Which statement about E. coli O157:H7 detection in Colilert testing is true?

Which statement about E. coli O157:H7 detection in Colilert testing is true?

• A. It is detected by Colilert testing
• B. It is not detected by Colilert testing
• C. It is the primary target of Colilert
• D. It is Gram-positive

Answer: (B)

Colilert detects bacteria by using enzyme-based substrates that signal the presence of total coliforms and E. coli. The E. coli signal relies on the enzyme β-glucuronidase. E. coli O157:H7 strains commonly do not produce this enzyme, so they typically won’t trigger the E. coli signal in Colilert. Because of that, Colilert is not reliable for detecting this specific pathogen. Colilert isn’t aimed at identifying a particular strain like O157:H7; it’s a general screening test for fecal indicators. Also, E. coli is Gram-negative, so the statement that this organism is Gram-positive isn’t correct.

Colilert detects bacteria by using enzyme-based substrates that signal the presence of total coliforms and E. coli. The E. coli signal relies on the enzyme β-glucuronidase. E. coli O157:H7 strains commonly do not produce this enzyme, so they typically won’t trigger the E. coli signal in Colilert. Because of that, Colilert is not reliable for detecting this specific pathogen. Colilert isn’t aimed at identifying a particular strain like O157:H7; it’s a general screening test for fecal indicators. Also, E. coli is Gram-negative, so the statement that this organism is Gram-positive isn’t correct.