Anaerobic blood agar is a solid media that can be used in qualitative methods for the isolation and cultivation anaerobic organisms. V.R. Dowell and T.M. Hawkins, Centers for Disease Control and Prevention Atlanta, Georgia. Anaerobic blood agar supports the growth of anaerobes with typical pigmentation, both fastidious and slow-growing, and other anaerobes that are of clinical significance.
Composition of Anaerobic Blood Agar
|Casein enzymic hydrolysate||15.000|
|Papaic digest of soybean meal||5.000|
Final pH: 7.4±0.2
Principle of Anaerobic Blood Agar
Anaerobic Blood Agar Base is a nonselective, nutritious medium that allows the cultivation not only of fastidious anaerobes, but also of microaerophilic and aerobic microorganisms. It also contains peptones, which provide nitrogenous substances as well as amino acids that are necessary for the growth anaerobic bacteria. Yeast extract is a growth stimulant and provides B-complex vitamins. Hemin, vitamin K and sheep blood stimulate growth of anaerobes such as Bacteroides species, and gram-positivespore bearers such as Clostridium species. Sodium chloride is an essential electrolyte and helps maintain osmotic equilibrium. The addition of blood helps to differentiate hemolytic organisms and provides nutrients.
Recommended for cultivation of anaerobic microorganisms, including very fastidious organisms from clinical specimens.
Preparation and Method of Use of Anaerobic Blood Agar
- 4.0 grams should be taken in 1000 ml of distilled water.
- To dissolve the medium completely, heat to boiling
- Add 1 vial Vitamin K1 solution to the rehydrated contents.
- For 15 minutes, sterilize by using an autoclave at 15 lbs pressure (121degC).
- Keep it at 45-50 degrees Celsius
- Aseptically, add 5% v/v defibrinated sheep’s blood.
- Mix everything together and pour onto sterilized Petri dishes.
- Before using, let the plates cool for at least 24 hours in an anaerobic environment at ambient temperature.
- Innoculate specimens for anaerobic cultures on selective and non-selective media immediately after they are received in the laboratory.
- For 48-72 hours, incubate anaerobically at 33-37degC.
- Subculture to anaerobic blood plate can confirm anaerobic growth.
Result Interpretation of Anaerobic Blood Agar
|Bacteroides fragilis||Luxuriant Growth|
|Bacteroides melaninogenicus||Luxuriant Growth|
|Peptostreptococcus anaerobius||Luxuriant Growth|
|Clostridium perfringens||Growth, double zone β-hemolysis|
|Prevotella melaninogenica||Growth; pigment (tan to brown)|
Uses of Anaerobic Blood Agar
- Anaerobic Blood Agar Base can be used to cultivate anaerobic microorganisms. This includes very fastidious organisms derived from clinical specimens.
- It encourages the formation of both Bacteroides melaningenicus pigments and Clostridium perfringens hemolytic reactions.
- The media supports the production of pigments by pigmented Prevotellas and Porphyromonas.
Limitations of Anaerobic Blood Agar
- To prevent the formation oxidized products, media must be stored in oxygen-free conditions before being prepared and dispensed.
- This Agar is not able to provide all information necessary for the identification of bacterial isolates. For complete identification, additional test procedures and media will be required.
- To ensure the growth of all species, it is recommended to inoculate with clinical specimens with a selective media like Anaerobic Brulla Laked blood Agar with Kanamycin or Vancomycin and/or Anaerobic Brulla Blood Agar With Phenylethyl Alcohol.