Do pathologists take blood from the heart to check for bacteria in the blood?

Yes

Explanation:

Blood and pathology tests leave many people squeamish, but they're an important part of detecting, diagnosing and treating disease. In fact, if you're sick, many decisions about your care will come down to the results of your blood and pathology tests.

Pathology means the study of disease and its causes and progression. Pathology tests cover blood tests, and tests on urine, stools (faeces) and bodily tissues.