This part of ISO 21528 specifies a method, with pre-enrichment, for the detection of Enterobacteriaceae. It is applicable to — products intended for human consumption and the feeding of animals, and — environmental samples in the area of food production and food handling. Enumeration is carried out by calculation of the most probable number (MPN) after incubation at 37 °C (or 30 °C)1) in liquid medium. This method is applicable — when the microorganisms sought are expected to need resuscitation before enrichment, and — when the number sought is expected to be in the range 1 to 100 per millilitre or per gram of test sample. A limitation on the applicability of this part of ISO 21528 is imposed by the susceptibility of the method to a large degree of variability (see Clause 11).