Last Updated on January 9, 2020 by Sagar Aryal
Cultural Characteristics of Bacillus cereus
Some of the characteristics are:
- Most Bacillus spp grow readily on nutrient agar or peptone media.
- The optimum temperature for growth varies from 20°C to 40°C, mostly 37°C.
- B. cereus is mesophilic and is capable of adapting to a wide range of environmental conditions.
- On Nutrient Agar at 37°C, it forms large (2-5 mm) grey-white, granular colonies with a less wavy edge and less membranous consistency.
- On 5% sheep blood agar at 37°C, cereus colonies are large, feathery, dull, gray, granular, spreading colonies and opaque with a rough matted surface and irregular perimeters.
- On blood agar, it is beta-hemolytic.
- Colony perimeters are irregular and represent the configuration of swarming from the site of initial inoculation, perhaps due to B. cereus swarming motility.
- In some instances, smooth colonies develop either alone or in the midst of rough colonies.
- When grown apart from the initial inoculum, smooth colonies are surrounded by a uniform zone of beta-hemolysis framing the centrally situated colony.
- The MYP agar has been the standard media for plating B. cereus, but it has little selectivity so background flora is not inhibited and can mask the presence of B. cereus. B. cereus colonies are usually lecithinase-positive and mannitol-negative on MYP agar.
- Bacara is a chromogenic selective and differential agar that promotes the growth and identification of B. cereus, but inhibits the growth of background flora. Bacillus cereus colonies turn pink-orange with an opaque halo.
- The chromogenic agar has been suggested for the enumeration of cereus group as a substitute for MYP. Typical colonies will grow as pink-orange uniform colonies surrounded by a zone of precipitation.
- Bacillus cereus HiCynth™ Agar Base. HiMedia Laboratories Pvt. Ltd.
- S Fazlani, M Abubakar, S Shah, M ul Hassan, M Arshed. Bio-Morphological Characteristics of Bacterial Species Identified from Mastitic Milk Samples of Camel. The Internet Journal of Veterinary Medicine. 2008 Volume 6 Number 1.