CLINICAL-EVALUATION OF DIFCO ESP CULTURE SYSTEM-II FOR GROWTH AND DETECTION OF MYCOBACTERIA

The reliability of the ESP Culture System II (ESP II; Difco Laboratori es, Detroit, Mich.), a continuously monitoring mycobacterial culture s ystem, was evaluated by comparing its performance,vith the BACTEC TB 4 60 (BACTEC TB) and Middlebrook 7H11/7H11 selective agar systems. A tot al of 2,283 specimens of all types (70.7% were respiratory specimens) were cultured; 149 (6.5%) yielded mycobacteria. The most common specie s recovered were Mycobacterium avium complex (MAC, 73 isolates) and My cobacterium tuberculosis complex (MTBC, 53 isolates). The recovery rat es by individual system were 87, 81, and 65% for ESP II, BACTEC TB, an d Middlebrook agar, respectively, for all mycobacteria; the recovery r ates were 89, 92, and 89%, respectively, for MTBC. For liquid plus sol id medium system combinations, recovery rates for all mycobacteria and for MTBC, respectively, were 91 and 94% for ESP II plus Middlebrook a gar and 85 and 96% for BACTEC TB plus Middlebrook agar. The difference between the recovery rates of all mycobacteria by ESP II and by BACTE C TB was not significant, whereas for the individual species, the only significant difference was recovery of more isolates of MAC by ESP II . For those isolates recovered in the individual systems, mean times t o detection of all mycobacteria, MTBC, and MAC, respectively, were 13. 1, 15.5, and 10.9 days for ESP II; 14.4, 16.6, and 12.1 days for BACTE C TB; and 17.8, 18.3, and 18.8 days for Middlebrook agar. ESP II is a reliable, nonradiometric, less labor-intensive alternative to BACTEC T B for growth and detection of mycobacteria, but as with other liquid c ulture methods, ESP II should be used in combination with a solid medi um, not as a stand-alone system.