Gram-negative bacterial culture with probe-based identification and antibiotic susceptibility testing (from a blood sample)

Why This Test Is Done

Your healthcare provider may order this test if you have symptoms of a serious blood infection, such as fever, chills, or signs of infection like confusion or rapid breathing. It’s also used in monitoring patients who are at higher risk, such as those with weakened immune systems, recent surgeries, or severe illnesses. Blood cultures help confirm whether bacteria are present and identify the type of bacteria causing the infection.

What to Expect Before the Test

You may receive instructions to avoid certain medications or supplements before the test, depending on your medical condition. Typically, you’ll have a small needle inserted into a vein (usually in your arm) to draw blood. The blood sample is then sent to a lab for culture and testing.

What Happens During the Test

The blood sample is placed in special containers that support the growth of bacteria. A probe-based test may also be used to quickly identify certain bacteria and assess antibiotic resistance. Results can take several days to a week, depending on the lab’s methods and whether additional testing is needed.

What the Results Mean

Positive results indicate the presence of bacteria in your blood. The probe test may provide preliminary identification of the bacteria and suggest potential antibiotic treatments. Negative results mean no bacteria were detected in the sample, but further evaluation may still be needed if you have symptoms of infection.