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Brilliant Green Bile (BGB) broth
InternationalJournal of FoodMicrobiology, 5 (1987) 206, 20
206
Elsevie JFM 000M5
Brilliant Green Bile (BGB) broth Description and history This broth is a modification of MacConkey's liquid medium for the isolation of Enterobacteriaceae, formulated by Dunham and Schoenlein in 1926 to attain maximum recovery of bacteria of the coli-aerogenes group, while inhibiting most Gram-positive organisms which might hinder the development of the bacteria sought. It contains brilliant green and bile as the inhibitory agents for Gram-positive organisms and lactose as the carbon source, which is dissimilated rapidly by the coli-aerogenes group, mostly by a heterofermentative pathway, leading to gas formation.
Composition (grams) Peptone Lactose Ox bile Brilliant green Distilled or deionised water
10.0 10.0 20.0 0.0133 1 000.0
Preparation Dissolve the ingredients in water, distribute in the required volumes in flasks or tubes and heat at 100 o C for 30 min. Although lactose media are markedly less sensitive to heat damage than those containing glucose, the performance of the medium, with respect to both selectivity and productivity is much more consistent when it is decontaminated by standardised pasteurization as recommended.
Physical properties Appearance pH
Green, clear. 7.4 _ 0.2.
Shelf life Ready to use medium
1 month at 4 + 2 ° C in screw-capped containers.
Inoculation method for samples Use food macerates or decimal dilutions and inoculate the broth in the proportion 1 : 10. When large volumes of enrichment fluid are not feasible, BGB broth can be used at double strength; in this instance sterilisation of the medium should be replaced by pasteurization as recommended above. 0168-1605/87/$03.50 © 1987 Elsevier Science Publishers B.V. (Biomedical Division)
207
Incubation method At 4 4 ° C for 18 h, 320C for 24-48 h or 4 ° C for 10 days in air, dependent on groups of coli-aerogenes bacteria to be recovered; psyehrotrophs, mesophiles or thermotrophs. For E. coli the temperature of 44 + 0.1oC is specifically recommended.
Reading of results and interpretation Turbidity and often change of colour of the medium towards yellowish-green provides presumptive evidence of the presence of bacteria of the coli-aerogenes group, particularly when accompanied by copious gas formation. This should be confirmed by isolation on violet red bile agar and subsequent study of the mode of attack on glucose and negative oxidase reaction, preferably by the technique described in the monograph on VRB agar.
Quafity assessment (i)
Productivity Test strains
Escherichia coli ATCC 11775/NCTC 9001 Salmonella gallinarum NCTC 9240 Shigella flexneri ATCC 29903 Yersinia enterocolitica 0 : 3 C C U G 4586 Otrobacterfreundii NCTC 6272
Inoculation method Criteria
Dilution to extinction. Recovery in BGB broth should be within one titre unit of the recovery in tryptone soya broth and copious gas formation should occur with Escherichia coli and Citrobacterfreundii within 18-24 h at 30 o C; while the same should apply for Escherichia coli only after incubation for 24 h at 44 + 0.1 ° C.
(ii) Selectivity Test strains
Inoculation method Criteria
Staphylococcus aureus ATCC 6538 Micrococcus luteus ATCC 15307/NCTC 2665 Streptococcus lactis A T C C 1 9 4 3 5 / N C T C
6681/NCIB 6681/BUCSAV 302 Bacillus cereus ATCC 11778 Lactobacillus plantarum ATCC 14917 Dilution to extinction. Recovery in BGB should be less than 5 titre units of the recovery in tryptone soya broth after 18-24 h at 30 o C. At 44 5: 0.1°C the medium should be even more selective.
References Dunham, H.G. and H.W. Schoenlein, 1926. Brilliant Green bile media. Stain Technol. 1, 129-134. MacKenzie, E.F.W., E.W. Taylor and W.E. Gilbert, 1948. Recent experiences in the rapid identification of Bacterium coil, type 1. J. Gen. Microbiol. 2, 197-204. Richard, N., 1982. Monitoring the quality of selective liquid media by the official French dilution technique used for the bacteriological examination of foods. In: Quality assurance and quality control of microbiological culture media, edited by J.E.L. Corry. G.I.T.-Verlag, Darmstadt, pp. 51-57.
206
Elsevie JFM 000M5
Brilliant Green Bile (BGB) broth Description and history This broth is a modification of MacConkey's liquid medium for the isolation of Enterobacteriaceae, formulated by Dunham and Schoenlein in 1926 to attain maximum recovery of bacteria of the coli-aerogenes group, while inhibiting most Gram-positive organisms which might hinder the development of the bacteria sought. It contains brilliant green and bile as the inhibitory agents for Gram-positive organisms and lactose as the carbon source, which is dissimilated rapidly by the coli-aerogenes group, mostly by a heterofermentative pathway, leading to gas formation.
Composition (grams) Peptone Lactose Ox bile Brilliant green Distilled or deionised water
10.0 10.0 20.0 0.0133 1 000.0
Preparation Dissolve the ingredients in water, distribute in the required volumes in flasks or tubes and heat at 100 o C for 30 min. Although lactose media are markedly less sensitive to heat damage than those containing glucose, the performance of the medium, with respect to both selectivity and productivity is much more consistent when it is decontaminated by standardised pasteurization as recommended.
Physical properties Appearance pH
Green, clear. 7.4 _ 0.2.
Shelf life Ready to use medium
1 month at 4 + 2 ° C in screw-capped containers.
Inoculation method for samples Use food macerates or decimal dilutions and inoculate the broth in the proportion 1 : 10. When large volumes of enrichment fluid are not feasible, BGB broth can be used at double strength; in this instance sterilisation of the medium should be replaced by pasteurization as recommended above. 0168-1605/87/$03.50 © 1987 Elsevier Science Publishers B.V. (Biomedical Division)
207
Incubation method At 4 4 ° C for 18 h, 320C for 24-48 h or 4 ° C for 10 days in air, dependent on groups of coli-aerogenes bacteria to be recovered; psyehrotrophs, mesophiles or thermotrophs. For E. coli the temperature of 44 + 0.1oC is specifically recommended.
Reading of results and interpretation Turbidity and often change of colour of the medium towards yellowish-green provides presumptive evidence of the presence of bacteria of the coli-aerogenes group, particularly when accompanied by copious gas formation. This should be confirmed by isolation on violet red bile agar and subsequent study of the mode of attack on glucose and negative oxidase reaction, preferably by the technique described in the monograph on VRB agar.
Quafity assessment (i)
Productivity Test strains
Escherichia coli ATCC 11775/NCTC 9001 Salmonella gallinarum NCTC 9240 Shigella flexneri ATCC 29903 Yersinia enterocolitica 0 : 3 C C U G 4586 Otrobacterfreundii NCTC 6272
Inoculation method Criteria
Dilution to extinction. Recovery in BGB broth should be within one titre unit of the recovery in tryptone soya broth and copious gas formation should occur with Escherichia coli and Citrobacterfreundii within 18-24 h at 30 o C; while the same should apply for Escherichia coli only after incubation for 24 h at 44 + 0.1 ° C.
(ii) Selectivity Test strains
Inoculation method Criteria
Staphylococcus aureus ATCC 6538 Micrococcus luteus ATCC 15307/NCTC 2665 Streptococcus lactis A T C C 1 9 4 3 5 / N C T C
6681/NCIB 6681/BUCSAV 302 Bacillus cereus ATCC 11778 Lactobacillus plantarum ATCC 14917 Dilution to extinction. Recovery in BGB should be less than 5 titre units of the recovery in tryptone soya broth after 18-24 h at 30 o C. At 44 5: 0.1°C the medium should be even more selective.
References Dunham, H.G. and H.W. Schoenlein, 1926. Brilliant Green bile media. Stain Technol. 1, 129-134. MacKenzie, E.F.W., E.W. Taylor and W.E. Gilbert, 1948. Recent experiences in the rapid identification of Bacterium coil, type 1. J. Gen. Microbiol. 2, 197-204. Richard, N., 1982. Monitoring the quality of selective liquid media by the official French dilution technique used for the bacteriological examination of foods. In: Quality assurance and quality control of microbiological culture media, edited by J.E.L. Corry. G.I.T.-Verlag, Darmstadt, pp. 51-57.