Not easily culturable but well ble and used in epidemiology are:

Ans. (b) Mycobacterium TB S. aureus: grow rapidly on ordinary media within a temperature range of 10-42degC. E. coli: good growth occurs on ordinary media. Salmonella: grow readily on simple media over range pH 6-8 and temperature 15-41degC. M.TB: grow slowly, colonies appear in 2-8 weeks. Culture remain ble at room temperature for 6-8 months and may be stored up to 2 year at -20degC.