ISO 7402:1993

Gives general guidance for the enumeration of Enterobacteriaceae present in products intended for human consumption or animal feeding stuffs: 1) by calculation of the most probable number after incubation at 35 °C or 37 °C in liquid medium (MPN technique), or 2) by counting colonies in a solid medium after incubation at 35 °C or 37 °C (colony-counting technique). For low numbers, the MPN method is preferable, otherwise the colony-count method is preferred.