BLOODAGARBASE(血琼脂基础培养基)
| Typical Formula* | gm/litre |
| `Lab-Lemco’ powder | 10.0 |
| Peptone Neutralised | 10.0 |
| Sodium chloride | 5.0 |
| Agar | 15.0 |
| pH 7.3 ± 0.2 |
* Adjusted as required to meet performance standards
Directions
Suspend 40g in 1 litre of distilled water. Bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes.
For blood agar, cool the Base to 50°C and add 7% of Defibrinated Horse Blood SR0050. Mix with gentle rotation and pour into petri dishes or other containers.
Description
Oxoid Blood Agar Base is a non-selective general purpose medium widely employed for the growth of pathogenic and non-pathogenic bacteria:
(i) Without additions, the medium may be employed as a nutrient agar (a richer medium than Nutrient Agar CM0003), or as a medium for the short-term maintenance of stock cultures.
(ii) With added serum or other enrichments, the medium becomes suitable for the cultivation of many fastidious organisms. Serum and other thermolabile enrichments should be added to the sterilised medium cooled to 45-50°C.
(iii) With added blood, the medium is not only enriched, but becomes suitable for the determination of the typical haemolytic reactions which are important diagnostic criteria for streptococci, staphylococci, and other organisms. For blood agar, 7% of sterile blood should be added to the sterilised medium cooled to 45-50°C.
Blood Agar Base was used during investigations on irradiated Escherichia coli and other bacteria1,2. It was the most suitable medium for investigating the phages of Clostridium perfringens 3 and as the basis of a selective medium for Clostridium perfringens 4. It was used with added phenolphthalein phosphate for the detection of phosphatase-producing staphylococci5 and with added salt and agar for the assessment of surface contamination on equipment and pig carcasses6. It was used for determining the salinity range of growth of marine flavobacteria7.
Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared plates of medium at 2-8°C.
Appearance
Dehydrated medium: Straw coloured, free-flowing powder
Prepared medium: Straw coloured gel
Quality control
| Positive controls: | Expected results |
| Staphylococcus aureus ATCC® 25923 * | Good growth; grey-white coloured colonies |
| Streptococcus pyogenes ATCC® 19615 * | Good growth; pale colonies; Beta haemolysis |
| Streptococcus pneumoniae ATCC® 6303 * | Good growth; green-grey coloured colonies; alpha heamolysis |
| Negative control: | |
| Uninoculated plate | No change |
* This organism is available as a Culti-Loop®
Precautions
The haemolytic reactions of organisms inoculated on to this medium will be affected by the animal blood used e.g. horse or sheep and the incubation conditions e.g. aerobic, capnoeic or anaerobic8.
When horse blood is added to the medium Haemophilus haemolyticus colonies will produce beta-haemolysis and mimic Streptococcus pyogenes8.
References
1. Alper T. and Gillies N. E. (1960) J. Gen. Microbiol. 22 113-128.
2. Hodgkins Brenda and Alper T. (1963) J. Gen. Microbiol. 30 307-315.
3. Williams Smith H. (1959) J. Gen. Microbiol. 21 622-630.
4. Noble W. C. (1961) J. Path. Bact. 81 523-526.
5. Noble W. C. (1962) J. Clin. Path. 15 552-558.
6. Hansen N. H. (1962) J. Appl. Bact. 25 46-53.
7. Hayes P. R. (1963) J. Gen. Microbiol. 30 1-19.
8. Facklam R. R. (1980) in Manual of Clinical Microbiology. Eds. Lennette E. H., Balows A., Hausler W. J. & Truant J. P. 3rd Edn. Amer. Soc. for Microbiology. Washington D.C. pp. 88-110.