CHROMagar™ STEC Kit

For Detection of Shiga Toxin-Producing Escherichia coli (STEC)

CHROMagar™ STEC is a selective chromogenic culture medium designed for the detection, differentiation, and presumptive identification of Shiga toxin-producing Escherichia coli (STEC), including both O157 and non-O157 serotypes. The medium enables easy visual recognition of suspected STEC colonies, which typically appear mauve, while other Enterobacteriaceae appear colorless, blue, or are inhibited.

Developed to address the limitations of traditional culture media that focus solely on E. coli O157:H7, CHROMagar™ STEC is the first chromogenic medium on the market that offers broad-spectrum detection of clinically relevant STEC strains—including those responsible for emerging outbreaks.

Key Features & Benefits

• ✅ Distinctive Mauve Colony Appearance: Most STEC strains form mauve colonies within 18–24 hours, enabling quick screening and presumptive identification.
• ✅ Highly Selective: Inhibits or differentiates non-STEC flora (e.g., other Enterobacteriaceae), supporting effective large-scale screening.
• ✅ Non-O157 Detection Capability: Effective for both O157:H7 and non-O157 STEC serotypes (e.g., O26, O45, O103, O111, O121, O145).
• ✅ Flexible Enrichment: Can be supplemented with additional selective agents to improve performance for specific outbreak strains.
• ✅ Validated for Diverse Sample Types: Clinical (stools, rectal swabs), food products, animal feed, and environmental samples.

Intended Use

CHROMagar™ STEC is intended for qualitative detection and differentiation of STEC from:

• Clinical samples (e.g., stool, rectal swabs)
• Food and feed samples
• Environmental testing

The test aids in presumptive identification of STEC to support further confirmatory and epidemiological testing. It is not intended as a standalone diagnostic or to guide therapy.

Colonies Appearance

Performance Background

Recent public health studies and CDC reports have shown that non-O157 STEC serotypes are increasingly implicated in foodborne outbreaks and severe illness (e.g., HUS, hemorrhagic colitis). Traditional methods, often focused only on O157:H7, fail to detect the broader range of pathogenic STEC.

CHROMagar™ STEC was developed to fill this detection gap, enabling rapid, reliable identification of STEC across serotypes. The medium supports outbreak investigations, surveillance programs, and food industry quality control.

💬 CDC Statement: “Non-O157 STEC infections are as prevalent, or more so, than O157:H7 infections in some regions.” (CDC report: Prevalence of Non-O157:H7 Shiga Toxin-Producing Escherichia coli in Diarrheal Stool Samples)

Test Procedure

1. Sample Type: Stool, rectal swab, food homogenate, feed, or environmental sample.
2. Inoculation: Direct plating or post-enrichment in selective broth.
3. Incubation:
   • Temperature: 35–37 °C
   • Duration: 18–24 hours under aerobic conditions
4. Interpretation:
   • Presumptive STEC = Mauve colonies
   • Other bacteria = Blue, colorless, or no growth

Product Formats & Ordering Information

Storage & Shelf Life

• Store prepared medium or dehydrated components in a dry environment at 2–8 °C
• Shelf life typically up to 2 years when stored under recommended conditions

CHROMagar™ STEC is the first and only chromogenic medium enabling broad and reliable presumptive identification of STEC, including non-O157 strains, directly from clinical, food, and environmental samples. Its performance, ease of interpretation, and compatibility with downstream molecular or serotyping assays make it a powerful tool for labs committed to food safety, clinical diagnostics, and outbreak prevention.