klerk M., Kok F.J., " Fruits and vegetables

in the prevention of cancer and cardiovascular disease " , Public Health

Nutr, Volume: 3, Issue: 1 (2000), pp. 103

 

2. Liu S., Manson J.E., Lee I.M., et al. " Fruit and vegetable intake and

risk of cardio vascular disease - the women's health study " , Am J Clin

Nutr, Volume: 72, (2000), pp. 922

 

3. Cowan M.M., " Plant products as antimicrobial agents " , Clin Microbiol

Rev, Volume: 12, (1999), pp. 564

 

4. Nascimento G.F., Locatelli J., Freitas P.C., Silva G.L., " Antibacterial

activity of plant extracts and phytochemicals on antibiotic-resistant

bacteria " , Braz J Microbiol, Volume: 31, (2000), pp. 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 R.B., Bautista P.A., " Antibacterial activity of

green tea polyphenols against E " , coli K 12. Nahrung, Volume: 44, (2000),

pp. S60

 

7. Harborne J.B., Williams C.A., " Advances in flavonoid research since

1992 " , Phytochemistry, Volume: 6, (2000), pp. 481

 

8. Ankri S., Mirelman D., " Antimicrobial properties of allicin from

garlic " , Microbes Infect, Volume: 2, (1999), pp. 125

 

9. Uchida Y., Sato N., " The characteristics of the antibacterial activity

of garlic " , Jpn J Antibiotics, Volume: 28, (1975), pp. 638

 

10. Chowdhury A.K., Ahsan M., Islan S.N., Ahmed Z.U., " Efficacy of aqueous

extract of garlic and allicin in experimental shigellosis in rabbits " ,

Indian J Med Res, Volume: 93, (1991), pp. 33

 

11. Sivam G.P., " Protection against Helicobacter pylori and other

bacterial infections by garlic " , J Nutr, Volume: 131, Issue: suppl 3

(2001), pp. 1106S

 

12. Jonkers D., van den Broek E., Dooren I.V., et al. " Antibacterial

effect of garlic and omeprazole on Helicobacter pylori " , J Antimicrob

Chemother, Volume: 43, (1999), pp. 837

 

13. Gupta K.C., 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, Volume: 5, (1955), pp. 24

 

14. Gonzalez-Fandos E., Garcia-Lopez M.L., Sierra M.N.L., Otero A.,

" Staphylococcal growth and enterotoxins (A–D) and thermonuclease synthesis

in the presence of dehydrated garlic " , J Appl Bacteriol, Volume: 77,

(1994), pp. 549

 

15. Yamada Y., Azuma K., " Evaluation of the in vitro antifungal activity

of allicin " , Antimicrob Agents Chemother, Volume: 11, (1997), pp. 743

 

16. Tsai Y., Cole L.L., Davis L.E., Lockwood S.J., Simmons V., Wild G.C.,

" Antiviral properties of garlic - in vitro effects on influenza B, herpes

simplex and coxsackie viruses " , Planta Med, Volume: 5, (1985), pp. 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, Volume:

1379, (1998), pp. 233

 

18. Hamilton-Miller J.M.T., " Antimicrobial properties of tea ( Camellia

sinensis) " , Antimicrob Agents Chemother, Volume: 39, (1995), pp. 2375

 

19. Yam T.S., Hamiton-Miller J.M., 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, Volume: 42, (1998), pp. 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,

Volume: 50, (1999), pp. 299

 

21. Hamilton-Miller J.M., " Anti-cariogenic properties of tea ( Camellia

sinensis) " , J Med Microbiol, Volume: 50, (2001), pp. 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, Volume: 42,

(2001), pp. 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, Volume: 42, (2001), pp. 222

 

25. Lee Y.L., 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, Volume: 17, (1996), pp. 649

 

26. Lee Y.L., 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,

Volume: 26, (1999), pp. 552

 

27. Parry M.D.F., Panzer K.B., Yukna M.E., " Quinolone-resistance " , Am J

Med, Volume: 87, Issue: suppl 5A (1989), pp. 125

 

28. Lee Y.L., 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, Volume: 22, (1994),

pp. 346