Detection of bacteremia by biphasic and radiometric methods

During one year period our laboratory carried out 859 hemocultures. These have been evaluated with two methods: a conventional biphasic method (Castaneda bottles), and the automated radiometric method (Bactec System). 185 cultures were obtained with one or both methods. Of these 3.5% were considered contaminated, therefore the clinically significant isolation rate was 16.2%. Of these 86.4% was recovered by biphasic system and 79.8% by Bactec System. The recovery time to positivity and spectrum of isolates were similar for the two methods. Although there were substantially more contaminants isolated in the Vacutainer-Bactec System.