Evaluation of the ESP Culture System II for recovery of mycobacteria from blood specimens collected in isolator tubes.

The reliability of the ESP Culture System II (ESP II; AccuMed International, Westlake, Ohio), a continuously monitoring, nonradiometric mycobacterial culture system, for recovery of mycobacteria from sediments of blood collected in an Isolator tube was evaluated by comparing its performance to inoculation of the sediment onto Middlebrook 7H11/7H11 selective biplates. Of 1,704 blood specimens, 73 (4.3%) were positive for mycobacteria (68 Mycobacterium avium complex and 5 M. tuberculosis). Fifty-three specimens were positive by both methods; 13 were positive by ESP II only, and 7 were positive by Middlebrook agar only (chi square = 1.8; P > 0.05). The mean times to positivity were 15.6 days for ESP II and 19.0 days for Middlebrook agar (P < 0.01). The time to detection was the same for 13 specimens; ESP II was positive first for 33, and agar plates were positive first for 7. ESP II allowed recovery of more mycobacteria (90.4% of all isolates versus 82.2% for Middlebrook agar) from sediments of blood specimens collected in Isolator tubes, and it provided significantly faster detection than did Middlebrook plates.