A clinical laboratory evaluation of the vacutainer 20 ml tube for aerobic blood cultures.

Abstract

Clinical blood cultures with made in parallel from the same venipuncture in two Vacutainer 20 ml tubes, each inoculated with 2 ml of blood, a 50 ml blood culture bottle with plain (normotonic) broth and a 50 ml bottle with hypertonic broth, each of the bottle media being inoculated with 4 ml of blood. Of a total of 127 sets of monomicrobic blood cultures, growth was obtained from 115 bottles with plain broth, 108 pairs of Vacutainer tubes and 105 bottles with hypertonic broth. The hypertonic broth medium proved superior to the Vacutainer tubes in the time required for isolation of gram-negative rods. No significant differences were observed between the results obtained from the Vacutainer tubes and those from the plain broth medium. Of the 108 cultures positive in the Vacutainer system, 19 cultures (17.6%) yielded growth from one of the tubes only. Because of the small volume of blood cultured, the Vacutainer 20 ml tube is not recommended for routine clinical blood cultures, with the exception of cultures taken from newborn infants in the diagnosis of neonatal septicaemia.