Microbiology and culture of body fluids

At a glance

• Culture still decides the organism and its susceptibilities in most bacterial infections. The yield depends on the specimen more than the lab.
• Four rules: collect before antibiotics where safe, send enough volume, send fluid or tissue rather than a swab, and tell the lab what you suspect (TB, Nocardia, fungi, Legionella, gonococcus, Actinomyces need special media or longer incubation).
• A cell count often answers the question before culture does: CSF, synovial, ascitic and PD fluid all have thresholds.