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 ¤  Material and Methods
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ORIGINAL CONTRIBUTION
Year : 2001  |  Volume : 55  |  Issue : 7  |  Page : 376-381
 

Antibacterial activity of black tea (Camelia sinensis ) extract against Salmonella serotypes causing enteric fever


Department of Microbiology, KMC, Manipal, India

Correspondence Address:
P G Shivananda
Department of Microbiology, Kasturba Medical College, Manipal - 576 119.
India
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PMID: 11883337

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How to cite this article:
Ciraj A M, Sulaim J, Mamatha B, Gopalkrishna B K, Shivananda P G. Antibacterial activity of black tea (Camelia sinensis ) extract against Salmonella serotypes causing enteric fever. Indian J Med Sci 2001;55:376-81

How to cite this URL:
Ciraj A M, Sulaim J, Mamatha B, Gopalkrishna B K, Shivananda P G. Antibacterial activity of black tea (Camelia sinensis ) extract against Salmonella serotypes causing enteric fever. Indian J Med Sci [serial online] 2001 [cited 2014 Oct 2];55:376-81. Available from: http://www.indianjmedsci.org/text.asp?2001/55/7/376/12062


Medicinal properties of tea were known to mankind since antiquity. Antibacterial property of tea was first reported from Japan by using Japanese tea against various diarrhoeal pathogens. [1] Subsequent studies with four kinds of Japanese green tea and 24 bacterial isolates from infected root canals provided enough evidences to support the bactericidal activity of tea. [2] Extracts of tea have shown significant bactericidal activity against methicillin resistant Staphylococcus aureus Scientific Name Search  (MRSA) even at concentrations available in ordinarily brewed tea. [3] There have been studies conducted in the past to evaluate the antibacterial activity of tea against  Salmonella More Details serotypes primarily associated with diarrhoeal illness. [4] However there is paucity in the information available, regarding the antibacterial activity of black tea extracts against serotypes of Salmonella causing enteric fever. The aim of the present study was to determine the antibacterial activity of black tea extracts against Salmonella typhi and Salmonella paratyphi A.


 ¤ Material and Methods Top


A total of 64 strains of S. typhi and 11 strains of S. paratyphi A isolated from blood cultures were used in the study. Standard procedures were used for the isolation and identification of bacteria. [5] The bacteria were preserved in semisolid nutrient agar butts at 4° C and reconstituted with glucose broth and subcultured on blood agar and McConkey agar before the assay. The bacterial inoculum was prepared by emulsifying the colonies in saline to get a suspension of turbidity matching with that of McFarland 0.5 standard. [6] (approximately 1.5 x 10 [8] CFU/ml). Commercially available brands of black tea were used in the preparation of the extracts. Tea powder was suspended in absolute alcohol to get 20 (w / v) concentration and reflexed for 2 h. It was then distilled and reduced to a minimal volume. The concentrate thus formed was poured onto a wide watch glass and allowed to evaporate in order to remove the residual alcohol. The extract was suspended in Dimethyl sulfoxide (DMSO) to get 20 % (w / v) concentration and used for the assay. The alcoholic extract was added to molten nutrient agar to get a concentration of 2 % (v / v). Bacteria were spot inoculated on to these plates, incubated at 37° C for 24 h and examined for inhibition of growth if any. Plain nutrient agar was used as control.


 ¤ Determination of Minimum Inhibitory Concentration (MIC) of Tea Extract Top


The bacteria ( S. typhi -27, S. paratyphi A - 11) inhibited by 2 % alcoholic extracts of tea were used for this purpose. The MIC was determined by agar dilution method. [7] Tea extract was incorporated in nutrient agar to get varying concentrations, ranging from 0.25 % - 2% (v/v). The bacteria were spot inoculated on to plates having different concentrations of tea extract. The plates were incubated at 37° C for 24 h and examined for the minimum concentration of the extract inhibiting the bacterial growth. The test for MIC, mentioned above was extended by replica plating tech­nique to measure MBC. [8] Plates which showed no visible growth were selected and a replica of these were taken on to fresh nutrient agar plates. The plates were incubated at 37 o C for 24h and the minimum concentration of the tea extract required to kill the bacteria (MBC) was determined.


 ¤ Results Top


Of the 11 strains of S. paratyphi A tested, all were found sensitive to tea at 2 concentration. Only 27 (42.19%) strains of S. typhi were inhibited by this concentration of the extract. MIC and MBC of the alcoholic extracts of black tea against S. typhi and S. para - typhi A isolates is given in [Table 1].


 ¤ Discussion Top


Tea extracts have been shown to possess inhibitory effect against an array of pathogenic microorganisms. [4],[9],[10] Tea, from very ancient time has been used by the village folk in treating diarrhoeal disorders. Use of tea powder as a medicament in wounds to avoid suppuration, is still practiced in many parts of rural India. Likewise, tealeaves discarded after preparation of the infusion are used in the treat­ment of chronic eczema. Of the ingredients present in tea, the most important are tannins (1-5%), caffeine (7-24 %) and various volatile oils. [11] Tannins are poly phenol group of compounds that damage the bacterial cytoplasmic membrane. Chelating properties of tannins coupled with their ability for denaturing bacterial proteins contribute towards the antibacterial activity. [12] It has been shown that catechins the precursors of tannins also have antibacterial activity. Among the catechins tested epigallocatechin gallate, epigallocatechin and epicatechin gallate inhibited the growth of Staphylococcus aureus,  Vibrio cholerae Scientific Name Search  01 classical Inaba and El for Inaba strains. [12] Epigallocatechin gallate which accounts for more than half the total flavonal content present in the tea acts by causing the leakage of 5,6 carboxy fluorescein from phosphatidyl choline liposomes. [13]

Alcoholic extracts have wider spectrum of antibacterial activity than acqueous extracts ( data unpublished ). It also emphasizes the fact that antibacterial compound is released only after alcoholic extraction. Hence habitual drinking of tea may not be a prophylactic or remedial measure against enteric fever. However the actual compound responsible for the antibacterial activity has not been identified in our study. Solvents used for the preparation of the extract and residual activity of alcohol present in alcoholic extract are factors to be examined during an antibacterial assay. Solvent used in this study was DMSO, which is devoid of any anti - bacterial action. We have used controls with 2 % (w / v) DMSO in nutrient agar to confirm this. The removal of residual alcohol was completely ensured as mentioned before. To confirm that the antibacterial activity was a sole function of the extract, aqueous extract of black tea was dissolved in alcohol and allowed to evaporate freely as for the alcoholic extract. Antibacterial activity of this extract was found exactly identical to that of the aqueous extract. Enteric fever remains a major cause of morbidity and mortality in many parts of the world including the Indian sub continent. We presume that the identification and character­isation of the antibacterial compound in black tea will be useful in the treatment of enteric fevers. Salmonella serotypes tested have shown varying degrees of susceptibility against the tea extracts. The extracts had higher degree of antibacterial activity against S. paratyphi A strains when compared to S. typhi. These variations in susceptibility may be due to the differences in their cell structure or certain extra cellular products released by them. Studies at the cellular level may help understand the mechanism(s) involved in the susceptibility of bacteria to black tea.


 ¤ Summary Top


Alcoholic extract of black tea (Camelia sinensis) was assayed for its antibacterial activity against Salmonella serotypes causing enteric fever viz., Salmonella typhi and Salmonella paratyphi A. While all strains of S. paratyphi A tested were found sensitive, only 42.19 % of S. typhi strains were inhibited by this extract. Further minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of black tea extract against S. paratyphi A was less compared with that against S. typhi.

 
 ¤ References Top

1.Shimamura T, Toda M, Okuba S, Onishi R. Antibacterial and bactericidal effects of Japanese green tea. Nippon - Saikingaku - Zasshi 1989: 44 : 669 - 72.  Back to cited text no. 1    
2.Horiba N, Maekawa Y, Ito M, Matsumoto T, Nakamura H. A pilot study of Japanese green tea as a medicament : anti - bacterial and bactericidal effects. J Endod 1991 ; 17 : 122 - 24.  Back to cited text no. 2  [PUBMED]  
3.Toda M, Okuba S, Hara Y, Shimamura T. Antibacterial and bactericidal activities of tea extracts and catechins against MRSA. Nippon - Saikingaku - Zasshi 1991 ; 46 : 839 - 45.  Back to cited text no. 3    
4.Shetty M, Subbannayya K, Shivananda PG. Antibacterial activity of tea (Camelia sinensis) and coffee (Coffea arabica) with special emphasis to S. typhimurium. J Commun Dis 1994 ; 26 : 147 - 50.  Back to cited text no. 4    
5.Burrows GI, Feltham RKA. Cowan and Steels Manual for identification of medically important bacteria. 21A edn. Great Britain : Cambridge University press ; 1993 ; pp 140-2  Back to cited text no. 5    
6.McFarland J. Nephelometer an instrument for estimating the number of bacteria in suspensions used for calculating the opsonic index and for vaccines. JAMA 1907: 14: 1176­1178.  Back to cited text no. 6    
7.Colle JG, Duguid JP, Fraser AG, Marimon BP. Mackie and McCartney Practical Medical Microbiology. Vol : 2, 13"' edition UK Churchill Livingstone 1989 pp 162 - 176.  Back to cited text no. 7    
8.Elek SD, Hilson GRF. Combined agar diffusion and replica plating techniques in the study of antibacterial substances. J Clin Pathol 1954 ; 7 : 37.  Back to cited text no. 8    
9.Masaki, Toda M, Sachie 0, Roike H, Tadakatsu S. Antibacterial activity of tea and coffee. Letters Applied Microbiol, 1989 : 8 : 123.  Back to cited text no. 9    
10.John TJ, Mukundan P. Virus inhibition by tea, coffee and tannic acid. Indian J Med Res 1979 : 69 : 542 - 545.  Back to cited text no. 10    
11.Sinelair HM, Hollingworth DF. Hutchinson's food and principles of nutrition 12'" edition, UK, Edward Arnold , 1969, pp 478 - 486.  Back to cited text no. 11    
12.Shimamura T, Toda M, Okuba S, Hara Y. Antibacterial and antihaemolytic activities of tea catechins and their structural relatives. Nippon - Saikingaku - Zasshi, 1990: 69: 1126 - 34.  Back to cited text no. 12    
13.Ikigai H, Nakal T, Hora Y, Shimamura T. Bactericidal catechins damage the lipid bi-layer. Biochim Biophys Acta. 1993 ; 1147: 132 - 6.  Back to cited text no. 13    



 
 
    Tables

  [Table 1]IndianJMedSci_2001_55_7_376_12062_1.jpg

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