Culture of mycobacteria from the blood has not been used routinely as a method for diagnosing mycobacterial infections. It has been found, particularly with AIDS patients, that mycobacteremia can be detected using a new lysis-centrifugation blood culture system (ISO) as well as with a radiometric blood culture system (Bactec). It was thought that a combination of both methods would yield a more rapid and sensitive blood culture method than the ISO alone so a trial evaluation is now in progress. Blood from AIDS patients known to be infected with mycobacteria from any site is collected in Isolator blood culture tubes. After lysis and centrifugation, the remaining pellet is cultured onto routine mycobacterial culture media as well as into a Bactec blood culture vial. Patients with the acquired immune deficiency syndrome (AIDS) may develop infection with mycobacteria, particularly Mycobacterium avium - M. intracellulare (MAI). These infections can frequently be associated with demonstrable mycobacteremia with the organism. In this study we compared the sensitivity of using a radiometric (Bactec) culture system to the use of conventional mycobacterial culture media for blood cultures on these patients. Both systems were inoculated with blood concentrate prepared by lysis-centrifugation (Dupont Isolator). Twenty-eight percent of 46 AIDS patients cultured had blood cultures positive for MAI. Patients had from less than 1 to greater than 100 colonies/ml of blood. Both Lowenstein-Jensen and Middlebrook 7H10 agars were comparable in their recovery of MAI. Bactec 12A vials containing double the standard volume of media were more sensitive and slightly faster than vials containing the standard volume. Conventional media detected 98% of positive cultures, Bactec vials containing double volumes of medium detected 94%, while single volume vials detected 77%. Bactec vials were positive approximately 5-6 days sooner than conventional media.
