Blessing Agugharam,

pathogens isolated from blood culture:
– bacteria, like staphylococci, streptococci, Escherichia coli, Pseudomonas, and so on
– parasites, like Plasmodium malariae
– fungi, like Candida albicans
– viruses, like citomegalovirus (CMV)

Blood tests, like test for antibodies against pathogenes, are used to determine which pathogen has caused an infection.
Blood culture test is done to determine the pathogen AND to check which antibiotics stop their growth (antibiotic sensitivity test).
Besides blood culture, there are other tests to determine presence of pathogenes in the blood, like antibody tests, PCR tests and other.