Escherichia coli O157 Chromogenic Medium is a highly specific selective medium designed for rapid screening of enterohemorrhagic Escherichia coli O157:H7 in food, water sources, and clinical samples. Its core mechanism relies on colony color differentiation based on β-glucuronidase activity differences: O157:H7 strains, lacking this enzyme activity, produce colorless, pale purple, or grayish-white colonies, whereas most β-glucuronidase-producing common E. coli hydrolyze the chromogenic substrate, forming blue or blue-green colonies. The addition of selective inhibitors such as cefuroxime, potassium tellurite, and sodium lauryl sulfate effectively suppresses the growth of interfering microorganisms like Proteus, Gram-positive bacteria, and Aeromonas, significantly enhancing detection specificity and sensitivity.

Food rapid screening: After bacterial enrichment, isolate hemorrhagic Escherichia coli O157 by streaking, suitable for national standard testing.

Diarrhea specimen testing: Inoculation of bloody diarrhea feces/vomit, rapid initial screening for EHEC, to assist clinical diagnosis.

Purification of positive samples: Obtain characteristic single colonies for serum, biochemical, and molecular confirmation.

Water risk detection: assess O157 pollution in surface water and production water to ensure drinking water safety.

Import and export quarantine: Interpretation is more intuitive than CT-SMAC, shortening the screening cycle for pathogenic bacteria.

Disinfection effect verification: residual O157 live bacteria were detected, and the killing effect of disinfectants and high-temperature cleaning was evaluated.

Culture substrate control: Verify the antibacterial and colorimetric specificity of standard strains.

Escherichia coli O157: H7

Biological characteristics: G-short rod-shaped bacteria, flagella, facultative anaerobic, no spores; Shiga like toxin production; Non fermented sorbitol; β - glucuronidase negative; Can specifically decompose chromogenic substrates; Tolerant to cefuroxime and potassium tellurite; Resistant to low temperatures and certain high temperatures, it can survive for a long time in meat, fruits and vegetables, and water bodies.

Colony characteristics:

O157: H7 typical colony: purple/purplish red/burgundy, round, smooth, raised, with clear boundaries; 

Other Escherichia coli (non O157) appear blue-green or do not grow; Hermann's bacteria appear blue 

or yellow green; Other bacteria in the Enterobacteriaceae family appear colorless or blue; O157: H7 shows no fluorescence under UV, while some non-O157 STEC strains exhibit fluorescence; Selective additives effectively inhibit Gram positive bacteria and most interfering bacteria, and the background of the tablet is clean