Nutrient HiVeg™ Agar w/ Manganese

Principle and Interpretation

Nutrient HiVeg Agar with Manganese is prepared by using HiVeg peptone No.2 and HiVeg extract, veg substitutes for Pancreatic digest of gelatin and Beef extract respectively which are free from BSE/TSE risks normally associated with animal based peptones. Nutrient HiVeg Agar w/Manganese can be used against animal based Nutrient Agar w/ Manganese, conventionally abbreviated as NAMn which favours culture and sporulation of aerobic Bacillus species especially from canned foods.

HiVeg extract and HiVeg peptone No.2 provides necessary nutrients for growth of Bacillus species. Manganese is known to influence and enhance sporulation in the Bacillus species (1,2,3,4). It has been reported that organisms recovered from spoilage of foods such as fruit drinks, tomatoes, acidified onions and other canned foods sporulate well aerobically on Nutrient Agar with added manganese (5).

Thermophilic bacteria such as Bacillus stearothermophilus are capable of growth at 55 - 65°C while an incubation period of 30 to 35°C is favourable for culture and sporulation of mesophilic spore formers (5). This property is exploited to grow and therefore differentiate mesophilic and thermophilic spoilage bacteria. As recommended by APHA, in routine diagnosis for spoilage in canned foods, microbiological cultural procedures involves the use of primary recovery media and subculture media to identify spoilage bacteria and study their growth characteristics. Recovery medias for aerobes generally include DTA (Dextrose Tryptone Agar, M092) or DTB ( Dextrose Tryptone Broth, M122). Use of Cooked meat medium (M149) is recommended for recovery of anaerobic organisms. NAMn is widely used as subculture media for aerobes.

Nutrient HiVeg Agar with Manganese, like the conventional medium supports growth and enhances spore production by aerobic sporeformers and therefore serves the same purpose as NAMn. When rod shaped aerobes in pure culture are isolated on HiVeg DTA (or DTB) medias (MV092/ MV122) and sporulation is not evident, the isolates should be subcultured on Nutrient HiVeg Agar with Manganese, at the temperature of initial isolation. After incubation upto 10 days, if spore production has taken place, the spores are heat shocked to destroy all vegetative cells and cultured again on HiVeg NAMn at both 30 to 35°C and 55°C. The temperature at which outgrowth occurs from the spore state indicates whether the isolate is an obligate mesophile (growth at 30 to 35°C), an obligate thermophile (growth at 55°C) or a facultative thermophile (growth at 30° to 35°C and at 55°C).