Rapid detection of E. coli in a thin film culture device

A device for differentially enumerating colonies of coliform and Escherichia coli microorganisms, the device comprising:

• a water-impermeable first sheet;
• a water-impermeable second sheet attached to the first sheet;
• a dry, rehydratable culture medium adhered to the first sheet;
• wherein the culture medium comprises:
• organonitrogenous nutrients that facilitate growth of coliform microorganisms;
• a lactose-fermentation indicator system comprising D-lactose, a first inducer compound that enhances production of β-galactosidase, and a pH indicator;
• a β-D-glucuronidase indicator system comprising 5-bromo-4-chloro-3-indolyl-β-D-glucuronide and at least one compound that enhance β-glucuronidase activity in E. coli;
• a redox indicator;
• an effective amount of at least one agent that selectively inhibits growth of non-coliform microorganisms;
• and
• a first cold-water soluble gelling agent;
• a microbial growth zone disposed between the first sheet and the second sheet, wherein an area of the culture medium adhered to the first sheet defines the growth zone;
• and
• a second cold-water-soluble gelling agent adhered to the second sheet;
• wherein the first sheet is attached to the second sheet so that the culture medium is facing the second cold-water-soluble gelling agent;
• wherein the first sheet and second sheet are configured to facilitate the trapping of carbon dioxide gas;
• wherein the culture medium adhered to the first sheet has a coating weight of about 130 mg/100 cm2 to about 195 mg/100 cm2;
• wherein lactose is disposed in the dry culture medium adhered to the first sheet, wherein the lactose is present in the dry culture medium;
• and
• wherein the second sheet has a lower carbon dioxide permeability than 40 um-thick biaxially-oriented polypropylene (BOPP).