Blood Culture

• Blood culture media are enriched nutrient broth that encourages the multiplication of even one bacterium; hence these media will enhance the growth of any stray contaminating bacterium, such as a normal inhabitant of human skin. Therefore, careful skin preparation before collecting blood sample is of paramount importance.

Method of Collection – Disinfect the puncture site with 70 per cent alcohol followed by 2 per cent iodine (Betadine) keep for 1 minute – (Time is crucial) – Blood samples are inoculated into blood culture media (BHIB, GCB, Bile broth) in 1:5 dilutions. Bile broth when enteric fever is suspected – To ensure maximal recovery, minimum of two sets of blood culture is necessary. Timing and Number of Sample In acute febrile illness – 2 separate samples may be drawn at the same time from different sites. In PUO – Two samples may be drawn an hour or more apart. In Suspected Infective Endocarditis – Three samples, 30 minutes apart from different sites. Volume – 5-10 ml adults, 1-5 ml in children.

Precautions

• Do not touch disinfected puncture site before drawing blood. – Do not collect blood through indwelling IV cannulae line. – In case of delay, keep samples at room temperature or incubate. NEVER REFRIGERATE BLOOD CULTURE SAMPLES FOR BACTERIAL CULTURE Clot Culture (for S. typhi and paratyphi) – Plain blood (5 ml) in sterile container (Separated serum can be used for widal test and clot can be used for culture).