Antibody titer to *Escherichia coli* serotype O157:H7 (serum/plasma)

What This Test Measures

The test detects antibodies produced by your immune system in response to exposure to *E. coli* O157:H7. Antibodies are proteins that help your body recognize and fight foreign invaders, like bacteria. This test helps determine if you’ve been exposed to this particular strain, which is known for causing illness through contaminated food or water.

Why It Might Be Ordered

Your healthcare provider may order this test if you’ve had symptoms like severe diarrhea, vomiting, or blood in your stool that suggest a bacterial infection. It could also be used in outbreaks, food safety investigations, or if you’ve been exposed to someone with E. coli O157:H7.

Sample Collection and Preparation

A blood sample is drawn from a vein in your arm. The blood is processed to separate the serum or plasma, which contains the antibodies being tested. This sample is then analyzed in a lab using an immunoassay method to measure antibody levels.

What the Results Mean

Results are typically reported as a titer value, which indicates the highest dilution of your serum that still reacts with the E. coli O157:H7 antigen. A positive result suggests exposure, but it doesn’t confirm active infection. Higher titers may indicate recent or ongoing exposure.